ASX14 ASX24 Calculate Superheat and Subcooling Automatically in One Accessory Head from Fieldpiece Instruments

BREA, Calif., June 12, 2006 -- Fieldpiece Instruments announces the immediate availability of the ASX14 and ASX24 Superheat and Subcooling Accessory Heads, which enable DMMs to measure both refrigerant pressure and temperature simultaneously to calculate both superheat and subcooling. The ASX14 works on A/C systems, while the ASX24 works on refrigeration systems. Both accessory heads include the Fieldpiece Instruments’ ATC1 Clamp Thermocouple that features a spring-loaded clamp to firmly hold the thermocouple junction up against a pipe, important when measuring line temperature. After measuring suction line or liquid line temperature and pressure, the accessory heads calculate and display the actual superheat or subcooling, saving the technician the hassle of using charts to determine the numbers.

“When systems are undercharged or overcharged, the compressors are not running efficiently and they have a greater chance of failing. So it’s important to measure superheat and subcooling accurately,” said Rey Harju of Fieldpiece Instruments. “The new accessory heads do the calculations for the techs without the possibility of incorrectly reading the charts."

For charging A/C systems, the ASX14 Accessory Head can measure R-22 or R-410A refrigerant. For refrigeration systems, the ASX24 can measure R-134A or R404A refrigerant.

The included ATC1 thermocouple clamp can be used on pipe sizes up to 1 3/8”, which covers most refrigerator pipes. A “Stable” LED indicator is an important feature, especially when measuring superheat and subcooling. The heads also include a “T” refrigerant line connector.

The new accessory heads work with all of Fieldpiece’s modular instruments. They slide on to any of the HS30 series stick meters. The ASX14 and ASX24 heads can also be used with the data logger to record measurements over time. When used with the Fieldpiece Electronic Handle, EHDL1, the accessory heads become a standalone tool. They also connect to most DMMs using Fieldpiece's AHDL1 adapter handle.

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