Expanding foam / PVC insulation

[mache]

Guys I had to renew some insulation on supply pipes from my boiler that run thorugh a cavity wall from a ultility room (where the boiler is located) on the back of the house into the main living area. In addition to the pipes the boiler electrical feed, lighting spur and a twin socket spur had had also been through the same hole in the cavity wall. it's now time to seal up the remaining hole in the wall but wanted to check opinions on housing the cables. What are the options.
1. If I used expanding foam to fill the hole to prevent drafts entering the main building will this affect the PVC insulation (I am aware of polystrene sucking the plasticer out of PVC but not sure on general purpose expanding foam.
2. Run the cables into conduit to keep the foam of the cable insulation and then seal cables in conduit with silicone or similar.
3. If 2 could the cables run in the same conduit or should I run a conduit for each cable. (note the sockets run a washing machine and tumble dryer in the utility room).
4. Metal or PVC conduit ? it's only a 250mm thick wall run to get through.

Thanks in advance
Martin.

 

[HandySparks]

I think that the aspect of using expanding foam around electrical cables that is of most concern is that of thermal insulation. PU foam is a very good thermal insulator and it will severely reduce the long term current carrying capability of cables.

Of the three circuits that you describe, the only one that's likely to be heavily loaded is the socket spur. I would put in one good sized plastic conduit (a piece of plastic waste pipe would do), and run all three cables through it. Then put a small blob of silicone or flexible decorating filler at one end to stop drafts.

Leaving a reasonable amount of air space in the conduit and one end open (or even better, both ends) will help dissipate heat from the cables.

 

[Guitarist]

What Handy said...

 

[mache]

Handysparks / Guitarist
Thanks for responding, Thermal insulation of the cable had crossed my mind also, although bar the light circuit which runs a CFL bulb the boiler connection is run in 1.5 and the spur in 4mm so in theory are over rated I believe anyway. I have room to put a section of 32mm waste pipe so will go with that and close at the one end only
Appreciate the input
Martin