# Furnace wiring



## papaotis (Jun 8, 2013)

never saw it done thatway, but not sure about code, doesnt sound right.


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## B4T (Feb 10, 2009)

You shouldn't have to be running wire through a furnace.. :blink::blink:

Just run it to the side where the controls are... most are pre-wired and they give you a 1900 box for doing line voltage connection..


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## papaotis (Jun 8, 2013)

B4T said:


> You shouldn't have to be running wire through a furnace.. :blink::blink:
> 
> Just run it to the side where the controls are... most are pre-wired and they give you a 1900 box for doing line voltage connection..


totally agree!:thumbup:


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## ponyboy (Nov 18, 2012)

What's the problem. There's a whole mess of 120 volt to ground wires floating around behind the panel door of a furnace

If that bothers you then you'd flip your wig if you saw some of the cheap AHUs I've worked on


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## asphalt (Jun 2, 2011)

B4T said:


> You shouldn't have to be running wire through a furnace.. :blink::blink:
> 
> Just run it to the side where the controls are... most are pre-wired and they give you a 1900 box for doing line voltage connection..


This is my thought as well, but when you have HVAC installers trying to ruin your day at every turn and pinning the j-box side of the furnace against a wall, they just ask why you can't go through the other side and run through the furnace. I keep telling them no, but would love to give them a better reason so maybe they'll shut up for a few minutes and stop telling me how to do my job. 

Most of the time this sort of thing is not a problem at all, but when they're having a bad day, I get to have a bad day too.


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## asphalt (Jun 2, 2011)

ponyboy said:


> What's the problem. There's a whole mess of 120 volt to ground wires floating around behind the panel door of a furnace
> 
> If that bothers you then you'd flip your wig if you saw some of the cheap AHUs I've worked on


It doesn't make me flip anything really, but it just doesn't seem right. Just trying to be as educated as possible about my new job. :thumbsup:


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## B4T (Feb 10, 2009)

asphalt said:


> This is my thought as well, but when you have HVAC installers trying to ruin your day at every turn and pinning the j-box side of the furnace against a wall, they just ask why you can't go through the other side and run through the furnace. I keep telling them no, but would love to give them a better reason so maybe they'll shut up for a few minutes and stop telling me how to do my job.
> 
> Most of the time this sort of thing is not a problem at all, but when they're having a bad day, I get to have a bad day too.


So what happens when the same HVAC installer has to remove the sides to service the internal parts...

Sounds like these "installers" don't have a clue about planning a job right...

ALL furnaces need new replacement parts at some time... having access is basic common sense if you know how to do your job..


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## ponyboy (Nov 18, 2012)

Can't find anything on it in the book. I'd say it's fine unless it states somewhere on the unit that it's not allowed. It might not be considered good practice but I see no harm at all


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## davis9 (Mar 21, 2009)

Most "furnaces" these days have reversible jbs inside able to be used on either side. Easy to swap.


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## robnj772 (Jan 15, 2008)

asphalt said:


> The HVAC installers at my company keep telling me that it's okay to run wire through the furnace cabinet to the junction box inside the the cabinet. I keep telling them it's a no no. As the administrator I should probably know this, but can't for the life of me find a code about it. I seem to recall my last company being written up for something like this at some point, but it was a long time ago. Can I run wiring for a gas furnace through one side of the furnace to the junction box on the other side and inside the furnace? The wiring would be exposed inside the cabinet with all the other control wiring. Is this something you could do with MC or NM? Thanks in advance for any help. :thumbsup:


You could also just move the junction box to the other side, I have done that in the past.


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## asphalt (Jun 2, 2011)

davis9 said:


> Most "furnaces" these days have reversible jbs inside able to be used on either side. Easy to swap.


I try to do that when I can, but today the j-box was pinned against the wall and the screws to move it were on the outside (wall side) of the furnace. I'm mostly just looking for information to help deal with the questions these installers ask about why I can't do my job the way they want me to.


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## buddhakii (Jan 13, 2011)

So are you running this wire through the airway of the furnace? If so then the wire would at least have to be plenum rated.


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## asphalt (Jun 2, 2011)

ponyboy said:


> Can't find anything on it in the book. I'd say it's fine unless it states somewhere on the unit that it's not allowed. It might not be considered good practice but I see no harm at all


This is where I've been going with it; it doesn't seem right to me, it doesn't look right, and I won't do it just to make your job easier. HVAC installers can be big babies sometimes however, so I like to be as informed as possible. 

I'll have to look at the documentation for the furnace tomorrow.


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## Voltron (Sep 14, 2012)

Most furnaces have a 1/2" knockout where you should set your box and enter for a reason I'd imagine, like replacing parts...and staying out of their way. We usually sleeve a 1/2" emt down and set a handy box if just for sp switch for means of disco. I think it would be a matter of external location that would be the issue rather than having your wiring coming through one side or another.


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