Fieldpiece Superheat Accessory Head ASH3


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Fieldpiece Superheat Accessory Head ASH3


Designed for HVAC/R, the Superheat Accessory for Air Conditioning – model ASH3 measures refrigerant pressure and temperature and calculates superheat for two refrigerants in English or metric units. 

  • Display pressure in PSI or kPa.
  • Display temperature in ºF or ºC.
  • Display superheat in ºF or ºC.
  • Select R22 or R410A.
  • Auto-off can be disabled for data logging.
  • Includes "T".
  • Now accepts K-type thermocouples. ATC1included.
  • LED indicates when readings are stable.
  • Thermocouple calibration pot.
  • Push-button atmosphere pressure calibration.

Recent studies suggest that over half of the AC systems in operation in the U.S. are undercharged or overcharged. This causes decreased efficiency, and sometimes, premature compressor failure. The Fieldpiece Superheat Accessory for Air Conditioning – model ASH3 measures suction line, or low side, line temperature and pressure and calculates ACTUAL superheat in real time. Use it to get ACTUAL superheat on R-22 and R-410A fixed orifice systems. On systems regulated with a TXV / TEV you’ll want to look at our ASX14, ASX24 and SSX34 superheat and subcooling instruments. Use the “T” fitting to charge to actual superheat by putting the ASH3 in-line between your refrigerant bottle and the system.

How Does it Work? 
Finding ACTUAL superheat is easy with the ASH3. Simply hook it up to the system, let the system stabilize, and get your actual superheat in real time. No charts, no calculations. It’s all done for you in the instrument. The ASH3 measures refrigerant pressure and temperature simultaneously. It then calculates and displays ACUTAL superheat on your meter or electronic handle. It has a 1/4” industry standard fitting for actual pressure. An advanced pipe clamp k-type thermocouple model ATC1 is included for actual line temperature. Select R22 or R410A. Select English or Metric units.


  1. Connect to COM and Volts jack. Slide ASH3 superheat head onto Fieldpiece "stick" meter, data logger, electronic handle or connect to most other meters using Fieldpiece ADLS2 deluxe test leads or AHDL1 handle.
  2. Set meter to mVDC range.
  3. Calibrate if needed (see Field calibration)
  4. Hand tighten 1/4” flare to suction line as close to the evaporator as possible using an EPA approved service hose (not included).
  5. Select refrigerant (R22 or R410A) and units (English or metric).
  6. Connect the pipe clamp to the suction line at least six inches from the compressor and slide it under the insulation for best accuracy isolating the pipe clamp from the ambient air (pg. 2).
  7. Select parameter to display (superheat, pressure, or temperature).
  8. You must wait until the system you are testing has stabilized completely before you can take an accurate superheat reading, this usually takes about 10-15 minutes. The STABLE LED lights when superheat is stable.
  9. Disable Auto-off to data log any of the above parameters with the DL3 data logger.
  10. Once you have the superheat reading follow the manufacturer of the air conditioner’s specifications to properly charge or diagnose the system.

Competitive Advantages. 
Many AC system analyzers include PT charts you don’t want or need. The ASH3 is an alternative to expensive to system analyzers for the refrigerants you work with on air conditioning systems the most - R22 and R410A.

Recommended Accessories and Replacement Parts. 
Technicians who like the ASH3 may also enjoy these instruments and accessories: 

What's In The Box

  • ASH3: Superheat Accessory for Air Conditioning
  • ATC1: Pipe-Clamp Thermocouple 3/8” to 1 3/8” for Air Conditioning
  • Mini-calibration screwdriver
  • 9V battery (installed)
  • Operator’s manual


Operating environment 32ºF to 122ºF; 0ºC to 50ºC at <75%RH
Allow ~5 min. for ASH3 to come to ambient temp.
Storage environment -4ºF to 140ºF; 0ºC to 50ºC at <80%RH with battery removed from meter.
Battery life 25 hours typical. No measurable current draw when in "off" position.
Low battery indication Red LED lights
Battery 9V
Auto off Approx. 15 minutes
Overloads The ASH3 outputs 3.4V when temperature or pressure is outside of their working range (overloaded). For ranges below 3400mVDC, the normal overload symbol will be displayed on the meter (“OL” or depending in the meter). For ranges above 3400mVDC, reading displayed will be approximately 3.4VDC.


Working range (pressure) 0 to 500 psi; 0 to 4000 kPa
Maximum displayed pressure 800psi
Working range (vacuum) 29”Hg vac. to 0; 74cmHg vac. to 0
Vacuum will show up as negative value on meter.
Resolutions 0.1psi, 0.1”Hg vac.
Accuracy @ 50°F to 115ºF ambient, ±1 psi, ±6.9 kPa
@ 32ºF to 122ºF ambient, ±2 psi, ±13.8 kPa
Sensor breakdown pressure 1300psi


Range (temperature) -40ºF to 400ºF; -40ºC to 204ºC
Resolutions 0.1º
Sensor type k-type thermocouple
Pipe clamp thermocouple accuracy ±4ºF or ±0.75%, whichever is greater, -30ºF to 200ºF
System accuracy ±1ºF; ±0.06ºC @ 73ºF ± 5ºF after ice water calibration (see Field calibration).


Range (temperature) 0ºF to 80ºF; 0ºC to 27ºC Resolutions: 0.1º
System Accuracy ±1ºF; ±0.06ºC @ 73ºF ± 5ºF after calibration (see Field calibration).

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