cables and central heating

[Billybjo]

We live in an old house that has boxing around the upper floor skirting to contain the central heating and wiring circuits, because the floor/ceiling has no void.

I was checking a pipe leak recently and noticed that a lot of the wiring touches in places and in some cases is partially wrapped around a pipe. I've now added insulation around as much piping as possible (very tight space) to ensure there are minimal touches.

Maybe a silly question, do central heating pipes get hot enough to burn/affect electrical wiring. I couldn't see any melted sheathing or burning, but some discoloration.

Could be unrelated, but out downstairs lights often have a dimming spell. I've check all the terminations and can't see any broken or loose wires.

 

[luminaire]

If they're cold water pipes not so much a problem. Although having said that they still should not be touching. If they are hot water pipes then that could be very serious and need moving away before someone gets a shock off the pipes somewhere.

I take it your lights are not on a dimmer switch?
Sounds as though it could be a poor contact somewhere, quite often in the ceiling rose as the cables tend to deteriorate quicker here due to the heat.

 

[Billybjo]

No cold or DHW pipes in this part, its all central heating pipes, so can get quite hot.

The downstairs lights have no dimmer switch, just normal static switches. The lights are all the wall candle types (2 bulbs per fitting).

 

[JohnD]

the heat shortens the life of PVC insulation. If it is a cable carrying a current near its maximum rating (like an immersion heater or electric shower) this will get it even hotter. Lighting circuits, and ring circuits that are not running electric heaters, are very lightly loaded.

The PVC softens when warm, and if there is pressure on the cable (e.g. a tight pipe, or trapped under a floorboard) this can cause the soft plastic to be squashed and flow away from the copper wire. this is dangerous as it may even lead to exposed copper. If this has happened you may be able to see and feel the distortion of the plastic.

If the cable was installed in the early 1970s, it might be made with a grade of PVC that leads to "green slime" when the plastic attacks the copper, and becomes cracked and brittle. This is accelerated by heat. I came across this on such a cable that was close to a heating pipe (see pics below) and it needs attention. Many electricians have heard of this but never seen it and will be quite excited.

If the cable is not touched, and is protected from heat, and is not already distorted, it is not urgent, but it will be worth having it replaced. It is often convenient to do this next time the rooms are being redecorated, as you may need to chip out plaster and paint.

If you are getting an electrician in, verify that he is a member of a self-certification scheme, ask him which one and how long he has been a member. This is not a perfect way of finding a good electrician, but it is a qualification that permits him to do various work.

Green slime pics:
View media item 1630 View media item 1631 View media item 1632

 

[luminaire]

Many electricians have heard of this but never seen it and will be quite excited.

YES! YES! OH YES!

 

[Click-Sure]

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