NEC 700.10(B)(5) - Separate Vertical Sections

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lielec11

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I just watched a webinar regarding NFPA 110, NEC 700-702, 708, and 517 as it relates to emergency and standby systems. A question came up in the Q&A portion that relates to NEC 700.10(B)(5) (2011 version) which states the following:

"Wiring from emergency source to supply and combination of emergency, legally required, or optional loads in accordance with (a), (b), (c), and (d);

a. From separate vertical switchboard sections, with or without a common, bus, or from individual disconnects mounted in separate enclosures
"

The presenters basically said that they have spoken to numerous AHJ's and said that since it is unpractical to provide separate vertical sections for every OCPD, they have no problem with approving the design as long as when they leave the switchboard they are separated.

I just wanted to spark a conversation and see everyone elses opinion. I have a job where we have a huge EMDB because of this section, and if I could get away without the separate vertical sections, and only separate AFTER the swbd, it could be much smaller.
 
lielec11 said:
I just wanted to spark a conversation and see everyone elses opinion. I have a job where we have a huge EMDB because of this section, and if I could get away without the separate vertical sections, and only separate AFTER the swbd, it could be much smaller.
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Here is a application note from Schneider Electric:
http://static.schneider-electric.us/docs/Electrical Distribution/0110DB0901.pdf
Page 2 shows a switchboard where there is no barrier between individual 'emergency' breakers. But, notice how they are all the same type of load (e.g. Emergency, Required, or Optional) instead of a mix, like I think you are proposing.

FWIW, in Wisconsin we have recently had several inspectors require projects to be redesigned with individual OCPD's instead of using a panel as was the common practice.
 
Jim thanks for the link.

Interesting that barriers are not required. If there are no barriers how is it any different than all of the breakers being group mounted?
 
lielec11 said:
Jim thanks for the link.

Interesting that barriers are not required. If there are no barriers how is it any different than all of the breakers being group mounted?
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Notice how there are barriers between the Emergency branch breaker section and the section for the Require and Optional branches.

Effectively once you leave the generator the Emergency circuits must be isolated from other circuits.
 
Maybe I'm thinking of something else, but I thought that in the 2011 version, you needed separate enclosed breakers off of the generator for each type of backup source (Life Safety, Critical Branch, Equipment Branch, Optional Standby, etc.). And in 2014, they allowed one common breaker to feed a switchboard (or brought it back), and separation is not required until you get to the ATS.

Maybe I'm wrong? Is this topic about something else entirely?
 
Yes you're on the right track. However, I was in the 2014 Handbook this afternoon and they still have the requirement to have separate vertical sections, or separately mounted disconnect switches for each branch (700, 701, and 702).

In my scenario, we have a main breaker on the genset on the roof, and feed an EMDB in the basement which has 4 separate vertical breaker sections; one for 700,701,702 and fire pump.
 
I think the main difference is that the language in 700.10(B)(5)(d) changed. It used to apply to all loads but now only applies to emergency loads (i.e. Life Safety).

It is certainly possible that I am completely misreading the significance, however.
 
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