UFH Mixer Valve Query

[calama]

Hi I am wondering if the mixer valve would normally affect the flow rate? If I set the temperature to anything above 45deg then the flow meters barely register. But if I set it to minimum then I get 2lt/min at the flow meters. I can't get the correct temperature at the right flow rate to get a large room heated up. 

I would expect the mixer would just mix the hot input and cold return without affecting the flow...am I wrong or is it defective?

Thanks for any advice.

[dpmiller]

Are the flow and return from the boiler the right way round at the valve?

[calama]

Yes it it clearly marked hot and cold on the valve. The installation is around 15yrs old now and used to work ok, but last few years has struggled.

[Nickfromwales]

The mixing valves do die off with old age. Just put a new one in and you’ll be in the pub for Friday   15 years is a decent stretch for a part that’s constantly moving / adjusting etc.

Do you have a magnetic filter in the system? If not, I’d add one when you change the valve. 

[calama]

Ok thanks, yes I think that will have to be the plan. The system does have a mag filter on it and I flushed out the manifold separately...there was quite a bit just sitting in the bottom on the manifold so likely there is something in valve too.