PVC cables and Foam filler

adrian92

I've just installed 2.5 twin and earth cable down a cavity wall. Does anyone know if I use expanding foam to fill the gap would it be bad for the cable (this foam seems like it is very aggressive before it cures)

ptogher14

Expanding foam will attack the cable. Not today or tomorrow but over a number of years

2011

Best practice would be to install the cables in a conduit.

The cables will not be able to cool as effectively if they are in direct contact with the foam. This will reduce their current carrying capacity.

As above, I have also heard of the insulation of PVC cables reacting with some insulating materials.

Stoner

2011 wrote:

As above, I have also heard of the insulation of PVC cables reacting with some insulating materials.

I'm fairly sure that's been confirmed that they do not degrade cables. I'll have to find the report because up to reading it I agreed with the above

adrian92

Thanks to all for your replies

ptogher14

Stoner wrote: »

I'm fairly sure that's been confirmed that they do not degrade cables. I'll have to find the report because up to reading it I agreed with the above

Can't say I've ever read a report stoner but I will respectfully disagree with you. I was involved in a project a couple of years. We were stripping out parts of an installation. Originally pvc singles had been pulled through liquid tight conduit, then filled with expanding foam. We were stripping this out maybe 8 years later and you could see where the foam had starting attacking the cable. It wasn't enough to cause any problems but was still visible.

Stoner

Yeah I wouldn't put it on cables, even if I ever find such a report, and I've seen nymj look damaged due having foam on it too.

I have a feeling that

A) it was a certain type of cable in the report
it was a certain type of foam
C) it was on boards that I saw it.

But correct I'd default to it being incorrect too.

Tuco88

I have asked this before about the dangers of expanding foam on cables. Examples Fire seals it's being pumped all over cable entries,(I do remember seeing a can that was suitable for cables tho in) housing to keep with the sealing/ air tight it's all over the place.

If I were you I'd try to keep it off the cables as best as you can.

dathi

Stoner wrote: »

.

I have a feeling that
it was a certain type of foam


.

it polystyrene which most of the reports on damage to cables talk about ie the beads that are pumped into cavity's . it attacks the plasticizer which keeps the cable supple

Mrplod

Outside of the chemical reaction between the cable sheath and the insulation the other important thing to understand is that you have greatly reduced the safe current carrying capacity of the cable by installing it in insulation