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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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.
Example R-134A Refrigerant Temperature vs Pressure Data |
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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 |
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.
If you already know your refrigerant pressures are wrong or that you have a refrigerant leak, please see
If your air conditioning or heat pump system has lost its cooling capacity or won't start see
...
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