I did a kitchen remodel recently that was all in flex that had it's 15a light circuit on a 3 wire circuit with some 20a plugs so the neutral was pulled in 12 with a 14 and 12 for the hots. When I wired the new cans I used 12 romex to keep the neutral 12 throughout the circuit and the boss man wanked that I had used 12 instead of 14. Could I have used 14?
Quick question regarding neutral wire size for 3 wire 15/20a circuit.
- Thread starter Evan(CA)
- Start date
Mustang51js
Well-known member
If its a 20 amp line then it has to be 12. If its on a 15 amp breaker it could be 14. You cant have 14 on a 20 amp breaker
sberry
Banned
And they aint plugs.
It's a 3 wire circuit. One leg on a 15 and one on a 20 with a shared #12 neutral.
Alchymist
Well-known member
Never saw a double breaker where one side was 15 amp and the other was 20 amp. Are you running a MBC on two individual breakers?
wyliesdiesels
Well-known member
What size breakers and are they handle tied or common trip or double pole?
I dont even get why someone would do that. The cost savings are nil.
I dont even get why someone would do that. The cost savings are nil.
sberry
Banned
I saw a panel full of multiwire with different amps on the same 12 wire. The handyman didn't understand what the master ahead of him who came in and did what he did with everything proper ocpd, he used some 12/3 to go out to some Jboxes and they tied on to 14. Couple of them were wired on tandems and not next to each other.
There wasn't anything unsafe about it but it was not really for the non electrician, should have had a bigger panel to start with.
There wasn't anything unsafe about it but it was not really for the non electrician, should have had a bigger panel to start with.
I think you guys are misunderstanding the question. I simply want to know if it was necessary to keep the neutral sized to #12 on the light loads. The house was built in the 60's and was wired completely in flex. The lighting circuit is #14 on a sp15a breaker but is part of a 3 wire circuit with a #12 on a sp20a and a #12 neutral.
Alchymist
Well-known member
If you are running a 3 wire circuit (commonly called a MBC) and have a common neutral with one hot leg on a #12 with a separate 20 amp breaker and the other hot leg # 14 on a 15, you need to fix this. Reason being if you open up a box anywhere when one of the breakers trips and both hot legs are present, one wire will still be hot. MBCs require a common trip for that very reason.
Alchymist
Well-known member
Found this video:
wyliesdiesels
Well-known member
That circuit is a mess. Breakers need to be handle tied.
2 seperate single poles for a MWBC is a major no no.
Doing so makes it easy to overload the neutral.
Are they on opposite legs? Is there 240v potential between the hot legs?
theoldwizard1
Well-known member
Not sure if it is a code violation or not, but kitchen counter top outlet usually are NOT used to also power lights.
Alchymist
Well-known member
Agreed - AND, if both the #12 & the #14 are on the same phase, then even a #12 ground is undersized. CLuster F*** all the way around.
You guys are making a way bigger deal out of this than it is. Before 2008 MWBC's were not required to be on a 2p breaker and this was a VERY common way to wire tract homes and apartments etc in this area when using conduit. The breakers are phased correctly and everything is all existing and grandfathered in as code compliant as is. I'm simply replacing the 2 existing 4' fluorescent fixtures with 4 LED can lights.
My question was since I used romex and not flex to wire the cans and obviously couldn't pull a #12 neutral and #14 hot like the rest of the circuit so was I correct in using 12/2 or is the boss correct saying 14/2 would have been fine. Judging from all the overkill responses though I think it's safe to say no one is going to say 14/2 would have been fine
My question was since I used romex and not flex to wire the cans and obviously couldn't pull a #12 neutral and #14 hot like the rest of the circuit so was I correct in using 12/2 or is the boss correct saying 14/2 would have been fine. Judging from all the overkill responses though I think it's safe to say no one is going to say 14/2 would have been fine
alfredeneuman
Well-known member
The common disconnecting rule for the circuit breakers wasn't around in the '60s when this was installed. It didn't come into effect until 2008.
Pre-2008 it only had to come from the same panelboard.
Anywhere it branches off to the 15Amp circuit only (and not the 20Amp circuit) you could use #14 for the neutral
Pre-2008 it only had to come from the same panelboard.
Anywhere it branches off to the 15Amp circuit only (and not the 20Amp circuit) you could use #14 for the neutral
wyliesdiesels
Well-known member
For new construction, that is correct. The SAC(small appliance circuits) by code cannot power the lighting in a kitchen.
zmaxmotorsports
Well-known member
zmaxmotorsports
Well-known member
The 60's code went out the window when he started adding to the circuit.
wyliesdiesels
Well-known member
The 60's code went out the window when he started adding to the circuit.
Good point i didnt even think of.
The whole circuit needs to be updated now to be code compliant.
But it doesnt sound like the OP cares about that.
Alchymist
Well-known member
The 60's code went out the window when he started adding to the circuit.
Yup. When giving an advise on circuit changes , one should assume that any changes fall under current codes. OP got plenty of advise, most of it correct, weather he follows it or not is his choice.
sberry
Banned
He would be correct that the neutral of 12 would be safe and legal on an old install provided the circuits originated from alternate legs.
So in conclusion rather than spending an hour or 2 and 25' of romex you guys would spend a full day taking apart 15+boxes and pulling several hundred feet of wire or pulling a clean circuit from the panel and buy a new breaker because the 160w fluorescent lights were changed to 52w of LED lights? All this on a system that has worked flawlessly for 50+ years and up until 8 years ago would have been code compliant even as new construction. I'm glad I'm not your customer.
wyliesdiesels
Well-known member
Have fun when the inspector nails u for not updating a circuit after u added to it.
Wouldn't simply adding a handle tie to the breakers bring it into compliance? Is there anything in the NEC that prohibits using two breakers of different amperage for a MWBC as long as they are handle tied and the wire is sized for the higher amperage?
sberry
Banned
I mentioned above about a job with a congested panel with stuff hooked up all over the place. One circuit was shared N and has both on the same leg. It was a confusion error, not that the guy didn't know better but really didn't make much difference as it was on a light circuit with few watts and no recepts.
Cmreschke
Well-known member
This would be ok. There is nothing saying it has to be a 2 pole breaker, just has to be tied together so that you have to turn both off at same time. The breakers do not need to be common trip.
Mustang51js
Well-known member
No,i would change the breaker to a 2 pole 15 and be done with it. If its getting inspected.
Cmreschke
Well-known member
And this would be wrong, potentially. If the 20 amp ckt that is sharing a neutral with the lighting ckt is one of the small appliance branch ckts, then those must be 20 amp ckts.