Underfloor TMV without pump?

[ecogeorge]

I have a friend who is in the process of installing underfloor heating in his dinning room only. One circuit - no more than 15m2 .
He has oil fired central heating with a pumped radiator in this room (will be removed).
Obviously a TMV valve is required to keep the floor temp low but can anyone  devise a plumbing schematic without the need of an additional pump?
I cannot see how a TMV can work without extra ciculation  pump  or am I missing a cunning way?
Any info appreciated.
rgds George.

[Alan]

Hello George

Presumably the radiator being removed was on a pumped
system with one side connected to the boiler flow and other
side connected to the return.
With a pump on the boiler flow or return.

The under floor would be connected to the old radiator pipe
positions. With your temperature control device on one end
and your balance valve on the other end.

Some people manage to get radiators piped in series which gets
pretty painful when all the fitted carpets are in place.

Regards

Alan

Edit.

Quote " Obviously a TMV valve is required to keep the floor temp low."

Why do you need to keep the floor temperatue low. A wax / electric
thermostatic would shut of the water supply to the room when the required
air room temperature is reached.

[ecogeorge]

Not sure I follow !!
Need to keep the water temp in the floor to 25-35 c max.
Boiler temp anything up to 50, 60 or 70c - will melt pex under floor pipe and crack screed as welll being bl**dy hot.
I can't see how a TMV will work without additional pump.
If water flow is >say 35c then the TMV takes more cold , or when used in underfloor situations it just feeds the TMV with "return" water.
As soon as the flow <35c the TMV accepts more hot and the "extra" unwanted return water just returns.
If no extra pump fitted what pushes the water around the pipe if the hot flow has been shut by the TMV?
Have never seen the need to fit balance valves -whats that? no need to restict flow in circuits- we need the heat being pushed into the concrete not resticted.
rgds George.

[Alan]

Quote “ Need to keep the water temp in the floor to 25-35 c max. “

Why. I thought the object of any heating system was to heat the house / room.

Quote “ Boiler temp anything up to 50, 60 or 70c - will melt pex under floor pipe and crack screed as welll being bl**dy hot. “

Wrong. Pex pipe is rated at continuous use 95 Deg C at six bar.

Quote “ Have never seen the need to fit balance valves -whats that? no need to restict flow in circuits- we need the heat being pushed into the concrete not resticted. “

Don’t give up the full time job and start plumbing.

Regards

Alan

[ecogeorge]

So are you saying it does or does not need additional pump?
Sorry if I'm not seeing the point.
rgds George.

[dhaslam]

There probably isn't a way to work  out whether there will be enough flow.   If the  pipe went straight into the floor circuit it would be carrying the same heat supply as the radiator but with more resistance  and probably  would work.   By  introducing the mixer  valve  the  flow is  going  be be reduced  more.       I think it would be better   to have a separate pump  which could be operated by the room stat  but it  should really have its own  separate  supply.   This seems to be the only way the kit systems are setup.

www.underfloorheating1.co.uk/single-room-underfloor-heating-kit.html

I have the opposite situation, the pump is on the underfloor system and it  is able to circulate heat to the  mixer valve from the buffer tank.     It isn't however able to heat the  DHW cylinder at the same time as  below. 

[ecogeorge]

Thanks for that, I too have pumps set just like yours one on upstairs manifold and one on the downstairs.
My friend was hoping to avoid a pump but I cannot see a way to do that even if just for one zone.
He was hoping to just include a simple on/off tap to regulate temp and run it with his existing heating circuit.
I think prehaps a thermostatic valve in the circuit would help control the room temp - he currently turns his heating off / on as required so we have a little way to go in automating his heating.
rgds George.

[Iain]

Hi Ecogeorge
I run my system at about 50 deg c. Rads and underfloor. It is just enough for the rads but seems low enough for the underfloor. Just enough for the HW cylinder (for topping up after solar) to get to 45 deg c.
Iain

[biff]

hi george,
       the room is much too small to warrant the use of another pump,,i have done exactly this kind of job many times using only the existing pump and instead of doing away totally with the rad i reduced it in size to the smallest one i could get(tall and very narrow),i simply tee,d off down below floor level,leaving access to the tee,s for inspection.i used the thermostat on the rad to set the room temp,it was really important to lock the stat so that no one could acidentally raise the temp.it worked a treat,in one case i used a 3port honeywell zone valve (using no rad)and located the temp,settin sensor beside the light switch,(half way up the wall) this gave the best results,just make sure to charge the pipes with mains water to blow out any air.it will make the final bleeding much easier, you will have to tee off somewhere and fit a bleeding screw to remove the last of the air from the system. leaving a little rad means you can bleed the system easier.,,apples,,and oranges.
                                                                       biff