Wire Size vs. Breaker Size vs. Application

[89MustangGX]

I think/thought I knew the answer but I keep going back and forth, so allow me to ramble for a minute and then tell me the real answer...

Working on a small stable on my property that was here when I bought. It consists of a single duplex 20A GFCI receptacle, and several lights on a switch. It is wired with 12-2 from the breaker to a junction box, which then splits and goes 12-2 to the receptacle in one run and 14-2 to the switch and then 14-2 to lights in another run.

My first thought is that a 15A breaker is the safe bet, matches the lowest gauge wire, and would likely never be an issue in there with the limited items likely to use the receptacle. However it would require changing the current receptacle to a 15A unit instead of the 20A now installed to be right.

My other thought was that a 20A breaker would be ok since it is 12-2 to the receptacle and I don't see how a few 100 watt bulbs in there could overload that 14-2 wiring, let alone the 12-2 wiring. But I *think* the breaker should normally match the smallest gauge wire. But, does the fact that these are lights on the end of a run change that? Could a large draw at the receptacle feed into the 14 gauge wire and overload it since it is connected -- even though it is further downstream?

This is where I am going back and forth.

So, can this be a 20A breaker or does it need to be a 15A breaker?

Thanks!

 

[mbatarga]

By code, has to stay 15A due to the 14-2 wiring.

 

[Norcal]

Has to stay 15A due to the 14 AWG, there are those who thought that using the 12/2 for the lighting circuits then using 14/2 for the switch legs was fine too but that just means the same thing 15A circuit breaker max.

 

[89MustangGX]

That's what I initially thought - thanks for double-checking me.

 

[wyliesdiesels]

breaker is sized by gauge of wire. since theres #14, it needs to be protected by 15a breaker.

how is this stable powered? subpanel?

 

[89MustangGX]

how is this stable powered? subpanel?

Yes- there is a subpanel in the shop, wire runs underground to stable from there. If there was a panel in the shop it wouldn't even be a question I'd just split the branch. But I'm not inclined to re-run wires for an outlet that I'll probably never come close to maxing out. Although I suppose if I wanted to I could install another subpanel in the stable -- but again a lot of work for something I'll probably never need.

Unless you had another idea?

 

[TractorJeff]

Could the OP leave the feed and outlet on the 20 amp breaker, then come out of the receptacle box to a box that has a 15 amp breaker to feed the 14-2 switched lights?
In effect a "mini"-panel in the Stable?

 

[liliysdad]

Are you even in a location where it matters what code says?

 

[mike93lx]

Are you even in a location where it matters what code says?

Code always matters, inspection or not. It isn't just red tape, it is safety driven.

 

[mike93lx]

Could the OP leave the feed and outlet on the 20 amp breaker, then come out of the receptacle box to a box that has a 15 amp breaker to feed the 14-2 switched lights?
In effect a "mini"-panel in the Stable?

Sure, but why bother unless the 15a breaker poses a problem?

 

[liliysdad]

Code always matters, inspection or not. It isn't just red tape, it is safety driven.

Sometimes, sure. Other times, its red tape that serves no real purpose. TO each their own....but if I don't need to pass an inspection, I will use common sense...like the scenario in question.

 

[wyliesdiesels]

Are you even in a location where it matters what code says?

What if he is not?

Does that mean he could just use whatever wire size and to hell with the ampacity tables?

Lets say use a #12 for a 60a circuit. After-all, he lives in a location where code doesnt matter...

 

[wyliesdiesels]

Sometimes, sure. Other times, its red tape that serves no real purpose. TO each their own....but if I don't need to pass an inspection, I will use common sense...like the scenario in question.

Please cite a code that serves no real purpose. Go ahead, I’ll wait...

 

[theoldwizard1]

When my buddy rebuilt his horse barn, the electrician told him all wiring needed to be in EMT because the building was housing live animals.

Not sure how the horses would get to the second floor ...

 

[mike93lx]

Sometimes, sure. Other times, its red tape that serves no real purpose. TO each their own....but if I don't need to pass an inspection, I will use common sense...like the scenario in question.

