Recessing elec conduit in floor for floor plugs?

[Great_scot_selfbuild]

How deep into the PIR should I recess 20mm conduit for in-floor plug sockets?

 

Any tips on cutting the PIR? I’m assuming I cut a square channel with a thin layer of PIR over the top of the conduit just so the UFH pipe isn’t directly on the conduit.

[BotusBuild]

How deep is the PIR?

What is the build up of the floor upto and including the PIR?

Could you run the cable below the PIR and then bring it up to the location of the floor sockets?

 

I have 2 floor sockets. The cables were run between the joists and then a hole made to bring the cable up vertically to where the floor sockets would be.

[Great_scot_selfbuild]

1 hour ago, BotusBuild said:

How deep is the PIR?

What is the build up of the floor upto and including the PIR?

Could you run the cable below the PIR and then bring it up to the location of the floor sockets?

 

I have 2 floor sockets. The cables were run between the joists and then a hole made to bring the cable up vertically to where the floor sockets would be.

Concrete beam & block, 150mm PIR, UFH in 75mm screed, LVT to finish

[BotusBuild]

So your approach seems the only option 😉 

 

As for cutting the PIR, a reciprocating saw (I'd use a hand held one for control), and you'll have to break small chunks out as you go. Messy but a hot knife won't work.

 

Use the chunks to wedge the conduit down from the UFH.

[andyscotland]

I would put them as deep in the PIR as you can.

 

What you've described doesn't quite fit any of the standard installation Reference Methods in BS7671 but from first principles, surrounded by insulation and overlaid by heating pipes is about the worst possible case.

 

Slightly counterintuitively on a heated floor "not covered by thermal insulation" really means putting it on the cold side of the insulation e.g. at the bottom.

If you can get the conduit touching or at least nearest the concrete then I'd say it's similar to Reference Method A.

 

Be aware that the rating for 2.5mm flat twin & earth in method A is exactly 20 amps at an ambient temperature of 30 degrees.

 

Depending on what temperature you're heating the floor to, and what temp you expect below the beam and block, your ambient at the conduit might be above 30° - you might want to model that temperature gradient to check (or design the circuit to operate at higher temp e.g. by using a 16A radial).

[JohnMo]

Sorry no clue to the real answer, but don't sockets have to be a  minimum given distance from the floor, so wheel chair users etc can use them? So are you allowed floor sockets?

[garrymartin]

1 hour ago, JohnMo said:

Sorry no clue to the real answer, but don't sockets have to be a  minimum given distance from the floor, so wheel chair users etc can use them? So are you allowed floor sockets?

I believe the Part M document refers to "wall-mounted sockets" in relation to the minimum distances. AFAIK, floor-mounted sockets are still allowed, but always best to check with your BCO for their guidance.

[Alan Ambrose]

>>> Messy but a hot knife won't work.

 

Why not? Otherwise I would suggest a Winons hot knife.

[BotusBuild]

A hot knife is good for polystyrene. They just dont cope with PIR. Someone may be along to explain why. Most guidance for cutting is sharp knife, jigsaw or handsaw

[BotusBuild]

3 hours ago, JohnMo said:

Sorry no clue to the real answer, but don't sockets have to be a  minimum given distance from the floor, so wheel chair users etc can use them? So are you allowed floor sockets?

As long as there are wall sockets in the vicinity that comply with the height guidance then floor sockets are allowed