Where central heating pipes are running vertically on the brick wall of the garage, I need to run a PVC 1.0mm T&E to the consumer unit, horizontally high on the wall, crossing the pipe run. Is it satisfactory to run the cable along the mortar line behind the pipes?
It is hard to answer a question like this as the cooling of the cable is a real unknown but there are a number of ways to reduce the problem. Using XLPE cable will lift the working temperature from 70 to 90 degrees and would help also the new BS 8436 cables designed to be buried at less than 50mm without RCD protection i.e. Flexishield are often also to FP200 standard and have an even higher working temperature. Moving to mineral insulated cables you can go even higher but working which these cables is not for the DIY person.
Having talked about cables able to run at higher temperatures next is keeping cables cool and burying cables in plaster with metal capping over the cables will likely keep them cool with the capping transmitting the heat out of harms way.
Or combination of both.
If the pipes can be touched then their max temperature should be 80 deg C if the plumbers have done there job right so using XLPE cable will be most likely enough and except normally white rather than gray hard to tell difference between PVC twin and earth and XLPE twin and earth.
Going behind one hot pipe is a lot different from going behind 4 hot pipes and where there is free air to cool is different to being boxed in so final decision must of course be yours.
We being remote could be easy missing something.
Thanks to Topspark and Ericmark for your advice. I think I will likely use trunking in front of pipes to bridge them. I'm interested in both of your comments and their different engineering solutions.
I have to admit, I've seen the work of "electricians" in a number of house, they have clipped the cables to the brickwork, crossing behind the pipes, hot & cold, without any consideration of heat damage or the nearness to them etc. Thanks both, very professional.
to come at this from a plumbing perspective i would say that your pipes in the garage should be lagged anyway. not only to protect from frost and freezing but also to make your heating system more efficient. you are wasting energy by having exposed hot pipes in your garage you are paying to heat the exteriour of your house! insulate them with climaflex then you will have cured your electrical problem in the same stroke!
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