Underfloor Heating Issue

[Olly1982]

Hi everyone

I hope you may be able to help.
We have underfloor heating in our kitchen and have had no issue for the last 4 years.
Just this last we have started to have an issue with the heating not getting very hot.

I have done some research and I think it may be the mixer valve.

The water temperature is 50 degrees when the underfloor heating is not turned on but as soon as you turn it on the temperature starts to drop and comes down to 30 degrees.

I have turned the thermostat on the mixer valve to maximum and have also tried turning the thermostat on the boiler up and still have the same issue.

Does this sound like a mixer valve?

I have attached a photo for reference.

Any advice is appreciated

Thank you Olly

 

[Roger928]

Does this sound like a mixer valve?

The mixer valve is the one with the temperature gauge fitted and the red knob at the bottom where the adjustment occurs. The orange coloured device on the top manifold is an overheat pipe stat to prevent the pump operating if the mixer valve fails. To prevent the floors being roasted! Usually set to around 45c.

If the temperature on the gauge drops to 30c when the UFH pump operates then it sounds like its working OK.
However its a bad design imo. Because what ever temperature the mixer valve outputs, further mixing occurs at the T inlet to the ufh pump, which will reduce the response time.

If the gauge registers 50c when the UFH pump is off then the mixer valve might be acting as a by pass when you have the boiler turned on heating radiators or a hot water cylinder some where else in the property.
Which is why some systems will have a zone valve fitted before the manifold.

 

[Olly1982]

Thanks for your reply.

Just to clarify when you say it sounds like it is working ok do you mean the mixer valve or the pipe overheat stat?

 

[Roger928]

The mixer valve.

 

[Agile]

He means the mixer valve.

I don't like the layout and think the temp gauge may be measuring the inlet temperature and not the UFH temp.

Regardless I would always measure the temperature independently with a contact thermometer at the flow and return manifolds.

Would always expect a motor valve at the flow input to the mixer valve.

Tony