Just a few observations.

TRVs and zoning

Turning radiators down or off, zoning parts of the heating, or running the heating intermittently will reduce the average temperature of the house and hence reduce the heat losses from the house.

Operating the heat pump at a higher flow temperature will reduce its efficiency, so running it for longer at a lower temperature should make it more efficient.

The question is does the increase in efficiency outweigh the increase in house losses?

In some ways this is like comparing taking a bath or a shower. Baths are much more efficient because the energy in the bath far exceeds the losses in the pipework, but showers use maybe a quarter of the energy, so they are by far the most economic.

If the load on the heat pump is much less than its rating (excessive zoning), then the heat pump will be continually cycling, pulsing heat in, then waiting for the return flow to cool. Think filling a bowl with hot water in the kitchen, then taking it upstairs to fill the bath, then returning to the kitchen to repeat the process.

Heat up times.

The time for a room to re-heat is determined by the power output from the radiator. If the radiator has been resized so that it outputs the same power (at the reduced flow temperature) as the original radiator (operating at gas boiler temperatures) then the room will reheat in the same time.

Weather compensation may mean that the (initial) flow temperature may be less than the design flow temperature (for -3°C ambient), so the cooler radiator outputs less power and the room heats slower. 

However a "TPI" thermostat on a gas boiler system will adjust the heating duty cycle to run the boiler cooler (to increase efficiency), so it too will heat slower on warmer days.

Those are some really thoughtful observations @BeePee. 

I don’t know if you have seen this article yet but I would definitely recommend giving it a read 

Keep us updated with your findings

I Iive in a terraced house. Could I have a heat pump installed?  If so where would it go?

On the revised App there is a Heat Pump section on the Home page and you register your interest. It doesn’t commit you to a course of action but it does take you down the path where by the Heat Geeks can establish where the best place for all the elements of the system need to be.

If you commit to going ahead with the survey then I think the fee is £350 which I believe is refunded as part of the cost of the installation. I followed that process but for practical reasons I didn't complete but the house heat loss survey was very useful and I opted to stay with my gas boiler for the time being but I've upgraded a couple of large windows to triple glazing and upsized a radiator in the hallway which was an extension to the house and hadn't been sized properly.

Peter

Whereabouts on the home page?  I can't see it. Can you send a screen shot?

Hi, our new heat pump (not from OVO) has a COP of about 2.5 for water and 1.1 for room heating, so I’m looking for ways to improve it. I hope this is a good place for this question.

The installer quoted and agreed to link a Honeywell Evohome to it: it controls each radiator separately (i.e. a multi-zone system). I realised that this would mean the COP was not the best it could be, but we don’t want to loose the ability to leave some bedrooms unheated and save that way. The Evohome is an on-off control to the heat pump - Opentherm could give a graduated control system (as it does with boilers), but doesn’t seem to be implemented on heatpumps. Apart from going to single zone, does anybody have any suggestions about what to do? The pump is an Ecodan R32. I’m trying to get the installer to help, and asking here to help me talk sensibly with him. Thanks in advance.

If I was you I’d try running it without the zoning and see how it improves. Set the heat pump to run on a weather dependent setting. Unfortunately as we’re coming to the end of the heating season it’s going to be difficult to set this up now. Do you know how to set up the weather curve ? 
1.1 for space heating is dreadful though 2.5 for hot water is not bad. 
Search for the heat geek video which explains why you shouldn’t zone rooms with a heat pump.

Thanks Julia. It was left on constant flow temperature at 50C, it’s on temperature compensation mode now. I’ll need to install the wireless room thermostat they left before I can change zoning. It’s difficult to set a specimen room for the thermometer. I’ve seen the heat geek video. I get the point but there are rooms in an extension that are thermally separate from the rest so I will exclude some rooms. I’ll need to balance the system too, as with remote TRVs it wasn’t necessary. I know there’s a heatgeek video for that too. I can’t quite believe that we’d have warmer rooms all the time and it not cost more, but we’ll see. We were quite frugal with the Evohome and boiler. Thanks again.

Hey @Johnc99 

Welcome to the OVO Forum.

I hope the advice juliamc left you was helpful, keep us updated with how you get on with things. I’m sure it could be helpful to others in the community in future to learn from your experience.

Hi Julia. I have installed the Mitsubishi room temperature monitor and watched quite a few heat geek videos. There is also a document of his that gives a specimen calculation for cost with and without zoning, which is quite convincing. The weather has warmed so, as you say, it’s difficult to set it up now and see what’s happening. We really only need the bathroom warmed first thing and late evening. Our single zone is the dining room, lounge, kitchen and bathroom. Our heat pump can modulate down only to 60%, so with a low load it must cycle and so it will have a low COP. I have lowered the pump flow maximum temperature (which sets when it turns off) and minimum temperature (which decides when it turns back on), trying to slow the cycling. The energy used, morning and evening, is only a few kWh, so it may not be worth trying to improve COP for this time of year, when the dominant effect should be in the heating season. If anybody is still interested I will try to remember to update this if I get anywhere. Thanks

@Sandyeyes Sorry for the delay. I missed your message. I tried to find it again but it isn’t there any more. Possibly bypassing a few hurdles, try emailing Anna Gunstone directly at upgrades@heatgeeks.com to see if you can get some information on how you get started on this. It is dependent on Heat Geeks carrying out work in your area so you may not have the link if they aren’t. I hope that helps.

Peter