Return Water Temperature Limit valve

[mordzy]

Hello.

I have a small (12m2) area of floor to heat and rather than installing a pump/manifold was looking at using a Return Water Temperature Limit valve.

However im not sure if this is a good idea as I cant regulate the flow temp as the pipe enters the floor. I understand it should be somewhere around 45 degrees but it would be nearer 80 as it entered the floor if I just use a Return Water Temperature Limit valve and thus damage the flooring / slab?

Should also use a TMV on the flow or will this confuse everything.

Thanks

 

[ianmcd]

what ?????

 

[mordzy]

lol. The CH flow will enter the floor (UFH Pipe) at boiler temp of 80 degrees. I understand that a manifold would normally mix this water with cooler return water using a thermostat. Using a Return Water Temperature Limit valve on the return doesn't prevent the really hot water entering the floor.

Am I missing something?

 

[Newboy]

Am I missing something?

Yes- a fundamental understanding of how to install underfloor heating!

 

[ericmark]

Depending on surface the under floor heating is often limited to 28°C, which is also why it normally is back ground heating only, still needs radiators in the room. So the method used with wet systems is to re-circulate the water around the floor, adding just enough hot water from boiler to maintain the circulating water at 28°C.

Without a second pump the water will not circulate, the only way I have seen to get away without second pump is to feed it into a radiator first, so water is cooled by radiator and the lock shield valve controls flow so it can cool the water to 28°C, this is rather hit and miss, and only see in done in a bathroom where the radiator/towel rail was heated with the DHW not central heating, and to be frank it did not work that well as towel rail was really too cool, and I suspect if the building inspector had realised, he would have insisted it was removed. It was more to cool the Rayburn stove than to heat bathroom.

 

[Gasguru]

What you are proposing is a bodge but Danfoss and the like actually produce valves and kits to do it this way.
AFAIR there are serious health implications of having flooring too hot and I'm not talking about scalding temperatures.

https://www.bhfunlimited.co.uk/product/wet-single-room-underfloor-heating-kit-1-port-diy-ufh-system/

It's far better to use a proper underfloor setup with blending valve/circulation pump etc and then guarantee the floor temperatures.

 

[mordzy]

Yes- a fundamental understanding of how to install underfloor heating!

Well yeh... completely. Hence the question posted on... wait for it... a DIY forum!

I appreciate its not the 100% correct way to do it, a professional may consider a bodge, but also as Gasguru states Danfoss etc sell these so called Return Water Temperature Limit valves. Im unsure its a good idea considering the temp of the flow to the floor.

As the consensus seems to be avoid, I will go for a single zone manifold and pump with blending valve.