Wiring Electric Underfloor Heating

JohnW2 said:
Do the electronic ones have remote sensors (I didn't think they did)?

I have no experience of electronic ones, but I've often looked at all my non-electronic ones and wondered how on earth they even vaguely do what they are meant to do, since their heat sensor is usually sitting just a couple of inches away from a radiator which, when 'working' is virtually too hot to touch and, indeed, whose bodies are often pretty warm (probably warmer than the desired room temp) after the CH has been running for a while.

Kind Regards, John
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There are models with remote sensors, however mine simply have two sensors one for air and one for water, the latter auto compensates the air temperature reading, and the radiators are modulated just like the boiler, so other than first turn on with a cold house, they are not that hot, unlike the old mark/space control, the modern system regulates the output so neither boiler or radiator valves switch on/off both gradually reduce output.

The problem is although there are thermostats like EvoHome and Nest which use an industrial standard opentherm many boilers can only have the output modulated by either return water temperature or that manufacturers own modulating thermostat the latter may not be able to talk to electronic TRV heads. So in mothers house with a Bosch boiler if I used EvoHome it has to be set to use the mark/space ratio not modulate the boiler, it needs Bosch's own thermostat think it's call Wave to electrically modulate the boiler.
 
Seb101 said:
you could do all the work yourself without requiring Part P.
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No.

This is Part P:



It is not pointless pedantry to point out that the requirements for doing work safely apply to everything, not just notifiable work.
 
Seb101 said:
Hi Kadi, while the elders argue about the merits of old money versus new money, let me answer your question.

You say you have checked the ratings on the RCD, usually the there is an MCB (breaker) for the circuit and an RCD for multiple circuits (if it's a combined one it's called an RCBO). Either way, it's the breaker current you need to be sure you are not exceeding (technically the RCD max current and the total current for the incomer as well, but the chances of going over that with 1.3kw are slim). Whats the rating on the UFH breaker?

In general, yes, you can do as you suggest. If you are wiring it into an existing circuit (and not directly into the Consumer Unit) and the UFH is not in a special location (bathroom etc) then you could do all the work yourself without requiring Part P.

You could also likely safely wire 1.3kW as a fused spur off any ring-main socket in your house.
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Hi Seb, firstly thank you for your advice related to my original question - it's much appreciated.

Secondly i'll try and answer as best i can! My knowledge of the RCD/RCBO is limited although i seem to recall its 32Amps/30mA (if that helps?). I thought i had a picture which may have helped but i haven't... i'll take a look at it tonight. The current circuit has 1.3kW attached to it and its purely dedicated to the underfloor heating and all i wanted to know was if i could attach another 750w to the circuit from the junction box. If i can then i will go ahead and book in an electrician (even if i can carry out the work myself i wouldn't :/).

A fused spur off the sockets would be more work as there aren't any located on the outer wall of the hallway - they're on the other side of the rooms.
 
32A/30mA would almost certainly be an RCBO. If it is dedicated to the UFH (turn if off to check and see if anything else stops working) then you have plenty of spare capacity (32A x 240V = approx 7.5kW of capacity).

You're good to go.
 
Some UFH mats stipulate area allowed to be protected by one RCD, it would seem there is some leakage so exceeding the limit could result in it tripping with no fault, you need to read the paper work that came with the units, it varies make to make, you do have the power required. Because it is the earth leakage which limits, then will need a RCBO which is a RCD and MCB combined and it depends on the design of the consumer unit if it will take RCBO's and how many it can take.

I still ask the same question, how is the central heating controlled? As adding UFH could mess up the central heating.
 
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