"90 degree supply conductor" warning

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  #1  
Old 11-23-04, 10:20 AM
choo
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Question "90 degree supply conductor" warning

I am trying to replace some of the ugly (and, in some instances, not-working) ceiling lights in my older (1950s) house. Every fixture I can find has a warning that it needs a minimum of 90 supply conductors. Some mention that most houses built prior to 1968 (?) are only 60.

What does this mean in terms of wiring?

My ceiling wiring is HEAVY copper cable (black + white + bare copper ground). I find it hard to believe that this can stand less current than the skimpy little thread wires in the fixtures itself. It's like spider web vs. strong twine. So what is the real concern? Do I really have to rewire my house in order to light it?

The people in the stores either tell me I'm out of luck or that it's a silly warning and to ignore it!
 
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Old 11-23-04, 10:52 AM
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Might get the names of those who tell you it's a silly warning... and report them to management. They're wrong and are setting themselves up to be liable for a possible disaster.

The 90 degree rating refers to the insulation on the wires, not the wires themselves. 60 degree wiring can't withstand the same amount of heat as 90 degree wiring. Since the fixture is rated for 90, 60 could be damaged by it (the heat given off by the bulb). This could cause a fire and/or shock hazard. If the wiring is accessible above the fixture box, a junction box can be placed a few inches from it. The existing wiring is then run into the new box and a piece of new 90 degree rated wiring is run from the new box to the old. Note that all junction boxes must be permanently accessible and have covers on them. If that won't work, look for fixtures that don't carry a 90 degree rating.

Doug M.
 
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Old 11-23-04, 12:08 PM
choo
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Thanks for the explanation, Doug.

Anyone know how to find fixtures without the 90 degree rating? The only ones I've found that don't have the label on the outside of the box have it on the inside of the box (which means a trip back to the store for a refund).

For that matter, in these days of low-energy light fixtures, why do they have to run so hot?

The only stores I can find in my area that even sell light fixtures are Home Depot and Lamps Plus. When I look on the web, I don't see this sort of product information even available. (which gives me nightmares of trying to do returns with companies that won't deal with the post office).
 
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Old 11-23-04, 12:31 PM
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Look for fluorescent fixtures or fixtures where the bulb is not enclosed directly over the electrical box. The 90 degree rating is likely to appear on all fixtures even if it's not needed because we have become law suit happy. Bulbs haven't changed. Fixtures have become lower quality and don't provide as much heat insulation (or dissipation) as they used to. Putting a compact fluorescent (CFC) bulb in a fixture rated for 90 degree wire would make it safe on 60 degree rated wire, but the next owner of the house might not understand and create a hazard by replacing the bulb. You might consider making a label to attach to the light socket that read something like "60 degree rated wire - Use CFC light bulbs only" and installing the 90 degree fixture with a CFC bulb.

Doug M.
 
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Old 11-23-04, 12:46 PM
choo
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What a great suggestion! And what a relief!!!

THANK YOU! THANK YOU! THANK YOU!!!!
 
  #6  
Old 11-23-04, 12:50 PM
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You're welcome.

Doug M.
 
  #7  
Old 11-23-04, 03:01 PM
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Check to see what's stamped on the cable insulation. If it's NM-B you are ok. The "B" is the issue.
 
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