Climate control is the technology of controlling fluids and gases to vary temperature. Parker provides comfort, convenience and control through refrigeration and air conditioning.

• Air conditioning
• Heating
• Food retail refrigeration
• Commercial refrigeration
• Industrial refrigeration
• Precision cooling

• CO2 controls
• Electronic controllers
• Filter driers
• Hand shut-off valves
• Pressure regulating valves
• Refrigerant distributors
• Safety relief valves
• Solenoid valves
• Thermostatic expansion valves

Learn more about Parker's climate control technologies through our blog and  video links

Related Content on Climate Control Technology

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Using P-T Analysis as a Service Tool for Refrigeration Systems

Manufacturers of refrigerants, controls, and other suppliers distribute hundreds of thousands of pressure-temperature charts to the trade every year. It would be rare indeed to find a service technician who could not put their hands on a pressure-temperature chart or application at a minute’s notice.

In spite of the widespread availability and apparent reference to the pressure-temperature relationship, very few service technicians use the P-T chart/application properly in diagnosing service problems.

The purpose of this article is to demonstrate the proper use of the pressure-temperature relationship, and to illustrate how it can be used to thoroughly analyze a refrigeration or air conditioning system.

P-T Chart Features:

• Refrigerants 134a, 404A, 407A, 507, 744 - CO2
• Instructions fro determining superheat
• Systematic Analysis
• Handy pocket size
• Android / iOS Mobile App

Before getting into the proper use of the P-T chart/application, let’s review briefly the refrigeration system and examine exactly how the pressure-temperature relationship can be applied.

The refrigerant in a refrigeration system will exist in one of the following forms:

• All liquid
• All vapor
• A mixture of liquid and vapor

Figure 1 illustrates the form in which refrigerant is found at various points in a normal operating refrigeration system.

Notice that the high side contains refrigerant in all of the three conditions listed above. The discharge line contains all vapor. The condenser where the vapor condenses into a liquid contains a mixture of liquid and vapor. The line between the condenser and the receiver usually contains all liquid, although it would not be abnormal for this line to also have some vapor mixed with the liquid. Since the receiver has a liquid level at some point, it has a mixture of liquid and vapor at the surface of the liquid level. The liquid line leading from the receiver to the thermostatic expansion valve should contain all liquid. A sight glass or liquid indicator is frequently installed in the liquid line to assist in determining if the liquid refrigerant is completely vapor-free.

The low side of the system will usually contain refrigerant in only two of the three forms that were listed previously. That is, the low side will contain all vapor in the suction line, and a mixture of liquid and vapor from the outlet of the thermostatic expansion valve to nearly the outlet of the evaporator.

The important thing to remember is that the pressure-temperature relationship as shown by a P-T chart / application is only valid when there is a mixture of refrigerant liquid and vapor.

Therefore, there are only three places in the normally operating refrigeration system where the P-T relationship can be guaranteed with certainty. That is the evaporator, the condenser, and the receiver — places where a mixture of refrigerant liquid and vapor are known to exist. When refrigerant liquid and vapor exist together, the condition is known as “saturated.”

This means that if we are able to determine the pressure at any of these points, we can easily determine the “saturation” temperature by merely finding the pressure on a P-T chart/application and reading the corresponding temperature. Conversely, if we can accurately measure the temperature at these three locations, we can also determine the “saturation” pressure from the P-T relationship by finding the pressure corresponding to the temperature that we have measured.

At the points in the system where only vapor is present, the actual temperature will be above the saturation temperature. In this case, the difference between the measured temperature and the saturation temperature at the point in question is a measure of superheat. The temperature of the vapor could be the same as the saturation temperature, but in actual practice, it is always above. If these temperatures were the same then the amount of superheat would be zero.

Where it is known that only liquid is present such as in the liquid line, the measured temperature will be somewhere below the saturation temperature. In this case, the difference between the measured temperature and the saturation temperature is a measure of liquid subcooling. Again, it is possible to find that the actual measured temperature is equivalent to the saturation temperature, in which case the amount of subcooling would be indicated as zero.

Figure 2 shows some actual pressure- temperature measurements throughout a normally operating system using R-134a refrigerant. This may give a better insight into the condition of the refrigerant at the various points. The measured temperature at the evaporator inlet is 19°F (-7.2°C). A gauge installed at this point indicates a pressure of 18 psig (1.2 bar); 18 psig (1.2 bar) on the P-T chart/application indicates a temperature of 19°F (-7.2°C). It might also be said that the superheat is zero and the subcooling is zero. Therefore, the refrigerant is at saturation, or in other words, at the boiling point. This P-T relationship will hold true when refrigerant liquid and vapor are present together.

A gauge installed in the suction line measures 16 psig (1.1 bar). If there were a mixture of liquid and vapor at this point, the measured temperature would be the same as the saturation temperature or 16°F (-8.9°C). However, our actual measured temperature in this case is 27°F (-2.8°C). The amount of superheat in the vapor is the difference between the measured temperature of 27°F (-2.8°C) and the saturation temperature (according to the P-T chart/application) of 17°F (-8.7°C). Therefore, the superheat is 10°F (5.4K).

If we also measure 16 psig (1.1 bar) at the compressor inlet with the measured temperature of 47°F (8.3° C), our superheat in this case would be 30°F (30K), calculated by subtracting the saturation temperature equivalent to 16 psig (1.1 bar) (17°F /-8.7°C) from the measured temperature of 47°F (8.3° C).

Let’s now examine the gauge we have installed midway in the condenser which reads 158 psig (10.9 bar). According to the P-T chart/ application, the saturation temperature will be 115°F (46.1°C). This is the temperature that we would be able to measure if we placed a thermocouple in the refrigerant at the point where it is changing from a vapor to a liquid. At this point, there is no difference between the measured temperature and the saturation temperature. It might also be said that the superheat is zero and the subcooling is zero. Therefore, the refrigerant is saturated, or in other words, at the boiling point.

In our example we also measure 158 psig (10.9 bar) at a discharge line of the compressor. The measured temperature here is 200°F (93.3°C). Calculating the superheat in the same way as it was done on the suction line (difference between measured temperature and saturation temperature), it is determined that the superheat is 85°F (47.2K).

When a system employs the use of a liquid receiver, there can be no subcooling at the surface of the liquid in the receiver. The reason is that when liquid refrigerant and vapor exist together, they must obey the P-T relationship or the refrigerant must be saturated. In our example the measured pressure in the receiver is 146 psig (10.1 bar); the refrigerant at the surface of the liquid level in the receiver must therefore be at 110°F (43.3°C).

Once a solid column of liquid is formed, subcooling of the refrigerant can take place by lowering its temperature with the use of liquidsuction heat exchangers, subcoolers, or from lower ambient temperatures surrounding the line.

Subcooling is a lowering of a temperature below the saturation point or boiling point. In our illustration in Figure 2, subcooling of 5°F (2.8K) and 2°F (1.4K) has been determined as illustrated at two points.

Of course, it is important to maintain some liquid subcooling in the liquid line to prevent flash gas from forming in the liquid line and entering the thermostatic expansion valve.

With the use of a P-T chart/application, we should be able to determine the condition of the refrigerant at any point in the system by measuring both the pressure and the temperature and observing the following rules:

• Liquid and vapor are present together when the measured temperature corresponds to the P-T relationship. (It is theoretically possible to have “100% saturated liquid” or “100% saturated vapor” under these conditions, but practically speaking in an operating system, it should be assumed that some liquid and some vapor are present together under these conditions.)​
• Superheated vapor is present when the measured temperature is above the saturation temperature corresponding to the P-T relationship. The amount of superheat is indicated by the difference.
• Subcooled liquid is present when the measured temperature is below the saturation temperature corresponding to the P-T relationship. The amount of subcooling is represented by the difference.

In our illustration we have located gauges at points in the system where it is not always feasible to do so on an actual installation. Because of this, we must oftentimes make deductions and assumptions when dealing with an actual system.

As an example, we would normally assume that the 158 psig (10.9 bar) read on the gauge installed at the compressor discharge line is also the pressure that exists in the condenser. That is, we assume that there is no pressure loss of any consequence between the compressor discharge and the condenser. With this reasoning, we arrive at a condensing temperature of 115°F (46.1°C). If an undersized discharge line or other restrictions are suspected, we cannot make this assumption and other pressure taps may be necessary to locate the troublesome area.

It is also common practice to assume that the pressure measured at the suction service valve of the compressor is the same pressure that exists at the outlet of the evaporator at the expansion valve bulb location. This is particularly true on closecoupled systems where it has been determined that the suction line is of the proper size. By making this assumption, we can determine the expansion valve superheat without installing an additional pressure tap at the bulb location. However, to eliminate any doubt as to the amount of suction line pressure drop and to be absolutely precise in measuring superheat, a gauge must be installed in the suction line at the bulb location.

Care must be taken to make a reasonable allowance for pressure drops within the system. Excessive pressure drops can be detected by applying the principles of the P-T relationship. As an example, in Figure 2, with gauges installed only at the suction and discharge of the compressor and reading as indicated, a significant pressure drop through the evaporator would be indicated by a high temperature of, say, 50°F (10°C) measured at the evaporator inlet which would correspond to a pressure at that point of approximately 45 psig (3.1 bar). That would mean that there is a pressure drop of 29 psi (2.0 bar) from the evaporator inlet to the compressor inlet (45 minus 16/3.1 minus 1.1). While this would be considered excessive on a single-circuit evaporator, it should be remembered that on multicircuit evaporators there will be a pressure drop through the refrigerant distributor assembly. A pressure drop through the distributor assembly on R-134a may be in the vicinity of 25 psi (1.7 bar). This means that with the use of a refrigerant distributor, a measured temperature between the outlet of the thermostatic expansion valve and the inlet of the distributor of approximately 50°F (10°C) would not be abnormal in the system illustrated in Figure 2.

