How do calculate the superheat f an air conditioner?

When you are gauged up on the unit, as close to where your temperature reading will be taken as possible, (note: ofter times the there will be access specifically for this purpose very near the txv) use a good thermometer and obtain the temperature of the suction line 6 inches out from the evaporator coil. (right where the sensing bulb is in refrigeration or the equalizer tube for the txv in A/C is best.) Then, convert the pressure reading on your suction gauge to degrees for the type of refrigerant in the system and subtract it from the reading on your thermometer.

This is the amount of heat that is being added to the refigerant AFTER it has changed state from a liquid to vapor. Remember to use a temperature pressure chart to get your temps for what kind of refigerant that's in the system. A/C systems should be between 15 and 20 degrees F Refrigeration is more like 6 - 12 degrees .