underfloor heating

Dave coughed up some electrons that declared:

Could you be more specific Dave?

You put a source of heat (electric or warm water) under the tiles and they get warm (about 30C +/- some)

That heats the room, at, typically in the region of 100W per m2

HTH

Tim

Yes, I see what you mean.

What I was getting at was that they are obviously electrically heated But how is the electricity distibuted between the tiles? Local conections would be out. Is there a wire that goes under every tile?

Dave

Dave coughed up some electrons that declared:

Essentially yes - it's a heating mat (support mesh usually) with a long heating wire circuit (or groups of circuits in sections). These come out as tails near the edge and are terminated back to house wiring in a manufacturer dependant way.

There are extra IEE regs pertaining to electric underfloor heating in bathrooms.

Cheers

Tim

As I understand it, it's resistive cable or mats that go under the sub-floor Your single tile sized demo was misleading.

Graham. coughed up some electrons that declared:

I believe some can go in the tile adhesive layer. Wouldn't fancy it in a bathroom though, if mains driven...

Many thanks for clearing that up. I'm sure daughter or son would be asking me quite soon, as it looks like the way to go for the young and rich.

I can understand that under this nanny governm...

Many thanks again

Dave

Darren

The cable is completely screened inside an earth wire. The earth connections are made at both ends The stuff is more like resistive coax.

Thermal conduction

It's important, of course, when fitting it to a solid ground-floor room, to have adequate insulation *under* the heat source - otherwise you end up heating up the soil below rather than the room above!

Or the room below..

rather than the room above!

We've been having an interesting debate with a groundwork contractor about whether in this circumstance it's better to have the insulation underneath the 150mm concrete slab or over it. Obviously having the insulation underneath increases the amount of thermal mass in the UFH system: so it warms up more slowly but is more stable. But it means you're never going to be able to get to the insulation again, which is a bit of a nightmare if it starts degrading.

Most UFH cables are now 2-core, with overall screen, and are fed from one end only. This avoids large area current loops and thus keeps down the magnetic 'hum' field. 5 mm diameter cables are for in-screed applications and 3 mm for under-tile heating.

On larger installations the capacitive earth leakage can get quite high, so the high-integrity earthing requirements may apply and supply should be via a dedicated RCBO.

More like resistive screened twin...

Any chance of a quick overview of the additional reqs ?