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

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.

2008 is going to make the 42 circuit rule go away

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

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.

renosteinke,

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?

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.

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!

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?

All,

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.

Canada does not have that rule,

The 42 circuit limitation applies only to 'appliance' panels .... that is, panels whose circuits have neutral wires. That's what the 10% rule defines. Other panels are "power" panels.

As mentioned above, this arbitrary rule is about to leave us.

Also as mentioned above, 'legal' and 'good design' are not always the same thing. Personally, I will even go so far as to assert that a design that is deliberately intended to 'push the code' envelope is a bad design for every other purpose.

imo i would go with the MDP, i had this happen about 1 1/2 years ago to me on a job. I landed up going with a mdp in the basement and several panels though out the building. i would say cost can be slightly high or if you look at the fact of home run lengths slightly lower depending on your situation. Either way i feel this is a neater and much safer install for the homeowner. They are tought in an emergency go to the mdp and kill it one panel at a time then the main! Not the best of practices but it works rather then them running around a house trying to kill each little panel when they don't even know which one is causing the problem. i did mine this way and the inspector praised my design and install!!!

Here (Austria) the planning standards say you can only fill new panels to 80% to leave room for future expansions. IMHO a good idea (even though I don't always stick to it when doing work in my own home).

I'm a big believer in fitting the "next size up" board to alllow for expansion.

Case in point: with the low cost of split system airconditioners, it is quite easy to fill up a board with just one service call which then fils any spare poles in the board, some houses I have worked on have ended up with a sub-board being fitted just for split aircons & 15 amp welder/caravan outlets while the hot water service, cooking appliances, power & light circuits fill the original boards.