********

 

[alfredeneuman]

********

^^^^^^

 

[rlwhitetr3b]

I'm not an electrician, but have taught some residential wiring in a vocation high school years ago. I thought there was something about the switch loop for a light could be 14g on a 12g circuit protected with a 20 amp breaker. My definition of a switch loop is the wire running from the light to the switch. I'm not sure that is what the OP is describing. NEC 240.5 (B) (2) talks about wire sizes for fixture wires and seems to support my memory. If an electrician thinks I have misinterpreted the code, I will concede.

We used 12g for everything as I did not trust the students not to grab the wrong size wire.

 

[ssdave]

Code says 15 A breaker for 14 ga.

For years, most building inspectors have allowed, and residential wiring electricians have run, 20 amp circuits where they were needed (like baths) and wired the switch legs to lights with 14 ga.

Technically, not right, in reality, very low risk and commonly accepted. I would only do it for switch legs to a light fixture, or group of fixtures, not for multi-outlet or multiple light circuits.

Personally, I'd put in a 20 amp breaker, and not worry about it. The lighting part of the circuit will not see a deliberate overload, and a fault overload will very likely trip the breaker long before the 14 ga wire heats up.

 

[89MustangGX]

Thanks again for the replies. I see this has generated some good conversation and I'm not the only one who can see it go either way.

I don't have to pass an inspection, but I feel like if I'm not at least trying my best to meet code requirements, I'm really just doing hack work -- plus I might need an inspection some day, even if just for selling the property.

I appreciate the info, especially on the history of running 14 ga on 20 amp circuits in the switch leg. I'll probably just stick with 15 amp breaker because I don't need the 20. But, I don't think I'd feel bad about running a 20 in this case either after seeing some more experience.

Thanks again.

 

[sberry]

There is only 1 place they actually allow this, run a 14 to a light on a 20A. Anyone know where its at?
In a pure electrical sense it doesnt pose risk but,,,, where you draw the line and they write the code for really good reason, sometimes there is stuff doesnt really occur to us especially at first thought.
I got a call from the handyman at a local church, they were having some trouble with comprehending some matching wire and breaker sizes. It was a crouded ****** with a gob of tandems, the last guy in it was a real master,,,, he is not the type to find any extra work but he aint gonna leave it with the wrong breaker. Saved some congestion to use 3 conductor on some rework and he likely had only 12 on the truck and if they followed it to the first J box would have seen it changed to 14. It was really in there and I did find one p[lace he had got a multi wire on the wrong leg,,,, but,,, went to a couple minor light circuits, no outlets. I did fix it although it didnt create a hazzard. Risk of overloading the N pretty minor especially given a 12 on a 15.

 

[sberry]

I was in a house a while back that had a 16 lamp cord in the wall 60 years as a switch loop for a kitchen light. I was trying to decide if the guy really understood it or didnt??? ha

 

[liliysdad]

Code says 15 A breaker for 14 ga.

For years, most building inspectors have allowed, and residential wiring electricians have run, 20 amp circuits where they were needed (like baths) and wired the switch legs to lights with 14 ga.

Technically, not right, in reality, very low risk and commonly accepted. I would only do it for switch legs to a light fixture, or group of fixtures, not for multi-outlet or multiple light circuits.

Personally, I'd put in a 20 amp breaker, and not worry about it. The lighting part of the circuit will not see a deliberate overload, and a fault overload will very likely trip the breaker long before the 14 ga wire heats up.

Imagine that.. someone applying common sense.

 

[sberry]

The code doesn't have provisions that say do it any way you think you understand it. No where does it say if a guy thinks it's ok then it's fine to do it that way.

 

[mike93lx]

Imagine that.. someone applying common sense.

Justify it however you want

 

[ssdave]

Justify it however you want

And, you are free to install all the matched components you want. I could just as easily install a 15 amp breaker, but leave the 20 amp receptacle. Either way would be a technical violation, neither would be unsafe. To go to the effort and cost to change out a receptacle and a breaker, to make no practical difference in the safety of the circuit, is not particularly productive.

Given a perfect world, just conform to code, as a minimum, and exceed code where it makes sense to do so.

