Wiring setup for underfloor heating?

[macadonald]

Hi Guys,

Just planning ahead and trying to understand how loose wire underfloor heating is wired in. I'm looking at the Warmup loose wire system for a very small area in my bathroom. Basically the spec says it has a 3m cold wire, which I assume is the power supply cable. Now assuming that the thermostat will be halfway up the wall, how does this tie in with the power supply for the heating cable. Does the mains supply run down from the ceiling ring to the thermostat and then the cold wire runs from the heating wire to the thermostat? Is this the basic idea?

If the power supply can't run off of the lighting ring, does it then need to somehow be wired in from the closed ring of the sockets? A bit more of a challenge. I'd be very happy if my first idea was right?

Thanks

 

[ricicle]

Underfloor heating should not be supplied from the lighting circuit and must be protected by a 30mA RCD. The cold tails run from the elements into the controller. The supply will also go into the controller.

 

[macadonald]

Thanks for the response. can you tell me what size cable the supply would need to be? dimension and current. Only reason I'm asking is because I want to chase in some conduit before the plasterer smooths the walls.

Thanks

 

[ricicle]

Before you do this work you need to be aware of:-

-This work being notifiable under Part P of The Building Regulations
(Which requires notification before you start work)
-If you propose doing the work yourself (false economy for small jobs) then you need to be able to prove you work for compliance with safety. This means being aware of bathroom zones, design and testing procedures.

I know it seems a drag but that is what electrical safety is about - particularly in a bathroom !

 

[macadonald]

Ricicle,

Appreciate your response and I do have an electrician comign in to wire in and install the underfloor heating. What I need to do before hand is get the walls plastered. I planned to run some conduit in the wall from the floor level to the thermostat level. Probably 5 ft above floor level. The questions I'm asking are simply so I know what size conduit to install. Sounds like the conduit will need to house the cold wire as well as the power supply.

If you could let me know whether the larger oval conduit (must be close to 22mm wide) will be enough, I'd be grateful.

 

[RossR]

What I need to do before hand is get the walls plastered.

Why? It's so much easier if you do things in the right order.

1. First fix electrics
2. Plastering
3. Second fix electrics

 

[macadonald]

That's what I'm trying to accomodate for here. I clearly am not going to lay the underfloor heating cable, then plaster (probably ruining the wire), then tile. I can't imagine tiling before plastering either, so it's a no win.

I'm trying to allow for the electric cabling for the underfloor heating after the plastering is done. All other electrics have been done.

Still no answer to the question. Will a standard large oval conduit house the cold wire and the power supply cable.

Would be grateful for an answer.

Thanks

 

[RF Lighting]

This is all you need to put in.

Take the conduit in to the boxes by about 2mm. If you're using oval condit squeeze it with some pliers and it goes circular just at the end and fits perfectly into a flush box 20mm knock out.

Take your conduits 100 - 150mm below the level of your floorboards.

Your electrician will be able to do the rest from there.

 

[xr4x4]

This is all you need to put in.

Take the conduit in to the boxes by about 2mm. If you're using oval condit squeeze it with some pliers and it goes circular just at the end and fits perfectly into a flush box 20mm knock out.

Take your conduits 100 - 150mm below the level of your floorboards.

Your electrician will be able to do the rest from there.

Surly you want that to be the other way round in the picture, why would you want the heating controller near the floor?

 

[bernardgreen]

The "cold wire" is the power feed to the heating wire from the controller.

It cold because it doesn't heat up when the current flows through it on its way to and from the heating wire.

You may find there are two cold wires, one at each eand of the heating wire. Both cold wires go to the controller. There may also be a sensor to measure the temperature of the floor. This has to be installed in the floor as well and its cable taken up to the controller.

 

[RF Lighting]

Oops yes I cutted and pasted in the wrong order there.

The FCU goes at low level and the controller goes at switch height

 

[macadonald]

RF, your a star.. that's all I needed to know.

Thanks all for your help...

 

[Taylortwocities]

One thing you must pay attention to. The feed musr include an RCD. This may already be part of your consumer unit, or the FCU may need to be an RCD type.
Your electrician will be able to advise.