Chz
Stark Raving Sane
That's my understanding, as well. It's not the most efficient way to heat a room, but it does significantly reduce draughts that make the room feel colder than it is.
Air source heat pumps
- Thread starter WouldBe
- Start date
lazythursday
Averagely-Known Member
Gosh. An extra hole. Oh my god people couldn't tolerate that.It warms the cold air from the window stopping cold 'drafts'.
Doubling or tripling radiators requires the pipes altering to them with possible extra holes needed in floors and carpets.
I will report back on the chaos caused by my fatter radiators in due course.
two sheds
Least noticed poster 2007
placed carefully over the front of the radiators to keep them nice and warmCurtains.
I've got magnetic strip secondary glazing which does cut down on draughts through the sash windows.
existentialist
Tired and unemotional
It's OK until that extra hole ends up having to be made in a solid (eg concrete) floor!
I was watching a YouTube video recently which suggested that, if you wanted to know how your existing system would cope with a heat pump, you should turn your boiler output temperature down to 50C, which implies that that's probably a typical flow temperature for a heat pump. I do think that there's a lot of rather black-and-white stuff going on around heat pumps, and that the truth lies somewhere in the middle, but I do also suspect that, like so many energy-saving initiatives in the past (double glazing, cavity wall infill, loft insulation, solar PV, etc) this one has also morphed into a bit of a "jobs for the boys" thing, with suppliers overselling the benefits just to get their foot in the door and their hands on the grant money, which does nothing to add credibility to the process.
Chz
Stark Raving Sane
I think the installation costs themselves are a piss-take. I reiterate that there's no reason why a heat pump install should on average be triple what a gas boiler would cost. It's just milking the government subsidy.
Heat pumps still have some room to get better, whereas gas boilers are pretty much as good as they can be. So in another 5-10 years when costs come down it will be an absolute no-brainer.
I've got my boiler set to 62C and it still works quite comfortably. I'm tempted to see how low it can go before I start getting annoyed at cold feet.
Saul Goodman
It's all good, man
Despite the name, the radiated heat from a radiator is only around 20% of its output. The remaining 80% is convection. Forced convection is more space efficient than passive.
If you're running a heat pump system, aluminium radiators would be my choice. They have a heat transfer coefficient about 5X greater than steel. Steel radiators would need to be ~2.5X larger on a heat pump system than on a conventional central heating system.
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Chz
Stark Raving Sane
This is true, but if you have the space steel is half the price.
Saul Goodman
It's all good, man
I think it's more to create a barrier of warm air. Hot and cold air don't mix very easily. It's why they have those hot air curtains over the doors of supermarkets, to keep the cold air out when the doors open.
WouldBe
Dislicksick
teuchter
je suis teuchter
Nobody's arguing that switching to a heat pump based heating system is always straightforward or even economical.Holes in carpets don't look good.
Holes in laminate floor would be even worse.
Just countering the myth that such systems simply can't be used in badly insulated buildings.
lazythursday
Averagely-Known Member
Well yes, your existing system isn't designed for the lower temperatures. Which is why generally you do need some alterations to radiators as well as the heat pump.
I don't really get this. It probably is triple the amount of work. In my house there's a load of new pipework between the pump and tank, total change within my airing cupboard and of course removing the gas boiler and whole supply. Plus the new radiators. It will take most of a week, whereas just swapping a boiler is a day.
Chz
Stark Raving Sane
I had all of that done (bar ripping out tank instead of installing) when I changed a CH system to a combi boiler. £3k. Granted it was 10 years ago, but inflation hasn't tripled since then. Completely new location and pipework for the boiler, new rads, and the pipework in the kitchen had to be installed in the concrete floor.
Definitely didn't take a week either, though it was probably 3 days.
Edit: I can see a 5kW heat pump (should be adequate for a 3 bed flat) rolls in at £1800, which is about the same as the boiler after inflation. So that's a lot riding on the labour. I'm willing to bet that installation prices - which shouldn't be affected by economies of scale, or efficiency improvements to the heat pumps themselves - will come down quite a bit once/if the government rebate goes away.
