Problems with Underfloor Heating Cable

[Mark02]

I am having a problem with my underfloor heating cable in my bathroom. The cable was installed at about 5cm apart on top of a 6mm tile backer board. About 8-10 mill of SLC was then poured over the top before a 10mm slate tile floor was fitted over the top.

According to the thermastatic floor sensor it takes about 3 hours to reach about 25 degrees and 5 hours to reach 26 degrees. However when you touch the tiles they they do not feel hot. But as if the chill has been taken off them?.

Am I hoping for a bit much. Was at B&Q and felt there under floor heating set up. The tile was about 100 times warmer than I am achieving.

The bathroom is small at about 3 sqm. I have a 400 watt cable. This is wired to a breaker which then connects to a plug socket off the ring main.

Is this all normal?. I was thinking of pulling it all up fitting 30mm of tile backer board and a 500watt cable matt.

any help would be greatly appreciated

Mark

 

[Mike]

it doesnt sound like it's working properly, it sounds a bit extreme to rip it all up though. did an electrician fit it? is it new and has it worked before? have you tested the probe?

 

[Mark02]

Yes was all fitted by an electritian and part p tested etc . Its our second bathroom so we havent been using it that much until quite recently and hadnt used the underfloor heating until this winter. I have tested the resistance of the heating cable and thats fine. Havent tested the probe, the manual states that you would get an error message on the thermostat if there was a problem with this?

I dont want to rip it up, but hate things that dont work as there supposed to. Keep thinking that there is not enough insulation and the heat is just going downwards?

 

[Dan]

How long have you been running it for? Is this pretty much the first time you've turned it on?

I would guess that the 6mm insulation board would be fine to be honest. How big is the area, and how big was the mat? And what wattage per square meter is the cable that you chose?

 

[Mark02]

It was installed in July 2011 and first started to use the UFH in November 2011. The total floor area is about 2.6 sq m. Have a 40m cable length only had to take out toilet so covers 95% of the floor. The cable is 400 watts.

 

[Ian]

Is it an insulation board you have used or a cement board, under the wire?

 

[Mark02]

Its Cement Board

 

[Ian]

Its Cement Board

That may be part of your problem, cement board isn't as good for insulating as other products such as marmox, so a lot of your heat will be going down the way instead of into your tiles.

 

[DHTiling]

How long are you running it before testing tile temperature?

 

[Mark02]

its a cement based tile backer board and has same spec as marmox

 

[Mark02]

I ran if for 4 hours this morning. The thermostat stated it had reached 25 degress (floor temp only).

 

[DHTiling]

You need to run it over night to feel a benefit with stone.. UFH isn't like a radiator where you will get heat within a couple hrs.. and to maintain the heat you need to run it.. you cannot turn on and off and expect instant heat transference..

 

[Mark02]

You need to run it over night to feel a benefit with stone.. UFH isn't like a radiator where you will get heat within a couple hrs.. and to maintain the heat you need to run it.. you cannot turn on and off and expect instant heat transference..

How long should it take to feel any heat on the tiles. Normal floor temp is 20 degrees after 4 hours is 25 degrees but this just takes the cold out of tile.

The heating dosent turn off the mrs left it on for two days and it wouldnt get passed 26 degrees. Tile still felt luke warm??

Does UFH use electricity constantly as mine does as it wont get up to a reasonable temperature.

 

[kilty55]

has the probe been installed correctly?

 

[Discount Tile Supplies]

Hi Mark

Have you asked the company who sold you the product to come and look or explain why its not heating up correctly? I would also speak to the manufacturer of the heater to ask their advice. Did u buy to heat room or floor? What wattage is the heater?

Edd

 

[Mark02]

I believe so. If it was located too close to the wires, wouldnt the temperature be alot higher it was put in a flexible cable within the tile backer board.

 

[Mark02]

Hi Mark

Have you asked the company who sold you the product to come and look or explain why its not heating up correctly? I would also speak to the manufacturer of the heater to ask their advice. Did u buy to heat room or floor? What wattage is the heater?

Edd

Yes I have asked the company they cant see why its not working. According to the company it should heat the room, although we just bought it to heat the tiles. Its a 400 watt cable so should have ample power in such a small room. The wire covers 95% of the floor.

 

[CJ]

It sounds to me like.

A. Cement board, not Insulation used.......so more heat lost downwards.

B. Probe positioned too close to heating cable, causing floor to constantly turn on/off and never heating to max temp.



Who installed UFH anyway??

 

[Mark02]

It sounds to me like.

A. Cement board, not Insulation used.......so more heat lost downwards.

B. Probe positioned too close to heating cable, causing floor to constantly turn on/off and never heating to max temp.



Who installed UFH anyway??

It was installed by a a qualified electritian on a 6mm tile backer board. This formed a layer of insulation with a concrete polymer over the top. I have sat and watched the thermostat, it never turns off. Just to check I took out the thermostat last night and wired directly to the heating cable and the same thing happened?

Thats why im thinking of wriping it all up and putting down 30mm of insulation board?

 

[Dan]

This is insulating tile backer board with a cement face.....

And.... I can't find a picture of the type of board that is pretty much cement-only with some mesh in. I thought wedi board did it but their boards seem to be like marmox etc now by the looks of it.

