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Electrical Wiring

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

15 years ago

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

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Comments (4)

bigbird_1
15 years ago
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.
windchime
Original Author
15 years ago
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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"I have seen this warning on literature for fixtures that did not have especially heavy internal wiring, and have always wondered what the problem was. " It has nothing to do with the internal fixture wiring. Since only short sections are used, higher temperature rated insulation is not a significant cost. The problem comes about with compact fixtures and enclosed bulbs. You will often notice foil faced insulation on the back of the fixture mounting plate also. Older NM cable used PVC insulation only rated for 60 C. If the fixture generates heat it has to go somewhere, and it will cook the old PVC insulation in short order, causing it to become brittle and crack (sometimes without any movement of the wires). You do not have to rewire an entire house, just make sure that the permanent wiring entering the fixture box is 90 C rated. Newer NM wire uses a different insulation (THWN even though it is not marked that way). Some of the comments on the Bob Villa site are wrong and stupid. Unless you want to have overheated wiring and the possibility of arcs and resulting fires, change the wiring to the fixture box to 90 C or do not use the fixture.
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joed
15 years ago
The insulation on 60ÂºC 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 90ÂºC rating.
samneric
15 years ago
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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