If a manufacturer says their compressor can be used in a 2-1/2 ton compressor when the design ambient temperature is 100 F and the evaporating temperature is 45 F how do I measure/verify these temps for my location? Is the design ambient temp the outdoor temperature? Is the evaporating temp the temperature at the evaporator coil somewhere say just above it in the duct?

is the design ambient temp the outdoor temperature?

Yes but it is always good to set your design temp close to the highest operating temp the area will see.

Usually evap temp is taken on the discharge side of the coil. Many just take the temp at the closest register.

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