Reuse towel rad feed for underfloor heating?

[bennettp23]

Hi,

Renovating our two bathrooms. Both have towel radiators which are both electric and water fed. Looks like they are fed from a RCD's spur. See pics.

Thinking of installing underfloor heating and it would be helpful if I could reuse the cables already in for the towel radiators (obviously taking the cable out of the wall and straight to the underfloor heating). I would also use the same spots the electric controllers are now for the two thermostats.

Can that be done? I also think I would need to feed a thermo feed back to the controllers as well.

Thanks for your help!

Paul.

 

[ericmark]

I have fitted under floor heating in a shower room, first hurdle is find a suitable thermostat, in the main the sensor has 3 meters of cable and the cable needs to go around 0.5 meters under the floor and the thermostat has to be of course inside the room being heated so thermostat needs to be at least IPX4 I failed to find one.

Next to be frank it was a failure, needs to be on 24/7 and was very slow to heat up, needed the towel rail on as well, so may be not the thing to lose towel rail.

Underfloor heating for bathrooms needs either an earth mat or special cable which is earthed, could not use reychem without earth mat, may have change now.

Thermostat should be 900 to 1200 mm from floor, the existing timers look too low, it will need a pocket (tube) from thermostat to under the floor for the sensor. So wall will need chasing anyway. So may as well set at right height.

If on a ground floor then it also needs the floor removing first and insulation fitting, we found once that 9" of insulation fitted did not really need heated floor.

 

[bennettp23]

Oh dear. That does not sound great!

making me think twice now.

 

[DetlefSchmitz]

In case it helps, I am a great fan of wet underfloor heating, and have it in 5 rooms and find it very convincing. But I would never put underfloor heating, wet or dry, into a bathroom. The parameters just don't work.

 

[bennettp23]

Great info - thanks for taking the time guys.

 

[ericmark]

There must be some where a calculation, the extractor moves 15 litres of air I think, so outside at zero, there must be a kW requirement to reheat that air. However likely it is not the bathroom heating that needs to heat the replacement air, what I could never understand is why the shower which was hot water cooled the tiles, but it did.

First bathroom with under floor heating I used was in a guest house in London, and it was really good at drying the floor, so when sister said we should fit it in mothers new wet room, it seemed a good idea.

But I used sculptured tiles for grip, mother only had one leg, so risk of falling, however they stopped water running away, and then was time, it needed to be on an hour before using the room, and only warmed the floor, not the room, so still needed the large towel rail. Then a run of faulty thermostats, the the sensor got stuck in the pocket, OK floor had to be lifted to move drains, so there was around a foot of insulation below the plywood floor before heating cables laid, and only thickness of tiles and special cement above, but not really a success. And it delayed the wet room by a few weeks when the special cement would not dry, found out of date, and all had to be scraped off and started again with new heating cable where builders had damaged the first one.

I think in this house the central heating pipes must go under the shower room, as floor always warm, but central heating water around 70°C and proper under floor heating 27°C.

 

[hard-work]

Some electric UFH mats have an earth shield in the cable (like you see on co-ax) - simple to fit. The Heatmiser Touch-E V2 timer stat is good. It can be a timer or just a stat. It can sense the room temperature and floor temperature, or just the floor temperature. Best to fit it outside of the bathroom in the hall, not inside where there is moisture, then set it to control the floor temperature only. The floor sensor probe from the stat must be fitted so it can be pulled out and replaced, so it must be free to move in the corrugated plastic tube under the floor. Fit a fused spur just above the skirting in the hall with a 3A or 6A fuse. This could isolate the UFH mats and the towel rail. Both will not draw a great amount of current.

The mats consume approx. 140-150 watts per square metre. 2 square metres is usually big for a British bathroom, so low current draw.

 

[hard-work]

I see you have an RCD fused spur outside the bathroom. Good. The towel rail must have its own isolation switch outside of the bathroom, with the RCD fused spur as the master for both. The UFH can be switched on and off from the stat.

The HeatMiser Touch-E V2. It has a touch screen so easy to use.