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Gas furnace MCA and MOCP #189090
09/18/09 07:15 PM
09/18/09 07:15 PM
jem  Offline OP
New Member
Joined: Apr 2007
Posts: 8
I have been coming accross these Heil brand gas furnaces that do not have the MCA and MOCP on the nameplate. They list the maximum input current which I think is what the unit is rated. How do I calculate these values.

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Re: Gas furnace MCA and MOCP [Re: jem] #189091
09/18/09 07:25 PM
09/18/09 07:25 PM
gfretwell  Offline

Joined: Jul 2004
Posts: 9,186
This usually applies to HVAC compressors. Does this furnace have anything more than a blower, igniter and some controls?
When in doubt use 310.16 and 240.4(D)

Greg Fretwell
Re: Gas furnace MCA and MOCP [Re: gfretwell] #189106
09/19/09 02:09 PM
09/19/09 02:09 PM
jem  Offline OP
New Member
Joined: Apr 2007
Posts: 8
There is also a small combustion blower.

Re: Gas furnace MCA and MOCP [Re: jem] #189109
09/19/09 04:31 PM
09/19/09 04:31 PM
George Little  Offline
Joined: Jan 2004
Posts: 1,489
Michigan USA
Look at the manufacturer's installation guide for the furnace. Usually they will tell you what size circuit. Some even tell you what size wire to run and depending on the length of the run they may have you increase to the next size wire. I'm seeing some of your larger furnaces specify a 20a. circuit.

George Little


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