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Topic Title: Cables + copper pipe work in the same wall
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Created On: 12 October 2017 09:11 AM
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 12 October 2017 09:11 AM
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I am currently working on my bathroom - the house was built in 1985.

We intend to install a digital shower, this will involve putting copper pipe work in the paramount/honeycomb wall, up into the loft which will connect to the digital shower mixer.

The wall we intend to put these pipes into, on the reverse side is the landing and has a light switch for landing light and a single socket off the ring. Both of these circuits are protected by the RCD.

The wall is roughly 1000mm wide - the pipes will be roughly 650mm away from the bathroom door. The current light switch and socket are round 500mm away - so there would be roughly a 150mm gap between.

Without stripping down the wall where the cables would be, I can't be sure on what protection there is on the cables.

Would this be okay? Are there any regulations that would prevent this - I'm looking all over the place to get an answer.

As the switch and socket are 500mm away from the bathroom door and I need to put in a light switch for the bathroom on the same landing wall.... I could also move them further away from where the pipes will be and closer to the bathroom door?

Many thanks in advance

Edited: 12 October 2017 at 09:36 AM by brendanmu
 12 October 2017 09:57 AM
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In the case of cold water pipes I see no problem.
Most cables concealed in a wall require RCD protection, but that should not present a problem since the existing cables are RCD protected and the shower circuit should be on an RCD.

In the case of hot water pipes, then one should consider the risk of thermal damage.
 12 October 2017 10:03 AM
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I should of mentioned that, There will be 1 cold water pipe, 1 hot water pipe and the closest pipe to the switch/socket will be a mixed pipe shouldn't really be any hotter than 48 degrees. Would plastic conduit offer some thermal protection?

Also, with the wall being honeycomb type, I would of though the pieces of card would help reduce the heat over the gap?
 12 October 2017 11:16 PM
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In general there are rules that say the cable route should be direct and protected to avoid external influences that may damage it, like mechanical collision, excess heat, damp, corrosive chemicals etc, but no specific rules about how close you may to a warm pipe. Realistically direct contact would be imprudent, but a pipe diameter or two of spacing should be possible, and gets you safely out of the worst danger.
If a cable is in conduit in a wall, it will be isolated form heat coming from the pipes and the wall, but equally unable to lose heat to cool itself, so at worst the cable may need to be a size larger than if it was better cooled, but that is an easy thing to arrange if need be.
Conduit is almost certainly not needed but it may make the wiring up easier if some slack has to be pushed up or down the pipe, and is cheap to organise, but is also a potential moisture path, and would probably need sealing so the decision needs some thought.

regards Mike
 14 October 2017 08:32 AM
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As long as cables run vertically or horizontally from a "point" such as a light switch or socket then we would know their likely route thus avoiding damaging them with nails or screws to hang pictures etc. Cables can also run in "safe" zones hidden in plaster, that is routes allowed by BS 7671 so that we avoid drilling or driving nails into such routes. (Normally 150mm from the ceiling down the wall, or 150 mm from corners etc. is included within such "safe" route zones).

Cables to bathrooms or shower rooms (both special locations in BS 7671), need R.C.D. protection if the circuits serve the location or just pass through it.

Your shower cable will be quite short in length in the room, as it runs from the shower upwards to the loft. If it ran for many metres in say glass fibre thermal insulation there might be a heating effect that could damage the cable insulation. I do not think that an adequatly sized cable run up in the honeycombe wall poses any overheating problems. The shower is only used normally for a few minutes, plus the cable has a chance to cool at the shower and in the loft. Do not cover the cable in thermal insulation in the loft.

If the pipe is kept away from the cable by say 50mm or more there should be no problems.

Cables in the regs. are rated for current carrying capacity at 70 degrees C. Your cable will no doubt run cooler that that, with an ambient house temperature nearer 20 to 25 degrees C. But it may warm up slightly with prolonged use.



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