Heat Pump Pressure

I have a Ducane Model HP12B36 heat pump. Can anyone tell me what the high and low side pressures should be?

Thanks

I couldn't find anything on that heat pump. Do you have a link?

You need to find the operating temperature range and the refrigerant.

You would probably be using R22 or R134a. Here is a link to the properties of R22. http://www.engineeringtoolbox.com/r22-properties-d_365.html

As an estimate, take the lowest temperature (evaporator side) and subtract about 20 degrees F for the heat exchanger temperature difference.

Then take the condenser cooling fluid temperature (air or water) and add 20 degrees F for the heat exchanger temperature difference.

Then look at the vapor pressure for the refrigerant at those temperatures to estimate the suction and discharge pressures.

Let's say you are using it as a heat pump withdrawing heat from 55 F water, and the water is cooled to 45 F when it comes out of the evaporator. If the evaporator is operating at 20 degrees less, the suction pressure would be that corresponding to 45 - 20 = 25 F. From the table, the suction pressure would be 63.5 psia (psi absolute) which is 48.8 psi on a gauge. If you operate in that range you need to be careful that the water stays above freezing.

If the air going out of the condenser is 90 degrees, and you allow 20 degrees for temperature difference in the heat exchanger, the condensing temperature would be 110 F and the pressure from the table is 241.1 psia which is 226.4 gauge at sea level.

A larger heat exchanger will reduce the temperature difference to less than 20 degrees and will therefore improve the Coefficient of Performance of the heat pump system.

This is only an estimate based on the assumptions of temperatures and refrigerant. You need to get the real data for the system.

The capacity of the system will vary if you use a different refrigerant than the compressor was designed for or operate over a different temperature range than the system was rated for.

bobnh really knows his stuff!.