Is it the insulating type board that has been used like in the picture above?

If it is a problem with the probe, and your thermostat has an air sensor too, you might be able to disconnect the probe from the stat just to let it run with the air sensor only to see if that heats up to a higher temperature. Though you saying it doesn't switch off at 26 degrees and keeps trying to get warmer suggests it is an insulation problem or just underpowered.

You should be running around 150 watts per square meter if your heating was 400 watts total and the room is 2.6 square meters. That's about right for heating a room providing you have insulation directly under the cable.

The 10mm of levelling compound, then a few mm of tile adhesive, then tiles of the thicker variety might have been better with a 200 watt per square meter system instead. They're normally used in conservatories and the likes, or in instances where no insulation can be used due to floor heights etc.

 

[kilty55]

hi mark have you contacted techinacal support from the manufacturer regarding this?

i installed a mat last year...a make i wasnt used to installing i may add and we couldnt get the temp past 20 degrees it seemed to max out......called technical support and after a few simple programming issues it seemed it was set on the wrong setting.

none of this was present in the instructions either i may add so may be worth a call to manufacturer not the retail outlet if you havent done so already

 

[Mark02]

This is insulating tile backer board with a cement face.....

And.... I can't find a picture of the type of board that is pretty much cement-only with some mesh in. I thought wedi board did it but their boards seem to be like marmox etc now by the looks of it.

Is it the insulating type board that has been used like in the picture above?

If it is a problem with the probe, and your thermostat has an air sensor too, you might be able to disconnect the probe from the stat just to let it run with the air sensor only to see if that heats up to a higher temperature. Though you saying it doesn't switch off at 26 degrees and keeps trying to get warmer suggests it is an insulation problem or just underpowered.

You should be running around 150 watts per square meter if your heating was 400 watts total and the room is 2.6 square meters. That's about right for heating a room providing you have insulation directly under the cable.

The 10mm of levelling compound, then a few mm of tile adhesive, then tiles of the thicker variety might have been better with a 200 watt per square meter system instead. They're normally used in conservatories and the likes, or in instances where no insulation can be used due to floor heights etc.

The board I bought is described as follows

Tile Backer Boards are high performance, reinforced, insulation boards made of extruded polystyrene, this has each side coated with a fibreglass mesh embedded into it, and a cement polymer mortar coating is applied to both sides.
Tile Backer Boards are waterproof- rot proof, provide thermal insulation, and also have acoustic insulating properties.
Tile Backer Board are ideal for two primary purposes; as a superior waterproof surface to fix wall or floor tiles and as a first class heat insulation for underfloor heating systems. Heatstore insulation boards are particularly suited to underfloor and under tile heating applications. Installation below underfloor heating systems on an existing un-insulated, concrete or timber sub-floor will greatly reduce heat up time and running costs.

I am running out of ideas i really dont want to have to rip it all up and start again.

 

[Stewart]

What fixing method was used when installing the slate....

 

[Mark02]

hi mark have you contacted techinacal support from the manufacturer regarding this?

i installed a mat last year...a make i wasnt used to installing i may add and we couldnt get the temp past 20 degrees it seemed to max out......called technical support and after a few simple programming issues it seemed it was set on the wrong setting.

none of this was present in the instructions either i may add so may be worth a call to manufacturer not the retail outlet if you havent done so already

I have sent back the thermostat to the compant. They seem to be quite reputable, they are sponsors of the forum and seem to of been reccommended on this site alot. They have gone through the controls with me, but cant find any problem. My only hope is that its a faulty thermostat. However I have wired the power supply directly to the heating cable bypassing the thermostat. The same issues are still present.

 

[Mark02]

bal single part flexible adhesive

 

[Dan]

The board I bought is described as follows

Tile Backer Boards are high performance, reinforced, insulation boards made of extruded polystyrene, this has each side coated with a fibreglass mesh embedded into it, and a cement polymer mortar coating is applied to both sides.
Tile Backer Boards are waterproof- rot proof, provide thermal insulation, and also have acoustic insulating properties.
Tile Backer Board are ideal for two primary purposes; as a superior waterproof surface to fix wall or floor tiles and as a first class heat insulation for underfloor heating systems. Heatstore insulation boards are particularly suited to underfloor and under tile heating applications. Installation below underfloor heating systems on an existing un-insulated, concrete or timber sub-floor will greatly reduce heat up time and running costs.

I am running out of ideas i really dont want to have to rip it all up and start again.

That is the good stuff like in the picture. So I'm lost too.

 

[Gazzer]

If the method of bedding the tiles was wrong then this could cause issues.

 

[Mark02]

If the method of bedding the tiles was wrong then this could cause issues.

I have now pulled the tiles off the floor. Same issue?

 

[Gazzer]

The UFH will not work if the cable is exposed ???? It needs to be covered by the tile which should have the adhesive as a full bed. Any voids will cause heat up issues.

 

[Stewart]

I have now pulled the tiles off the floor. Same issue?

Could you post some pics...?


Created on iPhone.....

 

[kilty55]

mark have you removed the tiles? when you say pulled up the tiles you dont mean they literally just pulled of the floor?