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Underfloor heating supply

Postby jimuthy » Thu Mar 04, 2010 7:00 pm

I am planning to install underfloor heating under a laminate floor throughout a two storey house. Obviously the supply for this system will need to be from a dedicated circuit with RCD protection. Each room will have a thermostat capable of handling 3600 watts. My question is: would each thermostat also need to be connected to the new circuit with an FCU?
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Postby stoneyboy » Fri Mar 05, 2010 10:54 pm

"would each thermostat also need to be connected to the new circuit with an FCU?" It would be sensible to do so otherwise a fault in any one room would kill all rooms.
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Postby sparx » Mon Mar 08, 2010 8:10 pm

hi jimuthy,
several point here, each room stat may be able to switch 3.6kW, but what will be the load on each?
You say on A dedicated circuit, it may require one circuit per room or area!
It would be very unlikely that one circuit would do even one floor never mind whole house.
Presume you will be notifying LABC of your intent to install new circuit(s), as such will be notifiable work under 'Part-P' of building regs.
Also this may well need a larger consumer unit for extra circuit(s), again notifiable work.
As a guide for circuit loading, cable sizing, overcurrent protection device rating etc. : heating mat for each area -wattage divided by 230V = Amps. for each area.
NB all circuits require RCD protection at source.
This is really not viable DIY, you may be able to lay the mats but they require testing at each stage ie after laying but before flooring down, then after flooring down but before powering up.
Rooms containing bath/shower need special care with location of thermostats/FCU's
Damn the 'sheds' for selling this stuff to anybody,

take care,Sparx
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Postby ericmark » Mon Mar 08, 2010 11:49 pm

The one I laid had a special thermostat that measured both room and floor temperature can't see how any central control would work.
I was very disappointed the floor could not have been any hotter and walked on with bare feet. (In bathroom) Yet the room was not hot enough. Needed towel rail to get warm enough. Also any item placed on the floor can get very hot and the only way to prevent this is to use one of the chemical controlled types. i.e. RayChem. I have used this system for trace heating pipe work and it does work but unless the house is very well insulated so the heating is only trace heating then from bitter experience I would expect cold rooms.

Power is something else. Most houses with central heating have boilers around 25Kw and above. That is 108A far more than any normal supply to a house. So even if you could get it hot enough unlikely you can use it without having a three phase supply which to use safely will likely need re-wire of house.

As with many systems there are no restrictions to selling the system but loads to using the system and as Sparx says the DIY sheds do not seem to tell customers how hard it is to fit these systems safely and within the many rules. It is not a DIY job.
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