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Saul Goodman
It's all good, man
Assuming plumbers are still using copper, that's where a lot of the expense will be. A grand doesn't buy you much copper these days.
lazythursday
Averagely-Known Member
My install starts tomorrow. Quite stressed out about it to be honest - not the heat pump specifically, but the having yet more work done on the house. It's been about four months since this phase of work started (mainly new bathroom and insulation) and I'm really fed up of the disruption and the fact that every single time something goes wrong / something unexpected occurs.
On knocking out a cupboard wall to allow for larger tank, discovered a load of lead pipe between the old hot water tank and kitchen taps - that all had to be replaced last week because Octopus won't install where there is lead pipe. Still feel convinced they will find something else bad when they start.
Anyway I'm fucking off to the coast while they do it. Fingers crossed it all works.
On knocking out a cupboard wall to allow for larger tank, discovered a load of lead pipe between the old hot water tank and kitchen taps - that all had to be replaced last week because Octopus won't install where there is lead pipe. Still feel convinced they will find something else bad when they start.
Anyway I'm fucking off to the coast while they do it. Fingers crossed it all works.
existentialist
Tired and unemotional
Pretty sure it's all plastic these days.
WouldBe
Dislicksick
Can't use plastic within a metre of a boiler according to pipe manufacturer.
existentialist
Tired and unemotional
That's still going to save a lot of copper!
WouldBe
Dislicksick
Yeah. Just pointing out you can't replace all the copper.
lazythursday
Averagely-Known Member
Heat pump now installed and working, along with new radiators, water tank etc. House lovely and warm - currently set to 20 degrees on advice of installer who said the thermostats tended to overestimate, but it feels a lot warmer than my usual 18-19 so I'll adjust that when I've got the hang of it. House definitely feels heated more evenly, which I guess is mainly due to having all new radiators properly sized for the space. They're barely any bigger than the old ones. Only one is really noticeably a lot bigger and that is in a room that tended to be chilly before, so was probably undersized.
Happy so far. Now will start monitoring energy usage and tweaking.
Happy so far. Now will start monitoring energy usage and tweaking.
prunus
Tick tock.
This is absolutely key for any heating system. Since learning all about it (NB, it's not just raw space, it's about calculating the actual expected heat losses from each room, moderately complicated stuff!) for installing my heat pump it's become very obvious to me that a lot of (standard old-school boiler-radiator) installations have not been done that way - radiators have been sized to fit the physical location they want to put them in, not with regard to the job they are going to have to do.
two sheds
Least noticed poster 2007
I've read that portable heat pumps take air from inside the house with warm air being blown back into room and cold air expelled through exhaust hose stuck out of window. I'm wondering whether that gives some form of displacement ventilation effect. Anybody know?
I've also read that you shouldn't use single-hose heat pumps (i.e. the one I've got) because they're less efficient than dual-hose types. When I looked though I couldn't see any single-hose types being sold in the UK.
I've also read that you shouldn't use single-hose heat pumps (i.e. the one I've got) because they're less efficient than dual-hose types. When I looked though I couldn't see any single-hose types being sold in the UK.
WouldBe
Dislicksick
If it's expelling air out of the house then air will be getting in from elsewhere which will be cold air.
teuchter
je suis teuchter
What do you mean by "take air from inside the house"?
two sheds
Least noticed poster 2007
"Single hose portable heat pumps have one exhaust hose, which you stick out the window. The exhaust hose releases excess heat and moisture, while the heat pump absorbs air from inside the room, heats it, and releases it back into the room."
www.theecoexperts.co.uk
I think that's what it's saying, anyway
Portable Heat Pumps | Costs & Benefits in 2025
Portable heat pumps can be used to heat or cool a single room, using low-carbon technology. Read about all the costs and benefits here
www.theecoexperts.co.uk
I think that's what it's saying, anyway
