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Home > Archive > Electrical Engineering > May 2007 > Why do wires have a lower temperature rating?
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Why do wires have a lower temperature rating?
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| What problems might I run into by not using wire rated for -40=B0 in such=
=20
an environment?=20
I can see the insulation breaking (especially if flexed) if it is not=20
rated for low temperatures and possibly the wire itself but is there=20
anything else?=20
I'm also wondernig how much the temperature rating would matter if the=20
wire will remain stationary.
I'm amused that after obtaining a BSEE I feel that I need a class in=20
wire itself. I've read through primers on Globalspec and a few=20
manufacturer's sites but if anyone has suggestions for an excellent=20
educational resource please let me know. =20
I've been collecting samples since I find it is helpful to actually=20
see/touch it, especially after learning about the insulation material=20
properties.=20
Thanks,=20
David
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| Gerald C Newton 2007-05-20, 3:25 am |
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"David" <davidd31415@public.com> wrote in message
news:MPG.20b94d64630f6c9b98968a@news.comcast.net...
What problems might I run into by not using wire rated for -40° in such
an environment?
I can see the insulation breaking (especially if flexed) if it is not
rated for low temperatures and possibly the wire itself but is there
anything else?
I'm also wondernig how much the temperature rating would matter if the
wire will remain stationary.
I'm amused that after obtaining a BSEE I feel that I need a class in
wire itself. I've read through primers on Globalspec and a few
manufacturer's sites but if anyone has suggestions for an excellent
educational resource please let me know.
I've been collecting samples since I find it is helpful to actually
see/touch it, especially after learning about the insulation material
properties.
Thanks,
David
The last time I checked UL did not have a low temperature standard. Here in
Alaska we have learned that XHHW insulation is workable at low temperatures.
XHHW is used almost exclusively for outside installations here including the
Alaska Pipeline and the North Slope Oil facilities. THHN is the worst.
If you want to learn a lot about conductors try the 1957 Neher-McGrath paper
and several other references cited in the NEC handbook in Article 310.
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| Andrew Gabriel 2007-05-20, 3:25 am |
| In article <MPG.20b94d64630f6c9b98968a@news.comcast.net>,
David <davidd31415@public.com> writes:
> What problems might I run into by not using wire rated for -40=B0 in such=
> =20
> an environment?=20
>
> I can see the insulation breaking (especially if flexed) if it is not=20
> rated for low temperatures and possibly the wire itself but is there=20
> anything else?=20
>
> I'm also wondernig how much the temperature rating would matter if the=20
> wire will remain stationary.
There's a factor of 3 difference in the thermal expansion of
copper and PVC. The plasticiser will become ineffective below
a certain temperature and further cooling will see the PVC
shrink 3 times more than the copper it covers, which I imagine
would lead to cracking without any movement being required.
This is however just speculation on my part as I haven't tried
it.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
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