wire gauge change mid circuit

Discussion in 'Electrical Forum discussion & Blog' started by rockycmt, Jan 8, 2009.

  1. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    Question,
    Am I allowed to change a 12 gauge circuit to a 14 gauge lighting circuit? I would expect the other way to be an absolute no no.

    Thanks in advance
  2. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Only if the breaker was a 15A breaker.

    14awg = 15A
    12awg = 20A

    Why would you even consider that?
  3. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    Yes obviously. Just wanted to know if it would pass inspection if he saw 2 different gauges even though the breaker was still 15amp.

    TY
  4. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    What do you want to do?
    Put a 15a breaker (1800 watts) on 12g wire
    --allowed, but as stated - why? breakers are the same $$

    You can hook up lighting to a 12g circuit (2400 watts)

    Do you want to run 14g wiring now to lights from a 12g circuit?
    I would never mix wiring in a circuit, not sure about code on that
    The problem is when someone looks at the wire in the breaker panel, sees 12g wire & upgrades the breaker to a 20a
    The 14g wire may be hidden & unknown
  5. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    Sorry,
    I didn't answer your question.

    Well the house was rewired with 200 amp before I bought it and I see 2 cases of it done. I guess it was cause the installer had extra 3wire in 14 that he used instead of getting more 12/3. Kind of cheap. I plan to replace it when I redo that room so if I evern need to change 20amp I will be set in the future.

    Thanks
  6. jamiedolan

    jamiedolan New Member

    Messages:
    28
    Location:
    Wisconsin
    I would ensure the 12 awg in your panel is clearly labeled "warning connected to 14awg wire, must be protected by 15A breaker"

    Yes, I have seen this done, and I don't know why they did it either. It is wrong. You can have a smaller gage wire connected to the 12gage and maintain 20A protection, but only if that smaller gage wire feeds (and is attached to by the manfacture) a UL approved fixture (i.e. hanging lamp with 16 gage cord)

    What do you mean it was because he had an extra 3rd wire in the 14? When I hear things like that, I think MWBC, use due caution.

    Jamie
  7. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    I feel the installer used 14/3 (Cause he had it on hand) to wire a ceiling fan instead of purchasing more 12/3 to keep the gauges the same. He cheaped out.
  8. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    I doubt The installer was an elictrician....most likely a H/O not knowing any better.
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    I don’t know of a qualified electrician that would automatically up grade a 15 amp overcurrent device to a 20 amp no matter what size wire it was installed on.
    This type of question is one of those thousand question that the average Do-It-Yourselfer wouldn’t ask about that could end up getting someone hurt.

    Twice you have said that the installer did something that was cheap. I often will leave a panel with #10 and later change over to #12 and install a twenty amp breaker. This is something done every day where the well is a long way from the house.
    I have also left the panel with #12 and changed over to #14 where there was a long pull such as on the second floor of a house with the panel on the outside wall of a two car garage. This #12 being protected by a 15 amp breaker was installed for the same reason as the #10 to the well, voltage drop.


    First lesson is that it is the overcurrent device that determines the amperage of the circuit not the wire. There is no need to label anything as everyone should know that you never replace an overcurrent device with a lager one no matter what size wire is installed. This in itself is a big NO, NO!
  10. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    If a homeowner asked an electrician to upgrade a 15a breaker in the box connected to 12g wire an electrician wouldn't do it? I highly doubt that. I've had people post that their electrician didn't even run GFCI for an outside outlet
    I never downgrade wire in a run (12g or 14g), just asking for trouble down the road. I can see doing it with #10 for a long run to a pump
    And if the lower gauge wire is hidden, how is anyone to know its there?

    The majority of breakers in my old panel were 15a breakers. Wire was too old to properly judge the gauge, one circuit was 2 wire only, no ground. About 90% of my house has been rewired & brought up to code

    I would never replace a breaker without verifying what was connected & the wiring run. But again if the lower gauge wire is hidden in the wall your kinda screwed. But I doubt most homeowners would think that someone "went cheap" & used mixed wire in a run. Most know nothing about voltage drop. They see 12g wire, that can handle 20a

    The problem always is, not necessarily what is wired/ completed know - but what might be changed years down the road by a new owner or another electrician
  11. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    Not my problem, if you dont know what your doing then dont do it... :rolleyes:
  12. maintenanceguy

    maintenanceguy In the Trades

    Messages:
    107
    Location:
    Pennsylvania
    It seems a little odd but not wrong.

    Wouldn't raise any red flags for me. As long as the CB is sized to protect the smaller wire size, no problem. Feel free to run 4/0 bugged to 14g as long as it's got a 15A breaker.
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    An experienced electrician would not change a lower amperage with a higher amperage overcurrent device.
    Now maybe an inexperienced Do-It-Yourself Idiot might.
    Rule 1- Never change an overcurrent device for a lager one.

    Remember that at one time they wasn’t required to install them. Then again just because someone calls theirself an electrician does not mean that they are one

    This is a choice that you make but I can promise you that someone who is making installations for a living will do so simply because it is called making a profit.
    So why would it be alright for one installation and not for another?
    Ever thought about looking at the breaker size. This will give it away each and every time

    Why would you need to judge the gauge of the wire when you have a perfectly clear 15 amp overcurrent device telling what the amperage of the circuit is?

    Without knowing you are making the perfect argument for not allowing the Do-It-Yourselfer to enter the realm of electrical work. You are saying in a very loud voice that you don’t understand electrical installations.

    Again Never change out an overcurrent device for a larger one. This is the mark of ignorance. If one is going to just go around changing out overcurrent devices for larger ones why not just go all the way and do away with the darn thing completely. Shucks, it had a #12 so it must be good for at least 50 amps so lets just change it out, Silly, Silly, Silly.
  14. GabeS

    GabeS Remodel Contractor

    Messages:
    294
    Location:
    Brooklyn NY
    You can have a smaller gage wire connected to the 12gage and maintain 20A protection, but only if that smaller gage wire feeds (and is attached to by the manfacture) a UL approved fixture (i.e. hanging lamp with 16 gage cord)

    Is this really allowed? There's no danger of overheating?
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,834
    Location:
    New England
    It's the same idea of plugging in a lamp...the circuit is still protected at the CB and main wiring...the key is that the thing plugged in is adequate for its INDIVIDUAL load as an assembly. A table lamp certainly is unlikely to have 12G wire (more like 18g or even smaller depending on wattage), but will work and be fine on this higher current circuit. Same is true with wired in items - their individual internal wiring doesn't need to comply but they do have to pass tests verifying safe operation. I know for certain that my a/c compressor's internal wires are at least a couple gauges smaller than the required wiring up to it.
  16. GabeS

    GabeS Remodel Contractor

    Messages:
    294
    Location:
    Brooklyn NY
    Nice way to put it jad. Now I understand.

    What if someone added additional light fixtures to that one fixture that's on 14 gauge wire? Would that pose a risk? In other words if they added 6 or 7 high hats to that fixture.
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,834
    Location:
    New England
    As long as any wiring you add is adequate for the CB you have installed, you should be okay. To daisy-chain a bunch of lights, you wouldn't want to then switch to the small gauge wire they use internally - it must comply with the main circuit's requirements.
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