ASH3 Superheat Accessory Head Measures Refrigerant Temperature and Pressure

BREA, Calif., January 5, 2005 -- Fieldpiece Instruments announces the immediate availability of the ASH3 Superheat Accessory Head, which enables DMMs to measure superheat for both R22 and R410A. It does this by measuring both suction line pressure and suction line temperature simultaneously and calculating superheat. The user can display suction line pressure, suction line temperature and superheat. At $179, the ASH3 can pay for itself in time savings when using superheat to diagnose an air conditioner. The ASH3 includes not only the accessory head but also the Fieldpiece Instruments’ ATC1 Pipe Clamp Thermocouple. The ATC1 is a spring-loaded thermocouple clamp that’s designed to easily take suction line pipe temperatures. It firmly holds the thermocouple junction up against the suction line temperature measurements. The ASH3 has a “Stable Indicator” LED which is important when measuring superheat. It tells the user that the reading is stable. In addition, the head comes with a brass “T” so the head can be connected in-line when used with gauges, or can be used by itself on the end of a hose without the “T”. The ASH3 accessory head works with all of Fieldpiece’s modular instruments. It slides on to the HS30 series stick meter. The ASH3 head can also be used with the data logger to record measurements over time. When used with the Fieldpiece Electronic Handle, EHDL1, it acts as a standalone tool. It also connects to most DMMs using Fieldpiece's AHDL1 adapter handle.

“Now every technician can easily and quickly measure superheat. No more winging it!” said Rey Harju of Fieldpiece Instruments. “The ASH3 measures both suction line pressure and temperature at once, for either R-22 or R410-A refrigerant. And it works with the instruments you already have. Plus, as a bonus, you get the ATC1 thermocouple pipe clamp. You can use it with all your other Fieldpiece instruments." The included ATC1 thermocouple clamp can be used on pipe sizes from 3/8” to 1 ½” which covers most refrigerator pipes.

Measuring superheat is important because it can prevent damage to the air conditioner and make it run more efficiently. Superheat is the difference between the boiling point temperature of the refrigerant in the evaporator coil and the actual temperature of the refrigerant (gas) as it leaves the evaporator. After boiling, the refrigerant continues to warm up. The number of degrees it “warmed up” after boiling is called the superheat. Under worst case conditions (low load), the refrigerant in the evaporator boils off near the end of the evaporator coil. To make sure liquid doesn’t enter the compressor under the worst case condition (low load), the AC manufacturers publish charts indicating what the superheat should be at a given indoor wet bulb measurement and outdoor air temperature. If the superheat is too high, the air conditioner will be inefficient. If superheat is too low, you risk flooding the compressor. You can change the superheat by adding or taking away refrigerant.

Measuring superheat is the best indication on a fixed orifice system of the proper refrigerant charge and operating conditions. If everything else is working properly and the actual superheat is too high, add refrigerant. If it is too low, remove refrigerant. Using superheat to determine proper charge enables an air conditioner to deliver the best reliability and the best efficiency.

Client Contact: Russell Harju – Product Manager, (714) 634.1844
Press Contact: Beverly Steinberg, (714) 777-2760


Formed in 1989, Orange County, Calif.-based Fieldpiece Instruments has become the testing tool company that HVACR professionals trust. Because Fieldpiece focuses only on the HVACR industry, all products are developed to solve real world HVACR problems. Not only do the tools have the right functions and features, but also techs can trust them to work where and when they need them, because they withstand the use and abuse techs in the HVACR field dish out. Fieldpiece constantly develops new tools that allow HVACR professionals to do more than they otherwise could, increasing the tech’s capability and billable hours. For more information please visit our website at or call 714.634.1844.

  • Created: Thu, January 17, 2013