# 3 way switching & fluorescent lights



## jjapogee (Sep 6, 2010)

First time post- take it easy on me, folks...

I'm wiring new construction in a garage, and installing 3, 96" fluorescent controlled by 3 way switches. Power source at switch #1, 3 light fixtures, then switch #2. This is a 20A circuit, with 12 gauge wiring throughout.

I ran 12-3 from switch #1 to the first fixture, then two 12-2 wires between the 3 fixtures, and then 12-3 from the last fixture to switch #2. It worked- I got light, controllable at both ends- but the lights soon started to pulse and flicker slightly.

After an hour or two, one of the fixtures failed completely (not a bulb problem)- this is the fixture furthest from switch #1 (power source).

Does this wiring scheme sound appropriate? What would cause the flickering or outright failure? Thanks for any help.

Edit for below: I suppose that poor fixtures could be a problem- they are Lithonia T8 MVOLT 120-277v, about $55/ea from the Big Orange Box...suggestions for something better?


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## kbsparky (Sep 11, 2008)

Bad/cheap fixtures.


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## McSteve (Dec 8, 2009)

How exactly did you wire this up at each switch and light? I don't think you have enough wires to make this work.


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## AllanJ (Nov 24, 2007)

Just read this either from another part of this forum, or from another forum.

Many shop type fluorescent fixtures may not be mounted flush on the ceiling or else they will overheat and fail. The long metal housing acts as a heat sink for the ballast and needs to hang from chains.



> How ...?


Power to first switch -- 12-2.
First switch to first light -- 12-3 with white neutral and red/black travelers.
First light to second light -- One 12-2 is neutral continuing onward and switched hot coming back. Other 12-2 is traveler pair.
Second light to third light -- Same as preceding.
Third light to second switch (end) -- 12-3 with red and white travelers, and black for switched hot coming back.

Lights of course are connected to neutral and switched hot. Travelers just pass through the light boxes and could well have been strung unspliced past the outside of light box #2.


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## McSteve (Dec 8, 2009)

Whoops, I somehow missed the "_two_ 12-2 wires" bit. I thought you only had a single 12-2 between lights. :jester:

Assuming you have it wired like the diagram at the address below, and all the connections are good, then yeah, it's probably bad or overheating fixtures.

http://www.easy-do-it-yourself-home-improvements.com/images/Large-3-way-switch-4.jpg


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## jjapogee (Sep 6, 2010)

It is wired just as AllanJ has described (w/ 2, 12-2 wires between light fixtures). One of the 12-2 wires function as travellers.

The wiring scheme must have been correct, since it worked for at least an hour (controllable from either switch)...right?

The lights are essentially suspended (supported in the center and ends), running parallel/between truss chords- lots of airspace around them. Still, the ballasts were VERY hot.

Thanks for the responses thusfar.


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## frenchelectrican (Apr 12, 2006)

Most of the flourscent luminaire I have deal espcally with 8 footers you have to becarefull there is standard verison and high output verison 

The T-8 and T-12 do have same pin socket beside the slimline they are single pin { that diffrent story but I will leave this out due they are only oddball item on this class size }

So double check the ballast info to make sure you are useing the correct bulb.

And most flourscent luminaires I useally deal I put in a spacer a 2X4 will work very well on this one.

Due some of the flourcent ballast can get very hot as you noticed.

This part is true with High output ballast which I have ran into many time never surface mounted them that what kill the ballast pretty quick.

again I will remind you double check the flourscent bulb to the ballast to make sure they match up.

Merci.
Marc


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## jjapogee (Sep 6, 2010)

The bulbs are 32W T8 48", which is consistent with the fixture specs. The ballasts list this type of bulb as within the appropriate range.


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## frenchelectrican (Apr 12, 2006)

Ok if the case the ballast is bad talk to the big box store where you got it from and go from there I am pretty sure either they will have to replace the whole luminaire or the ballast one of the two.

Normally I get the luminaires from electrical supply they are better products than big box store { not aways the case }

The other thing with multivoltage ballast once you hit with surge or spike it will lock in higher voltage setting so only way you can deal it is replace it.

Merci.
Marc


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## busman (Nov 7, 2008)

I hope they're all plastic fixtures or using one knockout. No one worried about inductive heating?

Mark


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## rjniles (Feb 5, 2007)

While the way you wired your lights will work, it is a confusing method to me and uses more cable than required. I like to run my 3 wire between the switch boxes, bring the power into one switch box and a 2 wire feed to the light(s) in the other. It also minimizes fill in the ceiling boxes.

In the first switch box, connect the power feed neutral(white) to the white of the 3 wire cable, connect the black of the feed to the common of the switch, connect the red and black of the 3 wire to the travelers of the switch. In the second switch box, connect the white of the 3 wire to the white to the light(s), connect the red and black of the 3 wire to the travelers of the switch, and connect the black to the light(s) to the common of the switch. Straight forward and no remarking or changes of colors required.


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## AllanJ (Nov 24, 2007)

Too late for the OP but, for those eavesdropping,

Yes it is less confusing to start by running the 3 wire cable non-stop between the switch boxes even if the cable is routed past the outsides of the light boxes.

But depending on the locations of the switches, this method may use more cable than the method the OP used.


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