Could it be that the valve has stuck open so that the higher temperature water intended for the DHW circuit is also flowing through the UFH manifold? Toodles.

@toodles I suppose anything is possible. I wish I had took a better photo of the cylinder so I could perhaps look it up and see its connections. Perhaps its a thermal store? The UFH and Rad circuits each seem to have one two-way valve

@bontwoody My eyesight is not good enough to follow the pipework to those two valves so I cannot tell which from what however… another thing I cannot see is any insulation - I think most of those pipes need lagging! Regards, Toodles.

@bontwoody I can see 3 motorized valves but cant quite work out how one of them (which is on the pipework to the cylinder) is connected.  I also dont know how it is controlled although it looks like its linked directly to the cylinder stat.  

Posted by: @bontwoody

↑

Im not altogether sure how a system like this should be plumbed. It seems to me the optimum solution requires water at 3 different temperatures. Is the usual solution to heat the DHW as usual, but then use a lower temp for the radiators and perhaps use a mixing valve to lower the temperature again for the UFH?

yes, exactly that. 

But maybe the plumber has 'designed' the whole system to operate at a single FT of 50C without weather compensation, in which case it could be operated just like a boiler, with (or even without) mix-down for the UFH.  What I presume to be the feed to the rads also appears to feed the UFH manifold directly. Stupid but possible and if there is no mix-down for the UFH risk of burned feet or spoiled floor covering.  

Posted by: @jamespa

↑

@bontwoody I can see 3 motorized valves but cant quite work out how one of them (which is on the pipework to the cylinder) is connected.  I also dont know how it is controlled although it looks like its linked directly to the cylinder stat.  

 

Posted by: @bontwoody

↑

Im not altogether sure how a system like this should be plumbed. It seems to me the optimum solution requires water at 3 different temperatures. Is the usual solution to heat the DHW as usual, but then use a lower temp for the radiators and perhaps use a mixing valve to lower the temperature again for the UFH?

yes, exactly that. 

But maybe the plumber has 'designed' the whole system to operate at a single FT of 50C without weather compensation, in which case it could be operated just like a boiler, with (or even without) mix-down for the UFH.  What I presume to be the feed to the rads also appears to feed the UFH manifold directly. Stupid but possible and if there is no mix-down for the UFH risk of burned feet or spoiled floor covering.  

Looking again I think the slightly hidden motorized valve has 3 ports, one directing water to the middle of the cylinder the other to the bottom.  The flow to the CH and UFH (which does appear to be common without mixing) appears to come from the bottom.  So perhaps this is a combined cylinder/butter tank, with the buffer tank below and the cylinder above.  The bottom bit has an immersion, which may just be a backup.

Does that help?

@toodles LOL, I did point that out to her 🙂

@jamespa Its a lot more than I had managed to work out James, so thanks yes. Ive offered to switch the pump for her as a belated wedding present, so when I go back I will take some more extensive pictures and trace some pipes. She said she was spending £180 per month on electricity bills so Im hoping that can be reduced substantially.

The heat pump looks on the big size for the house, but was also tipped forwards about 15 degrees so Ive done my best to level it as a temporary measure. Long term its position will be changed.

@jamespa I think you are spot on about the integrated buffer vessel, she has sent me her documentation. It was designed for a 50C flow temperature with UFH! There is no thermostatic mixer valve on it.

Im going to try and find out how to access the control unit and see whats going on once I change the pump. It a modern one similar to the Samsung unit from the outside.

@jamespa @toodles

So I have changed the pump (all working again) and had a better look around. There appear to be 2 x two way valves one on the upstairs rads and the other on the downstairs UFH.

There is a 3 way valve switching between heating and DHW as normal. Ive been into the installer settings to have a look but need some advice on the LG way of doing things so I will start a new thread.

Thanks for all your help.

@bontwoody You are most welcome - not that I contributed much, but if it helped, I’m happy! Regards, Toodles.

That doesn't look like a thermal store to me.

I think it's a combined DHW cylinder (top) and 50-litre buffer tank (below).
Have a look at this diagram from the manufacturer's product literature.

At least that graphic has the ports labelled, which gives you a fighting chance of working out what each pipe is meant to do.