replacing cables running beneath parallel to radiator pipes

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Hi Folks, I have some lighting cables that have been damaged by mice that I'm trying to replace. The run I wish to replace travels underneath and parallel to a 4 meter length of the central heating pipes. The current holes in the joists are 50mm below the bottom of the pipes, is this enough clearance to avoid the cables getting damaged by the 60 degrees Celsius from the hot pipes?

I want to replace the damaged cable run properly, not just bodge it and create problems in the future(although the current cable has been there since 1984 without damage from the heat of the pipe). I could either;

a) insulate beneath the pipes to isolate the cables from pipes, by fixing sheets of 18mm foil backed PIR board(I've got loads of this and it doesn't conduct any heat!) above the cables,

or

b) reroute the cable about 150mm away from the pipes further along the joist by drilling new holes in the joists. Although this is just inside the building regs 40% distance from the end of the joist I am worried about weakening the joist at this point due being close to a fairly heavy block internal wall running across the joists, built on top of the floor boards.

So, do you think it is a proper solution to fix insulation to protect the pipes, rather than reroute the cable? or should I stop worrying about he joist strength and add another hole? The joists do seem extraordinarily strong!

The lighting cable(1.5mm replacing 1mm) is already derated, but I suspect that I may also yet find bite marks in the 2.5mm ring main cables as well and have to also replace this, which I'm guessing is more susceptible to heat, so would you be more likely to reroute the ring main rather than insulate it?

thanks for any help!
 
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2" or 50mm away from a radiator pipe at 60 degrees C is plenty of distance.
Just run them through the existing holes. No need for added insulation as most cables are rated at about 70 degrees C if I remember correctly.
 
The current holes in the joists are 50mm below the bottom of the pipes, is this enough clearance to avoid the cables getting damaged by the 60 degrees Celsius from the hot pipes?
The clearance is fine and will not damage the cables, there could be some issues with dissipation of heat in the area that could possibly affect the overall current carrying capacity of the cable, but should still be fine. You can improve this by lagging the pipework above, as that will prevent heat loss and also protect against accidental contact.
OuterSpaceHopper";p="3154679 said:
I want to replace the damaged cable run properly, not just bodge it and create problems in the future(although the current cable has been there since 1984 without damage from the heat of the pipe). I could either;

a) insulate beneath the pipes to isolate the cables from pipes, by fixing sheets of 18mm foil backed PIR board(I've got loads of this and it doesn't conduct any heat!) above the cables,
If you thermal insulate the area, this would again affect current carrying capacity, but reading your post, if your cable is 1.5mm2 T&E and on 6A breaker it should be fine, but I personally would lag pipes
or
b) reroute the cable about 150mm away from the pipes further along the joist by drilling new holes in the joists. Although this is just inside the building regs 40% distance from the end of the joist I am worried about weakening the joist at this point due being close to a fairly heavy block internal wall running across the joists, built on top of the floor boards.
I would advise complying to building regs whenever possible.
So, do you think it is a proper solution to fix insulation to protect the pipes, rather than reroute the cable? or should I stop worrying about he joist strength and add another hole? The joists do seem extraordinarily strong!
Lag pipes, prevents heat loss thus improving your central heating efficiency, prevents dissipation of heat, thus improving current rating of cable and prevents accidental contact, thus the cable will not be subjected to damage by heat.

I would consider dealing with the rodent problem though or alternatively protect the cables from being nibbled.
 
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Brilliant advice everyone, I couldn't see the wood for the trees on this one yesterday, especially in the heat, but the thrust is that structural strength is paramount, especailly with the unusual construction of brick walls ontop of floor boards, and I'm worrying over nothing about the heat clearance

Conny, I'll use the same holes my Dad also said he has seen hundreds of installations that have even less clearance so I think you are right.

Taylortwocities, that photo looks like a disaster waiting to happen! Mine aren't that bad. The notches are as shallow as can they can be for the pipes and have managed to use the originals notches to replace the heating pipes. There are only so many places they can go!

PrenticeBoyofDerry, I'll insulate the pipes and bear in mind the effect of the insulation on heat dissipation from the cables. Yep, 6A breaker on 1.5T&E(replacing 1mm and upgrading to low current LEDs!)


ban-all-sheds, the mice were a nightmare, I stop counting at 50 odd nests in the loft insulation, hundreds of mice skeletons after the previous occupants had used poison. I've not seen or heard any for several months now after I cemented up all the gaps around the outside of the house(round waste pipes, cables etc). I've just got some mesh to add to the weep vents so as to be doubly sure! I think they have gone now though.
 
Your concern should be with the mechanical strength of the joist. Hopefully its not as bad as this litle gem
I somehow doubt that's the worst you've ever seen (maybe you don't carry you camera all the time!) - have you not come across the soil pipe or 4" fan duct going through a series of joists (I have :) ).

Kind Regards, John
 

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