Climate Control

HVACR Tech Tip: Top 5 FAQs About Thermostatic Expansion Valves (TEVs)

HVACR Tech Tip: Top 5 Most Frequently Asked Questions About Thermostatic Expansion Valves (TEVs) - HVACR Technician diagnosing air conditioning unitNot everyone is familiar with all the intricacies of HVACR as we are at Parker Sporlan and that’s okay. Whenever you have questions, you can always contact our world class Technical Support team or check Parker.com/Sporlan for in-depth information and guidance. Our Climate Control Blog has many of the answers you need for questions on most topics, so dig in. Below, we’ve answered some of the most frequently asked Thermostatic Expansion Valve (TEV) questions – you’ll find easy answers to your need-to-know questions.

 

Where should the TEV external equalizer be installed?

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 down stream 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 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, alternative locations are acceptable as long as these pressures are essentially the same as 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 Parker Sporlan’s TEV design, this possibility is virtually eliminated.

 

Where should the TEV’s bulb be located?

In general, the TEV bulb should be installed on a straight section of horizontal suction line. When the compressor is above the evaporator – Locate the bulb on a straight, horizontal line, pitched slightly down, immediately after it leaves the evaporator. A short trap should follow before the vertical line rises to be connected to the compressor suction. With the line pitched down, any liquid refrigerant and/or oil will pass into the trap, away from the bulb. As the trap fills with oil, the velocity of the refrigerant will carry the trapped oil into the vertical section and be returned to the compressor. When the compressor is below the evaporator  No trap is required after the bulb location, but the line should be pitched slightly down to prevent any liquid refrigerant or oil from being trapped at the bulb location. When several evaporators are installed both below and above the common suction line – Observing the same principles outlined above, the piping should be arranged to prevent the accumulation of oil and/or refrigerant at the bulb location. Also, traps installed in the suction lines of evaporators prevent the refrigerant from one evaporator from entering the suction line of another evaporator.

 

Should a Parker Sporlan Thermostatic Expansion Valve (TEV) be adjusted after installation?

HVACR Tech Tip: Top 5 Most Frequently Asked Questions About Thermostatic Expansion Valves (TEVs) - Thermostatic Expansion ValveBefore leaving the factory, a specific superheat setting is made on each and every Parker Sporlan TEV. A standard superheat setting has been established for every size and every thermostatic charge. This standard-setting provides the proper superheat on the average system to which the particular TEV size and charge is likely to be applied. Therefore, in most cases, a superheat adjustment on the job will not be necessary. Parker Sporlan recommends a change in the superheat adjustment only after it has been determined that it is required. Careful measurement of the operating superheat, using the recommended procedure, will establish if a change would be beneficial. To reduce the superheat, turn the adjusting stem COUNTERCLOCKWISE. To increase the superheat, turn the adjusting stem CLOCKWISE. When adjusting the valve, make no more than one turn of the stem at a time and observe the change in superheat closely to prevent over-shooting the desired setting. On adjustable TEVs, Parker Sporlan attempts to position the adjusting stem at the half-way point when it is at the standard-setting. This allows maximum adjustment in both directions. Parker Sporlan supplies a number of OEMs with non-adjustable TEVs. The OEM determines the superheat setting through laboratory testing of the unit. Some of these valves can be converted in the field to adjustable models.

 

How can I tell if my TEV is adjustable?

Most of the TEVs listed in Parker Sporlan Catalog 201 or Bulletin 10-10 will be adjustable unless there is an “N” stamped in the valve body as part of the nomenclature (i.e. NSVE-5). Many of the valves made specifically for OEM customers are non-adjustable. One way to tell if a valve is adjustable or non-adjustable is to look at the bottom cap. Adjustable expansion valves will have a threaded joint between the valve body and bottom cap as well as a threaded joint between the bottom cap and a hex seal cap that is removable to expose the adjusting stem. Non-adjustable valves, on the other hand, will generally have only one threaded joint between the valve body and bottom cap. An exception to this rule is a factory adjustable valve with two threaded joints and a smooth, round non-removable seal cap. Many non-adjustable valves can be converted to adjustable by changing the bottom cap assembly. Contact Parker Sporlan’s Technical Support department for more information. They will need all the information you can get from the valve’s markings to assist you. CAUTION: Never attempt to determine if a valve is adjustable by removing the bottom cap assembly unless the system has been pumped down, it could result in serious injury.

 

Can I replace the powerhead on my Parker Sporlan TEV and how do I know what to get?

With a few exceptions, most Parker Sporlan thermostatic expansion valves manufactured after 1993 have replaceable thermostatic elements. The exceptions are valves with an “H” before the valve nomenclature (i.e. HSVE-10), the now obsolete Platform valves, and the relatively new HX valve. The Platform and HX valves can be identified by a stainless steel element. The valves with the “H” in the nomenclature have had the elements soldered to the valve body at the customer’s request. Parker Sporlan makes replacement element kits that are available through Authorized Sporlan Wholesalers. The thermostatic elements on Parker Sporlan expansion valves are identified by a series of numbers and letters. The number (i.e. 33, 43, 83, etc.) identifies the element size, while the letters (i.e. VGA, RC, JCP, etc.) identify the refrigerant and thermostatic charge. A replacement element kit can be obtained based on that information. For example, a valve with markings on the element of 83 and VCP100 will require a KT-83-VCP100 element kit. (For more information on element identification, consult Bulletin 210-60.) If markings on the element are no longer legible, contact Parker Sporlan’s Technical Support team for help in selecting a replacement element. They will need all the information available from the valve body, and a description of the application. To completely identify a Parker Sporlan thermostatic element the following information is required:

  • Element size number

  • Refrigerant Thermostatic charge

  • MOP (Maximum Operating Pressure) if other than standard E

  • Capillary tubing length

  • Bulb size if other than standard

For more information on Thermostatic Expansion Valves (TEVs) download a copy of Bulletin 10-10. For more troubleshooting information download a copy of 12 Solutions for Fixing Common TEV Problems - Form 10-143.

 

Jason Forshee

HVACR Tech Tip Article contributed by Jason Forshee, application engineer,  Sporlan Division of Parker Hannifin

 

 

 

 

 

Additional HVACR Tech Tips helpful for you: 

HVACR Tech Tip: Basic Troubleshooting Given Three Measurements

HVACR Tech Tip: Principles of Thermostatic Expansion Valves

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

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