Even if you don't use their bits (IMM will immediately rubbish them, but
my system is now towo years old and hasn't missed a beat) they have a
lot of design stiff.
Electric is expensive to run, unless you only heat at night on lo rate.
Water is a bit more complex, and will require you to lay new screed. It
is fabulous with tiled sufaces tho.
The key siiuse are laying teh correct pipe at teh correct spacing - ypu
probably need to aim for 50W/sq meter for decent insulated rooms, or up
to 3 times that for not. Pipe is relatively cheap compared with teh
screeding ind finishing you will apply, so put plenty in.
You have to have a separate pump to pump warm - not hot - water round
the special barrier pipe, and a temp reducing valve to get the water
down to sensible temps. Again polyplumb do a kit of pump, manifold,
motorised valve temp reducer and all ancillary bits, and its very easy
to wire up.
You will need some form of separate zone control and some form of relay
to get CH boiler running on UF demand, without e.g. HW demand causing
the UF pump to spin up.
Think a bit about thermostat siting - you can get radio ones, but cables
may be useful. If in doubt and a major refurb run lots of thermostat
cables, and consider multiple zones. The polyplumb manifolds allow
motorised valves to be applied to any or all zones, but it gets
expensive, and IMHO not worth it - one or at most two zones with master
thermos is adequate.
There are kits on the market which allow you to combine an existing
radiator system with underfloor in an extension or renovation.
You should check that your existing boiler and system pump are capable
of supplying the UHF circuit. You should also go for independent
control of the UHF circuit as it will need to be on earlier than the
rads.To achieve this you will need to fit a timer for the UHF circuit.
The Honeywell CM67 clockstat is a good choice as it combines time and
temperature. The rad circuit will have to have a two port valve
controlled by its own timer and stat.
There is some more advice at http://www.underflooradvice.co.uk
This site is owned by myself BTW.
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