So we did it.
Over four days in the third week of June three or four guys made a colossal mess of everything while they replaced 9 radiators (including two extremely heavy column radiators in the bathrooms that I had bought separately), removed the gas boiler, put a hot water tank in the airing cupboard and heat pump bits outside and in the loft. Either I misremembered the power of the outdoor unit or it changed at some point in the process but it's a 6kw unit, not an 8kw one as I wrote before. This pretty closely matches the heat loss from the surveys we've had, so it's unlikely to be oversized, I guess we shall see in winter if it's undersized, hopefully not!
They said it would take four days which seemed optimistic, especially when it seemed to take a long time to get the pressure relief valves piped to the outside world from various places, which felt like the most disruptive bit of the whole process despite being nothing at all to do with the heat pump! They sort of did it though; on the last day, a Friday, they were here until gone 7pm instead of the normal 4pm and they seemed a bit rushed towards the end, but one guy came back for a few hours on Monday and sorted a load of little things out. He also went round showing me what everything was in pleasantly surprising detail, over the whole system, much more than a quick poke at the controller.
We had one important but also minor snag depending on your viewpoint; to start with everything worked fine but the airing cupboard door slightly touched the tank before closing properly so it took a visit to shuffle the tank back a bit, then that caused a small leak with an old pipe joint that we didn't spot for a week. Everything was sorted pretty quickly though, so I'm happy with how it went.
The main install also happened during one of the heatwaves and it got above 40 degrees in the loft and low 30s outside, but they still worked like trojans throughout. The front and back doors and loft hatch were open pretty much all week so it was difficult enough trying to keep the house cool, but I can't imagine what it's like in winter with doors open and no heating for days...
I guess nobody completely finishes all the touch up jobs required afterwards so I've got a short list of small painting, filling and sanding jobs to do and I have a feeling some of the loft insulation has not been put back properly which needs checking before it gets cold again. We've certainly had tradesmen who have done smaller jobs but left more finishing up to do, so I'm not too bothered about that. I also need to find a home for all the stuff that used to live in the airing cupboard that seems to be now 1/3 free space, 1/3 water tank and 1/3 pipes going everywhere. Ours is a pretty small airing cupboard (hence the tank/door problem) and there's not as much space above the tank as I thought there would be due to an expansion vessel and random pipes (there are so many pipes compared to a combi) but I can make some shelves that fit in the space that is left.
The indoor circulation pump is where the old boiler was, and it is quieter than the old boiler, but because everything else is now silent the noise of that does stand out a bit. Some anti-vibration pipe mounts and a bit of acoustic insulation might hopefully improve that a bit, I'm not quite sure why they don't install those by the pump as standard.
I still like the look of their outdoor unit, I much prefer it over any other I've seen. When their salesperson first came round they had an app that could show a mockup of what it would look like; actually it's quite a lot shorter than that showed (and how I measured it too; as standard it's on quite tall feet, but ours isn't) so it fits under the kitchen window better than I thought it would. We're having some garden work later in the year so hopefully with that and a few plants nearby it will fit in well enough.
We haven't used the heating yet obviously but when they were testing it the radiators and pipes were a lot quieter than they used to be with the gas boiler. The wait for hot water to come through is greatly reduced from the old combi, and the flow rate is
much higher too; my daughter has had a few really deep baths recently when I've forgotten that the bath fills up a
lot quicker than it used to! It was a 37kw combi but the flow rate is much higher from the tank, I'm not really sure why. Having hot water without having to listen to the boiler slowly cranking up is generally a much more relaxing experience.
The app is pretty basic but seems to do everything it needs to. I wouldn't complain at all if they added Home Assistant integration at some point but it's far from a deal breaker, and I've got a shelly unit on its mains supply so I can compare it to previous years. The app gives some basic energy consumption / heat production statistics; it says the COP for hot water this month has been 3.6 but with the various visits and how much the system has been played with I don't know how representative that is yet, or what you would normally expect from a half height tank that presumably has a fairly small coil. Either way, on cheap rate electricity and with no gas standing charge any more that's a tiny fraction of the cost of gas so I'm not that fussed about it. It can do clever things if you tell it the details of your TOU tariff, but when I tried that it ran a hot water cycle mid morning one day so I've set it all up manually instead and haven't looked into any of that since. The app has had one fairly large update in the time I've had it, and to start with it showed a different amount of hot water remaining in two different places which it doesn't seem to any more, so there seems to be quite a lot going on behind the scenes in that regard.
Octopus seemed to stop billing us for gas, including the standing charge, from the day I emailed to ask about removing the meter; it was physically removed about a week later. What can you do with an old gas meter cupboard?
Roll on winter and we'll see how well it works when we need some heating. It must make it very awkward for installers to do loads of installs when the weather is nice and not really be able to test them properly until they all get tested in anger when the first cold snap comes...
I'm happy with how it went and the system we've ended up with. I think we did quite well on price so I'm not sure how valid that comparison would be but after our experience I would recommend them.
