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90 degree C supply wire warning. What does it mean?

Posted by windchime (My Page) on
Wed, Aug 6, 08 at 11:48

Hi everybody. I finally found a ceiling light for my bathroom that is rated for damp locations. Now I read the instructions and it says "Warning: Risk of Fire. Most dwellings built before 1985 have supply wire rated 60 degrees C. Consult a qualified electrician before installing."

Of course my house was built in 1955, and this fixture has a label that states 90 degrees C. It's an Energy Star fixture, which qualifies for California T24, and takes one of those round fluorescent bulbs (instead of using compact fluorescent.) I like saving energy, and I thought it would be a good idea. Now it looks like I might have to get rid of it. Anyone know what all this means and what are my options?

Here is a link that might be useful: Here's the light fixture


Follow-Up Postings:

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RE: 90 degree C supply wire warning. What does it mean?

A circline fluorescent bulb will never get anywhere close to 90C or even 60C for that matter. The labeling is all about liability if you should put a high heat bulb in there. If you stick with the fluorescent it's rated for you'll never have a problem.


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RE: 90 degree C supply wire warning. What does it mean?

Okay, thanks for the quick response. The thing is, I bought another/different fixture by this same manufacturer, and it does not have the 90C label on it (hence no warning.) The other fixture is incandescent, also rated for damp locations, exterior ceiling fixture. So I was thinking that the ballast had something to do with it (the temperature rating.) The reason I thought of that is that we have an aquarium with fluorescent lighting, and the ballasts get *very* hot. They heat up the whole room, literally! So could the ballast be the problem? I don't think that anything but a circline bulb would fit in this fixture. Thoughts?


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RE: 90 degree C supply wire warning. What does it mean?

The insulation on 60C wires will overheat, become brittle, crack and fall off if overheated. Heed the warning. Don't use the fixture unless you deal with the wiring issue.
If there is an attic above this room it is a relatively simple fix. Remove the cable from the fixture box and install it into a new box mounted in the attic. The box only needs to be about a foot away from the old one. Then run a new NM-B cable from the new box to the fixture box and you will be fine. The B in NM-B cable indicates 90C rating.


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RE: 90 degree C supply wire warning. What does it mean?

The warning label is NOT about lamp size. In order for the manufacturer to place the Underwriters Laboratories (UL) label on their fluorescent fixtures, the supply wires must enter the fixture over 3" away from the ballast. This is because UL requires that ALL wires within 3" of a ballast be rated for 90C. This 3"/90C UL requirement is the source of the requirement in NEC 410.33.

Yet some fixture sizes and/or designs don't allow for that minimum 3" spacing , so UL allows the UL label on fixtures where supply wires enter within 3" from a ballast -IF- the manufacturer also places a label requiring 90C supply wire only.

You don't need to add a box. Just pigtail a length of 90C wire to your house wires in the box, and bring the higher rated wires into the fixture to supply the ballast.


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