undertile heating not working properly

[GREN2908]

Hi guys, I wish i had seen this forum ages ago. I have had UTH, thermomat 150w 2m sq from B&Q with non-programmable thermostat installed. It was in bathroom directly onto concrete floor - while i was at work the wife didnt notice they did not put down insulation boards.

After 2 and a half hours the floor has had the chill taken off it but does not get any warmer. On turning down the thermostat, the light goes to green at about 4 (out of 10) but immediately red if i increase it. I have left it on for 24 hours but it does not get any warmer.

Im not happy as the kids really need a proper warm floor for the winter. Can anyone please suggest what i should check, is it more likely to be faulty thermostat - I wont be impressed if all the floor has to come up.

The firm who laid it keep giving excuses not to come back up to look at it.

Cheers
Gren

[Dave]

This thing is with no insulation boards etc..is that you have to heat the full concrete slab before you get any heat transferring back to the tiles and it will not get as warm if you are losing heat into the substrate.......This mats don't transfer heat instantly like a radiator they have to warm up....but without insulation it will take longer than 24hrs sometimes.......

[CJ]

As above...........

The heat is is being cooled by the concrete slab before it gets up to the tiles.

Get them back

[Sir Ramic]

Also taken from Warmups website
They would recommend 200w and not 150w
"200 W/m² Heating Mats
These heating mats will heat up more quickly than the 150w mats and are suitable in rooms with a high heat loss such as extensions and conservatories or in rooms where the sub-floor insulation might not meet the latest building regulations."

So basically, had the insulation mats been fitted then 150 may have been fine. As it is i think you will find that you will need to build the heat over at least 24 hours and you will probably have to keep it on full.

[poynton phil]

i agree with dave, without insulation it'll take forever to heat up. also i wouldn't buy thing like that from B&Q as its my opinion they only sell crapspent more time taking stuff back there, than anything else.

[Northern Bird]

Have you got an oprginal qupte. Does it highlight any of the insulation boards i.e. Wedi, Marmox, Aquapanel (many more brands available.)

I agree get them back

[eyebeetiling]

Hi
As Northern Bird says, check the quote, if it states that they should have layed insulation and they haven't then they have no legs to stand on.
If the excuses keep coming go the C.A.B. and see what legal route you would have to take.

Good luck

[GREN2908]

Thanks for your help guys, took ages insisting on the phone they come out and fix it, told them to look here and they caved in straight away, they are coming back tomorrow.

Cheers
Gren

[Dave]

pleased you got them to come out Gren.. let us know the outcome.....

[Sir Ramic]

Thanks for your help guys, took ages insisting on the phone they come out and fix it, told them to look here and they caved in straight away, they are coming back tomorrow.

Cheers
Gren

HA HA the power of the forums

[faithhealer]

Did a conservatory floor last winter, the builder had already put the UFH mat onto the floor ,'to tile over'!! The builder told them it would take TWO DAYS to warm up!! Anyway, advised them on insulation boards, warms up in an hour now. customer over the moon!

[Dan]

If the installation guy has said he'll install underfloor heating, he has, contact is fulfilled. He needs paying.

Electric underfloor heating and water underfloor heating system run at an ambient temperature.

If insulation boards were installed it would have warmed up quicker, if a 200 Watts per square meter system was installed it would have warmed up quicker.

If they've not installed the full amount of the floor space (due to your bath, loo, whatever, not their workmanship) then they can't fulfil full heating requirements. Electric underfloor heating mats (or cable) need to cover 90% of the floor at the correct spacings. Leaving a 100mm gap around the edge.

Your total cubic air space in your bathroom will exceed what your % of the floor has cable heating it. So your air in the room will never feel warm, but your tiles will have the chill taken off them. As you described.

You may find that due to the tile products using so much water that the concrete is holding that in. It can take upto 6 weeks for the moisture to full come out of a concrete floor. Though the products used will be fully cured after 2 in most cases. Whilst there is moisture in the floor you'll find it'll stop it reaching its max temperature due to the fast that water is a coolant, or its used as one.

