rathrbefishn

Can I mix 12/2 and 14/2 guage on a 15 amp circuit?

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I am trying to help my stepson reroute some light switches in his unfinished basement to better accommodate some new shelving.  The previous homeowner looks to have done a lot of the basement wiring when he built a workshop and finished part of the basement . It's a 15A circuit wired with 12/2.  I know that only 14 gauge is required for the circuit, but is it OK to blend gauges? I can see that there would be a concern that someone in the future might try to convert it to a 20amp circuit if they saw 12 gauge near the panel.  The reason I ask is that I have a big roll of 14/2 in hand and I am amazed at what wire runs these days.  It was about $80 for a 50 ft roll of 12/2 at the box store today. I also discovered that plastic switch boxes are now in short supply-  Tried to get a 3 gang old work box for another effort and there were none to be found at the box store nor local electric supply house. 

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Yes you can mix but the circuit breaker must not exceed the smaller wire. Now the problem comes later of someone was to see like you’ve stated a larger gauge in the panel with a smaller breaker size than typical. Confusion can be eliminated to some extent by bringing only the smaller gauge into the panel so it’s size matches the breaker. You can mark the wire in the panel and any junction boxes to indicate circuit size. Markings like, not to exceed 15 amps. 

 

The old work box, look for the metal style which can be ganged together to form a larger size. Mounting of them is either with Madison bars or a clip that mounts to the sides and you’d tighten them like a toggle. 

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I'm not an electrician, but my understanding is you don't put 14ga in a 20amp circuit, but there's no reason I can think of that you shouldn't put 12ga in a 15amp circuit. The reason being a 20amp breaker won't always trip before 14ga wire potentially gets too hot...that's not a concern on a 15amp circuit, both 14 and 12 would be fine.

 

**That doesn't mean some idiotic code says ya can't do it :) 

 

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54 mins ago, TimS said:

I'm not an electrician, but my understanding is you don't put 14ga in a 20amp circuit, but there's no reason I can think of that you shouldn't put 12ga in a 15amp circuit. The reason being a 20amp breaker won't always trip before 14ga wire potentially gets too hot...that's not a concern on a 15amp circuit, both 14 and 12 would be fine.

 

**That doesn't mean some idiotic code says ya can't do it :) 

 

This is why I was asking.  I cant' see a reason why it would be a safety problem but I dont' want them to hit a code issue when they go to sell their house in a year or two- 3 young kids and they are outgrowing their house

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I don't think that $80 is to much to pay for an easy sleep after.

44 mins ago, rathrbefishn said:

but I dont' want them to hit a code issue when they go to sell their house in a year or two-

 

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14 hours ago, TimS said:

I'm not an electrician, but my understanding is you don't put 14ga in a 20amp circuit, but there's no reason I can think of that you shouldn't put 12ga in a 15amp circuit. The reason being a 20amp breaker won't always trip before 14ga wire potentially gets too hot...that's not a concern on a 15amp circuit, both 14 and 12 would be fine.

 

**That doesn't mean some idiotic code says ya can't do it :) 

 

^This^ 

 

I don't believe it is against code. 

Personally I would not do this in the panel as someone could mistaken the circuit as 20 amp and change the breaker. 

BUT.... as a pigtail somewhere, I see no harm. 

 

There must be an electrician here who could answer this definitively. 

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You have to remember the elec code is minimum. This means you can go past these guidelines. 

 

There is no code violation if a larger sized wire is used on a lesser value breaker. We always have notes on our plans that dictate minimum size 10gauge wire. This includes any 20 amp circuits. If and when the distance increases but the circuit is still only a 20 amp breaker protected the wire could be significantly larger well up into 4 gauge plus if needed. If that size doesn’t fit under the screw of the breaker we have a couple options, you can pigtail a smaller size to fit the screw or they make a crimp which can take a much larger wire to a much smaller screw size. 

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I know this is well off the original path of conversation but we’ll do something like this when a circuit is decreased and we have existing wiring that is larger and there is no need to remove only to replace. This is also used for voltage drop situations of distance where the wire is much larger for a circuit size. 

 

You could physically take a 4/0 cable and fit it under a screw of a 60 amp breaker.  

 

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yes you can i have plenty of wire and boxes in stock in south jersey and our locations in PA.

Yes there was short supply of both items just like anything pvc as the resin to make them was in short supply due to the 2 main factories closed because of covid.

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If it was a very long run #12 would actually be required for that 15 amp circuit, so no I do not see any problem at all with using your cable. But some sort of note on the cable or box is an excellent idea.

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It is not a violation of NEC as far as I know, but some towns/states have weird things in their codes about mixing wire sizes. Also, even if it's not a code violation that doesn't mean a local inspector won't make you change it if he sees it. Inspectors can bust your chops on stuff like that because 1) it's not a common practice and they don't like seeing weird things and 2) it's not very professional and they don't like that either. 

Either way, it's not  safety issue as the breaker is sized correctly for the 14 gauge wire. 

That being said, why would they need an electrical inspection if they go to sell the house? Most routine home inspectors wouldn't be opening junction boxes to check wire sizes or anything. 

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8 hours ago, Finneus said:

It is not a violation of NEC as far as I know, but some towns/states have weird things in their codes about mixing wire sizes. Also, even if it's not a code violation that doesn't mean a local inspector won't make you change it if he sees it. Inspectors can bust your chops on stuff like that because 1) it's not a common practice and they don't like seeing weird things and 2) it's not very professional and they don't like that either. 

Either way, it's not  safety issue as the breaker is sized correctly for the 14 gauge wire. 

That being said, why would they need an electrical inspection if they go to sell the house? Most routine home inspectors wouldn't be opening junction boxes to check wire sizes or anything. 

Inspectors will never give you a problem for over doing the code. If a question were to come up and an inspector was being troublesome, a simple call to the states DCA gets the answer very quickly. The DCA, lets obviously state the electrical division will answer any question and send you a copy of the relevant code in response to your question for you to hand to the inspector. Yes, this won’t piss off an inspector if done with respect to them. When I had my own business if I questioned the decision made by an inspector I would call the DCA directly and talk to the person in head of the electrical there. 

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1 hour ago, saltfisherman said:

Inspectors will never give you a problem for over doing the code. If a question were to come up and an inspector was being troublesome, a simple call to the states DCA gets the answer very quickly. The DCA, lets obviously state the electrical division will answer any question and send you a copy of the relevant code in response to your question for you to hand to the inspector. Yes, this won’t piss off an inspector if done with respect to them. When I had my own business if I questioned the decision made by an inspector I would call the DCA directly and talk to the person in head of the electrical there. 

In my experience most inspectors are more even handed and willing to work with professionals much more so than homeowners. I've seen them fail a job over minor issues and tell homeowners that they should just hire a pro to avoid these problems in the future. 

Even if you're correct on a code issue if it's a small matter it's sometimes easier to change it to make them happy rather than fight them on it. Obviously this doesn't apply with big issues where the change would cost you a lot of money. 

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