The proper use of the P-T relationship can be helpful in discovering the presence of air or other noncondensable gases in the system. These undesirable gases will accumulate in the condenser and add their pressure to that produced by the refrigerant, resulting in a higher total pressure. Therefore, if this condition exists, the P-T relationship will be distorted so that the actual refrigerant temperature in the condenser will be lower than the P-T chart/ application indicates.

Assuming an air cooled condenser, the relationship between leaving air temperature and actual refrigerant temperature (in condenser) is lower than a comparable system having no noncondensables.

This is the result of the noncondensable interfering with the amount of condensing surface and making the condenser less efficient.

Test your P-T know-how and use of P-T relationships by downloading Using P-T Analysis as a Service Tool Bulletin Form 10-35 / 52013 and taking the test at the end.  

With an understanding of the refrigerant pressure-temperature relationship, the widely available P-T chart/application is a valuable tool.

A P-T chart/application, along with accurate gauges and thermometers, allows us to determine at any point in the system if the refrigerant is saturated, subcooled or superheated. This is very important in properly diagnosing system problems.

Download our convenient ChillMaster P-T Chart Mobile App to help you on the road. Learn more about Parker's technologies in climate control.

Article contributed by Parker Sporlan Division

Climate Control Technologies and Key Markets

What’s Trending in Industrial Automation?

Lubricant-refrigerant mixture breakdown causes sludge formation and other corrosive materials that will hinder the normal operation of compressor valves and control devices in refrigerant and HVAC systems. Scale, solder particles, dirt, and all types of foreign substances must be removed to protect the compressor, solenoid valves, expansion valves, capillary tubes, and other close tolerance parts.

Follow this 11 step procedure to ensure you have cleaned up your system before proceeding.

1. Diagnosis— Make certain that a motor burnout has actually occurred by running the proper electrical tests. Determine the severity of the burnout by analyzing the acid content of the lubricant from the burned out compressor. This can be done on the job with a TA-1 One Time Acid Test Kit. Note the color of the lubricant, the smell of the refrigerant, and if carbon deposits are present in the suction line.
2. Plan the procedure— Consider the following factors: If the lubricant is not acidic and none of the other indications of severe burn out are present, then the system can be classified as a “mild burnout” and cleaned up accordingly. Under these circumstances, it is easier to save the refrigerant. If a lubricant sample is desired for checking the progress of the clean-up, then a trap should be installed in the suction line (see Form 40-141). A semi-hermetic compressor can be examined and cleaned by having the head removed. A heat pump system will frequently require replacing the 4-way valve, or other special precautions. Systems with a critical charge must have the charge adjusted due to the added volume in the oversized filter-drier that is normally installed in the liquid line.
3. Mild Burnout— If the analysis of the lubricant shows no acidity, then the system can be classified as a mild burnout, and cleaned up simply by installing an oversized Catch-All Filter-Drier in the liquid line. If the lubricant is not analyzed, and the other factors indicate some doubt, then the burnout should be considered severe and cleaned up as described below. CAUTION—Acid burns can result from touching the sludge in the burned out compressor. Rubber gloves should be worn when handling contaminated parts.
4. Severe Burnouts—These systems should be cleaned using the suction line filter-drier method. The refrigerant in the system can be saved,and must be removed using refrigerant recovery/recycling equipment. The exact method chosen depends upon the availability of shutoff valves, the amount of charge, and the other equipment available. See the section on “Saving the Refrigerant.”
5. Remove the burned out compressor and install the new compressor.
6. Install a Catch-All Suction Line Filter-Drier or RSF shell (selected from Bulletin 40-10 pages 34 and 35) ahead of the new compressor. The access valve on the drier permits the pressure drop to be checked by installing gauges on the access valve and at the gauge port on the suction service valve. For systems without service valves, install a line tap valve downstream of the Catch-All Filter-Drier for the second connection.
7. Remove the liquid line drier and install an oversized Catch-All (one size larger than the normal selection size). Check the expansion valve and other controls to see if cleaning or replacement is required. Install a See•All Moisture and Liquid Indicator.
8. Evacuate the system according to the manufacturer’s recommendations. Normally this will include the use of a high vacuum pump and a low vacuum micron gauge for measuring the vacuum obtained.
9. Recharge the system through the access valve on the suction line filter-drier. Then start the system according to the manufacturer’s instructions
10. The use of a Catch-All Filter-Drier installed permanently in the suction line permits the clean-up of a small system to be completed with one service call. The pressure drop across the suction line filter-drier should be measured during the first hour’s operation. If the pressure drop becomes excessive, then the suction line filter-drier should be replaced. If the equipment manufacturer’s recommendations are not available, the following maximum pressure drop levels are suggested. See table below.
11. In 24 hours take a lubricant sample. Observe the color and test for acidity. If the lubricant is dirty or acidic, replace the suction line and liquid line filter-driers. In two weeks re-check the color and acidity of the lubricant to see if another change of filter-driers is necessary. It may also be desirable to change the lubricant in the compressor. Before the job is complete, it is essential that the lubricant be clean and acid-free.

The refrigerant is not damaged by the burnout, and can be reused, provided the contaminants are removed. When a mild burnout has occurred on a system with service valves, the refrigerant can be saved by closing the valves and trapping the refrigerant in the system, while changing the compressor. The system can then be pumped down with the new compressor to save the refrigerant while installing an oversized Catch-All Filter-Drier in the liquid line.

If a severe burnout has occurred, the above procedure might damage the new compressor. Therefore, it is preferred that the refrigerant be removed from the system for reclamation. If no service valves are available then the refrigerant must be removed from the system. Recovery, recycling or reclamation of the refrigerant must be performed in accordance with EPA regulations. Sporlan recommends the use of our HH style cores for cleaning up all systems after a hermetic motor burnout. These cores contain a desiccant mix that is suitable for removing all types of system contaminants.

Form 40-109 is available for selection recommendations on suction line filter-driers after hermetic burnout and for new installations.

Information on cleaning up centrifugal systems is given in Bulletin 240-10-3.

Information on clean-up after a hermetic motor burnout is also given in Section 91 of the SAM Manual published by the Refrigeration Service Engineers Society.

Article contributed by Glen Steinkoenig, Product Manager,  Contaminant Control Products, Sporlan Division of Parker Hannifin                                                                                                                                                 

Other articles on this topic include:

Using P-T Analysis as a Service Tool for Refrigeration Systems

The Suction Line Filter-Drier method of cleaning up a system after a hermetic motor burnout is favored by service technicians and recommended by manufacturers throughout the HVAC and refrigeration industry. This method gives the most practical and positive protection of the new compressor, since the refrigerant lubricant mixture is filtered and purified just before it returns to the compressor. It is important that all contaminants remaining in the system be removed to prevent a repeat burnout of the new compressor. Suction Line Filter-Driers are designed specifically for clean-up after burnout with proven benefits.

• Positive protection for the compressor
• Most economical method of clean-up
• Minimum down time— system operates during clean-up
• Method is applicable to almost any size system
• Removes all contaminants — moisture, acid, sludge, dirt
• Recommended by the leading equipment manufacturers method of clean-up

The construction of the suction line filter-drier is not significantly different from the standard liquid line filter-drier. Both driers remove the important contaminants such as moisture, dirt, acid, and the products of lubricant decomposition. The suction line filter-drier utilizes the HH style charcoal core to obtain the maximum ability for lubricant clean-up and removing all types of contaminants.

The sealed models have an access valve (-T) at the inlet end to permit measuring the pressure drop during the first several hours of operation.

RSF shells have an access valve to measure pressure drop (see Parker Sporlan Bulletin 80-10).

Also, replaceable core Catch-Alls have a 1/4” female pipe connection (-G) in the endplate to permit the installation of an access valve to measure pressure drop.

If the proper style drier is not available, then a suction line filter-drier can be used in the suction or liquid line; and a liquid line filter-drier can be used in the suction line. The pressure drop characteristics of the two types of driers are essentially the same for a given line size.
 

The Catch-All Filter-Drier can be installed directly in the suction line by removing a portion of the line. After clean-up, the Catch-All Filter-Drier is generally left in the line. The cores in the replaceable model or RSF shell should be replaced with filter elements (RPE-48-BD or RPE-100) to obtain the lowest possible pressure drop.

A hermetic motor burnout produces large amounts of acid, moisture, sludge and all types of lubricant decomposition materials. To obtain the maximum ability to remove all these various types of contaminants, the Sporlan HH style charcoal core is preferred. If the HH style core is not available, the standard cores may be used.

OEM recommendations stress the importance of lubricant in cleaning up a system after a motor burnout. The lubricant acts as a scavenger, collecting the acid, sludges, and other contaminants. Therefore, the service technician should check the color and acid content of the lubricant. It must be clean and acid free before the job is finished. The acid content can be checked with an acid test kit. For procedures for system clean-up please check pages 30 and 31 of Sporlan Bulletin 40-10.
 

This is frequently a difficult task. A lubricant sample can usually be obtained from the burned out compressor. To obtain repeated samples after the system is started up, install a trap in the suction line with an access valve in the bottom of the trap. This permits collecting the small amount of lubricant required for running an acid test. Another method is to build a trap with valves, and connections for charging hoses. Then refrigerant vapor from the discharge service valve is run through this trap and put back into the suction service valve. In a short time sufficient lubricant collects in the trap for analysis. For more information request Sporlan Form 40-141.
 

Most hermetic motors rely on refrigerant vapor for cooling. Any large pressure drop in the suction line could result in reduced flow of suction gas, and thus improper cooling of the new hermetic motor. Field experience has shown that if the filter-drier is properly sized, the pressure drop across it should not exceed the values given in the table below.

