Generator Distribution - Emergency vs. Standby Systems

[FoxValleyRob]

I have a design dilemma i'm working through... I typically don't put egress lighting on the generator, as many local municipalities require battery packs regardless (start-up time is their explanation). But I have a distribution center that requires a generator to keep the facility up and running during an extended power outage. If this is the case, won't the lighting also be required to be on sustained power? I'm concerned that the local authority will require the building to be evacuated within 90 minutes, as that's the required limit of the exit/egress lighting battery duration. Also, if I do put the emergency egress lighting on the generator, will I need a separate transfer switch? I'm thinking I will, but I can only find that requirement in the healthcare section of the NEC (NEC 517.32).

 

[charlie b]

If you have a generator that is intended to keep the facility in operation, then nobody is going to require the facility to be evacuated within 90 minutes. You can keep the normal lighting systems in operation, so that the building?s occupants can keep doing their jobs. You can also keep the egress lights in operation 24/7 for the duration of the loss of normal power. Nothing requires the egress lights to be turned off after 90 minutes.

You will need separate transfer switches, if you plan to put both the egress lights and the ?optional standby? loads on the same generator. Relevant requirements are in 700.5 and 700.9.

 

[eprice]

I have a design dilemma i'm working through... I typically don't put egress lighting on the generator, as many local municipalities require battery packs regardless (start-up time is their explanation). But I have a distribution center that requires a generator to keep the facility up and running during an extended power outage. If this is the case, won't the lighting also be required to be on sustained power? I'm concerned that the local authority will require the building to be evacuated within 90 minutes, as that's the required limit of the exit/egress lighting battery duration. Also, if I do put the emergency egress lighting on the generator, will I need a separate transfer switch? I'm thinking I will, but I can only find that requirement in the healthcare section of the NEC (NEC 517.32).

If I understand correctly, you will be using battery pack emergency lighting, but will be putting it on the generator in order to provide a more long term supply of power?

700.9(B) requires that emergency systems be kept separate from other systems (legally required, and optional stand by systems). If you are providing emergency power for the lighting with battery packs, then I would not consider the wiring from the generator to the battery packs to be part of the emergency system, but rather, optional stand by. In this case, unless you have other loads that would require emergency power, I see no need for a separate transfer switch.

If, on the other hand, you do not install emergency battery packs, but will rely on the generator for the emergency lighting power, then you need a separate transfer switch (or a separate generator) and will need to keep the wiring to the emergency lights separate from other wiring. In this case your generator will need to meet the requirements of 700.12(B). You mentioned the concern about start-up time. This is addressed by 700.12(B)(5).

 

[MadWulf]

I have a design dilemma i'm working through... I typically don't put egress lighting on the generator, as many local municipalities require battery packs regardless (start-up time is their explanation). But I have a distribution center that requires a generator to keep the facility up and running during an extended power outage. If this is the case, won't the lighting also be required to be on sustained power? I'm concerned that the local authority will require the building to be evacuated within 90 minutes, as that's the required limit of the exit/egress lighting battery duration. Also, if I do put the emergency egress lighting on the generator, will I need a separate transfer switch? I'm thinking I will, but I can only find that requirement in the healthcare section of the NEC (NEC 517.32).

The local authority cannot require that the facility be evacuated within 90 minutes. The 90 minute rule is from the life safety code, to give adequate time for the building to be evacuated in an emergency.

If you have battery packs installed to meet the 90 minute requirement, and no other emergency loads, the generator is considered an optional standby unit. You can have one transfer switch for the entire facility, which I have done numerous times.

If you are using the generator for your life safety lighting, the generator is considered a legally required unit. You will need a separate transfer switch for the 700 loads. The 701 and 702 loads can share one transfer switch as long as the breakers are selectively coordinated.