Handle Tie in Multiwire Circuits

[Bob Hunt]

I inspected a house today. It had several multiwire circuits, i.e. red wire on one breaker for the family room receptacles and black wire on another breaker for the living room receptacles; ground and neutral wires are shared between the two circuits. Do the two breakers need an common handle tie, same as is needed when two circuits supply a single device?

[Jerry Peck]

Do the two breakers need an common handle tie, same as is needed when two circuits supply a single device?


My opinion has always been that they 'should' be on the same internal trip breaker or on two breakers with handle ties.

The NEC only recently took that position, having until only recently allowed multiwire circuits to only be required to be common trip when the two circuits were to devices on the same strap, now, though, all multiwire circuits are required to be on common trip breakers (internal common trip or with handle ties).

To me it was always a potential safety hazard and I addressed it as such.

[Jerry Peck]

It would seem to me that it would be prudent that if the red leg is connected to L1 it would be best that the black should be connected to L2 in order to prevent the possibility of a neutral overload.

If it is not wired that way, with 240 volts between the legs of the multiwire circuit, then it is not a multiwire circuit and would therefore not be allowed.


The easiest way would be to have two 1 inch breakers next to each other with handle a tie. This also would take down the other leg sharing the the neutral if the problem was such that the shared neutral was involved. 1/2 inch twin breakers could be used if the breakers were on different buss bars and the adjacent handles the twins were used.

The question was (see original post):

Do the two breakers need an common handle tie, same as is needed when two circuits supply a single device?

And the answer is (see previous answer):

The NEC only recently took that position, having until only recently allowed multiwire circuits to only be required to be common trip when the two circuits were to devices on the same strap, now, though, all multiwire circuits are required to be on common trip breakers (internal common trip or with handle ties).

[Roger Frazee]

I inspected a house today. It had several multiwire circuits, i.e. red wire on one breaker for the family room receptacles and black wire on another breaker for the living room receptacles; ground and neutral wires are shared between the two circuits. Do the two breakers need an common handle tie, same as is needed when two circuits supply a single device?

Bob

It is entirely possible that your panel and multiwires are fine for the time period they were installed .... as Jerry is saying that was allowed at one time but are no longer. And I agree they are a risk .. especially to the unqualified or the homeowner who thinks he is qualified. 9 times out of ten 10 they will only turn off one circuit. It is not necessarily the intent/job of the NEC to worry about a homeowner messing with a branch circuit he doesn't understand and is a code compliant installation. I've been approached by many homeowners who just can't seem to understand why they got shocked in that receptacle box or why it takes two breakers to remove the power. Yes they may see black and red wires but it just doesn't mean anything to them, they turn the single breaker off and what they plug into the receptacle ( their voltage tester ..ie lamp ) doesn't work therefore there is no power in the box. Homeowners have a tendency to disconnect every wire in a receptacle box more so than a fixture box when they are making changes and therefore come in contact with the other hot wire that is passing on thru the box or the neutral that might still be carrying current..

Also remember that changes to the NEC now require multiwire shared neutrals to be pig tailed to the receptacle... so that they are not opened during removal of the receptacle.
So I would suggest that separation of the breakers without handle ties (as Jerry points out) is a reasonable safety hazard that should be addressed..

[Jerry Peck]

Also remember that changes to the NEC now require multiwire shared neutrals to be pig tailed to the receptacle... so that they are not opened during removal of the receptacle.


That requirement for continuity of the grounded conductor of multiwire branch circuits at receptacles, lampholders, and the like has been in there for a long time.

Also, to clear some things up which I started: I said that *all* multiwire branch circuits now need to be on circuits which are protected either by internal trip breakers or breakers with handle ties ... and that is true for basically anything we will find in a home, but ... that is not true with regards to the word "all" as there are some very limited exceptions to that rule (the NEC has exceptions to many of the rules). Just wanted to point that out before someone pointed it out for me. :D

[Roger Frazee]

That requirement for continuity of the grounded conductor of multiwire branch circuits at receptacles, lampholders, and the like has been in there for a long time.

True ... I think it is in article 300 ..yeah looks like 300.13(B) but it was a recent change for me.....:)

This has been a local repealed section of the NEC for several years here in the great plains of Kansas, hasn't been required for some time though I can't speak for the last 2 or 3 years.

[Jerry Peck]

True ... I think it is in article 300 ..yeah looks like 300.13(B) but it was a recent change for me.....:)


That language was added into the 1971 NEC (was not there in the 1968 NEC, was not even revised, was not there and was added in 1971).

[Roger Frazee]

That language was added into the 1971 NEC (was not there in the 1968 NEC, was not even revised, was not there and was added in 1971).

You must have read my mind .. my next question was if you knew when it first showed up in the NEC ....

[Jerry Peck]

my next question was if you knew when it first showed up in the NEC ....


This is what is in the 1968 NEC:
- 300-13. Mechanical Continuity - Conductors. Conductors shall be continuous between outlets, devices, etc., and, except as permitted for auxiliary gutters in Section 374-8, and for wireways in Section 362-6, there shall be no splice or tap within a raceway itself.

That section of the 1971 NEC was revised to:
- 300-13. Mechanical Continuity - Conductors. Conductors shall be continuous between outlets, devices, etc., and, except as permitted for auxiliary gutters in Section 374-8, and for wireways in Section 362-6, and Section 300-15(a), there shall be no splice or tap within a raceway itself.
- - In multiwire circuits the continuity of an identified grounded conductor shall not be dependent upon device connections, such as lampholders, receptacles, etc., where the removal of such devices would interrupt the continuity.

[Roger Frazee]

Thanks Jerry

I've always found NEC history interesting.