Your COP is pretty decent so you will probably be looking at fine tuning and or system changes which might be expensive.

If your flow temperature is as low as you can go then I would be looking at insulation, length of pipe runs and the inclusion of any buffer or low loss headers.

The size of your emitters will dictate how low a flow temperature you can use.

Good monitoring is very useful if you want to really opitmise your system. 

Investing in a battery and getting a good time of use tariff would be worth considering. You probably would only need a 5-10 kWh one to make it worthwhile

Thanks for the response. 3.5 is well below the 4 plus suggested pre sales and I would like to coax all I can from the system.  Suggestions for tweaks re controls or instal would be great.

Sadly a battery is not an option as our smart meter is not smart.  I have had numerous engineer visits but we cannot connect.  So doing all I can with what we have  is my focus.

Emitters seem to be fine in terms of capacity.  This was a new system throughout and emitters specified with a low delta T

@davidb 

I'm presuming you are already running open loop 24*7, no external controls and have turned the weather curve down as far as possible consistent with heating your house, and balanced rads.  I also presume you have no buffer tank.

If you have done all of that then some monitoring would help identify what else you might do.  I have a Valiant 7kW and use home assistant for monitoring, no additional hardware other than something to run ha on needed assuming you have the internet gateway.  This gives a good insight as to what's going on.

@davidb Im not aware that you need a smart meter to have a home battery David.

@jamespa Yes to all the assumptions although I haven’t tried reducing below 0.6.  On installation the engineer set to 0.9.  

what is home assistant?  I have an internet gateway for external troubleshooting and to run the Vailant app

@bontwoody maybe I have missed something but I thought time of use tarrifs depended on an operating smart meter to record usage??

Posted by: @davidb

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@jamespa Yes to all the assumptions although I haven’t tried reducing below 0.6.  On installation the engineer set to 0.9.  

what is home assistant?  I have an internet gateway for external troubleshooting and to run the Vailant app

OK.  Well in case you haven't already the first thing to do is to disable all room influence and turn the WC curve down as far as you can until the house is only just heated sufficiently. 

Home assistant is free software for monitoring and controlling more or less everything in the home.  It connects to the same server as the Vaillant app and means you can see whats happening with flow temp etc.  Useful for diagnosis but takes a bit of setting up.  It really needs to be on 24x7 so I run mine on a raspberry pi, but if you have almost any computer it should run.

Here for example is my flow temp for the last 24 hours

@davidb Ah. I see. I was just thinking batteries not the tariffs

This week was very mild here so our 7kW heat pump reports a COP for the week of 4.8 for combined heating and DHW. Our house requires ~8kW when -5C which it was earlier in the month. Therefore our slope is 0.8 at present still, on room influence active. We set a temperature of 20.5.

If we were on inactive then I would need to drop the heat curve slope to ~0.65 now.

I suspect that our ashp is over-reporting heat production and hence COP by 5-10%. We do not have a calibrated heat meter, so are reliant of the app reporting which uses the dT of out and return water temperatures, which has an inherent potential inaccuracy.

What temperature do you set the room?

James’ advice is good and you present COP isn’t awful just your electric price has jumped up badly.

@judith Thanks Judith - that is a interesting comparison.  As you say, my COP is not awful but I feel it should be better.  Your 4.8 is the sort of figure I was hoping might be achieved given its between 5 & 10C ambient.

Our set temperature is 19C which seems to be an ok compromise and is fine when we are up and about during the day.  We also have a log stove and tend to light that from lunch time onwards and we are comfortable with an ambient of 20 to 21when watching TV etc.  Once going the HP turns off.

2 parts of your response made me think.  Firstly if the heat generated is measured based on flow and return temps at the outside unit then the insulation of the external pipework is important.  I don’t think that was an element of our instal which was optimal.  While the outdoor unit is 300mm the house wall, the pipes are not the shortest possible.  The contractor included a length of flexible pipe (to prevent any possible vibration fracture?) and also to allow external valves to be fitted as per Vailant circuit diagram.  Finally, with these fittings the way the insulation has been fitted could be improved and there is an early sign of rodent attack.  I am not sure how much heat might be being lost and if this is having an appreciable influence on the COP.  All thoughts on this topic would be appreciated.

Finally, what is “room influence active”?  As I said much earlier I am going up a steep learning curve without the benefit of a manual so apologies if this is a daft question.

Another factor which might be working against us is the heat demand of our house is low.  It was subject to a deep renovation with lots of insulation. I am wondering if, in the range 5 to 10C, the unit is struggling to dial back the heat produced to match the building heat loss is cycling instead??  Does this make any sense??