Cables running near hot water pipes

[philup]

Hi

I currently have the feed/return for my house's ring main circuit running over the top of the central heating manifold (approx. 2" over the top) just under the 1st floor joists.

Is there any requirement other than shielding it with some insulating material or poss rewire and re-route the cables that should be applied. I was concerned about the effect the heat would have on the insulation particularly under load.

Many thanks

phil

 

[DESL]

Apart from the heat I think you need to worry about weakening joists by the proximity of the holes.

 

[philup]

Hi

Many Thanks for that. Joists weakening not a prob as pipies running between joists and cables running over them at 90degrees thru joists

phil

 

[philrosenberg]

There are derating factors you need to apply to cable if it is going to get warmer than 30 degrees C. Ordinary pvc insulated cable shouldn't be used if it is warmer than 65 degrees C.
Do you know what temperature the pipes get to?
To give you some idea of what you are dealing with here are some examples
max Temperature derating factor
50 71%
55 61%
60 50%
65 35%

so if the temperature reaches 55 degrees, the cable can only take 61% of the current it is rated to, so a 20A cable could only carry 12.2A.
There are other derating factors to consider if you have semi-enclosed fuses, bunched cables, or if the cabling is in thermal insulation.

 

[philup]

Many thanks for that most helpful.

I will monitor temp as they are boxed in with central heating pipes and yes they are bunched together so will be a bigger problem.

phil