underfloor heating without ripping up tiles

[dmccormick]

We have two upstairs bathroom with tiled floors laid on plywood boards over the existing floorboards. In one of them a lot of the pipework to the hot water cylinders and towel rails runs under the floor and as a side effect the floor is always warm.

In the other, there are no pipes and the floor is cold.

To avoid ripping up the tiles I was hoping to somehow achieve the same result as the first bathroom has (accidentally). I was thinking to approach from an adjoining room and run hoops of copper pipe parallel to the joists and connect up to the heating water circuit. A friend recommended to use plastic pipe to make it easier to pass them along, but I am not sure if they will release enough heat.

Is this sort of thing anyone else has tried or any other ideas ?

 

[RigidRaider]

Yes, there was someone who posted some pics of that very same thing on here a few months ago. Dunno how you would find them - search Projects, perhaps?

If you are forced to do it from an adjacent room, why not do it with 10mm pipe? 10mm copper pipe is lovely to work, buttery soft and easy to bend so you could make up some serpentine "radiators" and slip them along between the joists, the pipe is soft enough that you could bend it around any obstructions and light enough that it wouldn't need much support. Your only problem might be removing trapped air but if you made them slope slightly up towards you it might be OK.

 

[dmccormick]

Thanks for the advice. I think I will give it a go. In terms of connecting up I assume I could split the flow and rerturn to the towel rail into 2 and use that as flow and return for the new pipework.
To control I was thinking of somehow putting a thermostat option in - either a TRV mounted in the partition wall, or some kind of 2 port valve connected to an electrical thermostat in the room - not sure if that is OK though as a bathroom.
Any ideas ?

 

[dmccormick]

Have now commenced this and am teeing off from an existing flow and return for a towel rail in 15mm copper, passing it through a 2 port valve connected to a wireless thermostat in the bathroom, and running 10mm copper branch loops off the 15mm.

I was wondering if I need to include any air bleed vents or will the air just flow round the pipes until it arrives at one of the towel rails and be vented out there ?

See diagram here:
http://domandsarah.co.uk/floor.htm

 

[DeltaT2]

You'd have been better connecting a 15mm tee onto the TR F&R, rather than teeing every loop. Then you can regulate the floor loops, you may end up with a nice warm floor & a freezing cold TR!!!

 

[dmccormick]

That is what I am doing though ? The existing f&r still go to tr and I have put a tee into both of them(or am about to today when I get started).
Have also planned to put a gate valve after the 2 port valve so I can control flow rate in underfloor part. I guess this is like balancing radiators.
Any thoughts about whether I will need the vent pipes to fill it?

One idea I had was to turn off the return valve on the tr's when filling so as to force the water through the underfloor part return pipe and into the flow pipe and bleed the tr's a bit before then opening their return valves as well.

 

[DeltaT2]

That is what I am doing though ? The existing f&r still go to tr and I have put a tee into both of them(or am about to today when I get started).
Have also planned to put a gate valve after the 2 port valve so I can control flow rate in underfloor part. I guess this is like balancing radiators.
Any thoughts about whether I will need the vent pipes to fill it?

One idea I had was to turn off the return valve on the tr's when filling so as to force the water through the underfloor part return pipe and into the flow pipe and bleed the tr's a bit before then opening their return valves as well.

That's not what your detail shows mate, it shows you putting lots of tees on the TR F&R?? Doing it that way you'll be unable to regulate your floor loops.

 

[Agile]

I think its unlikely that you will be able to get enough heat into the floor.

When fitting UFH under wooden floors its normal to use metal spreader plates to transfer the heat across a wider area than just the pipe and its usually in pressure contact too.

Tony

 

[dmccormick]

There is one tee on the tr flow and one on the tr return. Then from these tees I am running 15mm pipes with tees off them for the floor loops.

In effect this is splitting a branch off the tr circuit and using the two port valve tobturn it on and off and gate valve to regulate it's flow.

 

[DeltaT2]

Sorry mate you're quite right, I didn't read it properly, I'm a prat.
Yeah, that should work OK. But as Tony has stated; not too sure how well it'll heat the floor???!!

 

[Deluks]

Yet to embark upon similar idea, so am throwing the following questions up just for clarity.

Would a manifold with 4 10mm connections been a tidier way to do it?

Would one of the danfoss regulating valves be easier than wiring in a 2 port valve?

http://www.totalfloorheating.com/more/on/details/00045

 

[DeltaT2]

As with the above, it's all about flow rates & circulation pump head?? If your circulation pump is screaming, trying to circulate enough watts around your existing system & then adding to it, well, it just ain't gonna work.

To tell you for sure if any addition to your system will work, you need to carry out pipe sizing calcs on your existing system.