fluorescent fixtures

[jemsvcs]

Went to troubleshoot two 4' fluorescent fixtures (with rapid start ballasts) on the same circuit. The circuit cable has no equipment ground and as you can guess - the fixture lamps don't always come on at first unless the owners do the old scoot-your-feet-and-rub-the-lamp-trick :roll:

After looking at the building layout (which has been remodelled about a half dozen times over the years), there is not an easy way to pick up an equipment ground. Any other ways to get the lamps to start without the equipment ground?

 

[Leitmotif]

Re: fluorescent fixtures

I have seen an equipment ground required for something to work in only two cases
1. Proximity sensing switches for 110 V lighting
2. Computer UPS
I don't nessarily understand why but that is what the directions said so I did it of course.

You should not need a ground for the lights to work. Just a hot and a neutral (assumming 110 or 277). The ground should not be part of the circuit and should not carry current under normal circumstances.

What is voltage between hot and neut?
What is voltage rating on ballasts
Are you putting in the right tubes ie T 12 in a T 12 ballast etc etc? T 12 does not work well in T 8.

Dan Bentler

 

[wirenut1980]

Re: fluorescent fixtures

The lamps and ballasts might be low quality as well. If the fixtures are cheapo's, maybe they need better ones, or replace it with a new cheapo.

 

[infinity]

Re: fluorescent fixtures

The circuit cable has no equipment ground

What kind of cable is it? Type AC cable doesn't require a EGC since the outer jacket is one. Same holds true for 3/8" FMC without concentric or eccentric KO's.

 

[jemsvcs]

Re: fluorescent fixtures

The fixtures have old NM cable run to them (of the rubberized-cloth type).

 

[jemsvcs]

Re: fluorescent fixtures

The lamps are often (but not always) starting only when someone touches or brushes the lamp (i.e., static electricty).

I know that many fluorescent fixtures require the fixture to be grounded and the bulb to be within 1/2 inch or so of a grounded reflector or other grounded sheet conductor. All this affects the electric field distribution within a bulb undergoing a starting attempt.

It is possible that aging bulbs, a bulb-ballast mismatch, low temperatures, corroded socket contacts, low quality ballasts, or low line voltage could also be the problem. In this instance, however, everything points to grounding.

So, my original question...is there a way to initiate starting without an available equipment ground?

 

[jim dungar]

Re: fluorescent fixtures

According to Advance Transformers, the ground is used as a starting aide for rapid start lamps.
See page 9 in their pocket guide.

 

[jemsvcs]

Re: fluorescent fixtures

Great link Jim!

Going back to my original question... ...I know that the problem is that the fixture housings have no equipment ground, but there is no easy access to run one for these fixtures. Is there any other way to initiate starting short of replacing the fixtures with incandescent lighting?

 

[jim dungar]

Re: fluorescent fixtures

Actually the lamp is not looking for a ground but rather a large capacitor plate, that's why they work when you touch them. Maybe a connection to any large metal object even just a length of wire.

It is possible that electronic ballasts (which have a higher starting voltage) might work instead of magnetic ones.

[ September 28, 2005, 04:51 PM: Message edited by: jim dungar ]