Supply Conductors

Old 09-02-09, 10:13 PM
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Supply Conductors

I'm changing a ceiling mounted light, and the new one has a message saying: "Min 90 degree C supply conductors. Most dwellings built before 1985 have supply wire rated 60 degrees, ensure correct branch circuit conductor." My house was built in 1935 and still has some knob and tube, but the old ceiling light was installed within the last 10 years. How can I verify that it is safe to install the new one?
Old 09-03-09, 07:19 AM
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Bottom line you need to find a fixture rated for 65. Not easy to find but will almost certainly have an open not enclosed bulb design. Using only CFLs may give you some safety but will still be a violation.

With newer NM you can splice in 90 wire at a J box a foot are so away that remains exposed but with K&T you can't because it can not be altered or added too. From a code point of view to use a 90 fixture with K&T you can't. You must replace all the wiring back to the panel.
Old 09-03-09, 08:36 AM
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Knob and tube aside. If you can find the outer sheath of non-metallic cable you should see a labeling like NM or NM-B. NM-B is the 90 degree rated insulation. Without the -B it is only rated 60 degree or less.

If you can install a permanently accessible junction box you could feed the new fixture with a short jumper of NM-B. Spliced in junction boxes of course. If this is below the attic you could turn the box up into the attic possibly.

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