vtsoundman
Member
- Location
- NorCal
Split duplex receptacle application limited space, client concerned about aesthetics. Normally I trust my design engineers on things, but I have two with conflicting opinions and I feel like the code is somewhat nuanced on MWBC, vs multi-circuit in single duplexes.
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)?
Example: Two 20A 120V circuits with individual breakers feeding a split duplex (w/broken tabs fed - each recept fed by independent neutral & hot.)Answer : ?
2. How does GFCI change the situation : will code allow separate/split GFCI circuits on a split duplex w/o a handle tie?
Example : Split duplex with two 20A GFCI circuits present using separate neutrals & hot, broken tabs. No handle tie on the BC breakers. (Again Never a MWBC). Answer : ?
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 210.4(b) handle tie/2 pole breaker on MWBC split duplex for conventional circuits.
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 single neutral MWBC, but now a multiwire MWBC? I think no - 210.4(b) - It is still a MWBC, but can be convinced the other way too.
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 : ?
My thoughts...skip you don't care.
Per NEC, a MWBC is
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-...eaker-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.
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)?
Example: Two 20A 120V circuits with individual breakers feeding a split duplex (w/broken tabs fed - each recept fed by independent neutral & hot.)Answer : ?
2. How does GFCI change the situation : will code allow separate/split GFCI circuits on a split duplex w/o a handle tie?
Example : Split duplex with two 20A GFCI circuits present using separate neutrals & hot, broken tabs. No handle tie on the BC breakers. (Again Never a MWBC). Answer : ?
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 210.4(b) handle tie/2 pole breaker on MWBC split duplex for conventional circuits.
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 single neutral MWBC, but now a multiwire MWBC? I think no - 210.4(b) - It is still a MWBC, but can be convinced the other way too.
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 : ?
My thoughts...skip you don't care.
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-...eaker-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.
