Florescent Fixture problem

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fire_man

fire_man

Minister of Fire
Feb 6, 2009
2,702
North Eastern MA
Two years ago my 24 inch single T12 tube magnetic ballast fixture stopped turning the bulb on unless I touch the bulb. I changed the bulb, still not working. Changed the Ballast, same thing. If I touch the bulb it pops on. If I wrap a bare wire around just a few inches of the bulb and ground this wire to the fixture it lights without having to touch the bulb. I sanded the point that the main ground wire attaches to the fixture and tightened it really well, still won't work. This only happens in summer time. When the air dries out and it cools off in the house it works fine even without the wrapped ground wire. I cannot figure this thing out??
 
hi fire_man
check to see if your ground is attached to circuit panel. you could have lost a ground on the way to the fixture. get a tester or meter or something like that. go from the black or red wire and touch the ground wire to see if you have 120 volts. if nothing try touching the meter or tester from white to ground if you have voltage try to find the reversed wires or reverse your fixture wires to be ballast black to feed white or hot, then white to the other. most times i have run into this, is because of a lost ground. also double check the wire that go into the end caps.
let me know how you made out

frank
 
fbelec said:
hi fire_man
check to see if your ground is attached to circuit panel. you could have lost a ground on the way to the fixture. get a tester or meter or something like that. go from the black or red wire and touch the ground wire to see if you have 120 volts. if nothing try touching the meter or tester from white to ground if you have voltage try to find the reversed wires or reverse your fixture wires to be ballast black to feed white or hot, then white to the other. most times i have run into this, is because of a lost ground. also double check the wire that go into the end caps.
let me know how you made out

frank
Click to expand...
I am confused by your answer, the ground is for safety, neutral is for the electron flow back to panel, are you saying he has lost the neutral?
 
Oldspark I'm not sure about the physics of it but frank is right. If I lost my ground the bulb won't light. It's got something to do with the charges need to light the bulb. By touching the bulb with my hand and seeing the bulb light,I think it proves its a grounding problem. The fact that I wrap a bare wire around the bulb and ground it, and it works also supports the ground being the problem. The fixture is designed so that the bulb is physically close to the fixture's metal housing and the bulb depends on that proximity to turn on. I don't know why humidity affects it in my case. The fixture used to work fine and no wires were switched before the problem started. I will check the ground back at the panel tomorrow and post back. It really smells like a bad ground.
 
Unless you have some kind of special light the ground is for saftey, I have fixed all sorts of lights on my old job, the ground should be hooked to the frame work of the light and the neutral to the ballast and the hot to the other wire on the ballast.
 
I got this from a site specializing in electrical problems and have read it many times:


Rapid Start and some Instant Start fixtures must be connected to an electrical ground in order to start properly. In addition, the metal reflector of the fixture must be correctly installed so that it is within 1/2 inches of the lamps AND is in electrical contact with the ballast. A capacitive field is created between lamp and the metal reflector by the ballast during the starting process, and without this field, the lamps may reach normal operating brightness only by an external influence, such as an increase in capacitance caused by you touching the lamps, or by an increase in light (ionization) in the area coming from other sources.
 
Update: I measured the black fixture wire wrt bare ground wire and got 116 vac. Black wrt white Neutral also 116 vac. So all is good there. Ground wrt neutral measured nothing. I traced the bare ground all way into the panel and sure enough its solid on the ground bus, as is the Neutral from that branch circuit. I even sanded the Ballast where it makes contact with the metal housing of the Fixture so the Ballast has a good ground and measures 0 ohms wrt bare ground wire. What the heck is going on with this fixture, bulb only starts if I touch it! Could I have a SECOND bad ballast??
 
Is this a cheap fixture? It looks like they are wired the same as a standard ballast, will it work the same way if yu un hook the ground altogether just for trouble shooting the light.
 
fire_man said:
Oldspark I'm not sure about the physics of it but frank is right. If I lost my ground the bulb won't light. It's got something to do with the charges need to light the bulb. By touching the bulb with my hand and seeing the bulb light,I think it proves its a grounding problem. The fact that I wrap a bare wire around the bulb and ground it, and it works also supports the ground being the problem. The fixture is designed so that the bulb is physically close to the fixture's metal housing and the bulb depends on that proximity to turn on. I don't know why humidity affects it in my case. The fixture used to work fine and no wires were switched before the problem started. I will check the ground back at the panel tomorrow and post back. It really smells like a bad ground.
Click to expand...
try holding the wire & touching the bulb with the wire 2 see if it works same as touching bulb with finger?
 
Hate to say it, but I've had the same problem with two fixtures. Sometimes they light just fine, other times they come on dimly and then after awhile light as normal, and then sometime they don't come at all until I touch the fixture or bulb. I also replaced the ballast and tried new bulbs. Very frustrating.
 
sometimes a bulb that is marked energy saver gives you problems like this. brand new it may or may not work, and if it works, it only lasts a while. check the number on the bulb and check to see if it compatible with the ballast. i know your fixture is smaller, but i have this problem with the t12 size bulb that is 4 foot and 34 watts. nothing but a headache. sounds like you got a good ground, and it's wired right. if you don't have a 2nd bad ballast, i would try getting a small piece of tin foil and keep folding untill it is big enough to squeeze between the bulb and fixture and see if that works.
 
fbelec said:
sometimes a bulb that is marked energy saver gives you problems like this. brand new it may or may not work, and if it works, it only lasts a while. check the number on the bulb and check to see if it compatible with the ballast. i know your fixture is smaller, but i have this problem with the t12 size bulb that is 4 foot and 34 watts. nothing but a headache. sounds like you got a good ground, and it's wired right. if you don't have a 2nd bad ballast, i would try getting a small piece of tin foil and keep folding untill it is big enough to squeeze between the bulb and fixture and see if that works.
Click to expand...
Good point I have seen the ballast not rated for the type of bulb being used and it not working correctly.
 
The flourescant fixture over my sink does the same thing.
I even replaced the whole fixture and 6 months later the new one does the same thing.
Seems worse in Summer vs Winter.
 
this type of problem is why i think they made the move to t8 and t5 bulbs. besides being brighter and they start much faster. in the 4 foot size bulb if you had trouble with 34 watt bubls or 25 watt bulbs you drop in a 40 watt and the fixture works flausless.
 
Try touching the light with something insulated like a pencil and see if the light still comes on.
 
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