Electric Under Floor Heating newbe

JohnB47

Hi.

We've just had Thermonet electric under floor heating installed. The guy who installed it hasn't taken any time to explain things yet - he just left us the little guide leaflet and said not to turn it on until today and when we do, not to set it at too high a heat.

Well, I've battled with the instructions and think I understand them but some things seem odd.

Firstly, the thermostat/programmer comes with a default range of on/off times throughout the day (well, more start temperature/end temperature than on/off). This pattern is repeated every week day and there's a separate pattern that runs on weekends. The thing is, a typical 'on' temperature is 20d or 22 (please read d as degrees) and a typical 'off' setting is 15d. But I've found that, although the tiles are cold to start with, I have to set the 'on' temperature to about 23d or 24d to get it to turn on. And if I leave the 'off' or tickover temp set to 15, I think it would never come on again.

Can anyone tell me what their typical 'on' and 'off' temperatures are? (Mine is an upstairs bathroom, typical wooden floorboards on joists and ceramic tiles laid on an insulating board).

Secondly, the programmer is fitted on the wall outside the bathroom and it has a built in temperature sensor which allows it to show what appears to be the ambient temperature of our upstairs landing. Why is it measuring that? I thought the whole point was to measure the temperature of the tiles themselves (using a little sensor that I saw the installer fit under the tiles).

I should mention that we had the central heating on while doing all this (and we have a dual plumbed-in/electric heated towel rail) but the tiles themselves felt cold to the touch when we started. Perhaps the preset 20/15d temperatures assume no other form of heating in the bathroom? (in which case our bathroom would have to have been very cold to begin with).

Any help from a seasoned user would be appreciated.

Thanks.

evokit

i have electric underfloor heating on the whole of my down stairs (and in last house)
We set the cut off (tick over) at 14d, and we set it come on bout 30/40mins before we come down but as we have complete tiles down stairs we turn it off earlier than needed as heat is held.
the tiles take a little bit to feel toasty on the toe.
I only turn if off for our 3/4 days summer as costs a bit to keep turning on and off
the temp (ambient as you stated above) is the temp of the floor in the room you have the heating.
When fitted (i fitted both of mine) you get a temp sensor to put nearish the control, So the reading you see on the programmer is taken off this senor yet i dont feel this ever gives a 100% propper reading but i go off how the tiles feel on feet and how i feel in the house temp wise, so never look at it.
our off is 14 - on is around 22 - when colder wife slams it up just for me to turn down (whish i never showed her how to use it)

JohnB47

THanks.

You say "When fitted (i fitted both of mine) you get a temp sensor to put nearish the control, So the reading you see on the programmer is taken off this senor". When you say nearish, do you mean under the tiles or somewhere else?

The temp shown on my programmer is the ambient temp of my landing - it's nice to know this but I wonder why it is measuring it in the first place? There is another temp shown (it alternates between showing me the time and that temp) but this is the temp that is set as the tile temp that I want (as measured by the sensor buried under the tiles). Currently, with my central heating turned off, this tile temp reading is 21d but the tiles feel cold (and are definitely not being heated). I feel if I set it to 14 it would never come on, never mind act as a tickover temp.

Is this normal?

Thanks again.

evokit

I assumed the temp was taken off the sensor, the sensor always has to go under the tiles etc, it could be the room temp - mine being under that stairs wont ever help me.
was it self laying cabel or was it the underfloor heating mat?
Ive used self laying on both houses so you can space it to how much heat you want in that room.
Eg hallway & kitchen have laarge 60 x 60 x 1cm thick porcelain tiles with smaller grout lines so here i had the cable closer as the tile is harder to get heat through, but when it does it doesnt leave and stays warm
living room - ceramic larger grout lines was more spaced out as ceramic tiles heat/warm easy. At 21d you should have some warmth on the tile. Sometimes its hard to tell, unless you have a none heated tile.
Your fitter layed the insulation boards under the cable?? like link below?
http://www.ebay.co.uk/itm/Underfloor-Heating-Insulation-Boards-6mm-Special-Offer-/280699656291?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item415b00d863

JohnB47

Thanks.

"was it self laying cabel or was it the underfloor heating mat?" It was a mat. He had to cut it up to spread it around tho.

I had it set to 21d, to come on half an hour before we got up. Tiles were stone cold (although the central heating was on, of course).

Something seems odd.

It feels like I'm going to have to set the 'on' temperature to around 27d and the tickover to 24d. That doesn't seem sensible to me but what do I know? I'll have a chat to the installer and then to the manufacturer to see what thay say.

Anyone else have experience of this?

Thanks.

sillygoose

Mine has a room temperature sensor on the controller and a remote floor sensor under the tiles. The floor sensors job is only so the controller can limit the floor from getting too hot. The room sensor takes precedence and the temperatures you set are the target room temps not the floor temps.

If you have other heating and the room is warm enough already the underfloor will not be switched on and the tiles will be relatively cold.

The controller, if it has a built in room sensor should obviously be in the room the underfloor heating is in. But if the controller doesn't meet the safety rules or there wasn't an approved safe location for it you installer went for the easy option of positioning it outside. There are strict rules about what, where and who can put electrical fittings in bathrooms.

Problem is, if it works like mine having it outside the target heated room makes it a bit useless, unless the controller can be set to only control the floor from the floor sensor I suppose.

It sounds like you are having to set the temperatures unrealistically high because really you are setting the target ROOM temperature, the underfloor is therefore being switched on by the controller as it tries to heat the room to those settings, you are having to set them way above the current room temp.

JohnB47

Thanks for the help.

"...the temperatures you set are the target room temps not the floor temps."

