Underfloor heating not working

[Anneliese]

Hi

In our downstairs bathroom we installed electric underfloor heating beneath the travertine tiles. Since this went in, the floor has never been warm. We have checked the thermostat and it reads as getting up to temperature. Without wanting to take up all the tiles, how else can we figure out why the tiles do not get warm?

Many thanks
Anneliese

 

[mointainwalker]

Did you test to see if the heating worked before you laid the tiles ?

 

[ericmark]

This is where the clamp on ammeter comes into it's own. If the mat takes current it is working.

I laid one in my mothers wet room and was disappointed with the results. It does take a good 1/2 an hour for the tiles to warm up but after an hour just about limit to what one could walk on with bare feet.

Idea was to dry floor and they take about 15 minutes after the shower for tiles to dry which in the main is too long for my mother to wait before swapping wheel chairs so they did not do what was intended.

As to heating the room when central heating failed and my parents used that and gas fires to heat house the wet room was too cold to want to shower in. Yet if tiles were hotter one could not have walked on them. It needed the extra heat from towel rail to get the room hot enough.

We also had the sensor for thermostat fail and found it would not come out of the pocket. Had to revert to measuring room temperature. Also two thermostats have failed and the last time we did not bother replacing as the system is really a dead loss.

The first wire laid by builder was damaged we found builder had wound wires together and taped them up. This under a wet room floor. So all tiles had to be lifted and a new wire laid. The builder running off into wilds of Wales.

However my son fitted a water underfloor system in his narrow boat and it worked well. It was mainly to sink the extra heat when RayBurn was running but it was nice walking on that floor. Again tiled.

Testing the resistance is something we did all through tile laying so we would know if damaged. However our system used resistance wire so it remained the same reading. With the chemical type as the wire heats up so the resistance increases so it is quicker to heat up and avoids hot spots. But using a meter will likely show different readings day to day.

Of course being in a wet room the type we used was covered with an earth brad and it was also tested with a 500 volt insulation tester and fed through a RCD for safety. There is no way anyone should lay underfloor heating without the correct test equipment that would be very dangerous. And this was required of course by the LABC inspector who is responsible under Part P for site safety. But he is not really worried if it works or not only that it is safe.

 

[mointainwalker]

It does take a good 1/2 an hour for the tiles to warm up but after an hour just about limit to what one could walk on with bare feet.

Were you not aware of the regulatory limit of max 27 C on the floor surface or not bothered ?

 

[ericmark]

I was only aware of TABLE 42.1 but this was overseen by LABC so it was up to them to have ensured this was complied with.

With a max of 27 C to be honest can't see how any underfloor heating will work?

7 degrees will hardly transfer much heat.

 

[Anneliese]

Did you test to see if the heating worked before you laid the tiles ?

Thanks for the reply. The work was undertaken by our builder/project manager's subby. He assured us it was working as they had tested it twice and that we should give it a few hours to warm up as it was winter and the bathroom/wet room was exceedingly cold. But sadly, no joy. We also have a heating rail in there but it isnt enough to warm the room suffienctly.

I am loathed to removed all the tiles, hence asking about another way before going down that route.

This is one of many faults which has surfaced since the guy disappeared on us.

 

[Richard C]

Are you sure the controller is correctly wired/programmed & are you sure it’s not a sensor fault? I had one go down on a 2 week old system in a conservatory but a replacement sensor cured it & it’s still working fine some 6 years on although the sensor now lives behind the skirting & not actually in the floor. Have you checked the continuity of the heater mat? If it’s open circuit the cables have been cut somewhere so it’s a floor up job but if you’ve used cement tile adhesive straight over the top of the heater mat without bedding in an SLC it’s most likely the mat will never survive.

If the sensor is working & mat continuity is OK, can you give more info on the installation itself; type/size of floor, size of heater mat, any insulation, depth of the mat under the tiles, any insulation boards under the heater mat?

 

[Taylortwocities]

Get an electrician in. He can do a resistance test on the floor element and the temp probe.
Also he can test if the controller is working properly.

Do this before taking up the tiles. It'll take an hour to do the basic checks.


PS I don't suppose that anything has been screwed into the floor since the installation was done? eg
Towel rail supports
Door stop
etc
etc