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Discuss Ufh problems temp control and radiators temp in the Water Underfloor Heating Installations area at PlumbersForums.net

Hi guys
Our recently installed UFH system is causing us trouble and we are struggling to get the fitter to help, problem one is we have to slowly build up the heat as the new floor is tiled but the only way to do this is by turning the boiler heating controls down as low as it goes, 30 degrees, if we have it set to 60 the temp on the flow is 45 degrees which is the maximum we can run at.
The mixing valve is fully set as low as it will go so effectively we can’t run the UFH at any other temperature than maximum 45 degrees when boiler is set to 60.
The other problem is when the UFH is running the radiators through the rest of the house struggle to get to temperature!
System is a Wunda with a Wilo pump, please help?
 
We can’t run radiators effectively at the same time as the UFH and the UFH won’t run cooler than maximum which is a problem when your floor is freshly tiled.
 

chris watkins

Esteemed
Plumber
Yes I know and understand but there isn't a solution apart from additional heaters in the areas that are cold.
I say again what were you expecting, did they not explain the commissioning process?
 
Yes I know and understand but there isn't a solution apart from additional heaters in the areas that are cold.
I say again what were you expecting, did they not explain the commissioning process?
Yes we commissioned the ufh when screed was dry, then left it off for tiling then left it to dry for a further 3 weeks before we gradually raise the temperature, problem I have is in this cold weather the radiators won’t heat up because the boiler has had to be set to minimum temperature, from what I’m led to believe I should be able to leave the boiler set to 60 and use the mixer valve to reduce the ufh temperature but I can’t do this and would like to know why?
 

chris watkins

Esteemed
Plumber
So the mixing / blending valve isn't working then?
You should be able to set the boiler stat at say 70 & the mixer to give a circulating temp around the U/F of 50 degC.
 
Here you can see the inlet flow temp is about 25 degrees but I can only achieve this by turning the central heating on the boiler to minimum
 
Chris that is my guess but the system is new and the blender/mixer valve does operate but not as low as it should do
 
A

Aire

Have you been specifically told to run your underfloor at 30°? Screed should be left to dry for about 30 days before any tiling. If you waited the correct time before tiling and now waited a further 3 weeks, you will be fine to run your underfloor in the lowest setting of the blending valve and gradually increase it over the next few weeks.
 
All commissioning has been done to the letter, my problem is I can’t run my ufh at any lower than maximum temperature which I should be able to without turning my boiler ch control down to minimum as this affects my radiators in the rest of the house, you should never turn on ufh systems to full temperature from the offset as this can crack screed and tiles, it must be raised and lowered gradually
 

chris watkins

Esteemed
Plumber
What is the design temperature for the U/F heating ?
It is normally 50deg C water to give a floor surface temp of around 29 why do you think your should have lower temps ?
 
this is a screen shot of the instructions, maximum 45 degrees for my floor but I should be able to start much lower and work my way up to this temperature, from what I can gather many other people are able to operate their ufh systems at any temperature without having to turn the CH setting right down to minimum on the boiler
 
A

Aire

this is a screen shot of the instructions, maximum 45 degrees for my floor but I should be able to start much lower and work my way up to this temperature, from what I can gather many other people are able to operate their ufh systems at any temperature without having to turn the CH setting right down to minimum on the boiler
Your underfloor and radiator temp cannot be ran at separate temperature using the boiler controls. The only control you have of the underfloor heating water temp is with the blending valve at the manifold. Turn your boiler up, turn the blending valve to minimum and run your underfloor several times a day at 1 hour intervals and gradually increase the temp over 4 to 6 weeks.
 
Your underfloor and radiator temp cannot be ran at separate temperature using the boiler controls. The only control you have of the underfloor heating water temp is with the blending valve at the manifold. Turn your boiler up, turn the blending valve to minimum and run your underfloor several times a day at 1 hour intervals and gradually increase the temp over 4 to 6 weeks.
That’s my problem, the blending valve is set to minimum but the temperature is at maximum on the inlet gauge when my boiler is set normally, I’m guessing a faulty blending valve or installation issue?
 
A

Aire

So with your boiler set at max, and blending valve set at min, what temp is this gauge in the pic reading?

20190216_222655.jpg
 
Yes but when the boiler is turned up, are you saying that the temp of that gauge goes above the temp set by the blending valve?
When the boiler is set to normal 60 degrees the temp on that gauge is about 45 to 50 degrees which is or exceeds the maximum my floor can take, I should be able to run my boiler at normal settings and adjust the ufh blending valve to achieve a temperature lower than maximum, maybe I’m not getting this across clearly but for tiled screeded floors it is important to start off at a low temperature and gradually increase this which I am unable to do without turning down my settings on the boiler which in turn knocks out my radiators
 
Good man . the wallet always hurts .. don’t you know the name of the plumber?
Yes I have his name and number but I’m leaving it up to the builder to sort out, if I have to get another engineer out then the retained money won’t be paid
 
A

Aire

The blending valve should have a range of around 35 - 65 ° so if you can't regulate the temp down then there may be an installation issue or a fault with the blending valve. Ask your contractor to contact the manufacturer of the underfloor heating to get a rep out to check the system over.
 

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