The pressure drop across the filter-drier should be checked during the first hour of operation to determine if the cores need to be changed. Any pressure loss in the suction line also reduces system capacity significantly.  When an RSF shell or replaceable core type Catch-All is used, it is recommended that the cores be removed and filter elements installed when the clean-up job is complete. Obtaining a low pressure drop is particularly important for energy savings on supermarket refrigeration systems. Therefore, suction line filter-driers should be sized generously on these systems.

For more details on sizing and selection of filter-driers download Bulletin 40-10 (PDF)

Article contributed by Glen Steinkoenig, Product Manager, Contaminant Control Products, Sporlan Division of Parker Hannifin

For more articles on climate control:

Using P-T Analysis as a Service Tool for Refrigeration Systems

Technologies for Drying Compressed Air: Aftercoolers and Coalescing Filters

Calculating Superheat and Subcooling requires cumbersome equipment, writing down temperature and pressure readings, converting pressure readings using a PT chart, and finally subtracting totals to arrive at actual levels...until today. Now several of your common diagnostic/service problems for HVAC/R can be solved with one simple and efficient product: the SMART Service Tool Kit from Parker Sporlan.

The SMART Service Tool Kit includes lightweight wireless sensors that conveniently sync with an iPhone or iPad app, enabling you to read a system’s real-time pressure and temperature without using hoses or manifold gauges. The SMART Service Tools are compact, convenient, and can be used with most refrigerants and oils.

The impact resistant case includes; a low pressure wireless sensor, high pressure wireless sensor, two wireless temperature clamps, adaptors for service ports, 4 batteries for the sensors and 4 spare batteries.

The sensors and clamps transmit data via Bluetooth Low Energy wireless technology through a free app that works with iPhone 4s and newer, iPad 3 and newer, iPad mini and iPad Air.

When you open the app, you’ll see that the display shows Low side readings for Superheat in Blue, and High side readings for Subcooling in Red. These colors correspond to the Blue and Red caps on the Temperature Clamps and the Pressure Sensors.

The Pressure displays can be set to read in PSIG or Bar, and the Temperature displays can be set for either Fahrenheit or Celsius. Complete refrigerant tables for over 60 of the most common refrigerants are stored in the SMART Service Tool Kit App.

• The refrigerant color code is included along with its name for easier identification.
• You can assign a customer name and pertinent information for each session you run. 

Once the Temperature Clamps and Pressure Sensors have been switched on, they will begin communicating with the App to display the correct data after they are positioned on the system.

Signal strength and battery strength are also displayed next to each sensor and clamp.

Each Sensor reading can be viewed in different modes, either analog, trend, or digital, depending on the Technician’s preference.

While the device is charting data, there is a running time stamp at the bottom of the chart.

You can zoom into points in the data stream to isolate and analyze specific details on the chart like a spike in temperature or pressure.

The SMART Service Tool Kit app will automatically convert pressure readings into temperatures and calculate Superheat and Subcooling. The data is easier to read, calculate and store, allowing technicians to diagnose issues faster, look at trends over time, and provide proof of work when needed.

Once the data is recorded, the App gives you the choice of storing it or emailing it. One tap converts the information to a .csv file that you can send to a designated email recipient.

The Sporlan (Parker) SMART Service Tool Kit was developed to make diagnostic readings faster and simpler. With the SMART Service Tool Kit, diagnosing HVAC/R Systems just got a whole lot easier. It works as smart as you do!

Learn more about the Smart Service Tool Kit for HVACR Diagnosis and download the FAQ sheet here.

Watch this video to learn more about the ease of use of the Smart Service Tool Kit.

Other useful resources for maintenance and troubleshooting of HVAC systems:

Using P-T Analysis as a Service Tool for Refrigeration Systems

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Head pressure control on supermarket refrigeration systems is used to maintain a minimum high-side-pressure to low-side-pressure relationship.

Low side pressures are the result of established refrigerated case or walk-in cooler temperatures (and their saturated suction pressures), which remain relatively constant year-round. Therefore, minimum pressure ratio is a result of the minimum high side pressure. The system’s minimum pressure ratio is dictated by the compressor’s capabilities and its minimum operating envelope. The design engineer selects the appropriate head pressure control system to maintain system performance and efficient year-round operation.

The greatest influence on thermostatic expansive valve (TEV) capacity is the pressure difference that exists between its inlet and outlet (the pressure differential). If the high side to low side pressure differential falls because of inadequate head pressure control, the resulting reduction in TEV capacity can create a number of problems, including:

• High evaporator superheats with loss of evaporator capacity
• Oil logging in the evaporator and suction piping
• Elevated compressor temperatures and short-cycling
• Poor refrigerant distribution with irregular evaporator frost patterns interfering with air flow and evaporator capacity
• Reduced evaporator pressure (unless controlled by evaporator pressure regulators or compressor unloading)

An additional consideration regarding the minimum design pressure ratio of a refrigerator system is the type of compressors being used. Very low pressure ratios in reciprocating-type compressors can cause valve damage. As pressure ratios decrease, the volume of gas pumped increases, causing the compressor valves to bend or flex beyond their design limits, leading to metal fatigue and breakage.

There are two ways head pressure control can maintain the high to low side pressure ratio: air side control and refrigerant side control.

Air side control consists of increasing or decreasing the air movement across the condenser coil. Supermarkets generally use remotely located, air-cooled condensers for heat transfer. This type of heat exchanger usually employs six or eight individual fans to move the air. Head pressure drops with decreased evaporator load and/or lower ambient temperatures. One way to hold head pressure within design parameters is to cycle each fan motor with pressure switches. This works well in geographical areas where ambient temperatures seldom fall below 50 degrees F (10 Degrees C).

Stable head pressures may be more difficult to achieve if ambient temperatures consistently fall below 50 degrees F (10 Degrees C). The entire system becomes increasingly unstable as lower-than-design air temperature is pulled across the condenser. The instability is caused when the fans suddenly start dropping the high side pressure rapidly, overshooting the corresponding liquid temperature. This creates bubbles in the liquid line as the refrigerant pressure lowers below its saturation temperature and boils, thereby cooling to the new saturation pressure. This reduces TEV capacity and ability to properly feed the evaporators.

Air side temperature control can also be obtained through fan speed control. A Variable Frequency Drive (VFD) can control the speed of each fan by changing the electrical frequency supplied to these fans. Variable speed fans can also be used to modulate the fan speed.  Both technologies can provide more stable operation to manage air flow while maintaining a minimum high side pressure.

This is advisable when outdoor ambient temperatures are consistently lower than 50 degrees F (10 Degrees C) . This control system may or may not be used in conjunction with air side controls.

Refrigerant side control systems accomplish head pressure control by effectively reducing the size of the condensing surface. This can be done by flooding a portion of the condenser with liquid refrigerant, thus reducing its condensing surface. This is the “flooded condenser method.”

Another control method is splitting the condenser into two or more sections. With the use of valves, discharge gas is diverted only to the section that is large enough to maintain discharge pressures under given ambient conditions. This is called the “split condenser method.” This method is usually used in combination with the flooded condenser method, along with fan cycling or fan speed control.

To maintain head pressure during winter operation, extra refrigerant must be available to partially fill the condenser. Furthermore, with the additional refrigerant being required for winter operation, consideration must be given to the size of the receiver, so it will have enough capacity to hold the extra refrigerant charge during summer conditions.

With the high cost of refrigerants, it is important to design the system to minimize the need for the extra refrigerant charge.

One way to do this is to combine refrigerant side control with air side control. This is accomplished by either cycling the fans or controlling their speed along with refrigerant side control. Both of these air side methods use pressure as the controlling signal to reduce air flow during periods of low outdoor ambient temperatures. The reduced or eliminated air flow across the condenser means that less heat is rejected to the air, and therefore less refrigerant flooding is needed.

Another method for minimizing refrigerant is to split the condenser into two or more circuits, usually within the same tube bundle. This kind of system uses both condenser circuits during summer operation when the load is high. During the winter, the second circuit is deactivated and drained of refrigerant. It is re-activated only during high ambient conditions when the maximum condenser capacity is required to keep condensing pressures as low as possible.

Operating cost may be higher or lower in different supermarkets, depending on the preventative maintenance program and regional climatic conditions. However, with the proper control mechanisms in place, engineers can take advantage of lower ambient temperatures to maximize efficiency and improve the supermarket’s bottom line.

Article contributed by Sporlan Division, Supermarket Refrigeration, Parker Hannifin. For more information, contact Sporlan Division technical support at 636-392-3906.

Additional resource on refrigeration in the food and beverage markets...

Using P-T Analysis as a Service Tool for Refrigeration Systems

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Climate Control Technologies and Key Markets

VFD Eliminates bottleneck in Canning Plant

Have you considered a CDS valve conversion for improving performance and reducing costs on your refrigeration equipment? Over the past ten years, Parker Sporlan has completed tens of thousands of these conversions. Sporlan is well-known for its innovative and economical solution for converting SORIT evaporator pressure regulators on refrigeration equipment into stepper motor-driven CDS valves. 

In response to ever-growing requests from customers for more productivity and cost efficiencies, Sporlan has released its next generation of CDS conversion kits. Nearly all A8 and SPORT pressure regulators can now be converted into Sporlan stepper motor valves using only one of three kits, with a simple retrofit that only takes about 30 minutes.

Sporlan CDS valves are electronically operated step motor evaporator pressure regulating valves. Synchronized signals to the motor provide discrete angular movements of the rotor, which translate into precise linear positioning of the valve piston through a lead screw attached to a series of gears. Valve pistons and ports have an engineered profile, providing high resolution flow performance, and are easily interfaced with microprocessor based controllers. As supermarket refrigeration equipment moves toward greater electronic control, Sporlan’s new conversion kit enables the conversion of a wider range of older mechanical valves to electronic valve control.  

