Electrician Talk banner
1 - 17 of 17 Posts

·
Registered
Joined
·
2,923 Posts
The Murray, ITE/Siemens, Bryant, Westinghouse, Crouse-Hinds, CHBR style breakers are interchangeable with each other dependent on their listings. Like you, I cannot remember which goes into which, but you seem to making your statement based on parent companies.

I'm pretty sure Murray and Siemens are interchangeable. They may be owned by the same parent company, but are different manufacturers IMO.
 

·
Registered
Joined
·
2,923 Posts
I quoted a broad statement you made and commented on that broad statement.

It's against code to put different manufacturers breakers in a panel..
The manufacturers don't decide who's breakers can be installed in their panels, they suggest what breakers the listing agency should test and the listing agency decides based on their testing.
 

·
Registered
Joined
·
2,923 Posts
Mr. Deep Cover, the whole point of a multiwire branch circuit is to utilize all phases.
You've never seen a 208V single phase water heater off a 120/208V 3 Phase panel? Or baseboard heat?

You stated...
2 pole and 3 pole breakers are only used for multiwire branch circuits See Article 210.4 for further reading.
That is completely false. What 480 is illustrating is 210.7.

210.7 Multiple Branch Circuits. Where two or more
branch circuits supply devices or equipment on the same
yoke, a means to simultaneously disconnect the ungrounded
conductors supplying those devices shall be provided
at the point at which the branch circuits originate.
 

·
Registered
Joined
·
2,923 Posts
Well you are mistaken. 2pole and 3pole breakers can and do exist as multiwire branch circuits. Think of a cubicle.

Your 208 "single phase" example is completely wrong and not even possible. As I said earlier, you need two of the three phases to get 208.
If something specs a 30A 208V single phase circuit and you have 120/208V 3 phase in the building, how would you wire it?
 

·
Registered
Joined
·
2,923 Posts
I'm not going to let you off the hook so easily...

This whole thing started with the question....

I never understood this. If a 2-pole 30a breaker will fit on the bus, isn't that the same possible amount of current as 2 tandem 15a breakers?
To which, you answered...

To answer your question no as you are not figuring in the neutral current.

The answer is yes. Each stab (phase) would see (potentially) 30A. The neutral load is of no concern when UL/Panel manufacturers decide where tandems can go.

2 pole and 3 pole breakers are only used for multiwire branch circuits See Article 210.4 for further reading.

We've discussed how wrong this is at length already.

Article 100 Defines a multiwire branch circuit as any branch circuit that consists of two or more ungrounded conductors that have voltage between them.

You left out the part about a neutral/grounded conductor being involved as well. What you stated as the definition would, in fact, mean that all circuits containing more than one ungrounded conductor would be MWBCs.


A multiwire branch circuit is essentially a 208/240 volt system and the remaining unbalanced loads are very very little.

When talking about MWBC's, many times the loads served are general purpose lighting/receptacles. In that case, you have no idea what the unbalanced load would be. You do know it cannot be over the rating of the circuit, but to say they are "very very little" is not always accurate.

In your example two tandem breakers may or may not be on the same phase. This not only puts all the load on one phase and directly the neutral, it also creates a risk for injury because the circuit is still open if only one tandem breaker is turned off.

CTLs are mainly a residential restriction. Non-CTLs have no limit to the amount of breakers.;)
Which some of it is misleading, and some of it is wrong. My explanation is in blue.

Then you chose to argue about how wrong we were. You even said a 208V single phase circuit was not possible. The term "single phase" may be misleading to a DIYer, but for someone claiming to be an electrician, they should know exactly what is being described when they see what voltage is involved.

It's OK to not know anything or to be corrected, that is how we all learn.
 
1 - 17 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top