Refrigeration Piping Charging Residential AirConditioning R

Total Superheat Method
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Some residential air-conditioning system with fixed orifice may be charged by the total
superheat method. Various equipment manufacturers furnish charts with their units
that explain the proper procedures to the installing or servicing technician.
This method, similar to evaporator superheat method, is effective only when the indoor
conditions are within 2F° of desired indoor comfort conditions and the suction
pressure and temperature is stabilized.
To measure total superheat:
1. Read and record the outdoor ambient air-dry bulb temperature entering the
condenser.
2. Read and record suction line pressure and temperature at the suction service valve
or service port at compressor.
3. From Table 5, the reading at the intersection of vapor pressure and outdoor ambient
temperature should coincide with the actual vapor line temperature.
4. If the vapor line temperature is not the same, adjust the refrigerant charge. Adding
R-22 will raise suction pressure and lower suction line temperature. Removing R-22
will lower suction pressure and raise suction line temperature.
Caution: If adding R-22 increases both suction pressure and temperature, the unit is
overcharged.
This method is very useful when performing preventive maintenance or corrective
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