Number of Breakers

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augie47

augie47

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State Electrical Inspector (Retired)
Now that Art 408 has removed the 42 circuit limit on panelboards is it permissible to use 42 tandem breakers in a panel.
I have an Siemens loadcenter that is listed for Type QP & QT breakers. Is there anything that prohibits the installation of 42 QT tandem breakers in that loadcenter ?
 
As I understand it Gus, the panel is listed for 42 circuits then you cannot add more circuits to it. It is a listing issue not necessarily a safety issue.
 
augie47 said:
Now that Art 408 has removed the 42 circuit limit on panelboards is it permissible to use 42 tandem breakers in a panel.
I have an Siemens loadcenter that is listed for Type QP & QT breakers. Is there anything that prohibits the installation of 42 QT tandem breakers in that loadcenter ?
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The panel would have to be listed for the tandem breakers and the quantity of them IMO.
 
Maybe semantics here, but if it is identified as a 42 circuit panel, but also accepts QT (tandem) breakers....are we limited to a total number of circuits at 42 ?
 
augie47 said:
Maybe semantics here, but if it is identified as a 42 circuit panel, but also accepts QT (tandem) breakers....are we limited to a total number of circuits at 42 ?
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As Dennis said, I don't think it is a safety issue but rather a marketing issue reinforced by the the way the panel is specifically listed by the NRTL. If you look at any catalog you note that each load center has a specific number of full size and tandem size listed for each.
 
texie said:
As Dennis said, I don't think it is a safety issue but rather a marketing issue reinforced by the the way the panel is specifically listed by the NRTL. If you look at any catalog you note that each load center has a specific number of full size and tandem size listed for each.
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Guess thats the answer, but it seems strange the would list a 40/40 panel as accepting QT brekers.
Kinda double-speak.
 
augie47 said:
Guess thats the answer, but it seems strange the would list a 40/40 panel as accepting QT brekers.
Kinda double-speak.
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What if you were using Switched Neutral breakers? They take up two pole spaces but only provide 1 circuit. The same thing goes for breakers with shunt trip and auxilliary switches.
 
augie47 said:
Guess thats the answer, but it seems strange the would list a 40/40 panel as accepting QT brekers.
Kinda double-speak.
Click to expand...

Another thing to consider here, from your viewpoint as an inspector, if you have a given load center with more tandems than the listing allows, how did they get them to fit? All modern load centers that I am aware of will not allow one to readily install more than it is listed for. Of course with some brands this can be done easier than others.
 
I am surprised that the panel is rated for 42 circuits and all the spaces can accept tandem. Also I have not seen a residential panel that would accept 42 circuits. They are usually rated for 40 circuits because it evenly divides "A" and "B" phases. Three phase panels are usually rated 42 circuit and I have never seen one that accepts twins.

If this is a new panel then perhaps that is siemens way of saying it is an 84 circuit panel. What is the panel cat. #
 
augie47 said:
Now that Art 408 has removed the 42 circuit limit on panelboards is it permissible to use 42 tandem breakers in a panel.
I have an Siemens loadcenter that is listed for Type QP & QT breakers. Is there anything that prohibits the installation of 42 QT tandem breakers in that loadcenter ?
Click to expand...

Wirenuts are cheaper!
 
I have used the 225 amp 42 circuit single phase in a number of residences. Try to give more circuits, even though load stays same. Some places around here limit the number of openings per circuit to "10". I had one house where they wanted sections of recessed lighting (6) on different switches, therefore I could only put 6 cans per circuit, definitely not overloaded circuits!:roll:
 
jim dungar said:
Oh, the sheltered life some of us live.:D

Square D QO142L225G, QO142M225, QONQ42LS400, and QONQ42MS400
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Sq. D used to be popular here but CH, Siemens, & Ge took over. The last 2 are 400 amp panels which are hardly ever used around here and not in a very very long time unless it is a meter main combo.

The others are 225 amp which is also never used here. Not sure I ever saw a 225 installed in a residence. I guess I am sheltered though-- Does sq.D make a 200 amp panel that has 42 cir.
 
texie said:
Another thing to consider here, from your viewpoint as an inspector, if you have a given load center with more tandems than the listing allows, how did they get them to fit? All modern load centers that I am aware of will not allow one to readily install more than it is listed for. Of course with some brands this can be done easier than others.
Click to expand...

The big box stores sell twin breakers that are made for "non CTL" panels, namely ones built before 1968 that do not have notched bus stabs, they fit in any position in a panel, & if someone is ignorant or just does not care, they will pop one in anywhere, there is also modification of a CTL type to make em fit, or just hacksaw a notch in a bus stab.

Edit: I hope that no thinks that I am suggesting that any of the above methods be tried, they are all poor ways of doing electrical work.
 
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