Form O-Y, PN 273647R5, Page 18
Check SUBCOOLING
Measure and record temperature and pressure of the liquid line at the condenser coil outlet.
STEP 1)
Record Measurements
: Temperature = ________°F (°C) and Pressure = ________ psig
STEP 2)
From Temperature/Pressure Conversion Chart (page 17), convert Measured Pressure (STEP 1)
to ________°F (°C)
STEP 3)
Subtract Measured Temperature (STEP 1) from Temperature from Conversion Chart (STEP 2)
______
__°F (°C) - ________°F (°C) =
________
°F (°C) degrees of Subcooling
Recommended subcooling with outdoor temperature range of 70 to 95°F (21 to
35°C) is 10 to 12 degrees F (5.6 to 6.7 degrees C)
.
Too much subcooling indicates a refrigerant overcharge. To reduce the subcooling, remove
excess refrigerant. Too little subcooling indicates a refrigerant undercharge. To increase sub-
cooling, slowly add R-410A refrigerant.
WARNING
Do not release refrigerant to the atmosphere. When adding or removing refrigerant, the
qualified technician must comply with all national, state/province, and local laws.
Determine SUPERHEAT
Measure and record temperature (insulate probe from surrounding air temperature) and pressure in the suction
line at the compressor inlet.
STEP 1)
Record Measurements
: Temperature = _______°F (°C) and Pressure = _______ psig
STEP 2)
From Temperature/Pressure Conversion Chart (below), convert Measured Pressure (STEP 1) to
________°F (°C)
STEP 3)
Subtract Measured Temperature (STEP 1) from Temperature from Conversion Table (STEP 2)
________°F (°C) - ________°F (°C) =
________
°F (°C) degrees of Superheat
Recommended superheat range is 8 to 12 degrees F (4.5 to 6.7 degrees C).
Typically, too much superheat indicates that the evaporator coil is undercharged. Too little superheat
typically indicates that the evaporator coil is overcharged and may potentially flood liquid refrigerant to
the compressor. To reduce the superheat, adjust the thermal expansion valve by turning the adjusting
stem counterclockwise. To increase the superheat, adjust the thermal expansion valve by turning the
adjusting stem clockwise
3.6 Check Refrigerant Pressure and Temperatures
(subcooling and superheat) (cont'd)
3.0 Maintenance and Service Procedures - Unit & Cooling (cont'd)
