Central emergency lighting inverters....code compiant? how?

[Noobdesigner]

So anyway i am a junior designer working under an engineer. One of our clients is insisting we use a central inverter for their emergency egress lighting. My engineer is fighting them and telling them that the installation would not be code compliant due to the fact that the fixture designated "emergency" in a given area needs to be on the branch circuit serving that area in accordance with

700.12(f)

"The branch circuit feeding the unit equipment must be the same branch circuit as that serving the normal lighting in the area and connected ahead of any local switches."

how does a centrally located lighting inverter comply with code if it is NOT powered by the local branch circuit serving an area. the idea is to have this single inverter power emergency egress lighting throughout the entire facility even though there are multiple local branch circuits for lighting. If for some reason one of the branch circuits drop, the room would be in darkness. I apologize if this is worded funny as i am still learning and my head has been in the 700 section of the NEC for 3 days trying to figure out how a central lighting inverter meets the most basic code requirements. Any insight would be appreciated.

 

[dkidd]

Hint: look at the definition of unit equipment. 700.12(F)

 

[steve66]

Yes, if you have a central lighting inverter, you do not have unit equipment.

Unit equipment lights are normally off. They turn on when the branch circuit looses power.

Lighting inverters are normally connected to lights that are on 24x7. Normally they just pass utility power to the lights. When the power goes out, the battery kicks in and the lights stay on.

It does have to be a listed emergency lighting inverter. Not just a regular UPS.

Tread lightly with your boss - some people willing to accept they are wrong, and others aren't.

 

[jcbabb]

The way I design egress lights using an inverter (most of the time) is to have the inverter constantly powering the egress lights. The lights are controlled with a local UL-924 transfer device such as a Bodine BCLD-20B. This device is a relay that is controlled along with the local lighting control (usually a switch). In the event of a loss of normal power (at the local branch circuit); the relay will turn the egress lights on regardless of the local switch status.

http://www.bodine.com/products/specs/blcd20b.html

 

[Electric-Light]

The unitary emergency lights have to be on the same branch in order to be able to detect lighting power loss. They work just like those little thing with a built in battery that you plug into an outlet. If the lighting loses power but the outlet continues to receive power, it won't know there's an outage.

Central inverter requires care in a very different way. If you have all the lights on same branch and fed from a UPS, a fault in any single fixture or anywhere in the branch will leave the entire area in dark. This includes things like non-compatible lamp shunting out a socket of a jury rigged non-compliant conversion such as ballast bypass TLED. For a narrow space like corridors, to successfully use remotely fed power requires two rows of fixtures with each row fed from a separate branch or have alternate fixtures on different branch so a short in one fixture will not cause the entire area to black out.

 

[IMFOTP]

For a narrow space like corridors, to successfully use remotely fed power requires two rows of fixtures with each row fed from a separate branch or have alternate fixtures on different branch so a short in one fixture will not cause the entire area to black out.

I'd be careful about the term "requires". Its good practice but I'm unaware of a code reference that requires this. If I'm mistaken, please let me know, wouldn't be the first time.

 

[ron]

Central inverters are a good idea because there is a single place to test monthly, and easier to maintain the batteries.

For the unit equipment scattered around the building, it never gets the NFPA 101 monthly tests and maybe only occasionally gets the required yearly tests (unless you buy one that tests itself automatically).

 

[Jon M]

I'd be careful about the term "requires". Its good practice but I'm unaware of a code reference that requires this. If I'm mistaken, please let me know, wouldn't be the first time.

Section 700.17 is pretty clear that you are required to have two branch circuits from separate sources in spaces containing emergency lighting, one of which is normal, and one that complies with subsections 1 or 2. So this would back up the "requires" in the post. Keep in mind that this is talking about the emergency lighting system at the branch circuit level so feeding an area from a single circuit that is supplied from a panel sourced from an ATS would not meet the requirements.

 

[IMFOTP]

Section 700.17 is pretty clear that you are required to have two branch circuits from separate sources in spaces containing emergency lighting, one of which is normal, and one that complies with subsections 1 or 2. So this would back up the "requires" in the post. Keep in mind that this is talking about the emergency lighting system at the branch circuit level so feeding an area from a single circuit that is supplied from a panel sourced from an ATS would not meet the requirements.

Thought he was saying you needed two emergency circuits for redundancy, hence...the "so a short in one fixture will not cause the entire area to black out" remark.