what is the ideal discharge temperature from a ac unit?

Answer 1

Ain't no such animal...

Ideally, an A/C unit would remove heat, moisture, and carbon dioxide at precisely the same rate they enter the conditioned space.

Ideally, it would run constantly and silently-- not in cycles.

Ideally, there would be separate control loops for temperature, dew point, and carbon dioxide concentration.

Ideally, every parcel of air that enters any part of the room would arrive back at the return air duct(s) at precisely the selected levels of CO₂, moisture, and temperature-- no more, no less.

Ideally, you would also be able to select a maximum permissible variation for each of those parameters. The system would warn you when the selected ranges start to tax system capacity.

Ideally, you would be able to mix controlled amounts of outdoor, indoor conditioned, and indoor unconditioned air (cooling air for the compressor, etc.) as needed in the return air flow and/or the evaporator output stream.

Ideally, there would be an intelligent controller to manage all this.

The controller would anticipate and sense wall temperatures, discrete heat sources within the room, sunbeams, and number of people in the room. It would do things like direct lower temperature, higher moisture air along hot walls while supplying warmer, drier air to the room itself. It would automatically increase the flow rate through the room to counteract increased CO₂, moisture, and heat loads.

I agree with Cambion that the evaporator should be capable of reaching 32 degrees to achieve maximum control authority over moisture. Any cooler than that and you'd have to provide for ice control. The controller would, however, run the evaporator at the most efficient temperature for the existing input conditions.

Depending on the nature of the insulation between the attic, walls, and the conditioned spaces- it may be desirable to build in air spaces separate from the general circulation. Being able, for example, to run cold air in a narrow space between the upper story ceiling and the attic may go a long way towards reducing gradients and increasing comfort within the house.

I think recent advances in sensor technology and microprocessor capability herald a whole new age in environmental systems.

Answer 2

I don't know about ideal. But most units are designed to operate between around 12 to 15 degrees below the return air temperature. You get much cooler than that and you're going to have a comfort problem.

If the temperature is difference is less than that the unit is not working properly.

Answer 3

The ideal temperature of the evaporator is 32° Fahrenheit or 0° Celsius.

Answer 4

20 degrees below the temperature out doors.

Answer 5

You should be looking for a 20 degree F delta-t.

Answer 6

60 degrees.