Residential Service Sizing Heat Pump (Testing soon)

[Dtylerjr]

I have read and re-read the code section on residential sizing for services and its relationship with Heat Pumps with auxiliary heat that can operate with compressor. Can someone "some up" the standard sizing method for a heat pump.. Thanks in advance.

 

[Dennis Alwon]

I have read and re-read the code section on residential sizing for services and its relationship with Heat Pumps with auxiliary heat that can operate with compressor. Can someone "some up" the standard sizing method for a heat pump.. Thanks in advance.

Are you talking about art. 220.82(C)?

If the heat pump and the backup electric heat in the blower unit are wired so that the heat pump and the strips cannot run at the same time then you can calculate the heat pump at 100% and the 65% for the supplemental heat. This is usually wired thru the T-stat controls.

If on the other hand the heat pump and the supplemental heat can come on at the same time then you must calculate them both at 100% since they will both be running.

Sometime the heat pump has no supplemental strips in the blower unit. In this case just the heat pump is calculated at 100%.

Terminology here can be a problem. The heat pump is generally just the outdoor unit-- looks like the a/c units. The blower inside the house( usually) may or may not have resistance heat strips.

 

[suemarkp]

And unless you live an a very southern area, I would hope the HVAC guy wire the auxillary heat and heat pump can run at the same time. Otherwise, you get a blast of cold air in the house during defrost. The temperature of the air blowing in the house is also too low when only the heat pump runs and it is below 25F to 30F outside.