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Thread: furnace wiring

  1. #1

    Default furnace wiring

    Hi again all,
    I just got a call from the furnace installer saying the existing wiring isn't going to work (no ground and looks sketchy). I'd like to knock this out as I do my other basement project, but I'm surprised to see that my wiring books don't include any info on it. Is this something that's better left to a pro? I figured it'd be simple, just a new power line, on its own breaker. if this is something I can do myself, can someone point me to a diagram?

    the furnace is a 90% american standard if that matters.
    Check out my house blog and see where we are and how it hurt me! http://house1244.blogspot.com

  2. #2
    Join Date
    Jul 2005
    Location
    London, Ontario
    Posts
    263

    Default

    It's a 15A dedicated circuit (most of the time). Code varries from area to area, but here, AC cable should be used to connect to the furnace. This can be connected to NM cable in a junction box above the furnace. The AC cable has to be attached to a structural component; A stiff piece of metal runs from the ceiling to the furnace to support the AC cable.

  3. #3
    Join Date
    Dec 2003
    Location
    NY State
    Posts
    906

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    IMO furnace and boiler wiring is best left to a pro. No two units are alike and they can get pretty confusing if it is anything more than a basic unit.

  4. #4
    Join Date
    Jul 2005
    Location
    London, Ontario
    Posts
    263

    Default

    True. You really shouldn't mess with electricity unless you know what you're doing.

  5. #5

    Default

    dunno if this clarification is needed or not...I got home last night after I posted and the installer told me that the furnace is ready to go and he just connected to the old lines. At this point assume I only need to supply power (it's got power, but I need to re-do it with ground and in newer better shape wire). There's a switch on the side of the unit and a conduit that runs up to the ceiling fron that switch. I am assuming that everything after the switch is done and all I'd need to do is run a new 15a wire to the box in the ceiling and put a dummy cover on the box. is that something still best left to a pro?
    Check out my house blog and see where we are and how it hurt me! http://house1244.blogspot.com

  6. #6
    Join Date
    Dec 2003
    Location
    Kent, WA
    Posts
    8,427

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    If you are comfortable with doing basic house wiring and have a clue what you're doing, this is one of the simplest things you can do. The junction box where the conduit to the furnace connects with your new cable will need to be accessible (means you can remove the cover and get to the splices when you're done finishing that room without damaging the room finishing materials).
    Mark
    Kent, WA

  7. #7

    Default

    I'm comfortable with basic wiring. A question on the junction box. It currently has a pull chain light socket in it. My understanding was that the furnace should be totally alone on the circuit, but the installer said they like to have a light right there so they can work on the furnace. The corner of the room is kind of dark otherwise. The light wouldn't get used any other time since there's really nothing there and we have lights for the rest of it. Is that something I should consider leaving or will I get nicked for having a light on a circuit that's supposed to be dedicated?

    thanks again. I can't tell you all how much help this forum has been during the huge project that is my 1st house. you're all invited to BBQ when we're done.
    Check out my house blog and see where we are and how it hurt me! http://house1244.blogspot.com

  8. #8
    Join Date
    Dec 2003
    Location
    Kent, WA
    Posts
    8,427

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    This will depend on how the inspector defines Utilization Equipment. The code requires that a furnace be on a Indicidual Branch Circuit, and that type of circuit is defined to serve only one utilization equipment. I think you could argue that an airhandler that needed a separate condensate pump could use same circuit for both items. The question is whether the light is part of the utilization equipment or not. If the furnace was not there, would you have a light there?

    Perhaps the best solution is to use a ceiling light box as the junction box, but put a blank cover over it when its inspected. After that, decide if you want to replace the blank cover with a pull chain light.
    Mark
    Kent, WA

  9. #9

    Default

    thanks for the tips. if the furnace wasn't there we wouldn't have a light there. The condensate pump doesn't need it's own branch does it? I've got a GFCI outlet within 3 (2 maybe) feet of the furnace as they requested. Since the pump is part of the furnace, could I wire the furnace and drop a recepticle down to plug the pump into?

    I'm not pleased about the pump part of the job. they drilled holles everywhere for the line (drain not power) to get it to the drain for the washing machine. the house is 100 years old and I would prefer not to have holes drilled through the middle 3rd of our beams. I'll probably do exactly as you say and put a plate over it for inspection and if I don't forget I'll put the light back. If I do forget I can always put the light in when it's time for service or they can use a shop light like they did on the instal.
    Check out my house blog and see where we are and how it hurt me! http://house1244.blogspot.com

  10. #10
    Join Date
    Nov 2005
    Location
    SC
    Posts
    593

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    A light at the furnace is required for servicing, as well as a receptacle withing 25ft. As long as the furnace power can be disconnected without killing the light, and since it is an old house, a reasonable inspector will allow the light to stay on the same circuit. A lot depends on how reasonable your inspector is.

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