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I need to install a cable which will come in contact with a central heating pipe. It is 2 core carrying 5V, 500mA DC power to a simple circuit that can't run on batteries. The pipe could get to 82 degC if the central heating is really cranked up.

Now, I can find heat resistant 2 core that will run to 100 degC but it is designed to handle 5 A so it a bit overkill in this situation, it's also twice as thick than I would like.

What are the alternatives for this problem? Could I use normal cable and cover it in something? I've used material sleeves for 300 degC work in the past but I am wondering if simple heat shrink will do the job seeing as it is much much cheaper?

Does anyone have any suggestions or experience that could solve this problem from the wire point of view and not simple adding a spacer between the pipes and the cable (which could get dislodged)

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    \$\begingroup\$ A better idea - space permitting - would be to insulate the pipes. Not only will it protect the wire from the heat, but will stop the heat being wasted, thus making your central heating more efficient. \$\endgroup\$ – Majenko Sep 2 '11 at 9:39
  • \$\begingroup\$ When I was solving a similar problem, I installed the cable in the outer layer of pipe insulation. In my case the insulation was 3 cm thick, so I had plenty of space for a small cable, but that may not work in your case. \$\endgroup\$ – AndrejaKo Sep 2 '11 at 9:40
  • \$\begingroup\$ Space is an issue sadly, poorly designed (and old) part of the house and there isn't the space to work at changing something with regards to the pipe \$\endgroup\$ – SimonBarker Sep 2 '11 at 10:46
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First check the cable you have. 82C isn't really all that hot, being well under the boiling point of water. Is there really a problem with that cable?

If you've got insulation not rated for 82C, then you do need something else. You don't need anything exotic, like teflon, at that temperature. You also don't need a fancy "cable". Since it's only carrying power, a simple twisted pair with the right insulation will be sufficient. There should be lots of choices out there.

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    \$\begingroup\$ Every single low power cable I have on my desk is rated to either 75 or 80 degrees. Most low power signal cable is. \$\endgroup\$ – Majenko Sep 2 '11 at 12:37
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Heat shrink is probably the way to go.

I'd recommend a "Heavy Wall" heatshrink as it has higher thermal insulation characteristics. One example:

http://www.rapidonline.com/Cables-Connectors/Deray-6-1-Heavy-wall-heatshrink-123497/?sid=f60511cd-1683-44ab-bc70-9dcd34fded23

As you can see that has "Continuous operating temperature: -55 to 110 degrees C" and shrinks at 120 degrees C.

One down side of the heatshrink though is it makes the cable far less flexible, so you should only use a short length of it where you really need it.

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I would consider sleeving your wires in PTFE tubing. It provides structural support as well as thermal insulation.

If you're going to go with heatshrink, I agree with @Matt and would recommend heavy-wall.

Can you use long cable-ties and 'hang' the wire a few centimeters under the pipe? Air makes a pretty good thermal insulator...

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Thanks for the suggestions, in the end I spoke to a few companies and got directed to glass braid sleeving, and example of which is on the link below:

Braided sleeving

as it will keep cable flexibility, where heatshrink would loose it. Apparently this stuff is used in lighting systems among other things.

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    \$\begingroup\$ Your link died, please consider updating the link. \$\endgroup\$ – Mast Aug 16 '16 at 10:58

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