Full Back-Up Generator and Emergency Loads

M

msilva94

Member
Location
PA, USA
Occupation
Electrical Engineer
Hello all,

I’m working on a site where the client wants the entire 800A Main Distribution Panelboard (MDP) backed up by a single generator.
They also want to avoid using battery backups for emergency lighting. I'm figuring to place the lighting on a new 100A Panel 'EM', but not sure how to provide normal power to it.

Per code, emergency lighting must be powered from a source separate from normal lighting.
Here was my brief thought:
  • 800A MDP powers:
    • Circuit 1 – 400A Panel 'A'
    • Circuit 2 – 400A Panel 'B'
    • Circuit 3 – 100A Panel 'EM'
  • 800A ATS feeds the MDP (normal loads backed up by generator)
  • 100A ATS feeds Panel 'EM' (emergency lighting backed up by generator)
The issue is that if Panel 'EM' is fed from the MDP, this creates a loop.
I’m struggling to figure out a simple solution without introducing more equipment.

Thanks in advance.
 
I don't know how to do emergency lighting without a battery pack. Either at the light(s) or some type of inverter system.

If this is normal lights that they want backed up by the generator then you are okay. That isn't considered emergency lighting. The lighting required for egress during an outage, fire or similar event are considered emergency lights. Like the exit signs.
 
Elect117 said:
I don't know how to do emergency lighting without a battery pack. Either at the light(s) or some type of inverter system.

If this is normal lights that they want backed up by the generator then you are okay. That isn't considered emergency lighting. The lighting required for egress during an outage, fire or similar event are considered emergency lights. Like the exit signs.
Click to expand...
If the fixtures are battery inverter driven, it’s not too big of a deal. It appears the transferswitch for the emergency lights is separate from the other loads which is required, but the generator will have to start, and that transferswitch transfers in under 10 seconds to qualify. If not, then the battery backup must be maintained. If the emergency lighting is battery powered heads, such as bug eyes, new wiring will be required to existing fixtures to provide illumination requirements.
 
Keep inn mind that if you use the generator as an emergency supply to e lights, that wiring must be seperate from other wiring. Suggest a review of Art 700. It’s much simpler to use battery e lights.
 
qcroanoke said:
Is this a legally required emergency system?
And as Tom said battery emergency lights would make life much easier...
Click to expand...
This is a really good point, many people call normal back-up generators, "emergency back-up" when they are not legally required.
 
don_resqcapt19 said:
You run circuits from an Article 700 Emergency System. Have done it a few times per project specs.
Click to expand...

I guess I am a little confused. Lets say we have a lighting panel feeding all of the lights with egress / EM lights on certain branch circuit(s). I thought those lights would require a battery system at the light or a panel that is feed by an inverter + battery from a feeder. Then the lights come off that.

I didn't think there was a way to feed it off gas generator because the loss of power for however many seconds was a problem. But I guess not. 700.12 give you up to 10 seconds. I just thought battery in the light or on an inverter battery system was the normal.
 
msilva94 said:
The issue is that if Panel 'EM' is fed from the MDP, this creates a loop.
I’m struggling to figure out a simple solution without introducing more equipment.
Click to expand...
If you really want to have emergency lighting, you will have to apply Article 700. The normal power for the 100 amp EM panel would have to come from the line side of the 800 amp MDP.
 
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