Ground wire question


Old 01-27-06, 01:59 PM
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Ground wire question

I am looking to install a new recessed lighting fixture in my 75 year old house. Some wiring has been updated, but where I am looking to replace an old light, the orginal wiring is present. What or how do I work with the ground wire on my new fixture, if a ground wire is not present from the old wiring?
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Old 01-27-06, 02:47 PM
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Connect the ground wire to the box, if it is metal. If the box is plastic then simply leave the ground wire unconnected.
Old 01-27-06, 04:51 PM
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ground wire

since the wiring in your house is 'old' there was not a ground in the cable. if you are repairing or replacing the fixture you can use what you have and not install a ground. if at any time you replace the old wire that is there, you must use new wire that has a ground. If the wiring that has been replaces runs through the bos that you are working with then you have to use the ground.
Old 01-28-06, 07:26 AM
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Most recessed call for 90 degree C wiring. Your original wiring will not have the proper rating to be used with these fixtures. Do not use on the original wiring.
Old 01-28-06, 04:53 PM
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Most recessed call for 90 degree C wiring
You may be right, but that's not my experience. The house wiring usually ends at the junction box, which is usually some distance from where the bulb is generating the heat.
Old 01-28-06, 06:19 PM
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Originally Posted by pcboss
Most recessed call for 90 degree C wiring. Your original wiring will not have the proper rating to be used with these fixtures. Do not use on the original wiring.
I concur. The 90C refers to the housewiring that terminates in the junction box of the fixture.

It depends on the fixture and aggravating factors like blankets of insulation above.

NEC 410.33 mentions the 3"-rule, though that is for ballasts in this article.

I think that the same principle applies to 90C recessed cans which are discussed in 410.64-72.

The rule is that conductors must be rated to handle the temperature where they terminate.
My personal rule is that any conductor within 3" of a recessed fixture must be rated at not less than 90C. These fixtures do get very hot.

Therefore, using 90C or better insulation on the conductors is wise.
60C insulation does become brittle at higher temperatures.
I've seen old (60C) white insulation that turned brown from folks using 75 or 100W bulbs in open fixtures rated for 60W. I would not take a chance with old wiring and recessed fixtures.

If the old wire can't be replaced completely, add 18" or more of new cable as a jumper between the old cable and the new fixture to provide ample thermal isolation.

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