A8 and SPORT valves, over time, may fail to operate due to system contamination or develop external leaks at one of the several gaskets. Converting these valves, using electronic CDS conversion kits, is the preferred method when faced with rebuilding a mechanical valve. Conversion also reduces valve complexity and can usually be done in less time than it takes to rebuild the mechanical valve. With the short term advantage of reduced installation labor costs coupled with the longer term benefits associated with upgrading to an electronic modulating valve, it is no surprise that theses CDS conversion kits have become very popular within the supermarket refrigeration industry.

Other advantages include:

• Laboratory testing and field trials indicate a 6-10 percent refrigeration system energy savings is possible after converting EPRs to electric CDS valves. The exact amount of savings is difficult to determine because so many variables are present in a real world supermarket refrigeration system, however, Sporlan has concluded that there is a direct correlation between energy savings and deviation from set-point of a mechanical valve. 

• Mechanical valves require a pressure drop through the valve to function properly and (because they are not always set correctly in the field), refrigerant and/or oil may back up into the condensing unit or evaporator. Because CDS electric valves are easy to set properly, and do not require pressure drop to operate, these back-ups do not occur and the refrigerant and oil is free to return to the compressors.

• Since a direct correlation exists between the pressure and temperature of a refrigerant due to its thermodynamic properties, outdoor ambient temperatures must be considered when determining set points for mechanical head pressure control valves.  It is not uncommon for a supermarket refrigeration system to need adjustments when the ambient temperature changes with the seasons in order to maintain consistent case temperatures. For mechanical valves, this always requires a refrigeration technician to be on site making the required adjustments, however, this is not necessary for electric valves. Since electric valves are electronically controlled, sophisticated algorithms are able to adapt the valve operation to ensure case temperature is maintained throughout all seasonal changes in the ambient conditions.

• Through modern manufacturing techniques, today’s electronic sensors have very tight tolerances which ensures incredible accuracy in valve performance. In addition, by using an electric CDS valve in place of a mechanical pressure regulator, the refrigeration system control is able to modulate the valve position based on case temperature rather than refrigerant pressure. This offers a huge advantage to the temperature pull down time when a case comes out of a defrost cycle. Rather than modulating to a specific pressure set-point, which is always attained before the case temperature set-point has been satisfied, the electric CDS valve remains open for case pull-down. The end result is a much quicker pull-down time, and increased product integrity. Controlling off discharge air temperature also allows the case to utilize the available pressure drop to ensure that the case temperature is maintained, even if the case is not running optimally, without experiencing an energy penalty.

• CDS conversion kits are compatible with standard Sporlan Kelvin II Pressure and Temperature Controls and can be integrated into enterprise control systems via MODBUS and BACnet communication protocol. Temperature control is recommended for suction applications to maintain case temperature and pressure control is recommended for high side head pressure control applications. Mechanical valves must be physically set by a technician on site, while electric valves can be set remotely and monitored in real time through the use of an enterprise control system commonly found in today’s refrigeration systems. These advantages are why many supermarkets have converted to electric valves. Complex refrigeration systems can especially benefit from centralized control, saving time and money on service calls and labor costs. For example, commissioning a new supermarket refrigeration system typically takes a 2-3 person team one week to set all the mechanical valves. With electric CDS valves, all the settings can be uploaded to the enterprise control system in a fraction of the time.  

• Just as the SORIT-to-CDS conversion kit, Sporlan’s next-generation electric CDS conversion kit utilizes the existing valve body installed in the refrigeration system. This means no brazing is required to complete the conversion. Without the need for brazing, extra installation steps such as burn permits and fire spotters, off-hours work, and wet ragging valves to dissipate heat can be eliminated. In addition, if done incorrectly, brazing can damage valves or cables which results in rework and added component costs.    

The Sporlan A8, SPORT and A9 CDS conversion kit are a unique aftermarket solution that easily converts existing A8, SPORT, or A9 pressure regulators into modulating, stepper motor driven CDS valves. Valves that qualify for conversion include Refrigerating Specialties mechanical pressure regulators such as the A8A, A81, A82, SPORT and A9 valves. Conversion kits can be driven directly by Sporlan’s Micro Thermo control systems or other common third-party enterprise control systems. 

The conversion kit reduces the seal surface area of the installed valve, making it an ideal upgrade opportunity compared to a seal rebuild, or even a full store scheduled retrofit. The conversion provides tight seating for defrost and pump-down applications, requires no pressure drop for operation, and maintains, or slightly increases, the capacity of the valve. In some instances, stability of the system may improve due to the high resolution and accuracy of the step motor actuation incorporated into the electric CDS valve.   

Installation typically takes about half an hour. Once the retrofit is complete, the solution pays for itself through improvements in system performance and improved future serviceability and diagnostic capabilities.

Payback is dependent upon the type of application (for example, condenser holdback, EEPR, etc.) and system-specific details, including how well the store is set up or maintained. In general, however, return on investment is typically about two years or less, followed by improved performance, continued energy savings, and reduced maintenance for years to come. 

Article contributed by Dustin Searcy, Product Manager, Electric Valves, Sporlan Division, Parker Hannifin

Related content:

Head Pressure Control for Supermarkets

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Using P-T Analysis as a Service Tool for Refrigeration Systems

How to Use the Smart Service Tool Kit for HVACR Diagnosis

Climate Control Technologies and Key Markets

Many refrigeration compressors break down simply because they overheat. There are two main reasons why overheating can have such a devastating effect on compressors:

• Loss of the lubricating properties of the refrigeration oils
• Chemical decomposition of the refrigerants and/or oils, which can occur suddenly

Oil breakdown in the refrigeration system has plenty of negative side effects. Sludge and solid particulate matter can plug the oil inlet screen in the compressor sump or the lubrication passages in the crankshaft—loss of lubrication can quickly result in failed bearings. Oil-breakdown deposits can also line the internal surfaces of the refrigeration system, especially the inner walls of the piping, compressor and control valves, plugging up thermostatic expansion valves (TEVs) and other control valves.

All these problems can be the result of a dirty condenser, which results in a higher condensing temperature. According to EPA research, a heat transfer coil with a meager 0.042-inch-thick film of dirt on its surface can result in nearly a 21-percent loss of heat-transfer capacity. A higher condensing temperature, combined with increased suction temperature (from underfeeding TEVs), can result in excessive discharge temperatures that accelerate oil decomposition.

Before they can fix the problem, technicians must know what caused the excessive discharge temperatures in the first place. The four most common root causes are listed below:

• High suction superheat—common system conditions that cause increased suction temperatures are high TEV superheat settings, ineffective or missing insulation and restricted TEVs.
• Reduced condenser capacity—typically the result of poor maintenance, this occurs when the condenser fins become restricted with dirt and the airflow necessary to deliver the condenser’s rated capacity is reduced.
• Lowering the suction pressure—this is important to operate the system with the highest possible suction pressure. When system suction pressure is reduced, instead of fixing the true issue, the compression ratio increases creating higher discharge temperatures.
• Refrigerant characteristics—because R-22 is subject to higher compression ratios, which can stress bearings and reduce compression efficiency, R-22 can be problematic as a “refrigeration” refrigerant, particularly in low-temperature applications.

In many cases, system problems and compressor failures are directly related to high discharge temperatures.

Condensers should be cleaned regularly to keep them operating at their rated capacity. The suction vapor temperature should be kept within acceptable limits by setting TEV superheat appropriately and insulating the suction line properly. Compressors should not be allowed to operate below design suction pressures, because this will lead to higher discharge temperatures.

With some refrigerants and applications, other solutions (for example, a compressor body cooling fan motor) may be required to solve high discharge temperature issues. A temperature responsive expansion valve, which responds to discharge temperature, may also be used. By injecting saturated liquid/vapor into the suction line temperature responsive expansion valves will reduce the temperature of the superheated suction vapor, which in turn reduces the excessive discharge temperatures.

Article contributed by Sporlan Division, Supermarket Refrigeration, Parker Hannifin

Additional articles include:

Using P-T Analysis as a Service Tool for Refrigeration Systems

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Head Pressure Control for Supermarkets

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Is the Compressed Air in Your Food Plant Safe?

Parker's HVACR Tech tips cover service tips for the HVACR technician servicing commercial refrigeration systems as well as  HVAC  for both commercial and home. The following are service tips for working with blended refrigerants. 

Good service practices dictate that only liquid should be removed from the cylinder. The proper cylinder position for liquid refrigerant removal is indicated by arrows on the cylinder and/or cylinder box. Once liquid refrigerant is removed from the cylinder, the refrigerant can be charged into the system as a liquid or vapor as desired. Use gauge manifold or a throttling valve to flash the liquid to vapor if required.

Do Not  mix refrigerants with different “R” numbers. Uncertain safety criteria, performance and/or system damage could result.

Newer HFC blends and HFO blends are compatible with POE oil, so there is no need to change oil types if retrofitting from an HFC such as R404A to R407A, R407C, R448A, or R449A. The same is true of retrofits from R134a to R450A or R513A. If an existing HCFC  system (such as R22 with mineral oil) is being retrofitted it will be necessary to change oil type to POE. 

In situations where it is not necessary to change oil types, it is still good practice to drain as much existing oil from the system as possible, and refill with new oil. This will help to remove contamination from the system.

Refer to the OEM system or compressor manufacturer's guidelines for the proper lubricant. If this information is not available, you can refer to lubricant recommendations published by the refrigerant and oil suppliers.

