Legally Rquired Standby System

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sandsnow

sandsnow

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Location
Southern California
I'm searching for opinions on 701-10.
Do you feel it allows one transfer switch to supply legally required standby and optional standby loads.
My opinion is it needs to be seperate back to genset. The code only allows you to share enclosures, not equipment.
Related section 701-6
1999 NEC
Thanks
 
Re: Legally Rquired Standby System

Opinions are easy, and mine is based on the 2005 NEC. 700.6 Transfer Equipment requires that transfer equipment shall supply only emergency loads. In 701.7 Transfer Equipment there is not a similar requirement. Therefore it is my opinion that a single transfer switch can supply legally required and optional standby loads. If it is not forbidden then it is allowed.

Fred Bender
 
Re: Legally Rquired Standby System

Larry in my opinion no way what so ever and that is how it is enforced here in MA and RI.

701-10 allows article 701 systems to mix with general systems, not emergency systems.

There is also 700-9(b) to consider.

1999 NEC
700-9(b) (b) Wiring. Unless otherwise permitted in (1) through (4), wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads shall be kept entirely independent of all other wiring and equipment. Wiring of two or more emergency circuits supplied from the same source shall be permitted in the same raceway, cable, box, or cabinet.

1. The normal power source wiring shall be permitted to be located in transfer equipment enclosures.

2. In exit or emergency lighting fixtures, wiring supplied from two sources shall be permitted.

3. In a common junction box, attached to exit or emergency lighting fixtures, wiring supplied from two sources shall be permitted.

4. The wiring within a common junction box attached to unit equipment, containing only the branch circuit supplying the unit equipment and the emergency circuit supplied by the unit equipment shall be permitted.
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IMO the key part is this

"wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads shall be kept entirely independent of all other wiring and equipment."

This to me says that from the emergency source distribution overcurrent protection (the breaker on the generator) to the utilization equipment has to be separate.

I am sure we have all seen a branch circuit fault open a feeder breaker along with the branch breaker. IMO 700-9(b) is in place to prevent a non-article 700 emergency load from opening any breaker on the emergency system

We install many generators that we order with one, two or three breakers on them, one will feed only true emergency loads fed through dedicated transfer switches and distribution. The other breaker(s) on the generator will feed separate transfer switches for 701 or 702 type loads. The 701 and 702 loads can be mixed but sometimes the engineer keeps them separate as well.

I also think 700-6(d) is very clear

"Transfer equipment shall supply only emergency loads."

Article 701 loads are not NEC 'Emergency Loads'

700-1. Scope
The provisions of this article apply to the electrical safety of the installation, operation, and maintenance of emergency systems....
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701-1. Scope
The provisions of this article apply to the electrical safety of the installation, operation, and maintenance of legally required standby systems....
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Re: Legally Rquired Standby System

So you're saying Bob, one generator but the emergency system only has to seperate back to it's own breaker on the generator?
 
Re: Legally Rquired Standby System

Originally posted by physis:
So you're saying Bob, one generator but the emergency system only has to seperate back to it's own breaker on the generator?
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That's a big Ten Four Rubber Duck.


(Are you old enough to get that one?)
 
Re: Legally Rquired Standby System

Headin' fur Bear on I 10 bout a mile out o Shakey Town.

Yeah, I'm not sure it's one of our prouder historical moments. :D
 
Re: Legally Rquired Standby System

BOB,
When you say that is the way we do it in MA and RI, is that saying the legally required system and optional standby system must be seperated, as the original post asked, or are you on a tagent and simply stating emergency must be isolated from the other two systems? Thanks

Fred Bender
 
Re: Legally Rquired Standby System

Fred, we're on the '99 at present, but since you brought it up, check out the picture in the 2005 handbook. Exhibit 700.1. Shows all loads seperate but not back to the genset. One feeder from the genset to a distribution board, then to 3 xfr switches, one each for 700; 701 and 702 loads.

Bob,
My problem is 701 stops short of saying you need a seperate xfr sw.
It only states you can share enclosures, not equipment.
It doesn't make sense to have smoke control systems(as in a high rise) mixed in with someone's back up for a computer system.
That said in the past we have allowed 701 and 702 to mix, even using the same xfr sw. Just wanted to get some more input, considering the diagram in the handbook. Yes, I know how much you love that book ;)

As far as 700 loads, only those required by the building code are allowed. Everything else is either 701 or 702. Got no problem with that.
 
Re: Legally Rquired Standby System

I don't want to speak for iwire but his posting of 700.9(B) seems to me to cover his assertion.
 
Re: Legally Rquired Standby System

Originally posted by physis:
Headin' fur Bear on I 10 bout a mile out o Shakey Town.

Yeah, I'm not sure it's one of our prouder historical moments. :D
Click to expand...
Don't have my c/b anymore, but I think I still have an 8-track player if you want it.
 
Re: Legally Rquired Standby System

That was 8 track era wasn't it Larry. :D

Larry I'm not quite clear on the question here. I'm not done rereading the posts either but maybe you could save me some time.

Are you agreeing that the emergency system needs it's own breaker at the source but may still need a seperate transfer switch even though it goes back to the same generator?

Edit: Error B, missing words.

Edit: "If I want it" :D :D

[ July 11, 2005, 05:00 PM: Message edited by: physis ]
 
Re: Legally Rquired Standby System

I don't know how related this is but the book just opened itself to 517.41(B). You might be interested in the FPN figure.

Edit: After looking at it some more, maybe not.

[ July 11, 2005, 05:07 PM: Message edited by: physis ]
 
Re: Legally Rquired Standby System

Originally posted by physis:
That was 8 track era wasn't it Larry. :D

Larry I'm not quite clear on the question here. I'm not done rereading the posts either but maybe you could save me some time.

Are you agreeing that the emergency system needs it's own breaker at the source but may still need a seperate transfer switch even though it goes back to the same generator?

Edit: Error B, missing words.

Edit: "If I want it" :D :D
Click to expand...
Emergency systems (700) are not my question. It's the mixing of 701 and 702 systems sharing a xfr sw and panelboards etc.

700 loads are completely seperate.

edit: Can't use those diagrams, wrong article. Would be nice to have diagrams for 700, 701 and 702.

[ July 11, 2005, 05:11 PM: Message edited by: sandsnow ]
 
Re: Legally Rquired Standby System

I just figured that out. I see.

Edit: I don't have 99 and the sections don't match so I'm out. :(

[ July 11, 2005, 05:33 PM: Message edited by: physis ]
 
Re: Legally Rquired Standby System

Sandsnow,

Between 701.6 and 701.7 My read is if you have enough capacity you can run both LRS and OS systems thru a single ATS,if not you need load shedding equipment to ensure the LRS will operate as designed. ATS needs to be identified for standby use etc.

frank
 
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