Heat Pumps in commercial occupancies

[sceepe]

Just wondering how others deal with heat pumps in article 220 calcs for commercial buildings. The 220.82(C) gives pretty clear instructions for dealing with heat pumps but this does not apply to commercial occupancies.

In my neck of the woods we use a lot of split system heat pumps with supplimental strip heaters. The strip heat and heat pumps can both run at the same time during the "defrost cycle". However all the units are not in defrost at the same time.

I have always been very conservative in sizing services but was wondering how others deal with this. Also, do any of you guys know of a demand factor for occupancies with multiple split systems?

 

[bob]

In my neck of the woods we use a lot of split system heat pumps with supplemental strip heaters. The strip heat and heat pumps can both run at the same time during the "defrost cycle". However all the units are not in defrost at the same time.

The electric heat may be installed in several units. Example a 20 kw unit may have 2 10 kw heaters. During extreme low temperatures both of the units may be on as well as the compressor. The code does allow a 60% factor on the heat in section 220 but I would use 100%.

 

[Mr. Bill]

The code does allow a 60% factor on the heat in section 220 but I would use 100%.

Where do you see the 60% factor? I'd like to be able to derate electric heat in a commercial occupancy.

I'm looking at 220.51-2005 that states fixed electric space heating loads shall be calculated at 100 percent of total connected load.

 

[bob]

Where do you see the 60% factor? I'd like to be able to derate electric heat in a commercial occupancy.

I'm looking at 220.51-2005 that states fixed electric space heating loads shall be calculated at 100 percent of total connected load.

I was looking at 220.82C4 for residential. I don't think you can derate.