main disc. over 400 amp res. service?

[howardrichman]

Large home new service-under 400 amp calc. load. 3-200 amp panels for house. JCP+L wont supply CT w/ low load calc. Inspector states IF CT is allowed from JC; main disconnect (fuses or non-fused ?)must be installed ahead any service size over 400 amps-including residential. I'm looking @ art. 230(services disconnecting means); and cant seem to locate this demand of a disconnect in this article. Inspector suggested a I-Line 400 amp ML panel w/ 3-200 amp breakers ahead of the existing panels to accomodate the three 200 amp panels so to not exceed 400 amps. Problem is ; No physical room
for the enclosure w/three panels.
Howard Richman

 

[roy g]

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roy g

If you are you using a single phase 400 amp service, you can use a 400 amp meter base, and a wire way with the three 200 amp disc for feeding the 2 -200 amp panels, or as your inspector said an I line panel with the three 200 amp breakers. Section 230.71 of 2005 code say up to six disconnects (all in one location (230.40) can be used without main. If costs is an item, its less expensive to use the disconnects rather than line panel.

 

[macmikeman]

Check with the poco, they usually have a say in the matter and they could care less about the nec for the most part.

 

[howardrichman]

Well; According to Art. 230.71, the three 200 amp panels on a shared panelboard should comply w/ that 6 sw rule, and should be able to tye them together in a wireway, unless the combined breaker ratings of the 3 panels exceeds the K4U(meter) rating of 400 amp.
Thanks for reply;

Howard Richman

 

[howardrichman]

Check with the poco, they usually have a say in the matter and they could care less about the nec for the most part.

Unfortunetly; the final say is always the Electrical Inspector; and even if JC allows a CT,inspector may want a 600 amp main disconn. ahead of service even w/ limited exterior space.

Thanks for reply;
Howard Richman

 

[benaround]

If you are you using a single phase 400 amp service, you can use a 400 amp meter base, and a wire way with the three 200 amp disc for feeding the 2 -200 amp panels, or as your inspector said an I line panel with the three 200 amp breakers. Section 230.71 of 2005 code say up to six disconnects (all in one location (230.40) can be used without main. If costs is an item, its less expensive to use the disconnects rather than line panel.

I'm pretty sure the 400a meter base is rated 320a continuous, is the load calc. on this house over 320a ?

 

[howardrichman]

The inspector looked up the specs for the Milbank K4, and states the pan is rated 320A, and 400A continuous.
The Load Calc JC calculated was only 255A, but I calculated 360-380A.
HR

 

[infinity]

Unfortunetly; the final say is always the Electrical Inspector; and even if JC allows a CT,inspector may want a 600 amp main disconn. ahead of service even w/ limited exterior space.

Thanks for reply;
Howard Richman

I'm not exactly following your setup but I wouldn't agree that the inspector has the final say if he's wrong. What code section does he cite requiring the 600 amp disconnect?

 

[howardrichman]

I called the inspector today; and what he actually stated is that since the incoming feed conductor are rated to 400 amps, the sum of the existing panel mains could not exceed the largest conductor rating of the service. To comply; I would have to have a main 400A disconnect ahead of the panels, and wouldn't matter how many main panels i'de use or how I configured them.

Howard Richman

 

[scwirenut]

If I were you Id mount a 320 MB, then on each side mount a 200A Mobile home panel, it has a 200 amp MB with feed through lugs on the bottom, it also has 8 circs. Now, feed all your Condensing units, well pumps, ect from the 16 exterior circuits. feed throughs then feed 2 200 ml panels inside for everything else.

 

[LarryFine]

I called the inspector today; and what he actually stated is that since the incoming feed conductor are rated to 400 amps, the sum of the existing panel mains could not exceed the largest conductor rating of the service. To comply; I would have to have a main 400A disconnect ahead of the panels, and wouldn't matter how many main panels i'de use or how I configured them.

So, he wants the 400a main for current limiting, not to specify where in the chain it's located. If you used two MB panels instead of three, you'd be okay.

If you need three panels merely for the space, how hard would it be to sub-feed the most lightly-loaded panel from the next-most lightly-loaded one?

 

[howardrichman]

Well; thats what I'll end up doing. The problem is that I'm using only a single run of 500mcm as my primary feeders from the pole. According to code for residential use ,I could get away w/ 400mcm, but just wanting to be safe for E-drop and future loads. I'll just balance the remaining loads between the two panels. I was thinking; would a 6 meter service w/ 100amp mains each in a apartment blding require 100% rated feeder conductors @600 amps? isn't this is the same senario of the service I'm working?

HR...

 

[hurk27]

Well; thats what I'll end up doing. The problem is that I'm using only a single run of 500mcm as my primary feeders from the pole. According to code for residential use ,I could get away w/ 400mcm, but just wanting to be safe for E-drop and future loads. I'll just balance the remaining loads between the two panels. I was thinking; would a 6 meter service w/ 100amp mains each in a apartment blding require 100% rated feeder conductors @600 amps? isn't this is the same senario of the service I'm working?

HR...

The problem with having 3 200 amp mains protecting your 500 Kcmil service entrance conductors, is you have the ability to over load them, maybe not by your calculations but by those who might come after you.

500 Kcmil only has a 380 amp capacity @ 75? and 400 Kcmil its only 335 amps, but because of it being a single dwelling, Table 310.15(B)(6) allows the reduced size because of the diversity factor of a dwelling.

But if this is an apartment building, you are not allowed this reduction, or can you use Table 310.15(B)(6)

serve as the main power feeder to a dwelling unit

Is singular, not plural.

I think the 2008 has even made this more clear in the re-wording of this section.

 

[Pierre C Belarge]

I called the inspector today; and what he actually stated is that since the incoming feed conductor are rated to 400 amps, the sum of the existing panel mains could not exceed the largest conductor rating of the service. To comply; I would have to have a main 400A disconnect ahead of the panels, and wouldn't matter how many main panels i'de use or how I configured them.

Howard Richman

This is not true for multiple service disconnecting means.

Show your inspector 230.90 Exception #3. This permits one to have up to 6 service disconnecting means with the overcurrent sizes exceeding the amperage rating of the service conductors, as long as the calculated load does not exceed the amperage rating of the service conductors.

 

[infinity]

This is not true for multiple service disconnecting means.

Show your inspector 230.90 Exception #3. This permits one to have up to 6 service disconnecting means with the overcurrent sizes exceeding the amperage rating of the service conductors, as long as the calculated load does not exceed the amperage rating of the service conductors.

I agree. The connected load will determine the size of the service entrance conductors.

 

[infinity]

Well; thats what I'll end up doing. The problem is that I'm using only a single run of 500mcm as my primary feeders from the pole. According to code for residential use ,I could get away w/ 400mcm, but just wanting to be safe for E-drop and future loads. I'll just balance the remaining loads between the two panels. I was thinking; would a 6 meter service w/ 100amp mains each in a apartment blding require 100% rated feeder conductors @600 amps? isn't this is the same senario of the service I'm working?

HR...

Yes, IMO the scenerio is the same and the inspector is incorrect. (iwire had a good photo of one small set of service entrance conductors feeding 6-100 amp disconnects). Pierre gave you the proper reference. Show it to the inspector. If he still won't buldge you have a few choices, install 2-200 amp panels with mains, install the 400 main OCPD ahead of the panels or the last choice call Trenton and get the answer faxed over in writing from Suzanne Borek.