@ivanopinion where are you up to and have you made any further decisions?

Posted by: @editor

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@ivanopinion where are you up to and have you made any further decisions?

I might change my mind again, but I'm currently unlikely to go with Aira, mainly due to their product being brand new, so an unknown quality. And worries about it being so dependent on them maintaining the app and cloud services for the life of the product. Although they are cheaper than Heat Geeks, the cost difference is relatively small, so between the two I favour Heat Geeks.
The other contender is Octopus, who are more than £7k cheaper than Heat Geeks, so are the clear winner if cost is the only determinant. Even assuming Heat Geeks gave me a SCOP significantly higher, I'd never claw back the extra cost in power savings. I'm waiting for Octopus to do a resurvey, one of the purposes of which is to reconsider the heat loss (and thus the size of ASHP). If they agree to a lower power ASHP, they will have fixed one of my main concerns. My other main concern is that they include a buffer in their system, but is it worth £7k extra to get an unbuffered system? If Octopus insist on specifying an overpowered ASHP, I think that will make it easier for me to justify paying the extra.
 

Interesting development: they have formed a partnership with Heat Geeks. https://www.linkedin.com/posts/airahome_airaheatgeek-cleanenergytech-decarbonisation-activity-7211360941412651008-5PCa?utm_source=share&utm_medium=member_desktop

They aren’t really specific about what it means, but I’m guessing heat geek will be training Aira staff. That makes Aira a more attractive proposition I think.

@ivanopinion I'm actually scheduled to speak to Heat Geek next week, so will be sure to ask them about the specifics of the partnership.

Posted by: @majordennisbloodnok

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touting seems to be focused on removing control from the customer's hands. That's worrying.

But could be sensible for 90% of the public that would change it to heat for an hour in the morning and 6 hours at night. Then wonder why they use so much electricity (immersion in buffer kicking in) and the house is cold.

Posted by: @ivanopinion

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The other contender is Octopus, who are more than £7k cheaper than Heat Geeks, so are the clear winner if cost is the only determinant.

The real difference in performance is gained by radiators and the size specified. Big rads low flow temps. Fully open system single zone. Save £7k run and see how low you can flow, if required spend another £1k upping the main living space radiators size. Save £6k

Posted by: @ivanopinion

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include a buffer in their system

Can you get them to plumb as a 2 port buffer? Then you only get flow through the buffer if zones are closed, keep them open nothing flows through it?

Posted by: @ivanopinion

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Octopus insist on specifying an overpowered ASHP, I think that will make it easier for me to justify paying the extra.

But only if minimum turndown is significantly different. As a good system volume (50L plus) will support 6kW without short cycling, nearly all heat pump turndown to that level. They are also specifying a buffer, if it's a 2 port all good, if 4 port lots of mixing likely and CoP hit.

Posted by: @johnmo

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Posted by: @ivanopinion

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Octopus insist on specifying an overpowered ASHP, I think that will make it easier for me to justify paying the extra.

But only if minimum turndown is significantly different. As a good system volume (50L plus) will support 6kW without short cycling, nearly all heat pump turndown to that level. They are also specifying a buffer, if it's a 2 port all good, if 4 port lots of mixing likely and CoP hit.

Octopus may be relying on their tarifs to compensate for any 'loss' in efficiency.  The risk of course is that tariffs change, and unless there are guarantees then, as usual, caveat emptor.

I would press for a 2 port buffer/volumiser in the return and ask about turn down to half the design loss, which is where the heat pump will be operating most of the time.

If octopus are still fitting Daikin then it's worth being aware that Daikin appears to cap the output of some of their models in firmware, to give the appearance that they offer more variants than is really the case (and of course offer opportunities for price differentiation).  The turn down power is not affected, so from an engineering point of view you might as well go for the highest power in any group of models which in fact have the same hardware.  Octopus will know this so probably specify the 'top' end of each group anyway, and doubtless have a deal with Daikin that they are not charged extra for the different arrangement of bits in the firmware.

Thanks to you and Johnmo for the comments. In my case, Octopus have pulled out as their policy is not to do any work on flat or sloping roofs, which means there’s no viable path for the pipes from ASHP to cylinder. So Daikin oversizing no longer a problem. My choice is Aira or £4k extra for a Heat Geek firm (or a further £9k for another Heat Geek firm). But many of your comments apply equally to Aira, who currently specify buffers as standard.

Perhaps Heat Geek will convince them this normally unnecessary. I’m wondering how long it will take for Heat Geek training to impact on the Aira policies for system design. Mars, can you ask?

I hadn’t appreciated the distinction between 2 and 4 port buffers. Is there an explanation you can point me to? Can you tell from the photos whether the Aira buffer is 2 or 4? 

By turndown, do you mean the lowest power that the ASHP can modulate down to? Aira have told me their 8kW model modulates to 3.7.

 

Posted by: @ivanopinion

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By turndown, do you mean the lowest power that the ASHP can modulate down to? Aira have told me their 8kW model modulates to 3.7.

Yes that is correct
If you don't mind me asking, are those prices after the grant? If so what are you getting for that money? I went self installation because I really couldn't be bothered with all the over pricing going on. Think my total install came to about £3k. £1200 for heat of eBay, £900 for cylinder from city plumbing. Then mostly pipe, fittings and insulation. Assume you need radiators also?

Some info on buffers

https://www.kensaheatpumps.com/installer/tech-focus-part-2/