I am doing a very large lighting system and many of the fixtures are NM which represents 'emergency ballast'. They are to be wired before the contactor. Now doesa this mean the ballast has some sort of backup to keep the light illuminated in case of power failure?
Don't know the meaning of the acronym "NM", but if your fixtures are controlled by a contactor, then the fixtures that need to have emergency lighting must have battery backup somewhere. Battery packs can be installed on fluorescent fixtures easily. HID fixtures usually use a quartz lamp on a battery. Or they may all be on an emergency generator which will, by Code be up and running within 10 seconds. Hope this helps.
NM is just the way the emergency fixtures are identified on the print. I know what you are talking about with the HID's, I have used them. But the customer is ordering all the fixtures because they are a engineering/architect design firm and they wanted to get the fixtures themselves because this is what they do. Any way, the person I went over the job with said these 'NM' fixtures have emergency ballasts. The print also states that these fixtures are to be provided with 'emergency ballasts'
Your fixtures are going to have battery back up. The battery requires a non-switched supply fed from the same circuit feeding the fixture. When the battery loses power it kicks in to supply the lamps for a specified period of time. These fixtures can be wired either as night lights or so they turn off with the lighting control.
I've installed EM ballasts for a restaurant, and the addition of the red ballast and a test switch and indicator light was all there was to it. I'm guessing the red EM ballast has a battery pack built in it...
Interestingly enough, the directions said to cut the "common" (neutral) with the momentary test switch for testing purposes.
I also remember that they were expensive beasts too...
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
Run the EM fixtures off of the same light circuit as the lights in that room. Pick it up ahead of the switch. The fixture itself can be switched or not, but you"ll have to have a continuous supply to the EM ballast.