multi-wire.

[paul renshaw]

I do not have my code book here at the facility right now, any help is appreciated. On a 3-wire circuit (12-3 cable) run to a double duplex receptacle, with each single being a seperate circuit, is a two pole breaker required? If so, what is code reference? Thanks.

 

[jumper]

2 pole maybe used, but handle tie if not. 210.4(B)

(B) Disconnecting Means. Each multiwire branch circuit
shall be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where
the branch circuit originates.

 

[paul renshaw]

Thanks, that's what I thought, but I like to have references for my arguments. Have a good one!

 

[augie47]

Just in case you are not under the '08 or later NEC, the situation you describe (devices on the same yoke), was covered under 210.7 in '08 and earlier Codes.

 

[scauri]

210.4b

210.4b

Muist be double pole breaker or breaker tie.Refer to 210.4B exibit 210-1 and 210-2.What i do not agrre with is that if you have 3 phases and one neutral going to 3 different branch circuits{no 2 circuits on same yoke}also haVE TO HAVE BREAKER TIES AND OR 2 OR 3 POLE BREAKERS!

 

[augie47]

Muist be double pole breaker or breaker tie.Refer to 210.4B exibit 210-1 and 210-2.What i do not agrre with is that if you have 3 phases and one neutral going to 3 different branch circuits{no 2 circuits on same yoke}also haVE TO HAVE BREAKER TIES AND OR 2 OR 3 POLE BREAKERS!

You don't agree that the Code states that or you don't agree with the concept ?

 

[Dennis Alwon]

You don't agree that the Code states that or you don't agree with the concept ?

I think he is saying that he does not like the new rule in 2008 of needing handle ties or pole breakers. When there are two circuits on one yolk he is okay with it.

 

[mivey]

Wouldn't the receptacle limit the loads to single-phase L-N? Then we have 240.15(B)(1):

Multiwire Branch Circuit. Except where limited by 210.4(B), individual single-pole circuit breakers, with or without identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.

 

[220/221]

Just in case you are not under the '08 or later NEC, the situation you describe (devices on the same yoke), was covered under 210.7 in '08 and earlier Codes.

I believe he described two devices.

On a 3-wire circuit (12-3 cable) run to a double duplex receptacle, with each single being a seperate circuit

If he's 2008 or later, yes. Two pole/handle tie.



AZ is still 2005 on this issue. AZ seems to slowly bring in current NEC changes instead of adopting the whole new cycle. Personally, I think it's a good idea in most cases (ie: tamper proof and AFCI's everywhere).

 

[scauri]

interpretation of 210.4 B

interpretation of 210.4 B

You don't agree that the Code states that or you don't agree with the concept ?

I don't agree weith the concept by all means.Case point:I worked in hospitalsd all my carrer.99% of 120v circuits come off 3 phase with common neutral and no breaker ties on brteakers up to now.Questios remains that ,if i had to shut off only one circuit,as is the case most of the times,I couldl NOT,if i had breaker ties on installed.Let me tell you:that is very dangerous to do in a health facilityI believe in other places too}.You might be putting off somebody respirator or computer,right?Besides I do not interpret 210.4 B of 2008 code that way.If you look at the 2008 handbook,it gives you an example{exibit 210.1}that refers to ,what i believe to be}an interpratetion of 210.4 B.The way i see it :the two different phases and one neutral are going to the same yokes,therefore you do need a double pole breaker!If those ywo lines were going to different branch circuitswith separete divices,I don't think they should have tie breakers or dopuble pole breakers installed at panel.I certainly don't read it that way.Would love to get an answer from Mike holts himself!

 

[George Stolz]

You're not required to pull a MWBC anywhere. You can install a neutral for every circuit and not use any handle ties if you don't want handle ties.

 

[augie47]

It's rare for Mr. Holt to post here, but I think you will find a number of competent
folks who can answer most Code questions. The Forum is lucky enough to have some highly experienced electricians, contractors, engineers and others many of whom are in contact with members of the Code Making Panels.
Often if you read the ROPs and ROCs which show the input to the Code changes, you will understand the intent.
From those (ROPs & ROCs) it is fairly obvious that the CMP agreed the hazards from a "back-feed" on a MWBC neutral was significant enough of a problem to support the "common means of disconnect".
Your situation is not without merit. Fortunately the section is not retroactive so
existing MWBCs don't need to be addressed. Now that 210.4 (B) is in the Code, it might be prudent for your future installs to use individual neutrals thus the common disconnect won;t be needed. I have found a number of E/Cs are doing that to avoid situations such as yours.
In addition, you, or anyone else, may submit a Code change request requesting that there be an exception for certain situations,

 

[roger]

I don't agree weith the concept by all means.Case point:I worked in hospitalsd all my carrer.99% of 120v circuits come off 3 phase with common neutral and no breaker ties on brteakers up to now.Questios remains that ,if i had to shut off only one circuit,as is the case most of the times,I couldl NOT,if i had breaker ties on installed.Let me tell you:that is very dangerous to do in a health facilityI believe in other places too}.You might be putting off somebody respirator or computer,right?

That has no bearing on using MWBC's, the solution is to not use them in Patient Care Areas and in fact the 2011 solves this problem by prohibiting their use in Patient Care Areas.

Besides I do not interpret 210.4 B of 2008 code that way.

I don't know how you can interpret any other way

(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.

If you look at the 2008 handbook,it gives you an example{exibit 210.1}that refers to ,what i believe to be}an interpratetion of 210.4 B.The way i see it :the two different phases and one neutral are going to the same yokes,therefore you do need a double pole breaker!If those ywo lines were going to different branch circuitswith separete divices,I don't think they should have tie breakers or dopuble pole breakers installed at panel.

Look at 210.1 again and take notice of the two seperate duplex receptacles in the lower illustration, I don't know why it shows breaking off the tab but that is irrelevant. BTW the handbook illustrations and commentary are just opinions and don't really carry any weight.


Roger

 

[jrohe]

I don't agree weith the concept by all means.Case point:I worked in hospitalsd all my carrer.99% of 120v circuits come off 3 phase with common neutral and no breaker ties on brteakers up to now.Questios remains that ,if i had to shut off only one circuit,as is the case most of the times,I couldl NOT,if i had breaker ties on installed.Let me tell you:that is very dangerous to do in a health facilityI believe in other places too}.You might be putting off somebody respirator or computer,right?

The 2011 NEC took care of this concern for you. Section 517.18(A) and section 517.19(A) prohibits branch circuits at patient bed locations in general care areas and critical care areas, respectively, from being a multi-wire branch circuit.