Heat Pumps: anyone have one/thought about it?

b0rn2sk8 said:
Pretty much all sensible low carbon water heating options require a thermal store of some kind.

The point above about knowing what you are doing is not about the physical installation of pipe work, it’s about the design of the system itself. Understanding the theory and the practical application of it. Even something as small as using the wrong valves can impact performance because of the pressure loss.
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Yeah I know the whole designing for low temperature flow rates and calculating deltaTs. Been there done that. My boiler happily runs along at minimum most of the time with flows below 30c.
I am slowly in the process of changing the radiator valves to the newer self balancing ones as it's impossible to balance as it is.
 
I'm sure I saw some dodgy lifetime savings stuff. Ie it's so marginal it's not worth it.

And it completely omitted having to retrofit your house with possibly 10s of k of insulation, piping and rads.

If homes were built better, or would be different. But here we are
 
413x said:
I'm sure I saw some dodgy lifetime savings stuff. Ie it's so marginal it's not worth it.

And it completely omitted having to retrofit your house with possibly 10s of k of insulation, piping and rads.

If homes were built better, or would be different. But here we are
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The insulation point isn’t relevant, the heat pump is slightly cheaper to run than a boiler so the less insulation you have, the bigger the savings.

The lifetime costs point should include all installation costs and most houses don’t need significant work to re-pipe them.

The irony is actually that older houses often have high flow pipework and large radiators installed already to account for their larger heat loss when the system was installed. Those houses may have subsequently had double glazing, wall and improved loft insulation installed making the radiators oversized.

That makes retrofitting a lot cheaper compared to a newer property that has smaller rads and micro bore pipework because it was better insulated from scratch.
 
b0rn2sk8 said:
The insulation point isn’t relevant, the heat pump is slightly cheaper to run than a boiler so the less insulation you have, the bigger the savings.

The lifetime costs point should include all installation costs and most houses don’t need significant work to re-pipe them.

The irony is actually that older houses often have high flow pipework and large radiators installed already to account for their larger heat loss when the system was installed. Those houses may have subsequently had double glazing, wall and improved loft insulation installed making the radiators oversized.

That makes retrofitting a lot cheaper compared to a newer property that has smaller rads and micro bore pipework because it was better insulated from scratch.
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I know for sure we'd need bigger radiators. A lot of ours are single. We'd probably need new windows too.

Everything I've read suggests heart pumps do need you to have a better insulated house due to inefficiency at colder temps.. Ie when you need heating.

I wonder if we'd even need new piping. But I'm not that clued up on if that's BS or not.
 
The way the insulation point is portrayed is a bit of a myth. It reduces your heat loss which is great because it reduces overall running costs, but it also does the same for gas so it’s all relative.

It’s not actually a requirement to have good insulation install one, as with a gas system, if the heat loss is bigger, you spec a bigger system.

In practice, improving insulation can make installation easier so there could be a trade off. For example a small reduction in heat loss may mean you can get away with existing micro bore piping. It may have no impact what so ever on install costs, it depends on each individual property. That’s why the typical installer mentality of licking your finger and plucking out a 30kw combi ‘cuz it’s a 4 bed’ doesn’t work anymore (and never really ‘worked’).

You may or may not need new piping, it depends on what’s there and what’s needed. No one can really say either way because every house is different.
 
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It may come to a point that insulation of the property could make a difference between running the heat pump at 45c or 55c or even higher. The efficiency of the heat pump will change massively then again it is like chicken and egg, If the radiator and pipe is big enough then just flow more 45c water and over come the heat lost in the really cold weather. If the radiator or pipe is not big enough then crank up the flow temperature and pump more heat to cover the heat loss at the expense of COP.

I really hope my survey will show some light on how the calculations are made and what are the restriction of installation ASHP, I have paid the £500 deposit and waiting for a free Friday slot for the survey.

I am also following the Octopus own heat pump, apart from cheaper, make in UK and the funky look it does not look like any new tech involved.
413x said:
I know for sure we'd need bigger radiators. A lot of ours are single. We'd probably need new windows too.

