408.54 in the 2008 code

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wyboy

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On a residential remodel may a twin breaker be added to an existing 42 circuit panel. I did a load calculation and there is lots of capacity. Is this allowed per 408.54 in the 2008 code?
 
wyboy said:
On a residential remodel may a twin breaker be added to an existing 42 circuit panel. I did a load calculation and there is lots of capacity. Is this allowed per 408.54 in the 2008 code?
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If the panelboard is listed to accept tandem breakers, I don't see why it would be a problem.
 
In the 05 book we used to refer to 408.35 which limited you to a maximum of 42 poles. This was deleted in the 08 book, it now states the number of circuits the panel is listed for. So if your panel was made for 42 circuits you can not add anymore. To use mini breakers, the panel must be listed for mini breakers.

Sound like you need to add a sub-panel to make this job compliant.:)
 
shepelec said:
In the 05 book we used to refer to 408.35 which limited you to a maximum of 42 poles. This was deleted in the 08 book, it now states the number of circuits the panel is listed for. So if your panel was made for 42 circuits you can not add anymore. To use mini breakers, the panel must be listed for mini breakers.

Sound like you need to add a sub-panel to make this job compliant.:)
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But if a 42-pole panel is listed for tandem breakers, doesn't that technically mean the maximum number of circuits the panel is listed for would be 84?
 
DetroitEE said:
If the panelboard is listed to accept tandem breakers, I don't see why it would be a problem.
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jimport said:
If this puts you over the maximum number of breakers allowed by the panel listing it could not be used.
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shepelec said:
In the 05 book we used to refer to 408.35 which limited you to a maximum of 42 poles. This was deleted in the 08 book, it now states the number of circuits the panel is listed for. So if your panel was made for 42 circuits you can not add anymore. To use mini breakers, the panel must be listed for mini breakers.

Sound like you need to add a sub-panel to make this job compliant.:)
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The Code pretty much spells it out...
408.54 Maximum Number of Overcurrent Devices. A
panelboard shall be provided with physical means to prevent
the installation of more overcurrent devices than that
number for which the panelboard was designed, rated, and
listed.
For the purposes of this section, a 2-pole circuit breaker
or fusible switch shall be considered two overcurrent devices;
a 3-pole circuit breaker or fusible switch shall be
considered three overcurrent devices.
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If for some reason you can install more overcurrent devices than the panel is designed, rated, and listed for, then the panelboard is non-compliant... not installing the tandem breaker... so even installing a subpanel does not make the panelboard compliant if this be the case.
 
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Smart $ said:
The Code pretty much spells it out...
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If for some reason you can install more overcurrent devices than the panel is designed, rated, and listed for, then the panelboard is non-compliant... not installing the tandem breaker... so even installing a subpanel does not make the panelboard compliant if this be the case.
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The way it's worded makes this seem like more of a requirement for panelboard manufacturers than the electrician installing the circuit breakers.

I'm still not clear on why tandem breakers are a problem if the panel is listed for it.
 
DetroitEE said:
The way it's worded makes this seem like more of a requirement for panelboard manufacturers than the electrician installing the circuit breakers.

I'm still not clear on why tandem breakers are a problem if the panel is listed for it.
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That's the way I see it in part. The other part is it also prevents one from reusing or reconfiguring any older, non-compliant panelboard (but I doubt that compliance would even be checked in most cases).
 
Mini breakers would count as 2 poles. If the box is rated for 42 cir that is the same as 42 poles. Being this is an older panel, we know it is not listed for more than 42 circuits.

Which is why I stated a sub-panel would need to be used. Move two circuits from the existing panel into the sub to make room for the sub breaker. That is how a sub would make this install compliant.:cool:

I flag services all the time for having too many breakers in the panel.
 
shepelec said:
Mini breakers would count as 2 poles. If the box is rated for 42 cir that is the same as 42 poles. Being this is an older panel, we know it is not listed for more than 42 circuits.

Which is why I stated a sub-panel would need to be used. Move two circuits from the existing panel into the sub to make room for the sub breaker. That is how a sub would make this install compliant.:cool:
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If the panel was installed prior to 2008 code being adopted and compliant with the maximum of 42 circuits installed everything is okay.

However, once this panel is involved with an installation under the 2008 code, it must meet 2008 requirements. If the panel permits more than 42 circuits to be installed by the use of tandem breakers (whether more is actually installed or not), yet listed at a maximum of 42 circuits (mind you spaces are not the same as circuits), the panel is non-compliant with 408.54. It makes no matter how many circuits you shift around, the panel physically permits more circuits than its design, rating, and listing.

That said, I haven't checked to see if any older models of panelboards are non-compliant.

The only alternatives here (if panel is as noted) is to leave the panel untouched and install another panel via feeder tap (assuming OP calc is correct), or replace panel with a newer 2008 compliant one... (or try to slide one by :D)...

...but I suggest the OP'er first verify exactly what the panel is designed, rated, and listed for.
 
Hendrix said:
Yes it would.
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Not necessarily. It may be listed at 42 "spaces"., but that does not automatically mean 84 circuits via tandems.

There may be physical deterrents in place to prevent tandems being installed in certain spaces. You certainly can have a panel, for example, designed, rated, and listed as say 42/60... meaning 42 spaces, 60 max circuits, where 36 circuits could be fed by tandems.
 
I think we said the same thing just differently. It does not matter what code it is installed under if it is listed at 42 circuits max. I have not seen a residential panel listed for more than 42 circuits yet, does not mean it is not out there.

The OP said a 42 cir panel, if it is listed as a 42 cir panel you can not under any circumstances install more than 42 circuits in it. If it is not listed for mini breakers you can not install mini breakers in it.:)
 
shepelec said:
I think we said the same thing just differently. It does not matter what code it is installed under if it is listed at 42 circuits max. I have not seen a residential panel listed for more than 42 circuits yet, does not mean it is not out there.

The OP said a 42 cir panel, if it is listed as a 42 cir panel you can not under any circumstances install more than 42 circuits in it. If it is not listed for mini breakers you can not install mini breakers in it.:)
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That pretty much sums it up. Check the panel label, obey it, simple!


SQ D now has load centers that accept up to 60 circuits. 40/50 and 42/60 in QO and Homeline
 
DetroitEE said:
But if a 42-pole panel is listed for tandem breakers, doesn't that technically mean the maximum number of circuits the panel is listed for would be 84?
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only if you were allowed to put twins in every space. A 20/40 panel has 20 spaces but with twins can be 40 circuits. Some panels only allow twins is certain places.
 
DetroitEE said:
But if a 42-pole panel is listed for tandem breakers, doesn't that technically mean the maximum number of circuits the panel is listed for would be 84?
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No, absolutely not. In fact, as others have said, it wasn't until 2008 NEC that panelboards were allowed to have more than 42 cir. I have not seen one yet but I hear that Sq. D has made a 60 cir. panel.

Many panels are mark with 20/40 circuits. This means 40 full size breakers or 20 twins. Either way it is 40 circuits max.
 
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