Ring Main Cable under Bathroom Floor

[r.rain]

Is this a no no? I have located a ring main cable under the wetroom floor and was planning on cabling in a switched FCU in zone 3 for my UFH. Just stumbled across a posting which seemed to indicate that it's against regs to even have ring main cable running under the bathroom floor, is that correct? all these regs are soooooo confusing to interpret.

Also presuming this is ok could I run my towel rad from this too? The towel rail will be in zone 3 also.

Any issues regarding regs with this lot?

TIA

Cheers

Richard

[John Rumm]

Can't think of why there would be a problem with it under the floor - it will be outside Zone 3

Yup, with suitable FCU... You may want either a pull switch for functional swithing or perhaps some sort fo timer - depends a bit on how you plan to use the towel rail.

The usual part taking the P nonsense... Also the towel rail will need equipotential bonding, but that can be handled by its CPC assuming it has one.

[r.rain]

Now there's an idea, a timer for my towel rail. Thanks as usual!

Cheers

Richard

[Stefek Zaba]

Ideally, long-term substantial fixed loads don't run on rings, but on a dedicated radial. How close your UFH comes to being 'substantial' depends on its rating: if it's a small bathroom with say 1kW's worth of UFH on an otherwise lightly-loaded upstairs ring, no real worries; if it's 3kW of UFH (12A of the available 32A) on the only ring in the house which also runs kitchen appliances, definitely *not*. Somewhere in between is 'maybe' land. Like I say, optimal is a dedicated radial running to the CU.

Towel rail is just fine from the ring - typical ratings are low hundreds of watts.

Rings routed under the floor of a bathroom is completely OK - although running PVC cable buried directly in a concrete floor incorporating UFH would be a Bad Thing and no mistake (for one thing, ambient temp for such cable would be up around 50+ degrees, requiring substantial (60%? figures not to hand!) derating).

HTH - Stefek

[Martin Angove]

[...]

The main problem running *anything* under the bathroom floor is that of accessibility. Don't put any junction boxes down there if you are planning on installing flooring in the bathroom which cannot be easily lifted for maintenance. Given that you are looking at UFH, your flooring may well be tiles...

Ummm... and part P too.

Hwyl!

M.

[Dave Plowman (News)]

Well, any first floor bathroom is certain to have the lighting wiring for the room below under its floor, so I'd say this is rubbish.

[r.rain]

Based on the advice you gave me regarding my kitchen UFH sometime ago I did some pre investigation work into this and the cable that I have under the bathroon floor is a lightly loaded upstairs ring. Its a real strange setup here being it 2 places converted into one and the ring mains are not logical in the way they have been wired. Anyways doing the math I think I'll be pretty safe here.

Thanks again!

Cheers

Richard

[Ed Sirett]

One I did 'last year' (yeah right) had 1200 Ohms for the element. So we are talking a small load.