# Multiple furnaces on 1 ckt.



## Dash Dingo (Mar 3, 2012)

I got a building that has 12 forced air furnaces that I have to feed. I'm going to need all the panel space i can get.
Now I know in the code it says that central heating equipment shall be supplied by an individual branch circuit. 422.12.
But it does not specify if that branch circuit can serve multiple pieces of equipment.

Could you feed multiple furnaces on one circuit? Or does each furnace need its own circuit? I know its probably not the best idea, but I need panel space.


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## k_buz (Mar 12, 2012)

I would say no. It gives specific exceptions and multiple furnaces sharing the same circuit isn't one of the exceptions.


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## 3xdad (Jan 25, 2011)

:blink:
Dash, use as many feeders, sub panels and circuits, it takes. Don't put less importance on your install just to gain circuit spaces. :thumbsup:


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## Dennis Alwon (May 9, 2009)

IMO it is not an individual branch circuit if you serve more than one furnace besides most systems around here draw about 12 amps.


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> IMO it is not an individual branch circuit if you serve more than one furnace


Exactly that.


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## mbednarik (Oct 10, 2011)

Run a larger circuit, such as a 6/2, and you could feed 3 or 4. Just tap off of this 6/2 with a 14/2 and a fused disconnect for each furnace. I think a little sub panel would actually cost less, but I don't know your exact situation.


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## Amish Electrician (Jan 2, 2010)

OK: Put up or shut up time!

WHAT code says that? Where? Exactly what is said?

Produce the citation, and I bet nearly every response so far can be safely deleted.


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## RePhase277 (Feb 5, 2008)

Amish Electrician said:


> OK: Put up or shut up time!
> 
> WHAT code says that? Where? Exactly what is said?
> 
> Produce the citation, and I bet nearly every response so far can be safely deleted.


Article 100 defines an individual branch circuit as being a circuit that supplies only one piece of utilization equipment.

422.12, as already cited, says that central heating equipment shall be connected to an individual branch circuit.

However, would this not fall into article 424? Article 424.3(A) suggests multiple units can be connected to a circuit, but not over 30 A.


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## Dennis Alwon (May 9, 2009)

InPhase277 said:


> Article 100 defines an individual branch circuit as being a circuit that supplies only one piece of utilization equipment.
> 
> 422.12, as already cited, says that central heating equipment shall be connected to an individual branch circuit.
> 
> However, would this not fall into article 424? Article 424.3(A) suggests multiple units can be connected to a circuit, but not over 30 A.


I think the difference here is that 422. 12 is quite specific to central heating while 424.3 talks of 2 or more outlets may be for baseboard type heat. This. imo, does not allow more than 1 central unit on a circuit


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## I_get_shocked (Apr 6, 2009)

Have you tried talking to the inspector?


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## Amish Electrician (Jan 2, 2010)

Glad we all have the citations .... now the discussion can begin.

422.12 says "Central heating equipment ... shall be supplied by an individual branch circuit."

A few comments on 422.12: This is a section framed to address appliance generally, so we can expect further details further in the code. Please note that 'equipment' is one of those word that can be both singular and plural. The exceotion to 422.12 makes clear that 422 means 'equipment' is a broad sense, including not just the furnace, but whatever is associated with it.

Now, for 424. 424 is a more specific article, whose scope is: "This article covers ... central systems." 

424.3A goes on to discuss "branch circuits supplying two or more outlets for fixed space-heating equipment." 

Now.... how can a circuit dedicated to one furnace be allowed to have more than one receptacle? It can't. So, the inference that 'equipment,' as used in 422, cannot be limited to one piece of equipment. 

If you can have more than one receptacle, you can have more than one furnace. "Equipment" is clearly used as a plural noun. 

I'll even take it a step further, and assert that a gas heater (infra-red or radiant type) is simple 'fixed space heating equipment,' and not the 'infrared' type heaters discussed further along.

So, I'd say you can have all manner of heating equipment supplied by that one circuit. Multiple igniters and multiple blowers, on multiple furnaces ... even in separate mechanical rooms. You can even supply the air conditioner from it - but that's another thread.

You can see now why I was so blunt in calling for a specific citation, and insisted on looking at the specific language. There is nothing to suggest that 422 meant 'only one furnace,' and plenty of contrary evidence. he authors could have said 'appliance' (a singular noun) rather than 'equipment,' had that been there desire.

In perspective, it would be pretty darn silly to supply multiple igniters with multiple circuits. 30 amps - allowed for the heating circuit - is a lot of power for an igniter. It should be obvious that the code panel presumed (per Article 90) that readers were already educated in the trade, and would not do anything so silly.


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## Dennis Alwon (May 9, 2009)

Unless you have radiant heat a gas unit generally has a blower motor that can draw 12-15 amps. Most of the units state in the instructions that it should be an individual branch circuit.

In the case of a radiant system I am not sure this would apply.


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## Amish Electrician (Jan 2, 2010)

Under the 'educated in the trade' catch-all, I would hope that readers of this forum would already know about circuit sizing, etc. A 30-amp furance won't work too well on a 15-amp circuit, even if there is only one.


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