I just want to ask you:-

• How long has it been installed?
• Is the concrete new? (exstension maybe?)
• Did he use a self leveling compound or tile directly over the cable? (compounds use much more water)
• Did he offer insulation? (perhaps the doors, skirting, other things stopped him suggesting it at quote stage? - it's a much bigger job if the floor is going to be raised - though only 12mm would have been needed for 6mm Marmox and the adhesive to stick it down with)
• Did you leave the heating for 2 weeks, then turn it on till the light came green, and then increase it every 24 hours by 1 or 2 degrees? Until it hits its max a week or so later? (max usually 22 - 26 degrees, though on a floor not 90% covered you can take a % off, about the same % as the % of the floor that isn't covered - approx - so if you're bath is 30 of the room, you're talking 16 - 18 degrees ish maybe?)

[mark neville]

or could it be the floor probe not taking correct reading in the floor ,and taking the room temp instead this is the first thing you check with ohms meter . cable plus probe check correct ressitance for both of these ;

[Dan]

As above...........

The heat is is being cooled by the concrete slab before it gets up to the tiles.

Get them back

i agree with dave, without insulation it'll take forever to heat up. also i wouldn't buy thing like that from B&Q as its my opinion they only sell crapspent more time taking stuff back there, than anything else.

Have you got an oprginal qupte. Does it highlight any of the insulation boards i.e. Wedi, Marmox, Aquapanel (many more brands available.)

I agree get them back

Hi
As Northern Bird says, check the quote, if it states that they should have layed insulation and they haven't then they have no legs to stand on.
If the excuses keep coming go the C.A.B. and see what legal route you would have to take.

Good luck

Underfloor heating systems do run better with insulation, obviously. But it's not possible in all installations. About 60% of my sales (out of a lot a month) couldn't have possibly installed even 6mm insulation - just due to the room structure and other factors all room related.

Water underfloor heating will ALWAYS have insulation, so it can't be directly compared, but even that will run at a very low temperature for a very long time during the day, not like electric with insulation and 200Watts per meter which can heat up in 15 minutes - and you feel it in the room too.

But the floor needs to be 90% covered and the heating would need to be 200W / 250W. And have 10mm minimum. But whatever you can squeeze in is wise.

If the guy didn't offer insulation, then perhaps it's just one of those jobs, perhaps he should have explained it will run very low, but perhaps he was asked by the customer to install it, and he didn't suggest it outright.

Be careful when you're stopping a mans wage.

I'm sure he should be paid in full, and then if the underfloor heating is still not working to the customers satisfaction then it should be looked into. But the floor hasn't got to come up at the installers cost unless he's suggested underfloor heating and said it will actually heat up the room and replace a central heating system. Which I think if he did know that much, he'd have suggested insulation as it's extra profit for minutes work.

[Dave]

The reason i offer customers insulation isn't just to speed up warm up time , it is to reduce the running costs associated with electric UFH as when installed straight onto concrete you can lose heat through the substrate...

[Dan]

or could it be the floor probe not taking correct reading in the floor ,and taking the room temp instead this is the first thing you check with ohms meter . cable plus probe check correct ressitance for both of these ;

If he's installed it correctly a continuity test would have been done on both the cable and probe. So no. They do fail, but they get spotted before installation.

It can't be the stat either. Though if you had a digital programmable Aube stat you'd be able to tell what temperature the floor is running it. And perhaps a little bit more information, but the proof is in the pudding. The bathroom could be 21 square meters, but the bath, loo, basin, is stopping you install the full 90%.

If you fell cold spots on the floor you may find he's not covered everything he can.

If the cable is broke anywhere, the whole cable will stop. Providing it's single or twin core.

[Dan]

Underfloor heating is a doddle to install and for those of you who prefer floors than walls (like me) then you're laughing. A £300 floor tiling job can bring in £750 - 800 without taking even double the time. You just have to install the right cable on the right jobs. I'd have suggested 200W on that floor, but not all makes have it. I'd have installed Fastwarm insulation too, but not all suppliers stock insulation. Sometimes even the B&Q stores. Plus it's more than the heating in B&Q.

The customer is half suggesting the floor may need to come up if it isn't going to heat up the room. It's not going to heat up the room. It may improve. But it wont be a heating system in the winter.

[Dave]

The amount of customers that are under the impression that UFH ( especially electric) replaces a standard radiator in a room is unbelievable..they seem to think it will heat a room.......i tell them it is an ambient heat not a heat replacement...

[faithhealer]

I remember a story told by Darren at NETT. He went to tile over a UFH mat to find it didn't cover the whole floor. It looked like the mat was too small for the conservatory and pulled the cable off the mesh to make it go further. Darren pointed out one paticular bald/blind spot and the customer said, 'the electrican told me I could put my chair there'.!!!!!