@cathoderay are you suggesting I am not being truthful? 

Downstairs in my kitchen was showing 13 degrees when the pump was turned on at 6pm. By the following morning at 9am it was at 18.5. In the living room of course we had the wood burner on which helped. Just like the person asking the question has.

the house is pretty low heat loss. I built it myself in 2016.

the immersion brought the water up to temperature quite quickly.

The upstairs of my house was at 15 degrees at 6pm. By just after 10 we had 19 degrees.

downstairs is underfloor and took much longer, apart from the living room and areas close to it.

@marvinator80 - I was suggesting that "It was turned on at 6pm and from a cold start in -10 temperatures and dropping we had heat and hot water that evening" seems unlikely given what we know about heat pumps, and could be misleading, as in misleading people into thinking that heat pumps can achieve more that they normally do. May I politely suggest that part of the problem is the brevity and consequent lack of clarity in your statement.

A cold start? A cold start for what? The house? The heat pump? If the house was already 13 (kitchen) - 15 (upstairs) degrees when it was -10 and dropping outside that is not a cold start. It now turns out that you also (a) had a wood burner in operation at the time and (b) the hot water was heated using an immersion heater. "We had heat" is also vague - it could be that you meant the house was warm (it was warm-ish in places, but not everywhere and a proportion, perhaps a significant proportion of that heat came from the wood burner) but equally "we had heat" would true if you had a guttering candle in the corner of a dark room, you would have heat, only not very much of it.

I personally find it much more useful to have specifics, ie actual temperatures , times and what was in play at the time. Thanks to the extra information you have kindly provided in your latest post, we know now that, over a period of 4 to 15 hours, a low heat loss house in -10 outside managed to raise the indoor temperature of a not that cold house by a few (max 5.5) degrees in some rooms and get hot water by using a combination, relative contributions unknown except for the immersion heater/hot water, of wood burner, immersion heater and heat pump. I do respectfully suggest that is a rather different picture to the one painted by your earlier statement, and it seems a more realistic picture, given what we know about heat pumps.  

Posted by: @cathoderay

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@marvinator80 - I was suggesting that "It was turned on at 6pm and from a cold start in -10 temperatures and dropping we had heat and hot water that evening" seems unlikely given what we know about heat pumps, and could be misleading, as in misleading people into thinking that heat pumps can achieve more that they normally do. May I politely suggest that part of the problem is the brevity and consequent lack of clarity in your statement.

A cold start? A cold start for what? The house? The heat pump? If the house was already 13 (kitchen) - 15 (upstairs) degrees when it was -10 and dropping outside that is not a cold start. It now turns out that you also (a) had a wood burner in operation at the time and (b) the hot water was heated using an immersion heater. "We had heat" is also vague - it could be that you meant the house was warm (it was warm-ish in places, but not everywhere and a proportion, perhaps a significant proportion of that heat came from the wood burner) but equally "we had heat" would true if you had a guttering candle in the corner of a dark room, you would have heat, only not very much of it.

I personally find it much more useful to have specifics, ie actual temperatures , times and what was in play at the time. Thanks to the extra information you have kindly provided in your latest post, we know now that, over a period of 4 to 15 hours, a low heat loss house in -10 outside managed to raise the indoor temperature of a not that cold house by a few (max 5.5) degrees in some rooms and get hot water by using a combination, relative contributions unknown except for the immersion heater/hot water, of wood burner, immersion heater and heat pump. I do respectfully suggest that is a rather different picture to the one painted by your earlier statement, and it seems a more realistic picture, given what we know about heat pumps.  

  

  

It was very, very obvious that I meant a cold start for the heat pump as it it being turned on for the first time, given this is the topic of the thread as opposed to the thermal mass of houses. 

it was turned on at 6pm, the temperature was -10 outside and that evening we had hot water and heat coming from radiators. Those are facts. 

Yes, we had a wood burner going in the house but I did not say otherwise. I even said explicitly that we had a wood burner and posted a picture of it. The person asking the question also has a wood burner.

Is using the ASHP’s immersion when starting it for the first time illegitimate in some way?

@cathoderay

This is an example(not mine) of a 5kW samsung on a 3.5kW ish Heat loss at -3 house, reheat after holiday, HP only, DHW 2 days later

https://emoncms.org/samsung5kw

Posted by: @marvinator80

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It was very, very obvious

I'm sorry, but what may be obvious to you as the writer is not necessarily obvious to the reader. I took it to mean an all round cold start, not a cold start of the heat pump supplying a house that was already quite warm and not only that had two additional heat sources running (wood burner and immersion heate).

The topic of this thread is "ASHP decision: Should I or shouldn't I?" and it important at least to me that when claims are made about heat pump performance the relevant material facts are presented, not assumed to be presented, or posed as part of a sort of 'just because I didn't disclose X, it doesn't mean X was or wasn't part of the picture' game. I have no way of knowing whether you deliberately sought to mislead, or whether it happened by accident, but the fact is at least one reader was misled.

"Is using the ASHP’s immersion when starting it for the first time illegitimate in some way?" Of course it isn't, each to his own etc, but failing to mention it as part of the picture could be said to be less than perfectly legitimate. 

@fazel - that is much more what i would expect, and the chart is 1000 times more informative than vague statements that may or may not mention relevant facts. If you zoom in on the room temp in the lower chart:

you can see it took over 12 hours to get from 11.4 to 17.4 degrees, but then also look at the subsequent rise in temperature: assuming a design temp of 18 or 19 degrees, it took another 24 hours to get there. This, I suggest, is more typical of of heat pump performance, and is certainly typical of mine when run in standard weather compensation mode (and no secret little helpers). 

