Red goes to ground, right Sparky?

April 17, 2006 6:53 PM

How to: multiple fluorescent light fixtures on one circuit

For a specialty lighting project, I'm backlighting a largish sign such that a single 24" lamp won't do it and a double lamp puts the bulbs too close together.

Can I wire up two 24" single bulb fluorescent fixtures in parallel?

If so, it's just black to black to the switch and then to hot; and white to white to neutral (and of course, ground to the lovely green screw in the fixture), right?

You can assume that I'm scrupulous about wiring, but that nearly all of my experience is either replacing existing wiring or with low-voltage wiring.

posted by plinth to home & garden (7 comments total)

That's how you do it.

Be careful about how the wire runs, make sure it is all held down securely - between the lights, and with cable clamps where it enters/exits all the boxes.

At 35W per 24" bulb you are a long way from overloading the circuit, but that is the next thing to worry about.
posted by Chuckles at 7:38 PM on April 17, 2006

>Can I wire up two 24" single bulb
>fluorescent fixtures in parallel?

Don't see why not.

>If so, it's just black to black to the switch and then to
>hot; and white to white to neutral (and of course,
>ground to the lovely green screw in the fixture),
>right?

Er, I assume the above means:

Black (hot) from the building to black (hot) wire on the fixture, this line leads to the switch and thence the load.

White (neutral) from the building connects to white (neutral) wire on the fixture, if you follow that wire it also goes to the load, which in this case would be the ballast (probably a rectangular black metal box)

The green or bare copper wire from the building is your ground and would connect to another green or bare copper wire on the fixture, or if the fixture doesn't have one, you would secure it to the metal housing of the sign.

Your second light would run in parallel to the first. Where you wirenut together the wires from the building and the wires from the fixture are logical points to add the second set of leads for the second light. You may have to go up a size with your wire nuts. A nice feature of your parallel wiring is that if one fixture dies the other will just keep on going.

Naturally, you realize that the switch on the one fixture will not stop current going through the other fixture while you're happily working on things. There is the question of the total load on the circuit, but two 24 in fl. bulbs is what, maybe 40 watts max, which is not that much.

I should mention that my answer is aimed towards North American wiring. If you're in Europe it could be different. PS. I'm not a real electrician, this is not real advice, yadda, yadda, yadda.
posted by Ken McE at 7:50 PM on April 17, 2006

We just had 5 48" Fluorescent light fixtures, each with 2 bulbs pulled out of our lovely kitchen today. They were all on 1 light switch. I don't think you'll have a problem.
posted by smithmac_99 at 8:08 PM on April 17, 2006

Um, you're just going to use one ballast, right? An electronic ballast will do up to four bulbs, includes wiring and everything. (Though *you* just need to buy a two-bulb one.) Sure, you might want two fixtures to spread the light, but you only need one ballast - two would be a needless waste.

Electronic ballasts use less electricity and don't buzz. Make sure you get an electronic and not a magnetic one.
posted by jellicle at 8:44 PM on April 17, 2006

Thanks for that tip Jellicle. I'm going to remember that the next time I string up some lights in a garage.
posted by odinsdream at 9:28 PM on April 17, 2006

Jellicle - thanks for the tip - I'll try that next time. I already have the fixtures and they both have independent ballasts/transformers.
posted by plinth at 4:23 AM on April 18, 2006

Perfect. Worked first time.
posted by plinth at 11:43 AM on April 20, 2006