@andrewj  Its worth remembering that recovery is, at least in principle, asymptotic not linear, so whilst it might take 6 hours fully to recover most of the recovery happens in the first couple of hours.  Ultimately its a function of your house, your emitters and yes the heat pump control algorithm as well as outside temperature, hence the impossibility of giving a definitive answer. 

Houses have a large heat capacity ("thermal mass") and the system has to deal with that.  My house, for example, has a heat capacity of about 15kWh/degC and a loss of 7kW.  This means that, even at -2 outside, it takes 2 hours to cool by 1C even if the heating is completely switched off.  Its therefore not surprising that it takes a while to warm up!.  Thus even if the rads were heated to 70C it would still only warm up at a little over 1C/hr if its very mild outside, half that rate if its -2.  Neither a heat pump nor a boiler, however sophisticated the algorithm, can do anything about that.

Is there a particular problem you are trying to solve or is the question  just for interest?

Posted by: @temperature_gradient

↑

I think the heat-pump manufacturers are going to have to raise their game on the control side, it

Thats why there is a market for Passiv, Havenwise Homely and Adia!  Some heat pump controls are really fairly simplistic in their operation (by modern standards), although still way more sophisticated than many boilers.  I think the first priority has to be user-friendliness however.  Many heat pump manufacturers effectively rely on installers setting up the weather compensation curve perfectly, which clearly they cant unless they live in the house during the cold season.

@jamespa no particular problem, just generally interested in how people would view such a situation.  Would 6 hours to recover from 21c to 22c be too much?  Actually, the start/end temperature isn’t that important - it’s not cold at 21c so you wouldn’t really care.  If it was taking 18 hours to recover from 19c to 22c I definitely would care,  it least because my wife would be bending my ear about how cold it is.

As I’ve mentioned, I have no access to any sort of detailed data so it’s hard to see what is going on.  My other thought related to this was perhaps it is taking so long because I’ve dropped the flow temperature too far and the heat pump is cycling to cope.  Maybe someone would recognise this and point out there may be an issue.  I assume not given no responses in this vein except perhaps hints from other posts on the data and graphs shown.

Really, it was just a general interest in people’s thoughts.  Since posting, I’ve turned off the setback I was using and further dropped the WC warm end temperature.  It seems to be managing although it only got down to 8c last night so it’s a bit early to tell.  My biggest problem is getting the house to warm evenly because of the thermostatic nature of operation.

On the control side, I see little reason for the majority of people to have a control for WC, holiday setback and overnight setback.  Once the thing is set up and running you don’t really want to be touching anything and getting it set up and running, once the installer has left, is generally a matter of tweaking the WC.  Under the covers there may be more going on but exposing it is probably just too confusing and unnecessarily worrying people.  Octopus hide a number of settings in their Cosy Hub, accessible only by turning on its web server and logging onto its network; some of these are further hidden behind an installer password.