3 pole breaker in place of 2 pole breaker.

Hello. I am adding a subpanel to my second story; since all the rooms on the second story are run off of a single, knob and tube, circuit I am going to replace it with a single circuit per room and 3 or 4 circuits for lights. I'm using a 100 amp panel, with separate ground and neutral bars and a 100 amp service main "cuttoff" bolted inside it. I plan on using 2 or more A/C's up there as well, which I intend to have on dedicated circuits and then also some outside lights, etc.... My question is this, I don't have a double pole breaker for the main panel but I have a 100 amp triple pole breaker that will fit in order to feed the subpanel. Is it ok to use this triple pole breaker and only use one of the outside lugs and the middle lug and leave the other outside lug "unpopulated"? I have no use for this 3 pole breaker but if I can use it for this it would be good since it will save me 30$+ but if its dangerous or unsuitable then its no good. I can't see any problem with it, but I'm looking at it through biased eyes, so I put the question to my favorite and most knowledgable compartriots. Thanks in advance and best regards.

 

Triple pole breakers are used in a three phase panel. Is your house single phase or three phase? I can't imagine a 3-phase breaker being listed for a single phase panel. Just because you can get it in doesn't mean it should be used. And if this is a 3phase panel someone installed on a single phase service that is another problem.

 

The answer is no, the three-pole circuit breaker is not "listed" for use in a single phase panel. Sorry.

 

I'm sure that there is a NEC ref that states it is a code violation? This breaker could care less if its in a 1 or 3 phase service. There is no continuity between the poles of this breaker, so each one is isolated, so it just seems that this is possible, at least until I get the proper double pole breaker to replace it. Its only going to tap into 2 bars and the unused pole will tap into the same bar as the first pole. I simply intend not to use the 3rd pole, so effectively it will be a double pole breaker... Its seems like it will work; I realize that its not pretty as a design but its not cause an explosion or anything. I guess I don't know why I bothered to ask. In a universe with/without code inspectors it would work just fine. It simply wouldn't pass code, unless the inspector waived it.

 

Yes it is a problem but only you can decide if you are willing to live with it. ALL electrical devices need to be approved for their intended use by a NRTL, a Nationally Recognized Testing Laboratory. Underwriter's Laboratories is the most well-known NRTL but their are others and in Canada it is the CSA, Canadian Standards Association that "lists" items for their intended usage.

Being listed means the device has been tested to ensure that it meets all requirements for the safe usage. Manufacturers have to submit their products to the NRTL and ONLY the combinations that are actually tested are given the okay. Since the process is expensive (for the manufacturer) they never submit products that would not be used together such as a three-pole circuit breaker in a single phase panel.

It is remote, but a definite possibility that IF you had a fire and the cause of the fire was traced to an electrical problem AND the inspection found unlisted circuit breakers in the panel the insurance company may refuse to honor the policy.

 

hmmm... well common sense must prevail... I looked it up and darn it, the double pole breaker is 2 times more expensive than the 3 pole breaker... I don't think I would be willing to live with it; it would probably drive me to an obsessive compulsive disorder... (do you think that the insurance co would pay out if they saw the single knob and tube circuit running 7 rooms in my upstairs?) Gosh, its a wonder I can sleep at all.... Thanks for the info!

 

The two pole breaker is 100% more expensive than the one you have in your hand at no cost. I would not use the 3 pole breaker, period. Yeah, YOU know the third tap is not to be used, but what if you sold the house and the next people tapped onto it and overloaded the circuit? Caused a fire? I really don't see how an $8 breaker is in question, here. Do it right, do it once.

K&T was approved when the house was built. Not that the load would be approved, today, but it was then.

 

The bus contacts may not be in the same locations as a 3 phase panel so the contact might not sit on the bus correctly.

The NEC rule is 110.3B, equipment must be used as designed and listed.

 

A 2 pole 100 amp breaker will run about $30 to $45, depending on the brand. A new 3 pole breaker of the same amperage is usually twice the price of a new 2 pole breaker. From your statement, you must have a used 3 pole breaker. A 3 pole breaker would probably fit, but I wouldn't use it for many of the reasons already stated and also because it would be a waste of space in the panel.