Contactor for Emergency Only Panelboard

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Sunny_92

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Electrical Engineer
I'm re-designing an emergency system backed up by a generator that contains a normal-emergency panel and an emergency-only panel. Many older installations I've seen use a typical lighting contactor to energize the emergency-only panel when the generator transfers to emergency. My question is, for new installations, does this contactor need to be listed for emergency use? Article 700.25 almost leads me to believe it does, however I haven't found any larger contactors/relays (>50A) that are listed for emergency use. One-line attached for reference.

Emergency One-Line.JPG
 
Typically you’d do this by feeding an essential power panel direct from generator switchgear with no ATS between. Of course this panel would normally supply power to one side of the ATS’s.

More info about the load would help. Trying to understand a load that only needs power when utility source fails.
 
Russs57 said:
Typically you’d do this by feeding an essential power panel direct from generator switchgear with no ATS between. Of course this panel would normally supply power to one side of the ATS’s.

More info about the load would help. Trying to understand a load that only needs power when utility source fails.
Click to expand...
That is my confusion here, that just doesn't normally happen that way. There may be occasional item that only comes on during normal power failure, but most the time we want to back up something that we don't want shutting down at all with emergency systems.
 
It’s an option sometimes employed to feed just the emergency lighting circuits, rather than have a bunch of individual Load Control Relays on each circuit. But the UL 924 listing issue gets in the way of that. I don’t know of anyone that has large contractors that are listed under UL 924.
 
Russs57 said:
Typically you’d do this by feeding an essential power panel direct from generator switchgear with no ATS between. Of course this panel would normally supply power to one side of the ATS’s.

More info about the load would help. Trying to understand a load that only needs power when utility source fails.
Click to expand...

Jraef said:
It’s an option sometimes employed to feed just the emergency lighting circuits, rather than have a bunch of individual Load Control Relays on each circuit. But the UL 924 listing issue gets in the way of that. I don’t know of anyone that has large contractors that are listed under UL 924.
Click to expand...

Exactly. The panel in question (EE) only feeds egress lighting. The existing system has panel EE fed from the "emergency input" terminals on the ATS as seen below. The contactor for panel EE is controlled by the ATS position. I'm guessing that the contactor was used so that the generator could be exercised without illuminating the emergency lights.

Existing Emergency One-Line.JPG

I'm thinking my best best would be to move all the egress lighting circuits from panel EE to panel NE and install a UL 924 ALCR on each circuit. Thoughts?
 
if they are egress lights (located on the means of egress path IE, corridors, stairwells) they have to be on all the time the bldg is occupied. It's code violation to have them turn on only on emergency.
 
Gshell82 said:
if they are egress lights (located on the means of egress path IE, corridors, stairwells) they have to be on all the time the bldg is occupied. It's code violation to have them turn on only on emergency.
Click to expand...

Is that true if there is other lighting normally on in these areas that is fed from panels not backed by generator?
 
Gshell82 said:
No I think you'd be good if they are always on and not switched.
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The hallways have 2x4 fluorescent fixtures, most of which are fed from a "normal power" panel and controlled by standard toggle switches which are located there in the hallways. About half of these fixtures contain an additional socket with a CFL that is wired to panel EE. However, there are also a few fixtures that have the 4' fluorescent bulbs wired to panel NE.

Panel EE only feeds these CFLs and a few other fixtures in various rooms and outside exterior doors that appear to be for emergency egress lighting. Panel NE feeds the exit signs, the few 2x4s mentioned above, and a few loads that would be probably be classified as optional standby (which will get moved to a different ATS when the generator is replaced).

Without running lighting calcs, it looks like all of the fixtures fed from EE & NE are required for emergency egress lighting. If that's the case, is NFPA 101 7.9.2.3(3) saying that the lights fed from EE need to come on automatically if someone accidentally hits one of the hallway light switches?
 
In general the emergency lights need to come on when *unswitched* power from the circuit goes away, not when the switch is turned off.
This is hard to achieve if only switched power is available. :)

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