Underfloor heating only luke warm

[stem]

Assuming that the floor surface temperature is the only control that you have, (ie there isn't a room thermostat or timer that could override it for example) then that doesn't sound right at all. 14 degrees will feel cold to walk on.

Provided that you are measuring the temperature of part of the floor that has the heating under it, the reading is accurate, and there aren't any other controls that are trying to regulate the heating, then it's not working properly. My bathroom floor isn't heated but it's warmer that that.

How long it takes to warm up will depend on several things, the room temperature, the insulation below, the thermal conductivity of the floor covering, etc but I would expect it to be warm after an hour or so.

 

[blackbirdxx]

Builders are telling me that it takes several days for the UFH to heat up. At the moment, the thermo has been set at 24 degrees C on manual for the last 3 days and its only reached a max of 12 degrees C. Is what I'm being told acceptable? Several days to heat up doesn't sound to good to me for a 160w/m2 fully insulated mat?

 

[Taylortwocities]

We used to have a member on here called BAS who always said UFH was a waste of money and furry slippers were better. Seems he was right.

And I agree with him. Which is more than YOU ever did, George.

 

[winston1]

I said it seems he was right. Isn’t that agreeing with him?
Who is George?

 

[big-all]

Builders are telling me that it takes several days for the UFH to heat up. At the moment, the thermo has been set at 24 degrees C on manual for the last 3 days and its only reached a max of 12 degrees C. Is what I'm being told acceptable? Several days to heat up doesn't sound to good to me for a 160w/m2 fully insulated mat?

are you saying the central heating is on a normal daily cycle bringing the room up to perhaps 20 degrees and the heated electric floor stays at 12 degrees ???

 

[blackbirdxx]

Just to be clear, at the moment the central heating is switched off. The UFH is set to 24 degrees manual and has only reached a max of c12 degrees C after 4 days.

HTH

 

[big-all]

the trouble you have is underfloor heating when applied is secondary for a specific area unless super insulated room
where a specific area [the floor] will be perhaps 5-10% warmer than the ambient room temperature when in use
as the room is perhaps 6 degrees your underfloor has insufficient output to make up the heat loss to raise it up much more to levels you hope for
you need to keep in mind electric will cost about 3 times as much to heat up a space compared to gas so for the same cost on gas central heating you can heat the same room toasty hot where as underfloor cannot
the most cost effective is not to use underfloor but iff you do warm the room on gas and just underfloor about an hour before you need it

 

[blackbirdxx]

Point taken, but as the thermostat is attached to the sensor in the floor, surely the temperature should raise to the 24 degrees C that its set to, especially after a fair few days of being on??

 

[big-all]

it wont heat up more because off the heat loss remember heat rises so most off the output will dissipate
think off playing in the snow without gloves on your hand although they have 32degree blood flowing through them but they still get cold
what are you actually trying to work out by using your underfloor on its own ??

 

[blackbirdxx]

Hi,
Only trying to check that the UFH is working properly as its just been fitted. The main central heating isn't on as the house isn't being lived in yet. I think what you're saying is that the 24 degrees C is only likely to be hit once the central heating is on as well, correct?

 

[Taylortwocities]

Not correct. The floor has its own sensor in the floor and will heat up to its set temperature.

 

[JohnW2]

Not correct. The floor has its own sensor in the floor and will heat up to its set temperature.

I think big-all's point was that if the house/room is cold (no CH on, in UK November), then the UFH might never be able to heat the floor up to the UFH's 'set temp', because the heat will all be rapidly lost into the cold room.

That (heat loss from floor into room) is obviously going to be true to some extent, but I don't know if it would be a large enough extent to explain what the OP is describing - but it wouldn't surprise me if it was (large enough).

Kind Regards, John

 

[big-all]

I think big-all's point was that if the house/room is cold (no CH on, in UK November), then the UFH might never be able to heat the floor up to the UFH's 'set temp', because the heat will all be rapidly lost into the cold room.

That (heat loss from floor into room) is obviously going to be true to some extent, but I don't know if it would be a large enough extent to explain what the OP is describing - but it wouldn't surprise me if it was (large enough).

Kind Regards, John

yes exactly the point
if you dont want to turn the gas heating on take a fan heater preferably thermo controlled and less than 2kw and an extension lead warm the room for about an hour preferably two if the underfloor is turned on at the same time setting the temperature on the fan heater around 2 degrees less than the required room temperature and see what you get

 

[flameport]

Builders are telling me that it takes several days for the UFH to heat up.

Incorrect - an hour or two would be more usual.
Unless they were thinking of old type 1960s electric heating which had the cables buried under several inches of solid concrete.

as the thermostat is attached to the sensor in the floor, surely the temperature should raise to the 24 degrees C that its set to

Yes. If it never gets there, something is wrong. Such as the installer placing the floor sensor directly on one of the heating cables rather than in the screed between the heating cables.

The UFH is set to 24 degrees manual and has only reached a max of c12 degrees C after 4 days.

12C is cold, not warm in the slightest.

Two things to do:
1. Is it actually using power? Ideally with everything else in the house turned off, check the electricity meter with the UFH off and then with the UFH on. There should be a noticeable difference in the rate that the red light flashes, or the disc rotates. If it's a smart meter, the actual consumption should change by whatever the rating of the mat is.
2. Put a rug or mat on the floor, and after half an hour with the UFH on see if the temperature under that is higher than the surrounding uncovered floor.

 

[JohnW2]

Just to be clear, at the moment the central heating is switched off. The UFH is set to 24 degrees manual and has only reached a max of c12 degrees C after 4 days.

Having just decided to re-read this whole thread, I'm getting a little confused.

Just to be sure, are we certain that it's the floor temperature (not the room temp) that has "only reached 12°C after 4 days of UFH"?

What temperature was the floor (and the rooms) before you switched the UFH on? I don't think that the dusty unheated far corners of my house have been down to 12°C in recent days?

Kind Regards, John