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Emergency Egress Lighting: Generator -vs-Unit Eq. #174980 02/18/08 09:56 PM
Joined: Oct 2000
Posts: 2,721
Scott35 Offline OP
Broom Pusher and
Hello all!!! smile

This question might be better suited in the Building Codes area, but it also is NEC relavent.

Question is in regards to Emergency Egress Lighting (Fluorescent fixtures, not Exits):

I am involved in the Design and Engineering of a very large, new Industrial project (+375,000 sq,ft. , then 230,000 sq. ft. in future).

The customer will have a Generator, which will be used for powering loads designated as "Emergency Loads" (critical loads).

We (the Electrical Design Team) wish to drive the Emergency Egress area lighting from the Generator, as opposed to having the typical Unit Equipment installed for the "Emergency Lights".
(FYI: "Unit Equipment" = Fixtures with Battery Back-up Ballasts included within the fixture assembly).

The problem with using Unit Equipment is there will be close to 100 Emergency fixtures installed in Freezer / Cooler areas, having normal ambient temperatures of -20ยบ C on average.

In these situations, the Battery Back-up Ballast is normally mounted remote from the fixture (outside the Freezer "Box"), and an Insulated Panel Penetration is required at each fixture's location.

BTW:, the Exit signs will be Unit types, and will be on the General Lighting circuitry.


Will it be compliant to not have Battery Back-up Ballasts on the Emergency Lighting Fixtures, and have them driven from the Generator "Emergency Power" Panelboards?

In County of Los Angeles, we had to use Unit Equipment + connected to the Emergency Panels - but this was for a high rise Commercial Building.

Any responses are greatly appreciated.

Thanks in advance.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
2017 / 2014 NEC & Related Books and Study Guides
Re: Emergency Egress Lighting: Generator -vs-Unit Eq. [Re: Scott35] #174982 02/18/08 11:09 PM
Joined: Jul 2007
Posts: 1,335
sparkyinak Offline
2005 NEC 700 partS IV & V for lighs and 701 for genset requirements. An emergency generator can be used if it provides power within 10 secs and the AHJ as well as local codes allow it

"Live Awesome!" - Kevin Carosa
Re: Emergency Egress Lighting: Generator -vs-Unit Eq. [Re: sparkyinak] #174984 02/19/08 12:27 AM
Joined: Jan 2004
Posts: 1,507
George Little Offline
You may run into some problems with the AHJ due to the fact that the outage of individual circuits will not cause the generator to start. All is well and good if you have a utility failure but probably not if you have a limited outage inside the building. We ran into that with an assisted living building and the Building inspector and Fire inspector would not permit it. As for the Electrical inspector (me) I could not find a problem just by referencing NFPA 70.

George Little
Re: Emergency Egress Lighting: Generator -vs-Unit Eq. [Re: George Little] #174985 02/19/08 01:59 AM
Joined: Oct 2000
Posts: 2,721
Scott35 Offline OP
Broom Pusher and
Thanks for the replies, Guys!!!

The real trouble of verifying this particular scenario with the AHJ, is I have left several messages with the Building Department (both voicemail and talking to an actual person), with no reply yet.
This is causing me to run behind on the total Lighting Design + Engineering, not to mention the total Emergency Power System's Equipment (Panels and Genny sizing).

If the trend of non-replies continues from this particular DBS, I might try querying another Building Department - one which is a large metropolitan area, and has stringent requirements.

Again, thanks for the replies and the references.

Will let you know the outcome.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Emergency Egress Lighting: Generator -vs-Unit Eq. [Re: George Little] #175002 02/19/08 11:49 AM
Joined: Jul 2007
Posts: 1,335
sparkyinak Offline
Typically in a design of such nature their are more then one lighting circuit in each area. For example one or two circuits from the emergency pane and others from the regular panel. Many designs of large areas have "nights lights" that are on 24/7. In the concept Scott35 is proposing, the NL's which double as emergency lights and exits would be on the generator panel and the other areas would be in other panels. The likelyhood is slim that both circuits in the same area and the same time would fail. Someone would notice if the emergency circuit had failed if wired in this manner.

And of course the AHJ must be on board with it.
You could even switch the NL's providing they were wired in a manner where if the generator would fire, it would energize a contactor that would by-pass the switch legs. It is not cheap but on the size of facility Scott35 is working on, that could finacial incentive that can be determined with some cost analysis to see the savings would offset the cost. The cost which is basically the cost of the contactor and parallel run of wire with each e-lighting circuit. In a sense it would like placing a three way switch (the contactor) under supervised control (to meet NEC 700) and switching the only one of "travelers" at the load end.

You could even wire it that if the coil or control circuit failed on the contactor, fail safe mode would engage the e-light circuits. It would be noticed and it could be fixed.

"Live Awesome!" - Kevin Carosa
Re: Emergency Egress Lighting: Generator -vs-Unit Eq. [Re: sparkyinak] #175007 02/19/08 12:11 PM
Joined: Mar 2005
Posts: 1,213
SteveFehr Offline
The best option is use both, especially if you're only using a single/non-redundant generator. You have battery ballasts while the generator starts, and you have generator to keep the lights on far longer than the battery can. And you have redundancy in case either the batteries or the generator fails- or if the breaker trips.


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