Multi-wire Circuits

[Jeffrey R. Pope]

NEC 210.4 (B) Devices or Equipment. Where a multiwire branch circuit supplies more than one device or equipment on the same yoke, a means shall be provided to disconnect simultaneously all ungrounded conductors supplying those devices or equipment at the point where the branch circuit originates.

A multi-wire circuit is serving a living area of a home. One branch serves the receptacle outlets, while the other serves the lighting outlets.

Question - Are the breakers required to be tied together for simultaneous shutoff?

Please qualify your answer.

[Bruce A. King]

I read a discussion on Mike Holt's forum once where someone said the 2002 code actually required the handle tie when outlets were on the multi wire branch circuits. The 2008 code then included devices and equipment as part of the handle tie requirement.

[Jeffrey R. Pope]

The question is, what is your definition of "equipment on the same yoke?" I generally define "yoke" as a device or piece of equipment contained in a single "space" or enclosure - such as a multi-wire circuit powering a single duplex receptacle.

My interpretation is that there is no need for a handle tie in the instance I described, as these are not "on the same yoke."

[Jeffrey R. Wicklander]

No requirement for a handle-tie, until a house is built under the 2008 NEC adoption that requires a MWC to include a handle-tie.

Jeff

[Jeffrey R. Pope]

CA is currently using the 2005 NEC. Can you post the 2008 section?

[Bruce A. King]

I did see that mentioned in lots of discussions, a yoke is simply the strap on an outlet or switch body used to mount it.

Some "experts" are posting on the web that ALL multiwire circuits must have handle ties or be a dedicated double pole breaker based on the 2008 code.

Here is a good article.....

http://www.ecmag.com/?fa=article&articleID=8741

[Jeffrey R. Pope]

Good article - thanks Bruce.

[Chuck Evans]

Originally Posted by jpope

The question is, what is your definition of "equipment on the same yoke?" I generally define "yoke" as a device or piece of equipment contained in a single "space" or enclosure - such as a multi-wire circuit powering a single duplex receptacle.

My interpretation is that there is no need for a handle tie in the instance I described, as these are not "on the same yoke."

That is consistent with the way that I have always treated it. If they are connected separately to a single duplex receptacle or stacked switches on the same yoke - yes; separate outlets and switches - no. I consider whether someone can safely work on one circuit and not be endangered by the other. Though the shared grounded conductor may present a potential issue.

[Jim Port]

Originally Posted by cevans

I consider whether someone can safely work on one circuit and not be endangered by the other. Though the shared grounded conductor may present a potential issue.

This is the reason the the 08 NEC now requires a 2 pole breaker for MWBCs.

[Robert Meier]

All multi-wire branch circuits require simultaneous disconnect (multi-pole CB or handle tie) under the 2008 NEC. This requirement was actually in the 2005 NEC {605.7} but only applied to freestanding type furniture partitions, and as mentioned MWBC's on the same yoke.

Here's the 2008:

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. All conductors of a multiwire branch circuit shall originate from the same panelboard or similar distribution equipment.
FPN: A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads may necessitate that the power system design allow for the possibility of high harmonic currents on the neutral conductor.
(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.