2011 NEC Article 701 & 702 Combined ATS

[ed downey]

Can (1) ATS be used to supply loads of Article 701 & 702 as long as the Generator is sized for the full load of the Article 700, 701 & 702 Systems in an Office Building?

I cannot find anything that says it cannot be installed with the following scenario
1.) (1) ATS for the Article 700 Loads
2.) (1) ATS for the Article 701 & 702 Loads combined - 701 Loads are Stair Pressurization & Elevator Loads, 702 Loads are I.T. Closets and a few Receptacles
3.) Generator Sized for all loads at once.

I am being told be the engineer that we are required to provide (3) separate ATS's.

Thanks

Ed Downey

 

[mbrooke]

It depends on what the building and critical circuits are listed as. Life saftey, critical or optional standby. If you have NFPA required emergency circuits my interpretation is you will need a dedicated ATS for that as well as the possibility of a dedicated breaker from the genset, ie one breaker for the optional load the other for the legally required.

Now, if your on site lighting has 90 minute or other code acceptable battery packs and no life safety circuits than 1 ATS is ok in that you then have an "optional standby" generator.

 

[mbrooke]

Can (1) ATS be used to supply loads of Article 701 & 702 as long as the Generator is sized for the full load of the Article 700, 701 & 702 Systems in an Office Building?

I cannot find anything that says it cannot be installed with the following scenario
1.) (1) ATS for the Article 700 Loads
2.) (1) ATS for the Article 701 & 702 Loads combined - 701 Loads are Stair Pressurization & Elevator Loads, 702 Loads are I.T. Closets and a few

Ed Downey

Just caught this part. Im guessing a fire pump too? Pressurized stairwells sound like NFPA classified life safety loads, and if so you will need a dedicated ATS for them (as well if a fire pump exists) along with a generator classified as life safety, (ie ISO certifications, one site fuel ect)

I would say your engineer is right about 3 ATS, at the minimum 2.

 

[ed downey]

I have (1) Life safety ATS I am not sure I need a 701 ATS & a 702 ATS.


Can the Article 701 Loads and the Article 702 Loads share an ATS if the Generator is sized for all of the loads.

 

[mbrooke]

I have (1) Life safety ATS I am not sure I need a 701 ATS & a 702 ATS.


Can the Article 701 Loads and the Article 702 Loads share an ATS if the Generator is sized for all of the loads.

From my interpretation of the code legal and optional standby loads can share the same ATS. This doc by Mike Holt says its ok for 701 and 702 loads to do so, however, the emergency loads will need a separate ATS.

http://www.google.com/url?sa=t&rct=...E-kvNQssECVnvrZzf4OLq4g&bvm=bv.52164340,d.cGE

 

[steve66]

In my opinion, 701 and 702 loads can share an ATS.

700 loads need their own ATS per 700.6(D) (NEC 2008).

701.6 specifically allows a single transfer switch to serve legally required and optional systems.

If you are in a hospital, 517.30(B)(4) might require 3 transfer switches, but a hospital wasn't mentioned.

 

[eprice]

I agree that the article 701 and article 702 loads can share an ATS as long as the necessary capacity is provided. I arrive at this conclusion because there is nothing in article 701 that says otherwise. Unlike article 700 where 700.5 (D) prohibits other loads from being on the emergency ATS.

 

[ed downey]

Thanks for the responses and confirmation of thought process.

I just wanted to bounce it off someone before I go talk to the engineer.

-Ed