fluorescent light fixture wiring

billeddJune 2, 2014

From what I can tell there are 2 fluorescent 6 foot 2 bulb fixtures wired together, meaning a wire runs from one to the next and then on to a junction box where there is an incandescent light fixture attached - just a simple fixture with an exposed bulb in a basement. I don't know if they are wired in series or in parallel. A switch turns on that incandescent light.

One fluorescent fixture has both bulbs in it and the other has no bulbs. Since an electrician lived in the house I am assuming that the fluorescent fixtures, since they seem to be wired to the incandescent fixture, would come on when the switch is flipped to turn on the incandescent light but they don't. Only the incandescent light comes on. I have not checked the fluorescent bulbs to see if they are good yet and obviously have not bought any to put in the empty one.

So, for now, my question is, assuming the fluorescent lights and the incandescent light fixture are all wired together and correctly to the one switch that turns on the incandescent light, should the one fluorescent light fixture that has bulbs also come on, assuming they are good? Or, with the same assumption at the beginning, will I need to have good bulbs in BOTH fluorescent fixtures to make them come on when I flip the switch? It only makes sense to me that they would have been all wired together but of course my logic does not mean that would be someone else's logic.


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They are not "in series". Each is an independent luminaire (light fixture). You don't need bulbs in one fixture for the other to operate.

Fluorescent fixtures can also have bad ballasts which can prevent them from working.

    Bookmark   June 2, 2014 at 5:11PM
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There are fluorescents that do have the lamps in series-- each lamp has a single larger pin on each end. Removing one lamp on those fixtures shuts off both lamps.
For most fluorescent ballasts of the past, powering the ballast with no or bad tubes actually increases the power drawn by the ballast and causes the ballast to overheat, there by shortening the life of the ballast. Not sure if that is true of the latest generation of ballasts-- but what is the point of powering the ballast if no light is being produced?

    Bookmark   June 2, 2014 at 6:01PM
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Forgot about those industrial lamps in series. Reading the OP, I didn't get that. A picture might help.

    Bookmark   June 3, 2014 at 12:11PM
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The OP's first question should be:
"Do I need to buy a cheap $10-$20 analogue multimeter, get familiar with it, and then take readings to sort out this puzzle?"

Why yes, as a matter of fact, you do.

    Bookmark   June 3, 2014 at 6:35PM
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The could be wired any way, but if there are no switches associated with the luminaries themselves, it is pretty safe to assume that they are all controlled by the same switch.

Some ballasts will keep one lamp burning when the other is shot. Some do not. The ballast in the luminaire with no lamps might have the ballast disconnected internally. The luminaire can be used as a passage for individual insulated conductors and if the luminaire is completely removed, a length of cable may need to be spliced in to keep the circuit complete if that luminaire is in the middle.

In my house and garage (formerly an electrician's), I have at least 15 of these twin-lamp, slimline, T12 luminaires. I have converted some of them to quad-lamp T8s. I would not do it on your scale of 2 luminaires.

Are these 8-footers going to be turned on and off a lot? If so, get rid of them and put up some new t8 luminaires. Make sure that the replacement luminaire ballasts are "program start", suitable for occupancy sensor. Unfortunately, a lot of inexpensive residential luminaires, shop lights and strip lights, have instant-start ballasts. These are pretty stupid for residential use.

The "instant start" ballasts, the only kind available for the 8' slimline equipment that you have, is suited for turning on and leaving on for several hours at a time. Striking them repeatedly and leaving them on for short periods shortens the lamp life considerably.

If you are going to turn them on and leave them on for long periods (all day), you might consider getting replacement t8 slimline ballasts and lamps (tubes). Consider installing some chain switches in them so they can be turned on after the switch is thrown on the light circuit turning on the incandescent if the incandescent is needed frequently.

What other salvaged electrical equipment has the former owner installed?

    Bookmark   June 4, 2014 at 9:12PM
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