Insulations & Electric Cables - Safety Advice Please


Postby wsimp71 » Thu May 06, 2010 6:29 pm

Hi

We are renovating a house built in 1911. We have taken down a lath & plaster ceiling (before it fell down), I have also removed lath & plaster from a partion wall as it was blown. Anyway the dirty deed has been done : )

I now want to insulate for heat and noise. I am going to hang a floating ceiling with resilient bars and want to insulate above them. The ceiling light cable is notched into the top of one joist, and then is through a drilled hole in the joist to the light fitting. How much clearance do i need to leave between Rockwool insulation and cables so they dont become a fire risk?

I have the same question for the walls - whats the safest way to place the insulation - do I leave the bits with cables in empty (even though this would defeat the object). The ceiling will have a small cavity for cable to sit in, but the walls will have no cavity as space is a bit tight.

Would appreciate some advice of any one who knows.

Thanks in advance
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Postby ericmark » Thu May 06, 2010 9:58 pm

Reference Method 103# (in a stud wall with thermal insulation with cable not touching the inner wall surface) reduces 1.5mm cable to 10A and there are formula to calculate according to thermal properties since most lighting is limited to 6A there is not too much of a problem.

However cable carrying power if somewhat difference and it's not that you can't run the cable through insulation be because it becomes de-rated it needs thicker cable or cable able to take more temperature.

Using Ali-tube cable rated at 90 degs rather than 70 deg can help although getting hold of ali-tube is not so easy. Tends to only be sold by the role.

I would look for Batt cables or other manufacture who normally have charts on internet. Sorry not allowed links on this forum.
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