Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, about the detrimental influences on polyurethane cable insulation, is answered by BASEC:
Answer: Polymeric insulation materials may exude potentially damaging chemicals. The effect of the chemical components of polystyrene insulation on PVC cable is well known, as are the precautions to be taken, particularly when the cable penetrates the insulation. The effects can occur fairly quickly. Conduit should be used to separate the materials.
It is feasible that other polymeric thermal insulation materials - such as phenolic, polyurethane or polyisocyanurate - might, in some circumstances, also exude the active chemicals or solvents used in their manufacture, or degradation products, but the chemicals, and the manufacturing and curing processes are different from the polystyrene situation.
There is currently very little information available as to the extent of this, or of any effect, on PVC or other cable sheathing or insulation materials. This does not mean that there is not a problem, only that it does not currently appear that it is significant, despite the widespread use of these materials.
Installers should approach the manufacturer of the insulation to see if they offer any advice on penetrations by cables. As a precautionary measure, if there are concerns, then conduit could be used.
BASEC will follow this up with insulation manufacturers.
Please also remember that cables should be de-rated if they pass through solid insulation, as described in the Wiring Regulations.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link:
https://www.voltimum.co.uk/consult.php?universe=consult.index.questions