How often does anyone see a shared neutral used with the (2) kitchen appliance circuits? I've seen it one other time, but decided to go with it instead of re-wire. Can someone share their philosophy as to why this would need to be replaced if given the chance, or accept it as we do the diswasher/disposal?
Kitchen Appliance Branch Circuit Shared Neutral
- Thread starter euclid43
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
There is nothing inherently wrong with a properly installed and used MultiWireBranchCircuit (MWBC). But you need handle ties on the breakers, so they had better be adjacent in the panel. And, of course, they have to be on opposite phases. Make sure that the neutral is not shared with any more than just those two circuits, and do not plan on installing feed-through GFCIs.
The voltage drop in the two SABCs will be no higher, and sometimes lower than it would be with separate neutrals.
You, or whoever works on the circuits in the future will need to keep in mind the shared neutral when troubleshooting, rewiring, etc. (the handle ties on the breakers will help for that.) And make sure that the neutral connections all the way back to the panel are solidly wired or you will likely burn up some other devices one day when you turn on the toaster or the coffee maker. Good wiring practices will minimize the chances of that.
- Occupation
- Licensed Electrician
Every circuit in my kitchen is a MWBC so I guess you could say I see a shared neutral used with kitchen circuits nearly every day. I wired it this way. I don't see any reason to replace them in my house or any other house.
Oh, and by the way, for about a hundred years we did not need handle ties to be safe or code compliant.
The reason to use them is because they are efficient and there is no good reason not to.
1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
I see it quite often in my area.
I was working on a Home Inspection Repair, just last week, where the SABC's were Multiwired. I had a neutral connection come loose and it caused the countertop Microwave to burn up.
First time I've had to replace and appliance.
I was working on a Home Inspection Repair, just last week, where the SABC's were Multiwired. I had a neutral connection come loose and it caused the countertop Microwave to burn up.
First time I've had to replace and appliance.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The services and feeders are multiwire circuits, unless there is only a single voltage involved.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
We see them around here quite often especially in older homes. We still install them especially when the home runs are very long. Makes sense to get twice as many circuits and running 1/2 the amount of cables compared to 2-wire home runs.
mjf
Senior Member
I almost always run 2 MWBC to kitchens. I hit the fridge, the micro, and 2 countertop circuits. No problems to date (knock on wood).
BTW, any reason not to use a DP breaker as opposed to handle ties?
BTW, any reason not to use a DP breaker as opposed to handle ties?
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
In fact, I think the move toward separate neutrals is a waste of money. Probably perpetuated by the wire manufacturers. I admit that one thing I never cared for was MBC's that were fed from nonadjacent breakers (1,4,5 instead of 1,3,5) but I just didn't allow it on my jobs and requiring handle ties does prevent this. Otherwise it is just another example of the nanny state protecting us from ourselves. At a cost to every customer we deal with.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
We never run multiwire branch circuit and in 2014 the Kitchen will need to be on an afci so that would discourage the use even more.
IMO, the only issue with a multiwire branch circuit is if you loose the neutral then you could potential have 240V thru all the appliance. I have seen this happen and burn up microwaves and any other digital items on the circuit
IMO, the only issue with a multiwire branch circuit is if you loose the neutral then you could potential have 240V thru all the appliance. I have seen this happen and burn up microwaves and any other digital items on the circuit
Cavie
Senior Member
- Location
- SW Florida
This is not a problem. GFI receptacle at the first outlet of each circuit will sense only that circuit.
MWBCs are not inherently dangerous, non-qualified personnel are inherently dangerous.
I have run thousands of them and I would take extra care to splice the first neutral where they changed to 2 wire circuits. There are several companies that make two pole AFCI breakers.
I have run thousands of them and I would take extra care to splice the first neutral where they changed to 2 wire circuits. There are several companies that make two pole AFCI breakers.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
I should have been more clear, thank you.
A GFI receptacle feedthrough can only be used if the downstream wiring is a single circuit with a dedicated neutral.
You cannot extend the shared neutral past the first GFI receptacle.
If you have an existing MWBC which contains only shared neutral wiring at the receptacles of interest, you will need to install a separate GFI receptacle at each protected outlet.
If you are wiring from scratch, on the other hand, you can choose to break out a single circuit branch from as many locations as you want on the shared-neutral backbone. Just do not reconnect to the neutral of the other branch anywhere downstream. (Which would be bad practice if not prohibited in any case.)
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