Fractionation: A change in composition of a blend by preferential evaporation of the more volatile component or condensation of the less volatile component. When servicing a system containing a blended refrigerant it is necessary to confirm that the existing refrigerant has not fractionated, therefore producing less capacity.

R407A has 10ºF glide, 26% more capacity than R404A
R407C has 11°F glide, same capacity as R22
R410A has almost no glide, same capacity as R22
R448A has 10°F glide, 30% ,more capacity than R404A
R513A has no glide, 16% less capacity than R134a

Download the guide on our website 

HVACR Tech Tip Article contributed by John Withouse, Senior Engineer Refrigeration, Sporlan Division of Parker Hannifin

Additional content on this topic:

Using P-T Analysis as a Service Tool for Refrigeration Systems

Compressor Overheating Is the Number-One Refrigeration Problem

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Head Pressure Control for Supermarkets

Six Reasons Why CDS Conversion Reduces Costs

Choosing the Right Tube Joint Seal for HFO-1234yf Refrigerant Compatibility

All refrigeration piping materials are subject to changes in temperature and will expand and contract with temperature change. Installation techniques must allow for expansion and contraction changes, as this will prevent stresses which may buckle and rupture the copper tube or joints. 

The average linear coefficient of expansion of copper is 0.0000104 inch/per inch/per °F. Copper tubing will expand about 1 ¼  inches per 100 feet per 100°F change in temperature. For example, a copper line 75 feet long is used to carry hot discharge refrigerant vapor at 225°F to the system’s condenser. The change in temperature could be 155°F, that is 225 - 70 (room ambient).

The expected expansion on this application could very well be 75 x 12 x 0.0000104 x 155 = 1.451 or 1½ inches. 

There are two common methods of taking care of expansion and contraction in copper lines used in the refrigeration industry. These are the use of “expansion loops” or “pipe offsets.” See Figures 1 and 2 for specifics on these two methods. 

In the installation of expansion loops, the expansion member should be “cold sprung” approximately one-half the estimated travel expected. In this manner the bend is subject to only about one-half of the stress, when the line is at the highest temperature, than it would be if the loop were installed in its natural position. 

Care must be taken during the installation of the lines to maintain perfect alignment, if not, there will be a tendency for the lines to bow, and possibly buckle or rupture, particularly on the smaller sizes. 

It is often possible to provide for expansion by offsetting the pipe line rather than to continue in a straight line. This method can be used only where there is plenty of space available. A single offset using two 90° elbows should have a minimum length of not less than three times the radius required in an expansion loop.

The legs of the offset should not be spaced less than two times the radius from each other, see Figure 2. This method is just as effective as expansion loops and can be made on the job, see Table 1 for fabrication details.

Offsetting by means of long radius allows the installer to vary the length to suit the job. Due to the amount of labor involved in the fabrication of expansion loops they are considered more expensive than offsets made up on the job. 

So far we have referred only to main lines in general; these are usually thought of as horizontal. Vertical lines or risers must also be considered in the same manner. Risers should have adequate support at or near the bottom. Where branch lines to fixtures are taken off they should be sufficiently long to take care of any movement in the main.Rigid fixtures should never be directly connected to risers. One or two turns or elbows in the line will take care of the short branches. Copper tubing may not break as readily, but if continually subjected to strain and bending it will ultimately fail. Designers and contractors must always keep the matter of expansion and contraction in mind.

A freezer operating at a SST of minus 30°F and 100ft from the mechanical room which is 70°F, the compressor discharge temperature is 225°F and the condenser 75ft away. 

Suction “shrinkage” is 0.0000104 x 12 x 100 x 100 = 1.248 or 1¼ inches. 

Discharge expansion is 0.0000104 x 12 x 75 x 155 = 1.451 or 1½ inches. 

Total expansion and contraction movement in this freezer application would be 1.+ 1.= 2¾ inches. The installation and servicing contractor must be aware of the potential problems that could arise if these factors are not taken into consideration in the original installation.

HVACR Tech Tip article contributed by Glen Steinkoenig, Product Manager, Contaminant Control Products, Sporlan Division of Parker Hannifin

Additional resources:

Using P-T Analysis as a Service Tool for Refrigeration Systems

Compressor Overheating Is the Number-One Refrigeration Problem

Clean-up Procedure for Refrigeration and Air Conditioning Systems

In air conditioning and refrigeration applications, the ability of the thermostatic expansion valve (TEV) to match refrigerant flow to the rate at which refrigerant can be vaporized in the evaporator makes the it the ideal expansion device for most HVACR applications. The TEV controls the flow of liquid refrigerant entering the direct expansion (DX) evaporator by maintaining a constant superheat of the refrigerant vapor at the outlet of the evaporator.

Superheat is the difference between the refrigerant vapor temperature and its saturation temperature. To measure the superheat the TEV controls, the difference between the actual temperature at the sensing bulb and the saturation temperature corresponding to the suction pressure at the sensing bulb location is determined. By controlling superheat, the TEV keeps nearly the entire evaporator surface active while not permitting liquid refrigerant to return to the compressor.

The purpose of the external equalizer is to sense the pressure in the suction line at the bulb location and transmit it to the TEV diaphragm. This usually means installing the external equalizer immediately downstream from the bulb. This ensures the correct pressure is signaled to the TEV.

In some situations this “ideal” location may not be possible. In these cases, an alternate location, such as at B or C (see diagram), could be used. However, the pressure at these locations must be nearly identical to the pressure in the line where the bulb is located.
 

In other words, locations B and C are acceptable as long as these pressures are essentially the same as A when the system is operating at full load. In the past there has been concern about installing the external equalizer “up-stream” from the bulb. This was due to the possibility of refrigerant leaking past the TEV push rods, passing through the equalizer line and into the suction line, thus falsely influencing the TEV bulb temperature.

Today, with Sporlan’s TEV design, this possibility is virtually eliminated.

HVACR Tech Tip Article contributed by Jason Forshee, Product Manager,  Sporlan Division of Parker Hannifin

Additional resources:

Six Reasons Why CDS Conversion Reduces Costs

Compressor Overheating Is the Number-One Refrigeration Problem

Head Pressure Control for Supermarkets

Using P-T Analysis as a Service Tool for Refrigeration Systems

Clean-up Procedure for Refrigeration and Air Conditioning Systems

How to Use the Smart Service Tool Kit for HVACR Diagnosis

Climate Control Technologies and Key Markets

We all know that a properly charged refrigeration system utilizing a receiver must have a liquid and vapor interface in the receiver. And we also know that saturated pressure and temperature conditions must exist at the liquid and vapor interface.

So, can we have a condition in which we have subcooled liquid from the receiver flowing into the liquid line?

This question is generally answered as follows:

1. No, except for the minor amount of subcooling generated by static pressure due to the liquid level in the receiver. For example, R-404A liquid will generate about 0.42 psi static pressure per foot of liquid level in the receiver, or about 0.13°F of subcooling per foot of liquid level at 100°F.
2. Yes, because I’m sure I’ve measured subcooled liquid flowing from the receiver.

When analyzing a problem such as this, it is often useful to consider it in its simplest form, i.e., we do not have any pressure drop from the outlet of the condenser to the outlet of the receiver, and we do not have any heat exchange between the refrigerant and the environment.

This allows us to make the following observations:

1.  The receiver pressure is the same as the pressure of the liquid leaving the condenser.
2. The refrigerant cannot gain or lose energy flowing from the condenser outlet to the receiver.

Now let’s say we have an R-404A system having a 110°F condensing temperature (273 psig) with 10°F subcooled refrigerant leaving the condenser. Given the above scenario, we must have a receiver pressure of 273 psig with 100°F liquid, i.e., 10°F subcooled liquid. This is a simple application of the law of conservation of mass and energy. How is this possible if we have a liquid vapor interface in the receiver?

It is simple: we will have 110°F at the liquid and vapor interface, but the refrigerant liquid immediately below the interface will be at 100°F. The 110°F saturation temperature will only be found at the interface, and with the vapor above the interface.

But don’t we need energy to create the 110°F interface? We’ve stated the refrigerant cannot gain or lose energy flowing from the condenser outlet to the receiver. Where is this energy coming from?

Yes, we do need energy to create the 110°F interface, but it is already being supplied by the 273 psig pressure. Enthalpy, or the amount of energy in the refrigerant, is the sum of both internal energy and the work created by pressure multiplied by the refrigerant volume.

The real world scenario would include pressure drop and some amount of heat exchange between the refrigerant and environment. But when you account for these factors, you find our simple scenario to be sufficiently accurate to show answer “2” to be the correct response to the subject question.

Answer “1”, however, is correct when the refrigeration system is not in operation.

Article contributed by Glen Steinkoenig, Product Manager, Contaminant Control Products, Sporlan Division of Parker Hannifin

Other related content:

The Importance of Using an Air Receiver Tank in a Compressed Air System

Using P-T Analysis as a Service Tool for Refrigeration Systems

Can Pressure Reduction Be Used to Dry Compressed Air?

Compressor Overheating Is the Number-One Refrigeration Problem

Six Reasons Why CDS Conversion Reduces Costs

​To ensure peak performance, solenoid valves must be selected and applied correctly; however, proper installation procedures are equally important. Aside from correct installation, troubleshooting the typical malfunctions is something all HVAC technicians should know.

Learn about the three typical malfunctions and download our installation and servicing guide for reference.

There are only three possible malfunctions:

1. Coil burnout.

2. Failure to open. 

3. Failure to close. 

Coil burnouts are extremely rare unless caused by one of the following:

• Improper electrical characteristics. 

• Under-voltage of more than 15%. This applies only if the operating conditions are such that the reduced MOPD causes stalling of the plunger, which results in excessive current draw. 

