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POST a QUESTION or COMMENT about refrigerant pressure readings in air conditioners, heat pumps, & other refrigeration equipment

R-134A refrigerant charge quantity for air conditioners & heat pumps:

This air conditioning repair article series discusses the the diagnosis and correction of abnormal air conditioner refrigerant line pressures as a means for evaluating the condition of the air conditioner compressor motor, which in turn, is a step in how we evaluate and correct lost or reduced air conditioner cooling capacity.

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HFC Example R-134A Pressure / Temperature Charts

Measuring the refrigerant pressure in air conditioning, heat pump or other refrigerant systems can diagnose a range of operating problems including a refrigerant leak, over charging or under charging.

Refrigerant pressure readings measured at the air conditioning compressor/condenser unit and which are found to be too low on the high pressure side (compressor output) or on the low pressure side (compressor input or suction line) can indicate a problem with the compressor's ability to develop normal operating pressure ranges and thus will affect the cooling capacity of the air conditioning system.

Abnormally high compressor output pressures are possible but less likely.

Notes to the table above

Other Properties of R134A Refrigerant

See several complete HFC R-134A pressure/temperature charts cited further below on this page
R134A temperature/pressure relationship: see the table above
R134A alternative name: 1,1,1,2-Tetrafluroethane or CH₂FCF₃
R134A boiling point: −26.3 °C (−15.34 °F) at atmospheric pressure (sea level or 1 ATM)
R134A density: 0.00425 g/cm³, in gas form - this is a colorless gas
R134A molar mass: 102.03 g/mol
R134A gas cylinder identification: light blue
R134A status: some efforts to phase out use of this refrigerant, replacing it with HFO-1234yf or other refrigerants

1. Outdoor ambient temperature

2. Typical low pressure or suction side, may vary by equipment and metering controls

3. Typical high side pressure, may vary by equipment

4. These psig readings for R-134A are what you'd expect the pressure of the gas to be in an enclosed container at the temperature given and at steady state.

R-134A Refrigerant Pressure / Temperature Chart & Table Downloads

HFC R-134A PRESSURE TEMPERATURE CHART [PDF], Pacific Sea Breeze Marine Products, 100 Grace Way, Scotts Valley, CA 95066 USA, Tel: 831-600-7878 Website: http://pacificseabreeze.com/technical_library
R134A REFRIGERANT PT CHART [PDF] Agas, Op, Cit. retrieved 2020/02/10 original source: agas.com/media/2404/r134a-pt-chart.pdf
HFC 142B REFRIGERANT PRESSURE TEMPERATURE CHART
REFRIGERANT PRESSURE / TEMPERATURE CHARTS for R-22, R-410A, R-134A, R-404A REFRIGERANTS [PDF],
Advantage Engineering, Inc. 525 East Stop 18 Road Greenwood, IN 46142USA, Tel: 317-887-0729 Web site: www.AdvantageEngineering.com Email: sales@AdvantageEngineering.com

Correcting R-134a Refrigerant Pressure & Leaks

Refrigerant Pressure & Leak Correction

If you already know your refrigerant pressures are wrong or that you have a refrigerant leak, please see

REFRIGERANT CHARGING PROCEDURE
REFRIGERANT LEAK DETECTION
REFRIGERANT LEAK REPAIR
THERMOSTATIC EXPANSION VALVE TEV INSTALL, DIAGNOSE, REPAIR - abnormally low or abnormally high suction side pressure

If your air conditioning or heat pump system has lost its cooling capacity or won't start see

REPAIR GUIDE for AIR CONDITIONERS.

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Citations & References

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Example R-134A Refrigerant Temperature vs Pressure Data
Ambient Temperature	R134A Vapor Pressure at Sea Level	R-134A Low Side Pressure²	R-134A High Side Pressure³
65.71°F (18°C)	65 psig	25-35 psi / 172-241 kPa	135-155 psi / 931-1069 kPa
69.24°F (21°C)	70 psig	35-40 psi / 241-276 kPa	145-160 psi / 1000-1103 kPa
75.86°F (24°C)	80 psig	35-40 psi / 241-310 kPa	150-170 psi / 1034-1172 kPa
90.37°F (32°C)	105 psig	45-55 psi / 310-379 kPa	250-270 psi / 1724-1862 kPa
100.40°F (38°C)	125 psig	50-55 psi / 345-379 kPa	315-325 psi / 2172-2241 kPa
105°F (41°C)	135 psig	50-55 psi / 345-379 kPa	330-335 psi / 2275-2310 kPa
110°F (43°C)	145 psig	50-55 psi / 345-379 kPa	340-345 psi / 2344-2379 kPa