Under floor heating questions for your edification and entertainment

[The Ghost]

So...Got a call late last night client who I have done work before asked advice re builder doing electrics. Advised re CPS membership he checked on ESR builder not on there. Asked builder was he CPS member. Builder said seems best we part company client left in the lurch with no kitchen just bare walls building work half done. Client down 8 G.
Agreed to do electrics on kitchen all good so far! UFH.. so he has UFH in bathroom adjacent to kitchen. And UFH under kitchen floor. Client suggested I put both heating mats on the one thermostat existing from the previous bathroom UFH. Bathroom is Klima/screwfix UFH and thermostat, new kitchen UFH is Heatmat. No evident thermostat cable coming up from floor. Clear so far? So for me its going to be a bit of a scramble sorting out three cables black and one cable white coming up from floor and sorting out thermostat(s) Any savants out there? This is a discontinued Tstat, and I have the file for it. I suppose the question is can you put an extra 12m² (Kitchen) onto existing 9m² (bathroom) existing thermostat. All answers will be treated in confidence of course.

 

[ruston]

I would too, trouble is you will not know if it has just been lashed in and you may still get problems.

 

[Toneyz]

I would too, trouble is you will not know if it has just been lashed in and you may still get problems.

All you can do is hope it has been installed with care, test it and maybe if possible use a heat source camera to see where elements have been laid to reduce the chance of it being drilled through by other trades etc.

 

[ruston]

Yes , the plan will not be there I bet. Are the utilities in , that would be a help.

 

[The Ghost]

@ruston there is no plan, the builder just disappeared like a ghost when asked if he was a member of a CPS. There are two supply cables coming from under the floor so maybe he put two mats in??? What size is difficult to say. The customer is not interested in regs and just wants it to switch on. I have told the customer I will not connect in any unconventional way, what they think they want to do with it is up to them I do not want to know. I have advised them of what is neccessary and will note the matter to cover my derriere in the cert

 

[Toneyz]

@ruston there is no plan, the builder just disappeared like a ghost when asked if he was a member of a CPS. There are two supply cables coming from under the floor so maybe he put two mats in??? What size is difficult to say. The customer is not interested in regs and just wants it to switch on. I have told the customer I will not connect in any unconventional way, what they think they want to do with it is up to them I do not want to know. I have advised them of what is neccessary and will note the matter to cover my derriere in the cert

If the builder was carrying on the work in a correct manor , compliance with regs etc. could of included it in with building regs approval .The fact that he has bolted spells a bit iffy. What was the standard of electrical and building work like ?.

 

[Dave OCD]

He's already described that pretty clearly Anthony - I think atrocious is around the standard. In this situation as it's a bit desperate I'd test/verify the mat connections then consider using a programmable room stat, via a contactor for the load if necessary. With a bit of trial and error the customer could set a temperature equivalent to a nice warm floor temp.

 

[The Ghost]

From what I could see on initial inspection, electrics not good. Bare live wires hanging about the kitchen. Intention to put double range ovens (4.5kw) gas hob on ring (final) circuit along with dishwasher, tumble dryer and washing machine along with toaster kettle microwave electric grill etc. So not too good on the design side. I have run in a 20a circuit for the oven. He was going to get an electrician in (he told the client) but decided to "do it himself" The client baulked at this due to a catalogue of expensive errors. From what I have seen the builder would have been overreaching himself with the electrics.

 

[Dave OCD]

It looks like it's just waiting to kill somebody, terrible ! I think this is more common than we realise but many unsuspecting customers who know no better trust builders to do electrics - I've had experience of a few [or the aftermath] who grab as many aspects of a job as possible, whether they know what they're doing or not doesn't seem to worry them.

 

[The Ghost]

It looks like it's just waiting to kill somebody, terrible

Precisely my thoughts one of the first things to deal with safe iso. and so on. Indicative of someone who has no idea of regs and H&S etc. At least the customer had enough nous to check and stop work, he has a wife and kids to think about.

 

[mattg4321]

I've done hundreds of these now. That thermostat/controller looks like an old heatmat one from around 10 years ago. Having said that I suspect theirs was a rebranded version of something else at the time.

Normally the thermostat/controller will run up to 16A of heating - you can obviously check this on yours.

You can buy heat mat between 120-200watts per sq/m, however in this case you don't know what's been fitted. You can find out the current rating of a mat by using ohms law. Measure the resistance of the mat and divide voltage by resistance.

The floor sensors normally read around 22kohms at around 20 degrees. They do vary though.