problem with underfloor electric heating

[jay]

:8:thats interesting did you bring the heating on slowley and a new floor will always take longer all the moisture to remove also reducing gap between wires would make a lot of diff is it norm to run at 28 c and thanks

 

[diamondtiling]

irecently installed a 600w loose wire heater on an 4.4m2 uninsulated concrete floor,10mm porcelain on top,this took 4 days to reach a temperature of only 28oc,the customer did not want insulating board as this would have created astep into the room. The manufacturers manual say 5-8 hours.The wire was layed at correct spacings 90mm. Having had many "UNHEATED" ! conversations with the manufacturer regarding the information regarding the "recommendation" of insulating boards being used, I have told them that the information given in the litreture is wrong and misleeading and that the boards are a necessity!!!! The whole floor has to be removed,boards installed,newloose wire system,and retiled, all at my own expense,except for the new ufh which the manufacturer is suppling FOC:hurray:I am installing a800w heater now as the extra wire o.1m2 can easily be lost under a free space on the floor,the wire can be layed at 60mm spacings insted of 90mm to prvide more heat per m2 and a extra 200w of heat for the whole room. So inslallers beware of manufacturers recommendations they may be a nessesity in certain situations

A 90mm gap between the wires would just take the chill off the floor, without insulation boards it will struggle to do anything at those space sizings. Loose cable is installed after you have calculated the area to be heated. You dont just buy a kit and hope that it will cover any size floor, you have to order the appropriate length of cable. 60mm is the norm to obtain a heated floor over the correct insulation. As for the laying of the insulation boards your customer said they did not want them so why are you having to re lay the floor at your expense?
Your cable should have been 73mtrs long to give a 60mm gap and you should have advised them that it will just give a minimal amount of heat without insulation.
They chose the cheap option here not you.

:mad2:

 

[daveaztec]

Yes but the recommended gap for a 4.4m2 square floor is 90mm with the 600w heater and the area was exactly 4.4m2,the manufacturer has advised me that they will be reviewing its marketing and installation instructions,l have installed many of these systems and the first time l have encountered a problem,just shows that 0.1m2 can make a lot of difference to the heat transfer to the floor

 

[diamondtiling]

Dave who was the manufacturer of the cable mate? Going on your heat area of 4.4 mts and having a 90mm gap is a cable of 49 mts in length, massively short for the rooms requirements. I think you should have insisted on the insulation otherwise its money down the drain.
I still cant work out why you are having to fork out for this work?

:incazzato:

 

[faithhealer]

I agree with Dom, why do you have to pay for it dave. Sounds like you advised boards and they turned it down!

 

[Phil22]

Hi, don’t know which product you have used, but as I understood it, electric under floor heating shouldn’t be relied on as a Primary heat source, as it is only intended to warm the floor and give it a comfortable floor temperature for walking on. (You may get better results out of it in upper floor situations, as the heat of the house naturally rises and helps warm up the upper floor better to start with, so there is less warming up to be done). So I would hate to think you are ripping out the flooring only to maybe get similar results again.
Any insulation under the mat will improve its performance sending more heat upwards, so if the customer cannot see that they are paying more to get the desired effect and more in the long run in wasted electricity (mainly warming up a concrete slab), then that’s up to them.
It’s a shame you’re picking up the tab for remodelling, especially if they’re expecting a toasty room/bathroom from the electric UFH
All the best!

 

[diamondtiling]

Hi Phil, UFH can be used as the primary source of heating in a room if installed correctly.
Running costs are relatively low if the correct insulation is installed from the outset.

 

[Phil22]

Hi diamondtiling, thanks for the update. I will stand corrected, especially if a room/building is properly insulated, but the information I provided is based on input I received when I attended a course with Devi, one of the leading manufacturers of electric UFH mats, who’s rep. kept reiterating their product was “Not a Primary heat source” and mentioned some customers disappointments when heat from them didn’t match expectation in heating the room they were installed in, as they had been installed as a primary heat source.
Devi’s literature states in small print “NB. The effectiveness of the heat output is dependent upon the heat loss of the room. Rooms with a high heat loss may require supplementary heating”.
Which I suppose could be said to some extent about any type of heating if your heat output can’t keep up with the heat loss of the room/building and even greater heat loss could be expected when installed onto a concrete substrate without any insulation.
So sorry if I confuse anyone by my comment, but it is based on sound information provided directly form a manufacturers rep through training on this type of product.
Thanks again[FONT=&quot][/FONT]

 

[daveaztec]

The manufacturer was warm up,followed their insallation manual to the dot,done my nut with warmup and their supplying me with new wire and probe,managed to get a good discount on the new tiles 60x 60 porcealain after explaining my plight to tilestyle manager,customer has offered to pay for insulating boards and half cost of tiles.all a bit of a sickener really cos the old floor was a slate mess all had to be taken up 6 freestanding appliances removed and put back plinths recut etc etc etc,done alot of work for these people last year so dont want to lose their or their friends / familys custom,not gonna lose money just not make any. will be in contact with warm up again to see about their spacing policy and insulating board recommendation/necessity

 

[Time's Ran Out]

We moved from Devi to Thermonet for the Primary source heating effect their mats provide. The concrete mats have a 200w output/metre and although heat will be lost into the room that's the idea!
From the original post I would have thought that any floor running at 28degrees with full coverage would be ideal!