[ejpalmer]

I'd like to know how low a temperature one should expect of a properly operating forced air residential A/C system measured at an air register (relatively close to the blower/evaporator unit) after the temp has stabilized at it's lowest point (10 min in this case). Also, I understand 20 deg F is a "nominal" target temperature differential, outside vs. inside temp. Where is this to be measured? At an air register, or at the thermostat? I'm getting 59 deg at a register with outside temp of 90. Thermostat is set at 79.

Thanks,
Eric

[esquire1]

Now measure your temperature at the return air (where your filter is) Subtract that temp from the supply air temp.( your register 59 degrees)