Electric UFH and thermoprobe issues

[cbk]

Planning to use electric UFH for first floor bathrooms.   My last experience of this was based on a WarmUp system installed as part of a kitchen refurb by kitchen supplier.  It included a thermal probe that switched the system on/off. Worked fine for 3 years and then the probe failed and as it was laid under the ceramic tiles could not be replaced and leaving the system on all the time was too hot so effectively never got used.  

Reading other threads I guess I could have replaced thermostat control with a timer control but never really got round to it and heating was not essential in the kitchen.  But for new bathrooms will be primary source of heat so need a reliable control solution that will work for more than 3 years!  Any recommendations welcome.

[ProDave]

Find as bit of small bore pipe that is just a little larger than the probe and use that to create a pocket for the probe.  With the open end somewhere accessible e.g under a cupboard, so if the probe ever fails you can pull it out and thread a new one in.

[Nickfromwales]

7 hours ago, cbk said:

But for new bathrooms will be primary source of heat

That's going to cost a few £££ to run. What about radiators?

 

+1 to fitting a pocket for the probe, that's standard practice.

[Temp]

The probes are typically 10k Ohm NTC resistors or similar which are pretty cheap. Around £1.50 to £3 on ebay so could afford to put half a dozen in the floor as well as a tube/pipe/pocket.

 

[cbk]

18 hours ago, Nickfromwales said:

That's going to cost a few £££ to run. What about radiators?

 

Should have said this is for a new house designed to close to passivhaus standards so heat demand will be low.  Plan to fit a heated towel rail run from ASHP and just need the bathroom UFH to provide that extra bit of warmth to ceramic tiles.  I doubt it will be on much but will be there if needed so thermostat needs to offer timed control function as well temperature.  General advice on another thread was avoid trying to run water based UFH to first floor bathrooms as complicated and fiddly, electric is easier to install if more costly to run.   

 

One other question I do have is whether electric UFH mats can be installed directly onto Caberdeck and then tiled directly onto mats?  I think the advice is generally to add an insulation board under the mats but I'm  trying to avoid too much of a level change between bedroom (carpeted) and tiled floor in ensuite.

[Nickfromwales]

Understood. That means they are for “auxiliary” heating then eg supplemental   
 

2 hours ago, cbk said:

 

One other question I do have is whether electric UFH mats can be installed directly onto Caberdeck and then tiled directly onto mats?  I think the advice is generally to add an insulation board under the mats but I'm  trying to avoid too much of a level change between bedroom (carpeted) and tiled floor in ensuite.

Firstly you shouldn’t tile directly to a wooden substrate. I typically use a binder layer of 6mm plywood, glued and screwed at 100-120mm centres, and then flexible tile adhesive over that. 
If you score the caber deck then you may get away with using something like Bal Superflex, which proclaims its ability to negate a decoupling membrane. That stuff is good, but expensive. 
If it were me, I’d want a minimum of 6mm insulation board under the UTH, but in a near Passiv / PH it’s quite academic tbh as these dwellings tend to sit at an extremely acceptable average ambient, and the tile heating will be strictly a comfort thing vs providing any ‘heating’. With the insulation boards you’ll be able to time this to come on as little as 30 mins prior to you using the room, but if it has to heat the substrate also, then you may need an additional 30 mins or more to achieve the same result.