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Panel Schedule - 10% Rule ??? #168573 09/09/07 05:22 PM
Joined: Sep 2003
Posts: 35
acetoday Offline OP

I'm doing work on a high end custom home for a architectural firm. This project has been in planning for the last 2 years. They had originally spec'd the service for 3 phase until the power company informed them they would not provide 3 phase to a residence. I suspect the panel schedule they provided was meant for the 3 phase system.

When I tried to obtain a quote from my Vendor for a Siemans Panel (see specs below) they said it exceeded the 10% rule and that they would not be able to provide the panel. Has anyone ever heard of this rule before? I did find in 408.13 (b) (2002 NEC) a rule regarding panel board protection.... Not sure if this is what they were referring to. Any feedback or guidance would be appreciated.

800 AMP Panel, 60 Spaces, Single Phase 120/240v, 42 KAIC
Circuit Details:
24 - 20AMP Single Poles
1 - 30AMP Double Pole
1 - 200AMP Double Pole (sub Panel)
1 - 225AMP Double Pole (Sub Panel)
1 - 100AMP Double Pole (Sub Panel)
1 - 400 AMP Double Pole (ATS for Generator)
2 - 80 AMP Double Poles
1 - 60 AMP Sauna

Work Gear for Electricians and the Trades
Re: Panel Schedule - 10% Rule ??? [Re: acetoday] #168577 09/09/07 06:26 PM
Joined: Dec 2000
Posts: 4,287
electure Offline
You need to go to 408.14 and 408.15 for the answer.
A lighting and appliance panelboard is one with more than 10% of it's overcurrent devices 30 Amps or less, and the branch circuits connected to neutral.

It's only allowed 42 circuits (which you have)

They don't want to sell you a 60 space power panel.

Re: Panel Schedule - 10% Rule ??? [Re: electure] #168582 09/09/07 08:48 PM
Joined: Jul 2004
Posts: 9,569
gfretwell Online Content
2008 is going to make the 42 circuit rule go away

Greg Fretwell
Re: Panel Schedule - 10% Rule ??? [Re: gfretwell] #168591 09/09/07 09:47 PM
Joined: Sep 2003
Posts: 35
acetoday Offline OP
Electure and Greg,

I just recounted the circuits in this panel (I missed a few on my earlier post) and the total is 44. So does this mean this would NOT be allowed? I really don't think my vendor doesn't want to sell me a 60 space panel. I guess I'm still not clear on this. I should also mention 2 other sub panels contain more than 42 circuits (one has 46 and the other has 54)

Would it be incorrect to inform the architect his panel schedules are not to code (i.e., 408.15)?

Thanks for the help

Re: Panel Schedule - 10% Rule ??? [Re: acetoday] #168592 09/09/07 09:57 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Ace, that would be a very good idea. IMO, the design is poor if all the spaces are filled from the very beginning.

Let's face it ... those panels will have a lot of wires in them ... never a joy to work in. I'd much rather have several 'sub' panels, than one monster panel.

Re: Panel Schedule - 10% Rule ??? [Re: renosteinke] #168601 09/10/07 07:15 AM
Joined: Sep 2003
Posts: 35
acetoday Offline OP

What confuses me about this issue is if you can only fill a panel with 42 circuits then why do they make panelboards with greater then 42 circuits?

Re: Panel Schedule - 10% Rule ??? [Re: acetoday] #168602 09/10/07 08:09 AM
Joined: May 2005
Posts: 984
ghost307 Offline
The 42 circuit limit is for "lighting and appliance panelboards". There is also a "power panelboard" that is not subject to any such limitation.

The 2008 NEC will remove the 42 circuit limit from the lighting and appliance panelboards, which are the only ones presently bound by it.

Re: Panel Schedule - 10% Rule ??? [Re: ghost307] #168610 09/10/07 08:42 AM
Joined: Oct 2002
Posts: 482
Zapped Offline
Maybe you should consider a main "power distribution" panel that contains the only the main breakers for a couple more subs. Although '08 will allow you more circuits, '08 is not active yet and a lot of municipalities won't adopt it right away anyway.

Good Luck!

Re: Panel Schedule - 10% Rule ??? [Re: renosteinke] #168612 09/10/07 09:44 AM
Joined: Dec 2000
Posts: 4,287
electure Offline
Like I said above, you need to read 408.14 and 408.15 for your answer. The answer is right there in black and white.
Your vendor might "like" to sell you a 60 space panel, but cannot.
Your single pole breakers alone add up to more than 10% of the total, and therefore, will not comply with the Code if they are in 1 enclosure.
Like Greg said, the '08 NEC will do away with the 42 circuit rule, but until it is adopted in your area, you are out of luck.
( I notice that your reference came from the'02 NEC).

The ONLY way that you will be able to comply will be to mount multiple panels as the Code requires. You can still have your power panel for the larger C/B's, but will need to have additional panels.

Did the architectural firm give you enough room to do so?

Re: Panel Schedule - 10% Rule ??? [Re: electure] #168614 09/10/07 10:26 AM
Joined: Sep 2003
Posts: 35
acetoday Offline OP

Thank you all for your assistance with this issue. And yes, there is plenty of space for additional panels.

Thank you again for taking the time to respond.

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