Posted by: @cathoderay

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Posted by: @marvinator80

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It was very, very obvious

I'm sorry, but what may be obvious to you as the writer is not necessarily obvious to the reader. I took it to mean an all round cold start, not a cold start of the heat pump supplying a house that was already quite warm and not only that had two additional heat sources running (wood burner and immersion heate).

The topic of this thread is "ASHP decision: Should I or shouldn't I?" and it important at least to me that when claims are made about heat pump performance the relevant material facts are presented, not assumed to be presented, or posed as part of a sort of 'just because I didn't disclose X, it doesn't mean X was or wasn't part of the picture' game. I have no way of knowing whether you deliberately sought to mislead, or whether it happened by accident, but the fact is at least one reader was misled.

"Is using the ASHP’s immersion when starting it for the first time illegitimate in some way?" Of course it isn't, each to his own etc, but failing to mention it as part of the picture could be said to be less than perfectly legitimate. 

what does all round cold start mean? Was my house supposed to be at -10? Should I have kept the wood burner off and opened all the doors and windows during the installation in anticipation of this discussion?

When our boiler was removed and the ASHP and tank was installed we did not have immersion heating available. It was only when then these systems were switched on that we could fairly quickly heat the hot water and then we were fairly quickly able to get heat coming out of the radiators. 

The underfloor took longer to get going but that’s also a feature of underfloor heating generally rather than ASHP.

you say the house was relatively warm. I don’t consider 13 and 15 degrees to be relatively warm. 

the conditions I have described are applicable to the question being asked by the OP. If he was having an installation done I wouldn’t expect his house to lose all of its heat during the installation process and especially if he does so in better weather than I did.

I have posted facts, and I am happily to provide any further clarity when asked. That you have been misled is on you and my view is that you have chosen to be misled because for some reason you don’t like what you are reading. 

The immersion is part of the functionality of the pump, so what is the issue with what I said? 

Posted by: @cathoderay

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@fazel - that is much more what i would expect, and the chart is 1000 times more informative than vague statements that may or may not mention relevant facts. If you zoom in on the room temp in the lower chart:

-- Attachment is not available --

 

you can see it took over 12 hours to get from 11.4 to 17.4 degrees, but then also look at the subsequent rise in temperature: assuming a design temp of 18 or 19 degrees, it took another 24 hours to get there. This, I suggest, is more typical of of heat pump performance, and is certainly typical of mine when run in standard weather compensation mode (and no secret little helpers). 

maybe your pump or install isn’t exactly the same as mine, Ray.

I would definitely recommend Grant to anyone and a grade 1 Grant installer on a property like mine. 

@marvinator80 Ah now… When you say “If he was having an installation done I wouldn’t expect his house to lose all of its heat during the installation process and especially if he does so in better weather than I did”. This rings a bell for me as we had our installation carried out from the end of January to the middle of February 2023 (why so long? A long story…) During that time, the first thing done was ripping out the old gas boiler so, from day one, no heating and we had to use the immersion heater for DHW. Probably a common factor with many installers is that they can only work with all doors and windows wide open! Being brass monkey weather at that time, my wife and I were attempting to live in one room with the door shut and the now removed gas fire keeping us warm. We did manage to warm the house slightly at weekends by using fan heaters - but we were very pleased when the work was completed and the ASHP commissioned. The level of heating in the house was minimal as just the one room had heating to make that space habitable. The commissioning took a few hours and I think the system had been running for about 6-8 hours by the time the installers left at 18:00 and by mid-evening, we were feeling distinctly warmer and fairly comfortable by 20:00 (Our DHW is handled by the Sunamp Thermino so no load on the ASHP) Your mileage may vary! Regards, Toodles

Posted by: @marvinator80

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That you have been misled is on you and my view is that you have chosen to be misled because for some reason you don’t like what you are reading.

That is a curious spin on being mislead and some might even say the phrase 'chosen to be misled' is something of an oxymoron. Perhaps a better term for doing what I did not do might be being disingenuous. Be that as it may, I stick with my original assertion that as originally posted your statement was short on the facts, and as a result left at least one reader misled.

Like @toodles and I suspect many many other having a heat pump installed, I had a lengthy installation period, weeks not days, and as it was also in winter (February 2022 for me), it was cold and I had a mains electric heater to keep at least a room at a bearable temp, but the house was cold, and so the cold start for me meant from a cold house, with no other heating bar that mains electric heater. Here's a quick and dirty chart of my kitchen room temp during the installation/start up period: 

As you can see, the kitchen with the heat pump not running was about 11.5 degrees. When the heat pump started up, seen in the three risers, it took not hours but days to get the room (and house) up to design temp. Even the third warm up, which is better than the first two, took a whole day. My point is that for someone trying to decide 'should I or shouldn't I', they may well want to know that the above chart is probably a more realistic picture of what to expect, rather than a brief blase statement that asserts that they can expect to be warm within hours, that unfortunately fails to mention that can only be achieved by not letting the house get too cold in the first place, running a wood burner, turning on the immersion heater and, for all we know, firing up the secret nuclear reactor in the shed at the bottom of the garden.

@cathoderay

You've let the cat out of the bag now, mentioning the nuclear reactor. Shame on you. 😋 

@cathoderay whatever you say, Ray. 😆

I must try to remember in future that I have to make sure any post I make going forward is tailored to your liking and meets your standards of content rather than addressing the situation presented by the OP. I should have known that your installation lasted weeks for some reason and that you were using just a mains heater to try to battle the elements.

*whispers to OP* we had hot water and heat within a few hours of the ASHP being turned on, even though it was -10 outside. You are allowed to use the immersion on your new ASHP system to get the water temp up quickly. That’s part of the functionality of the system. You are also allowed to use your wood burner to provide comfort during the couple of days installation.