@adrian thanks for the explanation Adrian.  Sounds as if I should experiment with pure weather compensation for a day or 2, keep the stove off and see what happens.

@davidb Further to my previous post one further comment I would make is that 300l system volume is not consistent with 7 radiators.  Unless you have a large buffer tank or volumiser (do you, if so how large) then I would guess a lot of this was used to flush the system

If you provide the data from the app that I mentioned it might clarify matters further.

Thanks for requesting this info - I hadn’t seen this data before.  Live and learn.  Not sure if 1000 cycles is good or bad or period of measurement.

January info

Yield info for January.  I live on a Scottish island.

OK.  What Im seeing looks fairly normal TBH:

1 start per hour is good (1028 on off cycles in 1303 hours); there is no evidence of short cycling

Unfortunately you haven't split out heating and DHW (you really should), which denies us some important information, but an overall COP of 3.6 in January given the ratio of DHW to space heating displayed compares to mine of 3.87 for the two combined, but with a much lower proportion of DHW in my case.  I would estimate guess you achieved a COP of perhaps 3.8 for space heating alone, which is pretty reasonable for January, and therefore that you can reasonably expect a space heating SCOP of 4 or more (mine is 4.2).  Your heating consumption of 241kWh compares to mine of 907kWh.  My house is 7kW at design temperature suggesting yours is actually only about 2kW.  This is consistent with 1 start per hour which is definitely OK but not 'top notch' for January,; the heat pump is somewhat oversized but with a 2-3kW loss thats absolutely inevitable and anyway necessary to give you decent DHW reheat time.

Basically I don't think you have any problem and should easily achieve a SCOP of 4 plus for space heating.  DHW will always have a lower SCOP because you are heating to a higher temperature, I don't know if you have the opportunity to reduce this but if you do it will help.

I don't think you have anything to worry about but can I suggest you keep monitoring however to monitor space heating COP separately from DHW COP?  

@jamespa Thanks for the commentary and reassuring comparisons with your own much larger system.

The energy consumed of 281kWhrs produced heat of 893 and DHW of 110 which equates to the given COP of 3.56.

40kWhrs was used in DHW production giving a COP of 2.79

241kWhrs was used for heating to produce 893kWhrs of heat so a COP of 3.7

i think those are the right figures but happy to be corrected.  I am still very much feeling my way on the whole HP journey.

you may not have seen it but I posted a separate but related topic concerning my UFH.  Mars has been helpful with a couple of suggestions.  Basically the flow from the manifold to the slab pipes was very low and it seems the flow adjusting valves may well need replaced.  A call with Vaillant tech support highlighted that my flow and return DT was only about 3.  This spurred me to review part of the physical set up and concluded the UFH pipes were doing very little.  As the floor should provide roughly 30 to 40% of my emitter output, it’s not surprising the system was struggling to get to the set temperature.  Currently water is clearly flowing in the UF pipes.  However heat is going into warming the concrete slab and I guess it will be some hours before the temperature starts to rise as a result.

is there any way for the home owner to monitor the return temperature? 

Also, do you know it it’s possible to review cycling over a defined period rather that what I assume is data since commissioning? 

Thanks for your assistance.

The system doesn’t seem to have return or deltat as a value. For that you’d need something like openenergymonitor. For the cycling I have home assistant connected via myValliant component, which gives the power consumption as a graph, so you can see the cycling via the power consumption. 

Btw, fixing your system so the underfloor heating is working is definitely by far the best you can do to improve your COP substantially. It also provides a large amount of thermal mass which means you can probably be quite aggressive in switching off the heating when your stove is on. 

@jamespa Hi James,  previously you have suggested invoking the inactive mode on my system (which I have done) and then turning off my heating when our wood stove is on.  Is it possible to set a time period to turn the heating off and on again?

I would like to set 02.00 to 14.00 on at 18C.  Typically we light the stove at lunch time and it goes out after 22.00 by which time the temperature is about 22C.  Is there a way for the controller to turn the heating off from say 14.00 to 02.00 so the heating would come on again at 02.00 once the retained heat in the fabric has dissipated back to roughly the 18C set temperature. Turning off manually and then on again manually would obviously work but it would be easy to forget to turn it back on and, in any case, would be before the temperature had dropped back to 18C.  

Having looked at the timed controls, I suspect what I would like to do is beyond the capability of the controls.  The obvious way is to invoke active so the increased temp from the stove switches the heating off and it comes on again once the retained heat has dissipated.  However, I think the advice is this uses more energy.

I get the question and what you are trying to do, I will think about the best way to do this and make a suggestion once I have.  A timed 'deep' setback might be a way, but there might be a better one.

I think you can set the temperature to very low 5C in the time weekly timer. Either do it for the full period when the fire is expected to be on, or you could just set it for a short time from 1:50-2:00 and then do it manually when you put the fire on (, which would mean the timed control would switch it back on at 2:00 and on a day you didn’t put the fire on the house would stay warm.