NEC 220.15 Fixed Heating, load calulations

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stevenj

Member
Code Question: NEC 220.15 (2002)
load calculation. For fixed electrical heating ( baseboard(s)

This is a code question , not a wiring question.

New installation for fixed electrical heating

The main source of heating in this home is two gas furnaces . The fixed electric heater(s) ,
will be installed in 4 bedrooms as a supplemental source of if needed. 2 per room and 1 in the 4th bedroom. The units from what im told will not be on all the time.


NEC (2002) Art 220.15 Load calculations states ? shall be computed at 100% of the total connected load.

The total load for the fixed electrical heating is 3500 VA 240\3500 =14.5A.

The gas furnaces loads with motors etc total 2880VA

AC Load 6200VA


My question is where does this fixed electrical heating ( not on all the time ) figure into the load calculations.

I know that in the load calculations you choose the higher of the demands of AC or Heating, but I don?t think this is the case because the furnace(s) are the main heating source for the house and the AC system is the higher KVA of the both. My question is where does this fixed electrical heating ( not on all the time ) figure into the load calculations. I was thinking of fasted in place appliances . But you de-rate fasted in place by a 75% demand factor. NEC 220.15 states 100%. For the fixed in place space heaters Im not sure where this goes, Never had this situation before.

Not sure where to put this calculation. Im the only one on this job. The boss is out of town, the lead electrician is with him, and no one knows at the office.

Great community. First time here.

Steven,
JE98 , 2 years
 
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bphgravity

Senior Member
Location
Florida
Re: NEC 220.15 Fixed Heating, load calulations

In my opinion, you simply need to add all the heating loads together and consider it as one heating load. There is the exception to 220.15, but this doesn't tell you how much less than 100 percent can be used when all the units do not operate at the same time. I guess that is up to the AHJ.
 
peter d

peter d

Senior Member
Location
New England
Re: NEC 220.15 Fixed Heating, load calulations

I find it a little odd that a home with 2 gas furnaces is using supplemental electric heat. ;) .

Electric heat is not cost effective here either. (Land of the 14 cent kilowatt hour)
 
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stevenj

Member
Re: NEC 220.15 Fixed Heating, load calulations

Bryan, thanks. I was thinking the same thing and looked up the 220.15 exception later today in the hardcover nec at I have at home. I have to go to the inspectors office for another job permit tomarrow. Im going to see if he will give the approval for ampanacity for less the 100% on this.
 
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stevenj

Member
Re: NEC 220.15 Fixed Heating, load calulations

John, I checked this out lastnight nec 424.3, today I checked 440.34 mentioned in 424.3. got it . I think some deffentions need to be added. , bit have,nt pick up the 2005 yet. I I'll being doing that this weekend. I still run this the by the AHJ tomarrow.

thanks.
 
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stevenj

Member
Re: NEC 220.15 Fixed Heating, load calulations

Pete, thanks. I see your point for sure. I asked the owner the same question Why. I guess his theory is less money spent during fall @ 70 cents per therm for gas,and 89 in the winter. very steep. electric .11 per kWh. much cheaper.

The electric company here has an advertisement here that states. " We don't make a profit on gas we just bring to your home".

I never heard of a company in business not to make a profit.
 
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