Maximum number of emergency lights?

[westgbazo]

Hello,

I have a new boiler building that will have 277v emergency light fixtures. The normal lighting would have to be 120/208v, since 277v normal power is not an option. The owner is asking that we put ALL fixtures in the building on the 277v life safety panel. NEC 700.15 and emergency/path of egress illumination minimums appear to allow this. I wanted to check if someone has done something similar or if I'm missing a code requirement somewhere.

Thanks!

 

[jimport]

How would the emergency lights be triggered with power loss from another source? Why can't you add the emergency lights to the 120?

 

[westgbazo]

The 277v panel is connected to a generator via ATS. If all fixtures in the building were put on this 277v panel, then all fixtures would be egress/emergency lighting when the generator kicks on. The available 120/208v source is normal power only. The owner does not want two different voltage fixtures in the building.

NEC 700.15 says "...no lamps, other than those specified as required for emergency use, shall be supplied by emergency lighting circuits."

"As required" would refer to the building code and NFPA 101 7.9.2 minimum footcandle levels required for egress.

Since there is no maximum footcandle egress lighting requirements, the owner wants all fixtures to be 277v and on the life safety panel. Is there any reason we can't do this?

 

[Fred B]

The 277v panel is connected to a generator via ATS. If all fixtures in the building were put on this 277v panel, then all fixtures would be egress/emergency lighting when the generator kicks on. The available 120/208v source is normal power only. The owner does not want two different voltage fixtures in the building.

NEC 700.15 says "...no lamps, other than those specified as required for emergency use, shall be supplied by emergency lighting circuits."

"As required" would refer to the building code and NFPA 101 7.9.2 minimum footcandle levels required for egress.

Since there is no maximum footcandle egress lighting requirements, the owner wants all fixtures to be 277v and on the life safety panel. Is there any reason we can't do this?

The way I see the wording is that it is referencing a limitation on number of lamps on the emergency circuit as limited to the minimum required. Just because there is no maximum listed doesn't change the first statement and is limited to the minimum. If minimum is X footcandle and that can be acheived by 10 lamps, all additional lamps ARE "other than those specified as required".
Additional requirements found in 700.17 also might have implications that would prevent what owner wants. 700.17 indicates emergency lighting systems shall be provided by either 700.17(1) or 700.17(2).
700.17(1) says "An emergency lighting supply, independent of normal lighting supply, ...."
700.17(2) says "Two or more branch circuits supplied from seperate and complete systems with independent power sources."
Thus I don't see how having all lighting on the emergency power will meet these requirements.

 

[d0nut]

The 277v panel is connected to a generator via ATS. If all fixtures in the building were put on this 277v panel, then all fixtures would be egress/emergency lighting when the generator kicks on. The available 120/208v source is normal power only. The owner does not want two different voltage fixtures in the building.

NEC 700.15 says "...no lamps, other than those specified as required for emergency use, shall be supplied by emergency lighting circuits."

"As required" would refer to the building code and NFPA 101 7.9.2 minimum footcandle levels required for egress.

Since there is no maximum footcandle egress lighting requirements, the owner wants all fixtures to be 277v and on the life safety panel. Is there any reason we can't do this?

The codes for the emergency egress lighting and other similar systems typically require us to cover one simultaneous failure mode. Designing for multiple failure modes gets very expensive, but can be done if the design dictates such as in a data center.

In your scenario, you could not put all the lighting on the emergency branch because you would create a couple of single points of failure. Under a standard design with both normal and emergency lighting, if you lose normal power, the emergency lighting kicks on and gives you the required egress illumination. In your scenario, a failure of the transfer switch or emergency panel when normal power was still available would plunge your entire facility into darkness. A single failure could leave your building in the dark. In the standard design with both normal and emergency lighting, it would take two failures to make your building dark.

 

[westgbazo]

Thanks for the replies, everyone! I think I've got a good handle on the codes intent now, I just wish (like most sections) that it was a little clearer.