• Incomplete magnetic circuit due to the omission of parts such as the plunger on the PKC molded model coils. 

• Mechanical interference with plunger movement which may be caused by a deformed enclosing tube. 

• Voltage spike.

• Valve ambient exceeds 120°F.

• Fluid or gas temperatures greater than 240°F, while the valve ambient is 120°F.

(Normally Closed Types)

• Coil burned out or an open circuit to coil connections. 

• Improper electrical characteristics. 

• In pilot operated valves, dirt, scale or sludge may prevent the piston, disc or diaphragm from lifting. This could also be caused by a deformed body. 

• High differential pressure that exceeds the MOPD rating of the valve. 

• Diameter reduction of synthetic seating material in pilot port because of high temperatures and/ or pressures, or severe pulsations.
   

The problem of dirt can be avoided by installing a Sporlan Catch-All® Filter- Drier upstream from the solenoid valve. The Catch-All® Filter-Drier will retain much smaller particles than a conventional strainer. Use a Sporlan strainer for water applications upstream of every industrial solenoid valve.

• Valve is oversized.

• In pilot operated valves, dirt, scale or sludge may prevent the piston, disc or diaphragm from closing. This could also be caused by a deformed body. 

• Held open by the manual lift stem. 

• In pilot operated valves only, a damaged pilot port may prevent closing.

• A floating disc due to severe discharge pulses.

• Have voltage feedback to the coil after the coil de-energizes.

Liquid Hammer – Industrial solenoid valves, or other liquid line valves, may cause liquid hammer when installed on liquid lines with high liquid velocities. If this occurs, it can be minimized by the use of larger pipes, (i.e.lower velocities), or a standpipe installed in the piping near the solenoid valve inlet. Commercially available shock absorbers may also be used to reduce this noise. Recommended maximum velocity is approximately 300 fpm.

AC Hum– This problem may be caused by a loose coil. A loose coil hex screw or coil locknut may cause this problem on the MKC molded model coils. Foreign material between the magnetic top plug and the plunger in the Types A3, E3, W3, E5, B6, E6, W6, E8, B9, E9, B10S2, E10S1, E10S2, B14, E14, W14, B19, E19, W19, B25, E25, W25, E35 and E43 Series Solenoid valves may cause AC hum also.

Water applications - Deposits may accumulate in the valve which could cause AC hum. This may be eliminated by cleaning or flushing the valve. 

Download the complete guide for installation and servicing instructions for solenoid valves

HVACR Tech Tip Article contributed by Jim Eckelkamp Solenoid Product Manager,  Sporlan Division of Parker Hannifin

Additional resources:

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Clean-up Procedure for Refrigeration and Air Conditioning Systems

HVACR Tech Tip: Guide to Servicing Blended Refrigerants

Compressor Overheating Is the Number-One Refrigeration Problem

With our recent introduction of the Smart Service Tool Kit, there have been many questions asked and answered. Let's review the ones pertaining to buying and general details here:

• a low pressure wireless sensor
• a high pressure wireless sensor
• 2 wireless temperature sensors
• 2 adapters for mounting sensors onto ¼” access ports 
• 4 coin cell batteries for the sensors
• 4 spare batteries
• brief instruction sheet 
• custom foam insert
• the rugged plastic case to transport the kit safely to and from the job site.

Q7: What are “Mock Sensors?” 

A: Sporlan placed mock sensors in the app so you can show others how the app works without having the sensors connected to a real system. You probably won’t need this, but you can add mock pressure and temperature sensors by turning on mock sensors in the settings menu. Then touch each sensor icon to connect to them. Finally, tap the default number that shows up for each sensor that flips the screen section. Tap the default numbers and add educated guess numbers in the prompt that pops up. Simply separate your numbers with a space and hit save. Now you have a simulator in your hand. Try changing your refrigerant selection now and show how quickly you can read a P-T chart. A mock session can also be recorded.

 

Q8: Will I need to individually reconnect each sensor to my device every time?

A: No, if you select “Automatic Reconnect” in the settings section of the SMART Sensor app, your sensors will simply need to be powered on, then hit “Connect All.” All sensors will be connected as you last assigned them.

 

Q9: What batteries are required?

A: Each sensor requires 1 small coin cell to operate - readily available in the CR2450 size. A complete spare set is included in the kit. Place them in the sensor compartment with the positive side (CR2450) facing you.

 

Q10: What is the expected battery life?

A: Battery life will vary with the brand or age of the battery, as well as exposures to extreme temperatures, shock, vibration, etc. Please see Form 140-426 SMART Service Tool Specifications for details.

 

Q11: What are the pressure ratings of the sensors?

A: Please see Form 140-426 SMART Service Tool Specifications for details.

 

Q12: What are the temperature ratings of the sensors?

A: Please see Form 140-426 SMART Service Tool Specifications for details. Note: For the most accurate readings, you should insulate the jaws onto the refrigerant line you are measuring. This is especially important when there is a large difference between the ambient temperature and the refrigerant line temperature.

 

Q13: Are the sensors water resistant?

A: Yes, the temperature and pressure sensors are water resistant. They are not intended to be submerged or exposed to high pressure water sprays. Please see Form 140-426 SMART Service Tool Specifications for details.

 

Q14: What is the communication distance range?

A: Many variables will affect the communication distance. Please see www.bluetooth.com for details on Bluetooth Low Energy.

 

Q15: Can multiple mobile devices be connected to the sensors at the same time?

A: No. As soon as the sensors are actively connected to a mobile device, they will not show as “available sensors” on another mobile device. However, once disconnected from the first mobile device, they will become available for any other compatible device. Each sensor that you connect to a compatible device will remain in the mobile device’s SMART Service app memory for future reference.

 

Q16: Can I use these SMART sensors with other apps? 

A: No, the sensors are uniquely identified by the SMART Service app.

 

Q17: Can I use the SMART app with other sensors?

A: No, the SMART Service app is designed to work with Sporlan SMART sensors.

 

Q18: Can I use the same sensor for multiple refrigerants?

A: Yes. The pressure sensors are made of stainless steel. There are no compatibility issues with most standard refrigerants or oils.

 

Q19: What do I need to do when switching types of refrigerant?

A: The app offers a drop down menu for selecting the next refrigerant. As far as cross-contamination concerns, due to the very small amount of refrigerant in these “hoseless” sensors, you may not need to do anything. While it may not be required, you could clean the pressure sensors as you would any other gauge or hose that has been connected to an air-conditioning or refrigeration system.

Download the full Smart Service Tool Kit FAQs and give Sporlan a call to answer any other questions. 

When responding to a refrigeration service call at a supermarket, the refrigeration technician immediately plays “problem percentages” upon entering the store. Most refrigeration equipment breakdowns are repeat problems to some degree. Playing the “percentages” when responding to a service call enables the technician to get to the root source of a problem as quickly as possible to prevent perishable product loss.

The purpose of this HVACR Tech Tip is to cover the higher percentage problems and repair procedures of TEVs in supermarket applications.

Download a copy of 12 Solutions for Fixing Common TEV Problems - Form 10-143.

A brief review of basic TEV operation is in order. The diaphragm is the actuating member of the TEV. There are three fundamental pressures acting on it:

• Sensing bulb pressure P1,
• equalizer pressure (evaporator pressure) P2 
• equivalent spring pressure P3.

The sensing bulb pressure is a function of the suction line temperature and acts on the top of the diaphragm causing the TEV to move in a opening direction. The equalizer and spring pressure act together underneath the diaphragm causing the valve to move in a closed position. Under normal operation (disregarding the pressure differential required across the diaphragm to move it), sensing bulb pressure equals equalizer pressure plus spring pressure, i.e: P1 = P2 + P3.

It is important to note that spring pressure is essentially constant once the valve is set. As a result, the TEV is actually controlling the difference between the bulb and the equalizer pressures, which is the amount of the spring pressure. The spring pressure represents the superheat the valve is controlling at the bulb location. Now with TEV basics aside, lets review some of the higher percentage TEV problems when servicing a supermarket. The subject valves had previously been operating at the correct superheat setting.

#1 — Check the TEV Adjustment: The factory setting of a Sporlan TEV is close to center stem. Count the total number of turns front seat to back seat, then front seat the adjustment stem to 50% of the total turns counted. Turn the adjusting stem counterclockwise in increments of 1/2 to 1 full turn every 15 minutes until the correct superheat is reached.

#2 — Check the Sensing Bulb Location: The sensing bulb should be securely fastened to a clean, straight section of the suction line. The bulb should be attached to a horizontal suction line at the evaporator outlet. If the bulb cannot be located in this manner it may be located on a descending vertical line only. On suction lines 7/8" and larger, it should be installed at 4 or 8 o’clock on the side of the horizontal line. On smaller lines the bulb may be mounted at any point around the circumference except the bottom of the line where oil may influence the sensitivity. On multiple evaporators, the piping should be arranged so that the flow from any one valve cannot affect the sensing bulb of another. The equalizer connection should be made at a point several inches downstream of the bulb.

Verify the sensing bulb is correctly installed.

Note: This check is also valid when the TEV is flooding the evaporator.

#3— Check for Moisture: Water or a mixture of water and oil frozen in the valve port (or working parts of the valve) prevent proper operation. Since the valve is the first cold spot in the system, moisture will freeze restricting flow. The fact that the system has not been opened for years does not eliminate the potential for this problem. Elevating the temperature of a liquid line drier (already at maximum water retention) beyond its normal operating temperature can cause it to release moisture into the system. Liquid lines increase in temperature during a slow refrigerant leak, dirty condenser coil, failed condenser fan motor, etc.

Pour a cup of hot water on the valve body to melt the suspected internal ice formation. A telltale audible surge in refrigerant flow will indicate system moisture. Install a new Catch-All® filter-drier.

