New Light Fixture / Old wiring

Posted by Jim Taylor on August 30, 2005, 11:53 pm

I purchased a energy efficient ceiling fixture to replace a kitchen
light. (It is not recessed). The directions warn that it should not be
connected to house wire not capable of withstanding x degrees Celsius.
(I think x is 70 or 90). Since my house was built in the 1960s, I
don't have any idea how hot max the wire is designed to get, but IIRC
most wire of that era was designed for 60 C.

So what is the proper way to wire a new fixture? I'm surprised the
wire temperature max rating is such an issue, the enegy efficient
florescent lighting seems to be much cooler than incandescent.

Thanks!

Posted by SQLit on August 30, 2005, 11:44 pm

> I purchased a energy efficient ceiling fixture to replace a kitchen
> light. (It is not recessed). The directions warn that it should not be
> connected to house wire not capable of withstanding x degrees Celsius.
> (I think x is 70 or 90). Since my house was built in the 1960s, I
> don't have any idea how hot max the wire is designed to get, but IIRC
> most wire of that era was designed for 60 C.
> So what is the proper way to wire a new fixture? I'm surprised the
> wire temperature max rating is such an issue, the enegy efficient
> florescent lighting seems to be much cooler than incandescent.
> Thanks!

As far as I know your correct about the residential wiring of the era.

My guess is that the manufacture said 90 c. Which is what the newer
residential wire is rated for, I believe.
You could always pig tail a piece of thhn or thwn to the home wiring and
then connect to the fixture.

Posted by HorneTD on August 31, 2005, 3:41 pm

SQLit wrote:

>>I purchased a energy efficient ceiling fixture to replace a kitchen
>>light. (It is not recessed). The directions warn that it should not be
>>connected to house wire not capable of withstanding x degrees Celsius.
>>(I think x is 70 or 90). Since my house was built in the 1960s, I
>>don't have any idea how hot max the wire is designed to get, but IIRC
>>most wire of that era was designed for 60 C.
>>
>>So what is the proper way to wire a new fixture? I'm surprised the
>>wire temperature max rating is such an issue, the enegy efficient
>>florescent lighting seems to be much cooler than incandescent.
>>
>>Thanks!

>
>
> As far as I know your correct about the residential wiring of the era.
>
> My guess is that the manufacture said 90 c. Which is what the newer
> residential wire is rated for, I believe.
> You could always pig tail a piece of thhn or thwn to the home wiring and
> then connect to the fixture.
>
>

No you can't. The lower rated 60C rated conductors need to be far
enough away to be unaffected by the heat the fixture gives off. If the
space above is accessible you move the old cables into a Jbox and run a
cable from that Jbox to the fixture box. If the old cables are not
relocated the heat from the fixture will cook the insulation right off
the wires and they will fault out. Because the process is gradual it
has a higher likelihood of arcing faults that can kindle a fire.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

Posted by Bill on August 31, 2005, 4:29 am

The light itself is cooler, but florescent lights have a "ballast" which
can get to be quite hot. (At least with commercial fixtures.)

Heat travels up, also heat can get trapped with insulation, in the metal
box holding the electrical wires, etc.

I've seen insulation from old wires just crumble when I removed a wall
fixture in a bathroom. And that was not even a ceiling fixture. Some of the
insulation had fallen off by itself. Note that this fixture was part of a
metal medicine cabinet, so could have been a shock hazard as there was no
grounding!

The heat from the fixture wrecked the insulation on the old wiring.

I would replace the wiring whether it needs it or not, since it may have
been damaged by the previous fixture. The new stuff is *so* much safer than
the old (grounding, high heat insulation, etc.)!

"Jim Taylor" wrote in message

Posted by Bud on August 31, 2005, 10:39 am

Bill wrote:

> I've seen insulation from old wires just crumble when I removed a wall
> fixture in a bathroom. And that was not even a ceiling fixture. Some of the
> insulation had fallen off by itself. Note that this fixture was part of a
> metal medicine cabinet, so could have been a shock hazard as there was no
> grounding!
>

I've run acoss the same thing - you move the wire and the insulation
still remianing cracks off. Old circline flourescent fixtures could
cause this.

> The heat from the fixture wrecked the insulation on the old wiring.
>
> I would replace the wiring whether it needs it or not, since it may have
> been damaged by the previous fixture. The new stuff is *so* much safer than
> the old (grounding, high heat insulation, etc.)!
>

The solution? Get a fixture that is rated for 60°C supply wiring. It is
common for fixtures to have insulation built into the top to limit heat
problems. I'm not impressed with the fixture manufacturer. Seems obvious
a lot of these will be installed with 60°C wiring.

Bud--

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