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Discussion Starter · #1 ·
Anyone know the difference between a 20 space, 20 circuit panel and a 20 space, 30 circuit panel. Seimens makes both and twin breakers fit in both. Home inspector called my customer out on it. Not a big deal. Just gonna install a 6 circuit sub. Is it a heat thing? They appear to be identical.


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Even if twins fit in the panel they are not allowed if the panel isn't made for twins. My suspicion is that someone modified the twin breakers to fit in the panel that is a straight 20 circuit panel. They also make a 20-40 cir panel.
 

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There are two types of twins, those made for CTL panels and those made for non-CTL panels.

The CTL types have a rejection feature that will allow them to be installed only in a space specifically designed for twins.

The non-CTLs will usually fit in any space, but are not legal for use in a CTL panel.

CTL means Circuit Total Limitation.
 

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Discussion Starter · #9 ·
I understand that. I just dont understand why there is a 20/20 panel and a 20/30 panel from the same manufacturer that appear to be identical. What allows one to be ok with twins and the other they are unacceptable.



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I understand that. I just dont understand why there is a 20/20 panel and a 20/30 panel from the same manufacturer that appear to be identical. What allows one to be ok with twins and the other they are unacceptable.



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The difference will be the configuration of the busbars.

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I understand that. I just dont understand why there is a 20/20 panel and a 20/30 panel from the same manufacturer that appear to be identical. What allows one to be ok with twins and the other they are unacceptable.
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you are supposed to read the literature or the label on the panel and know what it is good for before you install it.
 

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The non-CTLs will usually fit in any space, but are not legal for use in a CTL panel.
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But around here the only the non-CTLs are in stock:)

What is the actual physical difference? The main bus has to be rated for the full amount of current that the panel is rated for and as far as I know the tandems are only in 15 and 20 amp sizes, so the maximum load on a "bus finger" would be 40 amps. As long as the panel is rated for use with 40 amp breakers I don't see a real world issue here...just a listing and code issue.
 

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When is Home Depot going to start stocking 100 circuit panels?

I would assume that that Eaton would be all over that since they could push more afci breakers to fill them.
 
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