under floor heating

I am considering installing UFH in a bathroom, the arear to be warmed is 8 square meters my plan is to run the boiler flow pipe (22mm) to two
zone valves one of which runs the whole houses radiators and the other is to run to the bathroom in 22mm where it is reduced to 10mm JG speedfit for the UFH loop and back on to the 22mm return to the boiler.
The boiler is Worcester 28i junior (non condensing) and brand new.
My question is by reducing it to 10mm will this provide sufficient heat reduction ie if my boiler gives out 90 deg c will the sudden decrese fromn 22mm to 10 mm pipe reduce this? so as I dont have the full heat of the boiler on the floor tiles?
i.e. I dont want to cause them to crack through thermal shock.
I am a electrician not plumber but have a few years of experience in domestic heating systems
I am aware that thermal shock is possible the tiles are ceramic and 11mm thick as for the controls i was thinking that a radaitor valve works on
the principal of closing the lock shield slightly there by reducing the
flow, that is my reason for using 10mm pipe ie the reduction from 22mm to 10mm would severly reduce flow and temperature.
I could very well be wrong! but i hope not.
Thanks for any advice
Martyn
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I am considering installing UFH in a bathroom, the arear to be warmed is 8 square meters my plan is to run the boiler flow pipe (22mm) to two
zone valves one of which runs the whole houses radiators and the other is to run to the bathroom in 22mm where it is reduced to 10mm JG speedfit for the UFH loop and back on to the 22mm return to the boiler.
The boiler is Worcester 28i junior (non condensing) and brand new.
My question is by reducing it to 10mm will this provide sufficient heat reduction ie if my boiler gives out 90 deg c will the sudden decrese fromn 22mm to 10 mm pipe reduce this? so as I dont have the full heat of the boiler on the floor tiles?
i.e. I dont want to cause them to crack through thermal shock.
I am a electrician not plumber but have a few years of experience in domestic heating systems
I am aware that thermal shock is possible the tiles are ceramic and 11mm thick as for the controls i was thinking that a radaitor valve works on
the principal of closing the lock shield slightly there by reducing the
flow, that is my reason for using 10mm pipe ie the reduction from 22mm to 10mm would severly reduce flow and temperature.
I could very well be wrong! but i hope not.
Thanks for any advice
Martyn
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The pipe says " Wirsbo HePex 1/2 in SDR9 Pex A 100psi @ 180F 80psi @200F not for potable water ....
Here is Wirsbo's response:
Thank you for your inquiry. It sounds like the tubing may not be installed according to our recommendations. For the best heat transfer, the tubing should be no more than 1-2" below the bottom of the subfloor. There should be a 2-3" air gap, then your choice of fiberglass or bubblefoil insulation.
If left the way it is what will the down side be? Circulating pump will have to run longer to get floor and room to temp? Will it affect oil consumption at all?

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Have him redo it to the floor and use the aluminum plates.
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It may reduce flow, but it will not reduce temperature. Reducing flow may cause a couple of degrees difference in the leaving water temperature due to greater residence time, but it will not change the incoming temperature at all, and certainly not enough to make a big difference.
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