Trying to understand multiwire branch circuits

[infinity]

This may only help a tiny bit, but if you have 3 multiwire branch circuits, you don't have 6 circuits. You have 3 circuits.

A 3-wire MWBC is 2-120 volt circuits. Three 3-wire MWBCs is 6 circuits.

 

[James L]

A 3-wire MWBC is 2-120 volt circuits. Three 3-wire MWBCs is 6 circuits.

No. It's "a" (singular) multiwire branch "circuit" (singular)

 

[infinity]

No. It's "a" (singular) multiwire branch "circuit" (singular)

It's still 2 circuits. If I need two individual branch circuits for the kitchen counter receptacles and I run one 3-wire MWBC to feed the receptacles I have run two circuits (not one) and I have complied with the minimum number of two SABC's being required. It can be considered a single circuits for other sections of the NEC.

 

[roger]

The NEC let's us consider it as two but it is a single circuit.

210.4 Multiwire Branch Circuits.
(A) General. Branch circuits recognized by this article shall
be permitted as multiwire circuits. A multiwire circuit shall be
permitted to be considered as multiple circuits. .

 

[Tulsa Electrician]

I would consider the way it written.

 

[Tulsa Electrician]

Sorry, posted at same time.
Beat me to it. Had to pull it off my phone.

 

[infinity]

It can be considered a single circuit or multiple circuits depending on how it's used. As I stated earlier in post #23 a 3-wire MWBC for two separate circuits is two 120 volt circuits not one.

 

[James L]

a 3-wire MWBC for two separate circuits.

A circuit for two circuits

 

[wwhitney]

An MWBC is simultaneously one circuit for certain purposes, and two circuits for other purposes. Life is messy.

Cheers, Wayne

 

[Little Bill]

An MWBC is simultaneously one circuit for certain purposes, (dryer, or stove) and two circuits for other purposes (kitchen SABC) . Life is messy.

Cheers, Wayne

Bold = examples of each

 

[mtnelect]

How are you supposed to keep track of those neutrals in MWC ?
See my PI's.

 

[Necnerd]

How far are you running these flexes? What will be the wiring method after they split?

About 5 feet from top of panel to 12x12 in dropped ceiling. From there it will be mc cable.

 

[infinity]

How are you supposed to keep track of those neutrals in MWC ?

If they're in a cable you do nothing. In a raceway you just wrap a number tag around them or tie them together with the ungrounded conductors. I know that you've been pushing to get this continuous stripe thing into the code but IMO with the way the CMP's have been leaning lately it's not likely to make it.

 

[electrofelon]

How are you supposed to keep track of those neutrals in MWC ?
See my PI's.

I don't believe the CMP's will find "difficult and time consuming to troubleshoot" to be a valid reason to make a code change.

 

[Necnerd]

I’ve always just marked them with a number and zip tied neutral to ungrounded conductors…

 

[mtnelect]

Sometimes, it's not a good idea !