Bathroom bonding and cables through floors

[Jason Pearce]

Q1. All pipes in bathroom are plastic, with the exception of the central heating, which is all metal. I have a "class II" extractor fan and wish to fit a "class II", isolated, shaver supply. As I understand from the regs, as explained in this document

I now need to supplementary bond the radiator pipes to the fan and shaver outlets (despite them being class II devices, incase they are changed to class 1 in the future !) - do I need to run a 4mm cable between rad pipes, fan and shaver outlets, or can I use the cpc of the fan and shaver outlets as the supp. bond and run a single 4mm cable upto the lighting circuit, where the fan and shaver supply originate from ?

Q2. My consumer unit is mounted on a wall approx 10cm off of a suspended timber floor. A couple of years ago we had a visit from the local mice who decided to use the hole where my cables come through the suspended floor as an access point into our kitchen (SWMBO was not amused). What is the recommended method for sealing such a hole ? I have considered expanding foam, but a few posts in the archives seem to suggest that expanding foam and pvc cables should not be mixed. I have considered trunking, but that still leaves a hole into the consumer unit ....

Cheers,

Jason

[Stefek Zaba]

Good news: the use of CPCs as the bonding conductor is explicitly blessed in the Regs. The bond should be made "in or close to" the bathroom - so no relying on "but they're all commoned up back in the CU"! Depending on what jobs you prefer, you could replace a 2ft-or-more section of both flow and return piping to your bathroom CH rad with plastic pipe, to go for the "earth free" route. Not a totally practical suggestion in normal circs, granted, but worth bearing in mind if you were thinking of repositioning the rad anyway!

Is this hole visible? If not, a scrap of just about anything (wood, plasterboard, ...) should do the trick; if so, any chance of working from underneath the board? As for expanding-foam-meets-PVC, the thread we had ended up saying "almost certainly OK", with no experience of problems and a plausible claim that expanding foam is polyurethane, whilst it's polythene which causes the leeching-plasticiser problem.

[Andy Wade]

< big snip>

/s/polythene/polystyrene. Poly(e)th(yl)ene is inert in this context.

[Stefek Zaba]

Mea culpa; brain fart. Thanks for the correction.

[Dave Plowman (News)]

I use wire mesh with a size suitable to protect against such things. Easily fixed to wood with staples. Obviously, make sure any cut ends don't snag the cable insulation.