Note: This check is also valid when the TEV is flooding the evaporator, the valve may freeze in a “too open” position.

#4— Check for Contaminants in the Valve Body: Restrictive dirt or foreign material such as copper oxide scale, metal chips, oil breakdown, sludge, etc. Conventional strainers allow some types of these materials through ultimately obstructing the port of the TEV.

Pump the system down, disassemble and clean the TEV. Install a Catch-All filter-drier directly ahead of the TEV if additional contaminants are suspected between the main liquid line filter and the restricted TEV. If no contaminants are found, install a sightglass ahead of the TEV and go to step #5.

Note: This check is also valid when the TEV is flooding the evaporator, the foreign material may prevent the valve from closing.

#5— Check for Vapor Free Liquid to the TEV: Install a liquid line sightglass directly ahead of the TEV during step #4 while the system is pumped down. If flash-gas is present, check for a liquid line restriction or pressure drop caused by incorrect pipe size or poor piping practices.

Correct the pressure drop as required. If the pressure drop is because of the length of the piping run or liquid lift, install a heat exchanger to sub-cool the refrigerant to the required temperature for elimination of the flash-gas.

#6— Check Design Pressure Drop for  Required TEV Capacity: The capacity of the TEV is a variable dependent on the pressure  differential across the valve as well as other factors. Greater pressure drop across the TEV = greater TEV capacity.

Remove the source of the pressure loss on the inlet, or pressure increase at the outlet. If the reduced inlet pressure to the valve is due to low condensing pressure, install the appropriate head pressure controls. Installing a larger TEV is the last resort.

#7— Check for Element Charge Migration: Gas type elements ZP, CP and VGA charges have a limited volume of constituents. The bulb temperature must be lower than the element or the bulb constituents will migrate into the element causing the valve to throttle and or close.

Warm the element with a heat gun (not a rosebud torch) returning the superheat to normal. Relocate the valve body to a location with a higher temperature than the sensing bulb.

A TEV is a modulating type valve with the ability to modulate the refrigerant flow rate much lower than its full load design rating. The more oversized the TEV, the larger the valve superheat swings. The “superheat swing” references the number of degree’s change from high to low at the evaporator outlet as the TEV modulates. The superheat swings are also referred to as “hunting.”

A conventional non-balanced port TEV can modulate down to about 40% of its maximum loading. The TEV hunting (or swings) at this minimal percent are large enough that liquid refrigerant can spill past the sensing bulb before the valve throttles. A balanced port TEV can modulate down to approximately 25% of its maximum load rating before spillover occurs (the loading is lower with the balanced port valve because it is not influenced by inlet pressure).

Note: Increased pressure drop or decreased entering liquid temperature beyond design conditions increases the TEVs capacity.

#8 — Check the TEV Adjustment: The factory setting of a Sporlan TEV is close to center stem. Count the total number of turns from front seat to back seat, then front seat the adjustment stem 50% of the total turns counted. Turn the adjusting stem clockwise in increments of 1/2 to 1 full turn every 15 minutes until the correct superheat is reached.

#9 — Check for a Vapor Free Liquid to the TEV: The TEV adjustment stem may be opened enough to offset vapor in the liquid line in some applications. Should the condensing temperature drop, resulting in sub-cooled refrigerant, (vapor free liquid) the TEV may flood. A lighter evaporator load may also result in a solid head of refrigerant to the TEV, leading to a flooded evaporator condition that did not formerly exist.

Install a liquid line sightglass directly ahead of the TEV and verify vapor free refrigerant during the adjustment procedure.

#10 — Time Study the Flooding Cycles: A TEV with a severe “hunt” will go to zero degrees of superheat before the valve throttles closed. It may take up to several minutes for the liquid refrigerant in the flooded evaporator to boil off (exhibiting zero degrees superheat). The evaporator superheat may then conversely rise ten or more degrees for an additional minute or two before starting the cycle over. A TEV that is exhibiting this type of cyclical flooding condition should slowly be adjusted OPEN. Not only will the higher superheat value get lower, the zero degrees at the bottom of the TEV swing will increase to a superheated value. Reducing the  adjustment spring pressure result in a higher volume, less erratic evaporator feed, in most applications.

#11 — Check the Evaporator for Air Side Heat Loading: The number of air turns in a walk-in cooler or feet per minute air flow in a refrigerated fixture should not be reduced. A loss of air movement because of dirt, ice, missing sheet metal panels or incorrect product load levels results in a loss of heat transfer. The TEV may hunt and flood if loaded too lightly.

Verify air movement is at design conditions.

#12— Check the Evaporator for Unequal Circuit Loading: Multi-circuit evaporators and parallel evaporators connected to a single refrigerant distributor must receive an equal percentage of the total load. When each circuit is not subjected to the same heat load, the lightly loaded circuits will allow liquid refrigerant or low temperature vapor to enter the suction line and throttle the TEV. This will cause normally loaded circuits to be deprived of their share of the refrigerant. The net result is a loss of refrigerated evaporator surface and a potentially oversized TEV. Check the temperature of the suction outlets of each distributor circuit before the suction header. Unequal temperatures at these locations are the result of unequal loading.

Check with the equipment manufacturer for the correct distributor and nozzle assembly if poor distribution is diagnosed.

Download a copy of 12 Solutions for Fixing Common TEV Problems - Form 10-143.

HVACR Tech Tip Article contributed by Jason Forshee, Product Manager,  Sporlan Division of Parker Hannifin

Additional resources on HVACR Tech Tips:

HVACR Tech Tip: Where Should the TEV External Equalizer Be Installed?

HVACR Tech Tip: Troubleshooting Solenoid Valves in Refrigeration Applications

HVACR Tech Tip: Guide to Servicing Blended Refrigerants

HVACR Tech Tip: Can You Have Subcooled Refrigerant in the Receiver?

With more and more supermarkets upgrading from mechanical valves to the superior performance of CDS valves, knowing how to install a Sporlan CDS Conversion Kit will help save considerable time and expense. 

Sporlan presents the next generation of CDS Conversion Kits that make it possible to convert nearly all A8 or SPORT pressure regulators into Sporlan, stepper motor valves. The retrofit is easy with a typical installation only taking about 30 minutes and provides the following benefits:

• Reduced complexity
• Eliminates brazing
• Easy installation

The Sporlan CDS Conversion Kit eliminates the need for time consuming, and sometimes dangerous brazing, because the existing A8 or SPORT valve body stays in the system piping. The conversion kit reduces valve complexity and external seal surface area.

The conversion kit creates tight seating for defrost and pump-down applications and doesn’t require pressure drop for operation. Installation can be performed anytime of the year without worrying about how ambient temperatures will affect the valve readings.

To minimize downtime of the refrigeration system, it is recommended to install and set up the valve control and sensors before or while the refrigerant is being recovered from the circuit. Follow the manufacturer’s instructions for setting up your valve controller to complete the system upgrade.

Once installed, the Sporlan CDS Conversion Kit will pay for itself through improved system performance, future serviceability, diagnostic capabilities, food freshness, energy consumption and your bottom line. Ask your Authorized Sporlan Wholesaler about converting today. And for easy implementation and optimal performance, make sure to pair your conversion kit with a Sporlan Pressure or Temperature Control.

Follow our detailed video on how to perform this change in the field.

It is important to locate a filter-drier in a refrigeration system. Its role is to remove moisture from the refrigerant and lubricant by absorbing and retaining moisture deep within the desiccant granules.

The blend of desiccants used in the Catch-All is specially formulated for exceptional moisture removal. The high degree of activation ensures maximum water capacity, which means the core removes a large amount of water in one pass, thereby protecting the expansion valve from possible freeze-up. Since the refrigerant must flow through the core, maximum contact between the two ensures rapid system dehydration. 

It is not uncommon to see refrigeration and air conditioning systems that have operated for decades, without any service being performed, and with the Catch-All undisturbed since the original installation. This speaks well, not only for the reliability and durability of all the system operating components, but also for the Catch-All which has provided protection to these components over the many years of operation.

The solution to system filtration is the Catch-All Filter-Drier. The Catch-All has been designed to do the job with maximum efficiency. It removes these particles, down to the minimum size, in one pass filtration. Furthermore, the large filtering surface available on the core results in the ability to collect a large amount of dirt with negligible pressure drop. If plugged, the Catch-All will not burst allowing trapped substances back into the system.

• Stage 1 - Porous molded Catch-All HH Core filters the vast majority of particles. 
• Stage 2 - 10 micron filter to capture all but the finest particles. 
• Stage 3 - 1 micron final filter to capture remaining particles. 

The Catch-All Filter-Drier is unexcelled in acid removal ability. The hydrochloric, hydrofluoric, and various organic acids found in used oil samples are harmful in a system. These acids are adsorbed and remain on the desiccant in a manner similar to the adsorption of moisture.

Laboratory tests have shown that the Catch-All Filter-Drier’s desiccant has an acid removal ability superior to other desiccants used in other refrigeration driers. Compared to other filter-driers designed for today’s systems, tests show the Catch-All Filter-Drier removes much more acid (on an equal weight basis).
The Catch-All has demonstrated excellent field performance in cleaning up severely contaminated systems, whether due to acid, lubricant breakdown, or to hermetic motor burnout. Its success in field service work and in protecting new systems is largely due to its outstanding ability to remove acid and the products of lubricant breakdown.

At the initial start-up the Catch-All removed any dirt or excessive moisture that may have been in the system. During the years of operation, the Catch-All continued to provide protection by ensuring that no acid or contaminants formed during periods of high condensing or discharge temperatures. Unfortunately, things do not always go this smoothly and service calls are necessary. This is when consideration should be given to changing the filter-drier. 

