Motorhome wiring

[Guest Graham Peacock]

I had an article on installing a Fiamma Turbo Vent 160 in my motorhome published in the May edition of MMM and in the October (?) edition there was a letter pointing out that I had used plastic insulated cable to connect the light fitting supply to the ventilator. This it was stated could be dangerous as the cable insulation could reast with the polystyrene insulation through which it was drawn. I cannot find any information on this elsewhere so if there is a qualified Motor electrician around who could cast some light on this, I would appreciate it. I was advised - in the letter - to install the cable through a conduit which would be very difficult.

[Guest Ralph]

Unable to tell you where to find information on this problem, but from personal experience in H&V and C/Heating installation and maintenance and electrical installation. This was/ is quite a commom problem in house lofts with loose infill polystyrene insulation. It was discovered that the polystyrene balls or chips reacted with the PVC sheathing of the cables and caused a sticky clear liquid to form, the polystyrene balls or chips would then stick to the cable. However to my knowledge, the investigation that followed found that it was the polystyrene loft insulation that was deteriorating NOT the cable sheathing and the cure was to remove the polystyrene and replace with Rockwall or similar after cleaning the cables with a cleanser to remove the sticky mess, which was more inconvienient than dangerous. In the case of your problem you should only use butyl rubber sheathed wireing in conact with polystyrene as otherwise it will, eventualy melt the polystyrene.

[Guest Graham Peacock]

Ah!!!!!!!!! Thanks for that. Now I understand. I now have to ascertain exactly what type of insulation/sheathing the cable is. I used the loose description of plastic but it could well be butyl rubber (?). I have a spare piece so will take it to the retailer for an exact id. Graham