I came across this example of a correctly running cap/orifice system and wanted opinions on its acuracy before using it to evaluate our system to determine if we need to call for service. Just bought the building; 1900 sf and the 3 ton 10 SEER unit does not seem to be getting the job done:
This example is for a 10 SEER system. The unit is running normally, and the space is within about 5 degrees of the desired final temperature.
Condensing pressure should be equivalent to somewhere around 20-30 degrees above ambient.
Evaporator pressure should be equivalent to about 38-42 degrees.
Look for 20-30 degrees of superheat at the compressor: less than 20 degrees is not acceptable.
Look for 5-15 degrees of subcooling on the liquid line at the outlet of the condenser.
Look for return air temperature to drop about 15-20 degrees as it passes through the evaporator coil.
The temperature of the air entering the condenser should rise about 20-30 degrees as it passes through the condenser coil.