Here are some questions that will help determine whether to change the Catch-All: 

1. Did the See-All indicate moisture was present?
2. Was the system open during service?
3. Were there any unusual circumstances that could have permitted moisture to enter the system? (ruptured chiller or water cooled condenser; wet conditions in area where repairs are taking place)
4. Was there a hermetic motor burn-out involved?
5. Was excessive compressor heat involved in the failure?
6. Is the refrigerant oil discolored or found to be acidic? (A Sporlan Acid Test Kit will determine this)
7. Was it evident that dirt, metal chips or other contaminants were involved in causing the failure?

If the answer to any of these is “yes,” a new Catch-All is good insurance against a repeat problem. If questions 3, 4 or 5 are answered “yes,” both a suction line and liquid line Catch-All are recommended to remove acids and products of oil decomposition.

Sporlan Bulletin 40-10 outlines the procedure for this type of cleanup. The Sporlan See•All and Acid Test Kits are excellent service tools for determining if a replacement of the Catch-All or other filter-drier is required.replacement of the Catch-All or other filter-drier is required.

Article contributed by Chris Reeves, product manager, Contaminant Control Products, Sporlan Division of Parker Hannifin

For more articles on climate control:

Using P-T Analysis as a Service Tool for Refrigeration Systems

Technologies for Drying Compressed Air: Aftercoolers and Coalescing Filters

Use of Suction Line Filter-Driers for HVAC Clean-up After Burnout

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Compressor Overheating Is the Number-One Refrigeration Problem

Six Reasons Why CDS Conversion Reduces Costs

How to Use the Smart Service Tool Kit for HVACR Diagnosis

When designing a system using stepper motor style electric valves, such as CDS or SDR valves and A8-to-CDS conversion kits, in head pressure control applications additional precautions and items should be considered.

Electric valve/controller operation:

Electric valves operate without a feedback loop. It is possible that over the life of an electric valve step loss may occur, and reinitialization of the valve may be needed. This reinitialization occurs when the valve is closed and overdriven to guarantee its position. When driven at 200 steps/second the reinitialization sequence is completed after approximately 40 seconds.

The Kelvin II Series Pressure Controller and most other controllers reinitialize when power is cycled to the controller (at start-up or after power loss). The Kelvin II Pressure Controller has a built-in safety. If condenser pressure spikes during reinitialization; the controller alarms, terminates reinitialization and normal operation (pressure control) begins.

In general, periodic reinitialization during operation is not recommended for the Holdback Valve. Reinitialization of the holdback valve should only occur when the system is offline. Additionally, the Pressure Control has a built-in algorithm that monitors valve position over time. After 24 hours has lapsed and a 0% open valve position is observed, the controller will reinitialize the valve to verify its position. This only affects the Receiver Pressurization Valve since the Holdback Valve never fully closes.

Electric head pressure control recommendations:

• When using electronic valves for holdback and receiver pressurization, successful operation and control has been seen with setpoint differentials as low as 5-10 psid. When electronic holdback is used with mechanical receiver pressurization valves, the pressure differential should be maintained no lower than 15-20 psid.
• Reinitialize controller when rack is offline.
• The compressor high pressure safety limits must be set to rack manufacturer’s recommendations.
• After power loss, compressor restarts should be delayed 90 seconds to allow for the electric valve’s reinitialization to complete. If not possible, there should be a 45 second delay between subsequent compressor starts. These recommendations will serve to stop a compressor for tripping off on high pressure safety.
• During installation pressure transducer calibration should be verified.

Optional/Additional considerations:

• Reinitializing the valve, while the rack is down, as part of an annual preventive maintenance routine is suggested.
• Service valves may be installed around the electric valves and/or before and after the valve to aid in troubleshooting, servicing and/or reinitialization.
• A bypass valve can be installed in parallel with the electric holdback valve if desired (but is not required). This bypass valve can prevent a compressor trip due to high pressure spike if compressor delays are not implemented as recommended above. An A8 valve with a high pressure setting would serve this purpose.

Third party controller recommendations:

• Periodic reinitialization of the Electric Holdback Valve is not recommended. Its reinitialization should only occur when the rack is offline.
• Sporlan Electric Valves should be driven at 200 steps/second.

Troubleshooting excessive step loss:

If excessive step loss is forcing frequent reinitialization, further investigation in the cause is needed. Excessive step loss may be caused by:

• Damaged wiring
• Wiring run in parallel with high voltage lines
• Damaged or worn valve(s)
• Poor controller output signal

All these should be investigated and eliminated to provide reliable operation.

For more information on CDS valves and Kelvin II Pressure Controllers see Parker Sporlan Bulletin 100-40 and Parker Sporlan Bulletin 100-50-5.

A solenoid valve with a built-in check valve is designed to replace a liquid line solenoid valve in parallel with a check valve for reverse flow. This valve may be applied in the liquid line of a supermarket case for positive shutoff during pump down control, while allowing full flow in the reverse direction during reverse gas defrost. It may also be used in the liquid line of a heat pump to prevent migration of refrigerant to the outdoor unit during the heating mode, while allowing full flow in the reverse direction during the cooling mode.

CAUTION: This valve will not close in the reverse flow/cooling mode.

CE6-HP SERIES SOLENOID VALVES

• For Refrigerants 22, 134a, 404A, 407C, 407F, 410A, 507
• Bi-Directional Solenoid Valve
• Supermarket Pumpdown Control
• Prevents Heat Pump Refrigerant Migration
• Extended Solder Type Connections
• MKC-1 Coil, Class F

See Figure 1. The check ball is small and inserted into the pilot port of the disc. When the valve is energized for operation in the refrigeration flow direction, the pressure on top of the disc is bled off through the pilot port and the disc raises. When the evaporator goes into defrost or the heat pump switches to the cooling mode, the solenoid valve must be energized. The reverse flow causes the check ball to close the pilot port from the bottom, pushing the disc up, fully opening the valve. 

Figure 1

CE6S1-HP* BI-DIRECTIONAL SOLENOID VALVE* 

The “C” is used in this nomenclature to represent the check valve feature and the“-HP” designates high pressure.
The check valve disc also requires a modification in the stem and plunger assembly. Therefore, the disc and stem and plunger assembly must be changed to convert a standard solenoid valve to one with a built-in check valve. Internal parts kits are available for solenoid valves with the built-in check valve.

CE6S1-HP BI-DIRECTIONAL SOLENOID

HEATING MODE (shown above)
Typically, the valve is installed with normal flow to the outdoor coil. When de-energized, this prevents migration of refrigerant to the outdoor coil during heating mode.

COOLING MODE
Typically the valve is installed with normal flow to the outdoor coil. When in cooling mode, the valve is in reverse flow.

For Supermarkets
See Figure 3 below. For reverse gas defrost, a liquid line solenoid valve can be installed with a check valve in parallel, to allow reverse flow to the liquid header. This adds the expense of labor and materials. Or, a Sporlan liquid line solenoid valve with the built-in check valve feature can be installed, saving time and money. 

Additional HVACR Tech Tips can be found here:

HVACR Tech Tip: Troubleshooting Solenoid Valves in Refrigeration Applications

HVACR Tech Tip: Guide to Servicing Blended Refrigerants

HVACR Tech Tip: Can You Have Subcooled Refrigerant in the Receiver?

Six Reasons Why CDS Conversion Reduces Costs

Clean-up Procedure for Refrigeration and Air Conditioning Systems

Compressor Overheating Is the Number-One Refrigeration Problem

HVACR Tech Tip: Where Should the TEV External Equalizer Be Installed?

In order to understand the principles of thermostatic expansion valve operation, a review of its major components is necessary. A sensing bulb is connected to the TEV by a length of capillary tubing which transmits bulb pressure to the top of the valve’s diaphragm. The sensing bulb, capillary tubing, and diaphragm assembly is referred to as the thermostatic element. The thermostatic element on all standard Sporlan TEVs is replaceable.

The diaphragm is the actuating member of the valve. Its motion is transmitted to the pin and pin carrier assembly by means of one or two pushrods, allowing the pin to move in and out of the valve port. The superheat spring is located under the pin carrier, and a spring guide sets it in place. On externally adjustable valves, an external valve adjustment permits the spring pressure to be altered.

There are three fundamental pressures acting on the valve’s diaphragm which affect its operation: sensing bulb pressure P1, equalizer pressure P2, and equivalent spring pressure P3 (see Figure 1). The sensing bulb pressure is a function of the temperature of the thermostatic charge, i.e., the substance within the bulb. This pressure acts on the top of the valve diaphragm causing the valve to move to a more open position. The equalizer and spring pressures act together underneath the diaphragm causing the valve to move to a more closed position. During normal valve operation, the sensing bulb pressure must equal the equalizer pressure plus the spring pressure, i.e.: P1 = P2 + P3

Equivalent spring pressure is defined as the spring force divided by the effective area of the diaphragm. The effective area of the diaphragm is simply the portion of the total diaphragm area which is effectively used by the bulb and equalizer pressures to provide their respective opening and closing forces. Equivalent spring pressure is essentially constant once the valve has been adjusted to the desired superheat. As a result, the TEV functions by controlling the difference between bulb and equalizer pressures by the amount of the spring pressure. 

For more details on Thermostatic Expansion Valves - Theory of Operation, Application, and Selection - Bulletin 10-9. 

Article contributed by Glen Steinkoenig, product manager, Thermostatic Expansion Valves, Sporlan Division of Parker Hannifin

For more articles on climate control:

HVACR Tech Tip: 12 Solutions for Fixing Common TEV Problems

HVACR Tech Tip: Where Should the TEV External Equalizer Be Installed

Compressor Overheating Is the Number-One Refrigeration Problem