Split Duplex & MWBC...not MWBC...What is allowed?

[vtsoundman]

There seems to be some confusion (ok I am confused) around MWBC and Split Duplexes...
Hopefully some code experts can help me out here...

1. Does code permit two 120V circuits on a split duplex w/ separate neutrals w/o a breaker handle tie / 2 pole breaker. (Never/not a MWBC with shared neutral)?
Answer : ?
NO - Same Yoke - Need Same Disconnect/Handle Tie at circuit origination

2. How does GFCI change the situation : will code allow separate/split GFCI circuits on a split duplex w/o a handle tie?

Example : Single duplex on a kitchen counter / garage with two 20A GFCI circuits present using separate neutrals & hot, broken tabs. No handle tie on the BC breakers. (Again Never a MWBC).
​

Answer : ?
NO - Same Yoke - Need Same Disconnect/Handle Tie at circuit origination

3. Will code allow split duplex if a 2 pole GFCI breaker is used in a MWBC?
Answer: This is an acceptable workaround and is often used. Code mandates handle tie/2 pole breaker on MWBC split duplex for conventional circuits.
YES - Same Yoke - Need Same Disconnect/Handle Tie at circuit origination

4. Will code allow split duplex w/ GFCI circuits if a handle tie is used with two single phase breakers & GFCI outlets?
Example: Two 20A breakers w/ handle tie. GFCI function from two upstream Receptacles feeding a split duplex. From the panel, circuit has a shared neutral and is a MWBC. After the GFCI recepts, it now was a pair of neutrals - so is it no longer technically a MWBC?

A GFCI recpt can trip and cause only half of the duplex to be 'dead' - thereby tricking the technician into thinking the duplex is dead. If the case of drowned recept, a hazard still exists...
Answer : ?

YES - Same Yoke - Need Same Disconnect/Handle Tie at circuit origination. Code is silent on the question; therefore permissable.

Background...skip you don't care.

Working on a installation in my kitchen where I retrofit a few circuits/box openings (wife likes her electric appliances). I will also do the same for POU equipment stations in my workshop.

While it may seem to a waste of time for some, (use a pair of duplexes)
wife dislikes seeing a ton of receptacles in the kitchen. We will often have multiple 8-12A, ~15A, appliances going at the same time/same tiny spot in (coffee pot, toaster oven, instant pot, breadmaker etc etc etc).


Per NEC, a MWBC is

A branch circuit that consist of 2 or more ungrounded conductors that have a voltage between them and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.
​

- or more simply -
A grounded conductor (neutral) is shared between a pair of hot conductors.

The Code seems clear about MWBCs for (1) requires Handle ties for preventing overloaded neutrals, (2) neutral pigtails to prevent 240V /loss of neutral.

210-4(b) states; "In dwelling units, a multiwire branch circuit supplying more than one device or equipment on the same yoke shall be provided with a means to disconnect simultaneously all ungrounded conductors at the panelboard where the branch circuit originated."


The following link is what confuses me:

http://www.ecmag.com/section/codes-standards/using-two-pole-breaker-feed-split-wired-receptacles-break-tabs
QUESTION: "Your answer about split-wired receptacles on a multiwire circuit is okay, but what if the split-wired receptacles were fed by two circuits, each with its own neutral?"

ANSWER: Since this would not be a multiwire circuit, there is no requirement for the desired protection either in a dwelling unit or other than a dwelling unit.

I think the reason ECMAG is stating the above is 210.4(b) is permissive and does not specifically require breaker handle ties for independent BC on a shared yoke, but I'm hoping that some code experts & senior sparky's can help me out here.
Question is answered. ECMMAG might be on older code cycle or just wrong.

 

[Cmreschke]

1, 2 no.
3, 4 yes.

 

[Cmreschke]

Handle ties are required to make sure that all energized wires are disconnected together, when sharing a neutral and or sharing a yoke.

 

[vtsoundman]

Handle ties are required to make sure that all energized wires are disconnected together, when sharing a neutral and or sharing a yoke.

Awesome Thx.

I must have read 210.7 10x thinking it said MultiWIRE Branch when looking at this problem. Operational blindness. It is the yoke/strap that is common unit requiring the connection.

This has come up in the paste with some client installations too....and my wife (of all people forced the issue to have me chase down the issue for our kitchen). My design engineers have disagreed on it...and I have always told them to use the handle tie and move on...I'll have to give both of them the business for not citing 210.7 (they are young guys).

 

[ishiboo]

There are some interesting questions here! I don't think it as black and white as cmreschke does, and in fact I believe that #1 is not expressly prohibited by the NEC nor the device listing, which is why the neutrals of duplex receptacles have the same break-off tabs as the hots.

Regarding #4, I think since it's a MWBC that without question handle-tied singles or a dual-pole breaker breaker is required for this setup. Regardless of the fact one side of the duplex will remain hot, since it's a MWBC upstream of the GFCIs the MWBC rules are pretty clear.

Remember you can have multiple circuits in the same box and they do not all need to have a common shutoff. There is no requirement that a single trip/breaker has to shut off the entire box from being hot.

 

[ishiboo]

Ah, yeah... completely forgot about the "yoke" classification.

I don't believe that is the only cause of #4 though, but the fact it's a MWBC with a shared neutral for part of its life means it must meet MWBC requirements.

 

[vtsoundman]

Ah, yeah... completely forgot about the "yoke" classification.

I don't believe that is the only cause of #4 though, but the fact it's a MWBC with a shared neutral for part of its life means it must meet MWBC requirements.

Yeah! heh...

Full text of 210.7
Multiple Branch Circuits
Where two or more branch circuits supply devices or equipment on the same
yoke or mounting strap, a means to simultaneously discon-
nect the ungrounded conductors supplying those devices
shall be provided at the point at which the branch circuits
originate

A duplex has two receptacles on the same yoke/strap.
A box full of connections/duplexes/etc is not on the same yoke or strap.

Once and MWBC, always an MWBC...it is the origination that matters. Code requires simultaneous disconnecting means, not that it disconnect at the same time during a trip event. I think it is a loophole, but if I say it too loud, it will end up changed in the next cycle.

I love it how my wife, someone who works in the mental health field, always has a way of breaking the 'tie' - even in my techno babble world. Ha

 

[Cmreschke]

As a matter of opinion, there really is no reason to avoid using a MWBC if it can be used. It saves money. So you have to handle tie the breakers, this is a good thing as it insures the ckts are installed in the panel properly.
Until the poco pulls seperate neutrals for each leg there is no disadvantage to doing so.