Wire Temperature Rating


Old 01-16-05, 10:32 PM
Visiting Guest
Posts: n/a
Wire Temperature Rating

I recently bought 5 new light fixtures. The all say "Warning- Risk of Fire! Most Dwellings Built before 1985 have supple wire rated 60C. Consult professional electrician." The lights say they need 90C rated wire.

My house was built in the mid 70's. Is there anyway to check the temperature rating of my wire? If it is indeed 60C, can I still use these light fixtures if I use a lower wattage bulb? Do the energy effecient flourscent bulb put off less heat?

I do not want to rewire my whole house.....can't I get any new light fixtures?
Sponsored Links
Old 01-17-05, 04:28 AM
Join Date: Aug 2004
Location: Vancouver, Canada
Posts: 1,210
Your guess about lower wattage is correct. Using incandescent bulbs of the fixture's maximum wattage would be unsafe. But at just what point does it become safe?

And then someone else may go ahead and change the bulb...

So you can check your wires or settle now for different fixtures.

To check the wire temperature rating you will probably need to read the cable sheath (the individual wires aren't likely marked), but the sheath will have been stripped off where it enters the electrical box. So you would have to loosen the box from the framing and most likely use a small mirror and flashlight to peer inside the wall or ceiling at the cable. Then with luck the rating will be clearly printed on the cable.
Old 01-17-05, 04:42 AM
TomZ1's Avatar
Join Date: Sep 2003
Location: New Hampshire
Posts: 174
Assuming it's NM cable...if it's marked "NM" it is 60-degree wire. If it's "NM-B" it is 90-degrees.

Unless it is NM-B you'll have some work to do...

Old 01-17-05, 07:50 AM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Only the last couple of feet need to be NM-B. If you have access above, an extra junction box two feet away in the attic is a pretty easy solution. If you don't have access above, you can do the same thing from below but the junction box will need to be permanently accessible, so there will be a blank cover plate on the ceiling (barely noticeable and preferable to the fire).
Old 01-17-05, 01:55 PM
Join Date: Sep 2000
Location: Fayetteville, NY, USA
Posts: 1,052
Do not want to advise you to bypass the manufacturer's warning, but it was written by lawyers. You install their fixture and they are afraid if your house burns down they could be liable. So they explicitly advise cadillac wire where chevy wire will not be a problem. Most people have houses wired prior to 1985 and do not have 90 degrees C wire. The whole DIY movement would be dead if every time we changed a light bulb we'd hire an electrician to re-wire the entire house.

Most wire has 60 degrees C rating in existing homes. That is 140 degrees Fahrenheit. If you believe your light fixture will exceed that, go ahead and rewire your home to accomodate new fixtures.

On the other hand, go ahead and leave your older, less efficient, and more heat-spewing existing fixtures. Think there's an advantage there???

During the '70s many dwellings were wired using aluminum NM cable. People would ignore the "60 watt maximum" sticker on their light fixtures and put in 75s or 100s. This caused the aluminum wire insulation to crack up and cause short circuits. Fires happened.

Especially with fluorescents, which have low temperature output, this is not a problem.

But, that is just one juice head's opinion. The NEC says follow the mfr's recommendation.


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes