NFPA 101 Egress Lighting Performance of System

[cyriousn]

I have a question on everyone's interpretation of the following verbiage from the life safety code.

It states that the emergency lighting system is to be arranged to provide the required illumination automatically in the event of any interruption of normal lighting due to any of the following:

? Failure of a public utility or other outside electrical power supply,

? Opening of a circuit breaker or fuse, and

? Manual act(s), including accidental opening of a switch controlling normal lighting facilities.

What I'm trying to figure out is what circuit breaker or fuse they are talking about? Do they really mean to say is that its required to run two seperate branch circuits to a relay such as a Bodine GTD series, before you wire over to your emergency lights?

Thanks in advance for any input.

 

[skeshesh]

That is my understanding of it but, as I'm sure you know, this requirement can be satisfied using emergency battery packs rather than wiring a second circuit as is often the case in small jobs or partial remodels of smaller offices, facilities, etc.

 

[steve66]

Normally, most lighting in an area would be from a normal circuit. Then a few "emergency" lights would be wired to the emergency circuit (or to your GTD).

That way you are covered from any single breaker being turned off or tripping.

Steve

 

[cyriousn]

Okay, so by them saying the tripping of a single circuit breaker they don't mean the circuit breaker feeder the emergency lights? Maybee I'm way overthinking this but the Bodine GTD can be used to handle three conditions.

1. The emergency lights are being fed from a normal circuit breaker under normal conditions.

2. The normal panel main circuit breaker trips but the generator is not on but the relay senses the normal circuit trip and switches to the emergency panel using normal utility power.

3. The utility power fails and the emergency lights receive the generator power through the relay.

Is scenario 2 really anything to worry about?

 

[skeshesh]

Okay, so by them saying the tripping of a single circuit breaker they don't mean the circuit breaker feeder the emergency lights? Maybee I'm way overthinking this but the Bodine GTD can be used to handle three conditions.

1. The emergency lights are being fed from a normal circuit breaker under normal conditions.

2. The normal panel main circuit breaker trips but the generator is not on but the relay senses the normal circuit trip and switches to the emergency panel using normal utility power.

3. The utility power fails and the emergency lights receive the generator power through the relay.

Is scenario 2 really anything to worry about?

NFPA 101 7.9.2.3 Clearly says "in the event of any interruption of normal lighting due to any of the following...". So if any "normal" lighting is interrupted due to an open breaker, then the breaker must belong to the normal power distribution system.

The usual way this is done is either using battery packs, or connecting the emergency system to a few fixtures in the area. The method you're suggesting can be used but is not necessary. If you simply connect a few fixtures in the area to the emergency source making sure you reach the illumination levels required, then you've provided means to automatically provide emergeny lighting despite the fact that nothing is being switches.

Now one issue is that with that approach the emergency fixture is usually on an unswitched circuit. In larger facilities, specially for medical facilities, college campuses or military operations this is acceptable and I've seen it done many times. With a smaller client it may be unacceptable to leave some lights on all the time, but then again smaller clients usually dont have an emergency system and fixtures with emergency battery packs are used as they are the only solution.

 

[steve66]

Is scenario 2 really anything to worry about?

No, nothing to worry about because the emergency lights are still on.

 

[cyriousn]

thanks for the help.