Amprobe ACDC-620T Clamp-On-Multimeter - Manual (Page 59)

Once outside, the gas enters the compressor on the low-pressure side and is
compressed. As it is compressed, the gas temperature rises above the surrounding
air temperature. The hot gas dissipates its heat in the condenser, becoming liquid
once again, before returning to the expansion value.
In large systems the temperature and pressure are closely monitored to ensure long
life and minimum energy usage. In small systems, like a home refrigerator, tempera-
ture is often measured as a troubleshooting aid. Careful temperature measurement
at different points in the system can pinpoint trouble spots. Some of critical tempera-
tures are discussed below.
c Important Temperature Measurements
Evaporator Temperature
The entire mid-section of the evaporator is at the refrigerant's boiling temperature,
which is related directly to the evaporator pressure. The evaporator temperature
should be lower than the desired cooling temperature.
Evaporator Superheat
By the time the refrigerant reaches the last few turns of the evaporator coils, all the
refrigerant should have become gas with s temperature slightly warmer than the
evaporating temperature. The amount that the gas temperature exceeds its boiling
point is called superheat. Superheat is a sensitive indicator of evaporator efficiency.
The superheat gas temperature is usually taken at the expansion valve's sensing
bulb. Aproper superheat reading, ensures that all liquid has boiled.
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