@andrewj this is an interesting discussion.  I am curious to understand why you are asking the question.  You already have a heat pump, so surely you can experience this for yourself?  Are you finding it less comfortable than with the gas boiler?  Are you finding that the system is cycling on and off too much?

We have had our heat pump system since August.  While these are early days, my wife and I feel that the house is much more comfortable now.

Posted by: @majordennisbloodnok

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Posted by: @andrewj

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I think that concurs with what you are both saying and that I will see behaviour in line with my expectations as the weather gets colder.  I suppose that also means some rooms are likely to be cooler than others simply because of this thermostat-like behaviour.

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Yes, I think it does concur.

Regarding some rooms being cooler than others, I suspect that may have more to do with radiators not being as well balanced as they could be. There's another article - this time by @toodles - covering this and it's here. Balancing is often not done well by installers simply because it takes more time than they have available, but it's a straightforward process for a homeowner to do and gives good results once done.

 

Distinctly possible as it wasn't really feasible to test more than the radiators weren't leaking and some heat could be felt.  I did agree with Octopus that they would come back and properly balance later in the year - we shall see.  However, really I suspect it's because the heat loss is greater in some rooms than others and the impact is more obvious with the way it is running.  Once it settles down to always on then, assuming it is properly balanced, I expect things to be more consistent.

Looking at the graph Im a bit surprised it isnt running more 'continuously' at night.  Of course you could have a very well insulated house (although cosy 9 = 9kW? doesn't sound that way), the heat pump could be oversized, or it could be bouncing off the room thermostat because the cold weather FT setting is too high (57 is a very high 'cold 'FT, although in fairness I dont know what outside temperature that setting corresponds to so ).  Difficult to tell for certain until we get sustained colder weather at which point its worth tweaking the WC settings to get best performance possible.

Posted by: @grahamf

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@andrewj this is an interesting discussion.  I am curious to understand why you are asking the question.  You already have a heat pump, so surely you can experience this for yourself?  Are you finding it less comfortable than with the gas boiler?  Are you finding that the system is cycling on and off too much?

We have had our heat pump system since August.  While these are early days, my wife and I feel that the house is much more comfortable now.

I'm posting my experience really, and my confusion: it is cycling on/off rather than running continuously so to me it looks like it is operating no differently to a boiler with a thermostat control.  It could be related to the outside temperature not being that cold during the day, as mentioned in the last few posts, and it isn't really related to comfort at the moment as the house isn't cold. 

Posted by: @jamespa

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Looking at the graph Im a bit surprised it isnt running more 'continuously' at night.  Of course you could have a very well insulated house (although cosy 9 = 9kW? doesn't sound that way), the heat pump could be oversized, or it could be bouncing off the room thermostat because the cold weather FT setting is too high (57 is a very high 'cold 'FT, although in fairness I dont know what outside temperature that setting corresponds to so ).  Difficult to tell for certain until we get sustained colder weather at which point its worth tweaking the WC settings to get best performance possible.

I don't really know what I should be expecting to see as it's the first time it's been used for heating.  Last night was around 5c here; I'm trying to find out the related temperatures for "Hot Weather" and "Cold Weather" as I agree 57 seems high.  I'm reluctant to fiddle with anything until I have a better idea of how its working when its cold enough to be on more.  I don't have a setback temperature for the nighttime either, I've just left it at 22c on the basis of keeping it ticking over.

My last year's gas data was 8937kW for heating (at 21c in the living room) and 2221 for hot water and 100mm of loft insulation.  The design document was for 10000kW for heating (at various but 21c for the living room) and 2000kW for hot water with 300mm loft insulation.  I was looking for the determined heat loss for the house in the design document but it isn't there (just room-by-room): IIRC, it was something like 8200kW and Heat Geek calculated something like 8,400kW (or maybe it was vice-versa but in any case correlated.)  The house is a Finnish designed timber framed building built in 1985 so whilst the walls and floors are insulated it is still quite old; modern extremely efficient triple-glazing and passivehaus standard external doors.  It can warm up quickly and, conversely, cool down slowly: it loses around 2c over 5 hours at night during Winter which seems slow to me but I don't have much to compare it against as I've lived here for over 25 years.  Having said all that, in the old gas system, I think the radiators weren't appropriately sized for some rooms and never properly balanced so some rooms were warmer than others.