On the Square D Homeline panels there are 30 spaces but is considered a 40 circuit capacity due to the last several slots being designated as “tandem breaker” slots. The bus bar has two distinct “pins” for the tandem breakers should tandems be desired. So…supposedly the SqD models of panels are designed for tandems but only on for use on the last few slots.
So…..take a Cutler Hammer panel….I saw one recently where the HO had installed tandems in a variety of places on his panel with no issues. He has a 40 space panel, but he used them all up and started using tandems as needed in the panel. Some tandems are at the top of the Main panel, others elsewhere.
My question is…..can a tandem breaker be used anywhere inside a panel? To SqD it would seem they only want it used in the last few slots, but do you really HAVE to use tandems just there, could you use them on other slots?
I’m asking because I’m writing a proposal to install a circuit. I need to create some slots and the only way is to use tandems. Since he’s used tandems elsewhere in the panel randomly, is it acceptable to truly do this? Or do all panels have specific slots set aside for tandem breaker use only?
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bump
There are two types of tandem breakers. Exclusionary and non-exclusionary.
The NEC limits a panel to 42 poles.
And the maker limits the spaces where you an install breakers.
But using tandem breakers you could install many more poles than the panel was designed for.
So at some point UL came up with a requirement that only allowed tandem breaders to be installed in limited slots.
I have no idea when this was done.
But there where older panels that did not have the limiters. So tandem breakers are still made for the older panels.
So he might have an older panel or use tandems that where made for the older panels.
So you're writing a proposal to install a circuit; does this mean that you're the one who will be installing it?
Cliff
Subtle, but good point.
Dave
Yeah, I'll be installing it. The guy has a 40 space panel, he has no room for a double 30A brkr. He already has about 4 tandems in his panel in various places seemingly working fine for him. I need to create two spaces. I thought tandems were to be used on certain slots, here I saw them randomly used. I wanted clarification on what is acceptable and what was right.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I suppose if you wanted to get all technical you could take the panel manufacture code and check to see what they rate it for?
Or you could also do a load calc and go from there.
And Or shift some breakers and consolidate and presto chango.
Doesn't that get him up to 44, which is over the NEC limit of 42? Unless this is a really huge house, perhaps you can combine some lightly loaded circuits to free up space in the box.
-- J.S.