Given an existing situation, make it as safe as you can, while still making it usable. If a technical violation, but no safety problem exists, and moving it to code reduces the performance of the item, I'd go with safe, but technically violating. Or, if code for the sake of code really bothers you, just make it code compliant. This whole thing has been argued for 25 years or more, along with the use of 15 amp rated switches and receptacles on 20 amp circuits. Now the new thing to argue is whether you can install a 150 watt equivalent LED bulb in a fixture that is rated for 60 watt bulbs.

 

[wyliesdiesels]

And, you are free to install all the matched components you want. I could just as easily install a 15 amp breaker, but leave the 20 amp receptacle. Either way would be a technical violation, neither would be unsafe. To go to the effort and cost to change out a receptacle and a breaker, to make no practical difference in the safety of the circuit, is not particularly productive.

Given a perfect world, just conform to code, as a minimum, and exceed code where it makes sense to do so.

Given an existing situation, make it as safe as you can, while still making it usable. If a technical violation, but no safety problem exists, and moving it to code reduces the performance of the item, I'd go with safe, but technically violating. Or, if code for the sake of code really bothers you, just make it code compliant. This whole thing has been argued for 25 years or more, along with the use of 15 amp rated switches and receptacles on 20 amp circuits. Now the new thing to argue is whether you can install a 150 watt equivalent LED bulb in a fixture that is rated for 60 watt bulbs.

If the wire is 12ga then yeah no safety problem per se

But what if the wire is 14ga and the breaker is bad (zinsco, FPE, etc; take your pick of bad breakers) and doesnt trip upon overcurrent. THEN you have a problem... theres a reason the code is the way it is

 

[HenryAZ]

Why not just use 12ga for the lights, and a 20amp breaker?

 

[sberry]

He isn't wiring this new. The easy thing is to simply leave the 15 on it, long as it's not tripping and serving the load it's not a problem. Changing it doesn't gain anything if it's not tripped.

 

[ssdave]

If the wire is 12ga then yeah no safety problem per se

But what if the wire is 14ga and the breaker is bad (zinsco, FPE, etc; take your pick of bad breakers) and doesnt trip upon overcurrent. THEN you have a problem... theres a reason the code is the way it is

If you have a bad breaker, doesn't matter what amperage it is, if it won't trip. It will cause a fire just as easily with 12 ga wire as with 14.

My point isn't to come up with a bunch of "what-it's" to debate with.

The scenario this guy has, existing, is that he has the lights from a switch on a 14 ga wire. He wants to replace the breaker. He has a receptacle that will accept a 20 amp plug, and it is correctly wired with 12 ga. Depending on whether he puts in a 15 or a 20 amp breaker, one item or another is a technical violation of code.

His question was whether he should fix one of those things to totally conform to code, or whether to just leave it be.

My answer was, and remains so, that it is a technical violation of code, but not a safety one to install either breaker without changing out the wire or the receptacle. I'm not going to speculate that he's going to put in a select breaker that is defective. I also acknowledge that it's best to build to code. It was written for a reason, but also can't cover every scenario, so is very occasionally conservative.

If he puts in a 15 amp breaker and doesn't downgrade the receptacle, he's still safe. If someone plugs in a 20 amp item into the receptacle, it will trip the 15 amp breaker, and even if it doesn't, he has 12 ga wire feeding it. So safe.

If he puts in a 20 amp breaker, the receptacle will still be properly fed, and the 1 or 2 amps that the lighting circuit will load the 14 ga wire will be perfectly within it's ampacity. So safe. A very selective fault that causes more than 15 but less than 20 amps of overload will probably still be within the safety margin of the 14 ga wire, and cause a larger current that trips the breaker before it starts a fire.

We can put in a bunch of scenario's where a future owner wires a heater into the 14 ga wire, switched light circuit, or such, and replaces the breaker with a defective one, but the defect and safety problem would have been deliberately created by the future owner, not the OP.

I'm not talking about generally using 14 ga wire on 20 amps circuits. NO. Just wire it right, and use the right breaker. I'm talking about the very specific scenario the OP has. No more, no less.

 

[Aceman]

A 15 amp breaker would be the size to use for this circuit.

The 20 amp duplex is not correct on a 15 amp circuit, but it does not justify installing a 20 amp breaker on a circuit that is also utilizing #14 for lighting either.

 

[nadogail]

Add me to the list of those who are saying that if there is 14 Gauge wire involved, 15 Amps is the maximum breaker size allowed.