Design Temp: This is simply the temperature the air conditioning or refrigeration equipment should normally maintain.

Actual Temp: This is the measured temperature the air conditioning or refrigeration equipment is currently maintaining.

Suction Vapor Temp: Measure this temperature as close to the evaporator coil outlet as possible. If the system uses a TXV or EXV, measure the temperature as close to the location of the sensing bulb or temperature sensor as possible.

Liquid Temp: Measure this temperature as close to the condenser coil outlet as possible. If the system uses a receiver, measure this temperature on the drain line (line connecting the condenser and receiver).

Suction and Discharge Pressures: Having these pressures taken at the compressor service valves is normally adequate.

Ambient Temp: This is the temperature of the air entering the condenser coil.

The more accurate data you can provide this system analysis web app, the more useful information it will provide to assist in troubleshooting the system. Bad input will result in bad output.