Hmmm. I know you can get mats that are intended as a primary heat source (ours has been supplied as that type, although we didn't ask for that and never intended to use it that way) but you can also get ones that are not. So, I would have thought that those that are not intended as primary heat sources would simply allow you to set the floor temperature and leave the room temp out of it. To be honest, I thought that's how uf heating worked - you decide what temperature you want the tiles to be during peak times and what you want it to be at other times, regardless of the room temp.

"It sounds like you are having to set the temperatures unrealistically high because really you are setting the target ROOM temperature".

That's how it seems to me but that's daft 'cos we have central heating in that room, so they'll always be battling against each other. And as you say, if the system is trying to reach a room temperature, it seems that it is trying to heat the bathroom to the temperature of the landing, which is just plain silly.

It seems I'll have to have a discussion with the manufacturer.

BTW, what are your 'on' and 'off' temperatures?

Thanks again for the feedback.

Edit:

I've just had a play with the system. I put it into manual mode, then raised the 'tile' temp reading until the heating was switched on (theres a click and a flame symbol appears). Then I held my hand over the little thermostat window and watched as the main temp reading slowly went up. When it got to exactly two degrees above the tile temp setting, the heating was switched off. I checked the tiles and of course, they were stone cold. This seems to prove that I have two problems. One, I've been given a primary heat source uf heating system and two, for it to work as such the thermostat should be in the bathroom!

Perhaps I need to manfacturer to replace the thermostat/programmer with one that simply measures the tile temp and allows me to program that on and off, without reference to the temp in any room, bathroom or otherwise. What do you think?

sillygoose

JohnB47 wrote: »

Thanks for the help.

"...the temperatures you set are the target room temps not the floor temps."

Hmmm. I know you can get mats that are intended as a primary heat source (ours has been supplied as that type, although we didn't ask for that and never intended to use it that way) but you can also get ones that are not. So, I would have thought that those that are not intended as primary heat sources would simply allow you to set the floor temperature and leave the room temp out of it. To be honest, I thought that's how uf heating worked - you decide what temperature you want the tiles to be during peak times and what you want it to be at other times, regardless of the room temp.

"It sounds like you are having to set the temperatures unrealistically high because really you are setting the target ROOM temperature".

That's how it seems to me but that's daft 'cos we have central heating in that room, so they'll always be battling against each other. And as you say, if the system is trying to reach a room temperature, it seems that it is trying to heat the bathroom to the temperature of the landing, which is just plain silly.

It seems I'll have to have a discussion with the manufacturer.

BTW, what are your 'on' and 'off' temperatures?

Thanks again for the feedback.

Mine is the primary heat source of a conservatory so at times we are around the room temperature is set for 20C but the floor temperature is set to a limit of about 30C max. All other times a frost protection lower limit 5C is active.

I have heard of undertile 'comfort heating' and I suspect it just comes down to the controller and is a combination of time setting and tile sensor reading, so perhaps you have been given an unsuitable controller or perhaps its just down the settings... from the manual for mine it can operate various ways..

This thermostat is a combination model allowing you to
choose between 3 different models. A, AF and F model.
A model: air only, with built in sensor
AF model: air & floor , with both built in and remote sensor
F model: floor only, with remote sensor

so for your use it would be set to just F mode.

JohnB47

sillygoose wrote: »

Mine is the primary heat source of a conservatory so at times we are around the room temperature is set for 20C but the floor temperature is set to a limit of about 30C max. All other times a frost protection lower limit 5C is active.

I have heard of undertile 'comfort heating' and I suspect it just comes down to the controller and is a combination of time setting and tile sensor reading, so perhaps you have been given an unsuitable controller or perhaps its just down the settings... from the manual for mine it can operate various ways..

This thermostat is a combination model allowing you to
choose between 3 different models. A, AF and F model.
A model: air only, with built in sensor
AF model: air & floor , with both built in and remote sensor
F model: floor only, with remote sensor

so for your use it would be set to just F mode.

I think you've cracked it. After reading that last bit, I looked again at the advanced settings stuff in the leaflet. (I did look at it before but thought it was a. very complicated and b. not anything I needed to know). Now that I look again, it has a sensor selection bit. This is exactly what it says:

"Press the up/down key to select sensor working mode IN is internal OUT is external. ALL is both sensors.external sensor is limit sensor."

I checked and it was set to IN. I changed it to OUT and the large temp reading went down and won't respond now to my holding my hand over the thermostat on the programmer. So now it must be telling me the temperature of the floor and is gradually increasing as the floor warms up - success!

I wonder what the ALL setting would be for (or in your case AF). Any ideas?

Thanks sillygoose and evokit. Excellent help.

sillygoose

JohnB47 wrote: »

I think you've cracked it. After reading that last bit, I looked again at the advanced settings stuff in the leaflet. (I did look at it before but thought it was a. very complicated and b. not anything I needed to know). Now that I look again, it has a sensor selection bit. This is exactly what it says:

"Press the up/down key to select sensor working mode IN is internal OUT is external. ALL is both sensors.external sensor is limit sensor."

I checked and it was set to IN. I changed it to OUT and the large temp reading went down and won't respond now to my holding my hand over the thermostat on the programmer. So now it must be telling me the temperature of the floor and is gradually increasing as the floor warms up - success!

I wonder what the ALL setting would be for (or in your case AF). Any ideas?

Thanks sillygoose and evokit. Excellent help.

Good news, that will be it for what your after....

Mine is actually used in AF mode because it is overall controlled by room temp. sensor but applies temp. limits also to floor via its sensor - allowing underfloor heating (mine is 200w/m2 powerful!) to get too hot can damage it or shorten its life.

I suppose if someone had a low powered floor that can't overheat or maybe a defective floor sensor you might need a way to get some heat on - hence room thermostat only mode.

In your case of course room temp. is irrelevent, just warm toes... enjoy