NEC 701 Legally Required and NEC 702 Optional

[Hoyt2020]

Currently working on the design of a project that will require an emergency generator. Exterior, diesel.

I believe I have loads that fall beneath each of these systems:

NEC 701 Loads: Mechanical ventilation equipment for a hazardous space Class 1 Div I. (required per IBC 414) ("Standby Power" per the IBC).

NEC 702 Loads: Boiler loads serving both bldg heating and Owner equipment loads. I consider 702 Optional loads.

In my research, and in speaking with a State electrical inspector, it is my understanding that a 701 and a 702 can be served from the same automatic transfer switch. Do you believe this is accurate?

NEC 700 to serve egress illumination requirements. This system would require its own ATS.

So.... a total of (2) ATS for the project.
ATS #1 to serve NEC 700
ATS #2 to serve NEC 701 and 702

 

[tom baker]

If your only Art 700 loads are egress lighting, consider using battery backed up lighting. Wiring for Art 700 loads must be kept separate. What I don’t know is Since the generator is for art 700, 701 and 702 loads the gen requirements may be considered under Art 700.

 

[Hoyt2020]

If your only Art 700 loads are egress lighting, consider using battery backed up lighting. Wiring for Art 700 loads must be kept separate. Since the generator is for art 700, 701 and 702, the gen requirements may be considered under Art 700

If your only Art 700 loads are egress lighting, consider using battery backed up lighting. Wiring for Art 700 loads must be kept separate. Since the generator is for art 700, 701 and 702, the gen requirements may be considered under Art 700.

Yes I can utilize battery for the 700 loads. The question still remains if 701 and 702 can be served from the same ATS

 

[d0nut]

Whenever I have done any article 701 loads, I have served them from a dedicated ATS and distribution. That way those loads and the distribution is clearly identifiable, but I don't know that it is code required to design it that way. 701 does require selective coordination, so that may influence your design decision as well.

 

[majorminotaur]

Yes, we do this all the time; NEC 701.4 allows it. Hospitals it makes sense to divide up the three branches but rarely worthwhile to do in other contexts; so we have combination Standby/Optional most times. (Yes i know these are different code sections but they are roughly analogous)

For what its worth, I would not put emergency on battery if you are paying for a generator and having to maintain it. Batteries present their own maintenance issues. I try to stay away from batteries whenever possible.

 

[majorminotaur]

Also wanted to add that certain area's have their own take on this: I've heard that NYC doesn't even recognize the Legally Required Standby (they move them to emergency branch). Massachusetts used to not allow this split, but it doesn't look like that is the case anymore. I AM NOT VERY FAMILIAR WITH EITHER OF THESE MUNICIPALITIES SO DON'T TAKE MY WORD FOR IT ON THIS.

 

[Hoyt2020]

Yes, we do this all the time; NEC 701.4 allows it. Hospitals it makes sense to divide up the three branches but rarely worthwhile to do in other contexts; so we have combination Standby/Optional most times. (Yes i know these are different code sections but they are roughly analogous)

For what its worth, I would not put emergency on battery if you are paying for a generator and having to maintain it. Batteries present their own maintenance issues. I try to stay away from batteries whenever possible.

I agree on the lighting. I have been attempting to dig some more and make sure that this ventilation equipment does not fall under 700. I don't believe so.... but still digging.

 

[Grouch1980]

Yes, we do this all the time; NEC 701.4 allows it. Hospitals it makes sense to divide up the three branches but rarely worthwhile to do in other contexts; so we have combination Standby/Optional most times. (Yes i know these are different code sections but they are roughly analogous)

A few years ago I was involved in the design of a couple of high-rise hotels in NYC. We always had optional loads from article 702 on their own ATS switch. One switch for 700, one for 701, and one for 702.

NYC follows the 2008 NEC... 701.4 doesn't say much, only that "All equipment shall be approved for the intended use."

701.4 in the 2017 NEC says a lot more... but what I'm reading is that the legally required standby loads and optional loads can be fed by the same generator... I'm not interpreting it to say that both types of loads can be on the same ATS switch. It says the generator can feed both types of loads if it either has the capacity to serve all the loads, OR that there's enough load shedding that the generator can still serve the legally required standby loads. I don't read that it allows one common ATS switch for both types of loads. Maybe I'm wrong though.