Does Wet UFH need a floor temp sensor
Discussion
I guess it is theoretically possible that you could over heat the floor, if someone whacked the nest up to 35c and it was calling for heat all weekend
What you’d need to try and calculate though is the rate of energy into the floor via the water circuit, and the rate of heat loss out of it, and how that changes with the temperature differential
Eg it may be to get the floor over 27c you need a flow temp over 45c otherwise the differential is never high enough and there is too much heat loss into the air. So you would set the mixing valve to 45c and then it’s “theoretically” impossible via maths / physics to overheat thebfloor. And/OR you have a heat sensor in the floor which is akin to the overheat sensor on a cylinder
I’m guessing that it’s probably actually quite hard to keep a floornover 27c in the U.K. with the heat loss you’ll have hence a floor sensor probably not needed
What you’d need to try and calculate though is the rate of energy into the floor via the water circuit, and the rate of heat loss out of it, and how that changes with the temperature differential
Eg it may be to get the floor over 27c you need a flow temp over 45c otherwise the differential is never high enough and there is too much heat loss into the air. So you would set the mixing valve to 45c and then it’s “theoretically” impossible via maths / physics to overheat thebfloor. And/OR you have a heat sensor in the floor which is akin to the overheat sensor on a cylinder
I’m guessing that it’s probably actually quite hard to keep a floornover 27c in the U.K. with the heat loss you’ll have hence a floor sensor probably not needed
I've very easy to go over 27 degrees with ~40 degree UFH water running through it.
I would say 9 times out of 10 my UFH cuts out because the 27 degree floor temperature limit has been hit, even before the rooms get up to 21 degrees.
That's not to say the rooms then never get up to 21 degrees, because the floor slab will continue to release heat over a long period of time.
My concern without a floor stat is that my the time the air reaches the desired temperature that 1) the floor will get way too hot 2) the floor will continue to heat the room up after it has reached 21 degrees and you will overshoot the air temperature by some margin.
I would say 9 times out of 10 my UFH cuts out because the 27 degree floor temperature limit has been hit, even before the rooms get up to 21 degrees.
That's not to say the rooms then never get up to 21 degrees, because the floor slab will continue to release heat over a long period of time.
My concern without a floor stat is that my the time the air reaches the desired temperature that 1) the floor will get way too hot 2) the floor will continue to heat the room up after it has reached 21 degrees and you will overshoot the air temperature by some margin.
Muncher said:
I've very easy to go over 27 degrees with ~40 degree UFH water running through it.
I would say 9 times out of 10 my UFH cuts out because the 27 degree floor temperature limit has been hit, even before the rooms get up to 21 degrees.
That's not to say the rooms then never get up to 21 degrees, because the floor slab will continue to release heat over a long period of time.
My concern without a floor stat is that my the time the air reaches the desired temperature that 1) the floor will get way too hot 2) the floor will continue to heat the room up after it has reached 21 degrees and you will overshoot the air temperature by some margin.
My Heatmiser controlled wet UFH has 11 zones and I’ve only had an overshoot of 1 degree a couple of times in 3 years and that was only in the very small downstairs cloakroom. It’s probably because there is also a heated towel rail in there as well.I would say 9 times out of 10 my UFH cuts out because the 27 degree floor temperature limit has been hit, even before the rooms get up to 21 degrees.
That's not to say the rooms then never get up to 21 degrees, because the floor slab will continue to release heat over a long period of time.
My concern without a floor stat is that my the time the air reaches the desired temperature that 1) the floor will get way too hot 2) the floor will continue to heat the room up after it has reached 21 degrees and you will overshoot the air temperature by some margin.
It’s really not a problem in a wet system as far as my experience (of four systems in four houses over about 12 years) goes.
OMITN said:
This thread has got me thinking....
I've just (this weekend) had the rest of the Amtico laid in our house, with this final section being over the wet UFH.
I have a Nest thermostat for the dining room/kitchen, which controls the UFH and a separate Nest for the radiators in the rest of the house.
The Nests work fine, but the limit on temperature for the Amtico - 27 deg - means that, because I don't have a probe, the air temperature at the nest is going to be somewhat different from the floor temperature.
Other than common sense (I have a wife and a daughter to challenge that concept), anything else that would help? Infrared heat sensor?
you need to limit the manifold temp on the mixer valve.I've just (this weekend) had the rest of the Amtico laid in our house, with this final section being over the wet UFH.
I have a Nest thermostat for the dining room/kitchen, which controls the UFH and a separate Nest for the radiators in the rest of the house.
The Nests work fine, but the limit on temperature for the Amtico - 27 deg - means that, because I don't have a probe, the air temperature at the nest is going to be somewhat different from the floor temperature.
Other than common sense (I have a wife and a daughter to challenge that concept), anything else that would help? Infrared heat sensor?
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