Connecting single pole circuits to multipole breakers violates code.

[jrimbey]

I'm looking for feedback on the poor installation standard of connecting single pole loads to multi-pole breakers. I've seen projects red-tagged in the past by inspectors because this type of connection was outside the UL listing of the breaker. Otherwise, I don't know of a code prohibiting the practice.
I have a client with new critical space panels that will only accept 3-pole breakers. The breaker manufacturer will support 2 and 3 pole connections but not single pole connections. The client currently has many instances of multiple single pole loads connected to the same 3-pole breaker. 240/415V
Does anyone in this forum have experience with this issue?
Thank you.

 

[infinity]

Can you provide the wording in the UL listing to say that the practice violates the listing of the multi-pole CB?

Welcome to the Forum.

 

[JDBrown]

I've never heard of there being an NEC issue with connecting line-to-neutral loads to a multi-pole breaker. In fact, although it's not part of the language of the Code itself, the Commentary that goes along with 210.4(B) in the NEC Handbook specifically mentions multi-pole breakers as an acceptable simultaneous disconnecting means for multiwire branch circuits. It says, in part:

For a single-phase installation, the simultaneous disconnection can be achieved by two single-pole circuit breakers with an identified handle tie, as shown in Exhibit 210.1 (top), or by a 2-pole switch or circuit breaker, as shown in Exhibit 210.1 (bottom). For a 3-phase installation, a 3-pole circuit breaker or three single-pole circuit breakers with an identified handle tie provides the required simultaneous disconnection of the ungrounded conductors. Where fuses are used for the branch-circuit overcurrent protection, a 2-pole or 3-pole switch is required.

 

[jim dungar]

UL489 Listed breakers have been tested for all possible pole usage.
In general 1-pole loads can usually be connected anywhere, while 2-pole loads are sometimes limited to the outside poles of a 3-pole breakers (e.g. when used on corner grounded systems).

 

[kingpb]

Just my opinion, but I think it is a good practice to use a multi-pole breaker anytime single pole loads share a neutral. :thumbsup:

 

[petersonra]

given the voltage involved it may be that this is not a nec application.

 

[jrimbey]

The manufacturer (ABB) has stated to me their 3-pole breakers are not listed for single pole connections. They are listed for two-pole connections.
I've lost the reference but NEC requires breaker connections be made within their listed use. Therefore, when I connect single pole loads to the three-pole breakers I'm outside the listing of the breaker.
This seems to be a popular practice, but I'm not comfortable that the breakers being used in this way were intended for this use.

 

[jrimbey]

Jim,
Thanks for the UL489 reference. I'll see if the manufacturer is misinformed about their listing restrictions.

 

[Gregg Harris]

Just my opinion, but I think it is a good practice to use a multi-pole breaker anytime single pole loads share a neutral. :thumbsup:

Would it be because of these?
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.

240.15(B) (1)
(1) Multiwire Branch Circuits. Individual single-pole circuit breakers, with 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.

 

[jim dungar]

Jim,
Thanks for the UL489 reference. I'll see if the manufacturer is misinformed about their listing restrictions.

I cannot quote you any portion of the UL489 standard that supports all possible combinations as always being acceptable. You definitely need to follow the requirements of the manufacturers actual testing procedures.
Testing of individual poles for 'unbalanced loading' may not be the same as testing for a stand alone operation. For example, according to UL's White book "3-Pole ? 1-Phase Rated ? 3?pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, ?For 1?phase connections, use two outside poles,? or an equivalent statement. A 3-pole breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked."