Underfloor heating power wiring

[cmb2020]

Hi all

Im looking to locate my underfloor heating electric thermostat. The easiest place I can see is to change a double plug socket and wire it in to the thermostat and plaster around the old hole. Or relocate the power supply wire to near by the light switch so the thermostat and light are together. (As the image shows the sockets are in the middle of a wall so look odd)

my question is, how should I wire it safely, based on the wiring you see in the pictures...

theres 2 red and black and green cables leading in to both twin sockets. Am I correct in thinking I should swap to a single socket, and use one of each colour wire. Then the other ome of each wire go to the thermostat?

Or is there a reason there’s 2 wires in each socket?

ideally I’d like that wall to be clear of appliances and oddly placed sockets.

Don’t have money to my name so wanting to do this myself if possible.

tia

 

[Phil the H]

Hi cmb2020,
To be clear I'm not a qualified electrician but I feel a bit concerned that you're thinking of doing this work yourself when you don't appear to be aware of the basics of ring main wiring, which is what the two pairs of wires into each socket mean. Basically, each red, black and earth wire comes from another similar socket elswhere in the house thereby connecting each socket. The start and finish of this arrangement will take the cables back to the consumer unit to form a ring, hence the name. I suggest you need to initially trace where each of the incoming and outgoing cables travel from the two sockets in your photo to understand the route of that particular ring main if you're intending to connect the underfloor heating to that ring.
When you say 'wire it into the thermostat' I assume you really mean wire into the underfloor heating element because although the thermostat would be part of the installation it wouldn't be the only component.

I don't know the surface area of the floor you intend to heat so the other point to take into account is the loading of the underfloor heating element, i.e. is it less than 1 kw or several kw. If its several KW then you should at least ensure you know what is already connected on that particular ring main to ensure it's not going to be overloaded, although it's unlikely in a domestic setting.
Based on the above it will be a lot safer to get an electrician to look over the job.

 

[Deleted member 267285]

If the underfloor heating is being delivered by a boiler, are you able to use any of the boilers supply?

 

[cmb2020]

Hi it’s a 200 watt mat that you screed over. With a little digital box.

I can do basic wiring but I’ve no real idea how it works...

could I daisy chain the digital control box from one of the sockets? Say to put beside the double socket box?

I don’t want to follow cables or cause more stress. I just want to find a simple solution that works and can look half decent...

tia

 

[flameport]

m I correct in thinking I should swap to a single socket, and use one of each colour wire. Then the other ome of each wire go to the thermostat?

No. That will result in cables not having the appropriate protection if it's a ring, and other sockets not working if it's a radial.

The heating controller needs to be supplied via an FCU with suitable fuse in it, 13A or less.
The FCU can be connected in place of the existing socket, or depending on the circuit layout, another cable connected to the existing socket (3 wires in each terminal) and the FCU connected to the other end. Or take one set of wires into the FCU, add another cable from that to the socket, so both the socket and FCU have 2 sets of wires.

You will need to find out what type of circuit it is, and what protective device (fuse, MCB) it has.
The circuit will also need RCD protection.

Hi it’s a 200 watt mat that you screed over.

200W in total, or 200W per m² ?

If it's 200W in total, it's a complete waste of time - that will heat nothing.
If it's 200W per m² , the area of the mat is required so the total load can be determined.

 

[bernardgreen]

I just want to find a simple solution that works and can look half decent...

a simple solution can work and look neat but not safe.

For your safety please employ a competent electrician.

The best option may be to add a Fused Connection Unit ( FCU ) into the ring and use the FCU to feed the underfloor heating via it's thermostat / control unit.

 

[cmb2020]

Hi all

I tried connecting a third wire to the socket connections, and lead them to the relevant inputs of the underfloor heating control box.

It has worked and no problems, so would I be right in thinking put the FCU box in between, and it’s safe?

It heats up the floor to feel very cosy warm. I’ve previously connected one in another room which had just a single pair of wires for power.

 

[ericmark]

There are many types of electric underfloor heating, some need an earth mat between heating element and the floor you walk on, some the earth is built into the heating wires, some uses a special chemical which ensures it can't over heat, others required a thermocouple pocket in the floor to prevent over heating, so if you say I have fitted a Raychem T2 under floor heating system there may be a simple answer, but just a general statement I have fitted under floor heating not a clue what type or how wired is it OK, the answer has to be simply "I don't know."

The under floor heating I fitted was a flop, it worked, but keeping the floor to 27°C maximum it was not warm enough to heat the room, if I had not fitted the pocket and floor sensing probe it may have worked, although not to regulations or safe.

So fitted a hot water system, as has my bother-in-law, these can't over heat, and were both installed as Aga cookers fitted and wanted a way of cooling the side boiler when baking, it was never designed to heat house.

The Roman hypocaust is a very old idea, there is a reason why we stopped using it, at least in this country, it is too slow to heat, and too slow to cool, like the so called economy 7 electric radiator system it was a good idea, but does not work in a modern house to give a controllable heating system that people want today. Yes it heats, but the whole idea of only heat a room when required is just not possible, it is far to slow responding to changes.

 

[cmb2020]

The original one was just to heat up the wetroom floor to help it dry quicker and take the edge off those cold evening poo’s freezing feet in the process

it seems like there’s a lot of complicated scenarios being brought up and I understand electrics can kill. But I do have some sense and know to at least get some knowledge and turn off the power etc. Watch YouTube videos. Basic wiring on google images.

I’m just looking to wire the thing in and hoping someone could share a link or video or just give the answer.

As my last reply, I have managed to get it working but was the method correct? With a third wire going from socket to control box?

 

[flameport]

I have managed to get it working but was the method correct?

I tried connecting a third wire to the socket connections, and lead them to the relevant inputs of the underfloor heating control box.

No.

What type of circuit is it?
What rating is the circuit breaker or fuse?
Does it have RCD protection or not?
What rating is the heating mat?

Things working is not the same as them being safe.

 

[cmb2020]

I haven’t a clue sorry.

I know the controller has surge protection and overheating protection.

let’s say I put a plug on the heating control power supply, and plugged it in as a normal appliance?

Or a fuse box, and then powered it from a different place in the house? Say an old light switch wire? (2wire).

Would either of these be considered safe please?

If I had money for an electrician I’d pay but I’m very broke and just trying to get the house to a liveable / safe standard.

it’s solid stone old build

and thank you for the reply’s!

 

[Deleted member 267285]

Do you not have central heating?

 

[cmb2020]

I do have it but not in the wetroom

Also the power supplier I’m with it is cheaper at times costs nothing or can be payed to use electricity. So this is the cheapest option more often

 

[endecotp]

I tried connecting a third wire to the socket connections, and lead them to the relevant inputs of the underfloor heating control box.

It has worked and no problems, so would I be right in thinking put the FCU box in between, and it’s safe?

There’s a fair chance that that would be OK, but we do need to know at least what the power rating of the heating mat is.

 

[cmb2020]

There’s a fair chance that that would be OK, but we do need to know at least what the power rating of the heating mat is.

Hi I’ve just attached an image of the mat from eBay