Everything I've read suggests heart pumps do need you to have a better insulated house due to inefficiency at colder temps.. Ie when you need heating.

I wonder if we'd even need new piping. But I'm not that clued up on if that's BS or not.
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I have a relatively new house (about a decade old) so should think that the current insulation levels etc are good for a heat pump.

The only Gas burning thing is my Combi boiler, I don't currently have a hot water tank or anything.

Gas consumption last year was 4000 kWh at a cost of £425 for the year including standing charges. I was probably a little stingier with the heating than I usually would be given the higher pricing, but typically I think that would be say 5000 kWh if I was using it more normally.

I have Solar and Battery so can take advantage of a wide array of tariffs and import/export options to keep average electric price down, would be nice to remove gas SC but it looks like that's only £100/year or so currently.

I've asked Octopus, they've given me a quote, I can pay a £500 fully refundable deposit, and then maybe things like figures and locations/feasibility can be looked at in more depth.

I'm weighing up this cost vs the potential for my gas combi to die and need replacing, and if that were to happen, I'd probably wish I'd just pursued ASHP instead.

£3620 fully installed and with a new tank doesn't seem terrible to me. Not sure where the tank would go mind...

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fish said:
when i looked i thought octopus said they didn't do loft installs. I may be wrong though
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Guy I spoke with didn't outright say no, will keep the thread updated but surveyor appointment is 3 weeks out as I couldn't do the one they offered for 2 weeks away.

Boiler cupboard will presumably be empty afterwards as well, depending what kind of tanks they can do, not sure if one could not got in there, or if it needs to be a huge one. Cupboard isn't gigantic and water tank may be a lot heavier.
 
Watching this thread with interest. I'm with Octopus currently and would entertain a heat pump if the retrofit does not mean spending 5k plus but would only consider a water tank in the loft which is the only real practical place it could be located (location of the current combi boiler). I suspect my 10 plus year old Worcester Greenstar will fail eventually and my current thinking is to simply replace with a current comparable model.
 
darkgen said:
Watching this thread with interest. I'm with Octopus currently and would entertain a heat pump if the retrofit does not mean spending 5k plus but would only consider a water tank in the loft which is the only real practical place it could be located (location of the current combi boiler). I suspect my 10 plus year old Worcester Greenstar will fail eventually and my current thinking is to simply replace with a current comparable model.
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Pfft. 10 years. I think the boiler here is 20 years old! :D
 
I had a quote and a conversation with the Octopus installers earlier this week.

The price was good, £6k (inc £5k grant). I know I need a lot of remedial work to the heating system because of what’s installed now. I’ve got is a 20 year old Range Powermax on a vented radiator loop (delivers mains pressure hot water).

It’s not actually that much more than getting what I have replaced with an unvented cylinder and gas boiler based on what my neighbour paid in 2018. A combi would be cheaper to install but you lose the mains pressure hot water and the ability to heat with solar.

From the conversation I managed to gleam a few things. They are targeting flow temperatures of 50C and SCOP of 300%. It will be cheaper to run than a gas boiler based on that efficiency and lifetime costs will be in your favour.

I’d not want to go any lower on the SCOP for it to work out against gas. When you have the survey, see if there are any additional quick wins they can do (extra charge no doubt) to bring the peak flow temp (50c) down and therefore the SCOP up.

I forgot to ask if they install weather compensation - it’s quite important for efficiency. The 50C flow temp will be based on a -2 outside temp and 21 internal temperature. When it’s not -2 or you are just heating to set back temps, you’ll want the system to automatically bring the flow temp down to stop it cycling (on, off, on, off etc).

I’m pretty close to pulling the trigger, I think I’d want to speak to some other installers first and see what they can do in terms of target efficiency and cost. If Octopus can do it for that price, I’m sure others can as well.
 
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If you’d like to look at real world examples, there are some UK based ones here: https://heatpumpmonitor.org/

Watch out for the data length column. You want a full year to see a true SCOP.

The equipment to log this level of detail is quite expensive so the people logging on that page are probably very keen and working hard to improve efficiency - so it’s likely to be a slightly skewed view.
 
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