@rikiarn Out of intrigue, the thread reads as though Aira and Octopus are the only installation options you have considered, along with the Heat Geek option that was ruled out as being too expensive?

I'm not wishing to throw a spanner in the works, but you still have the ability to cancel with Octopus without penalty right up to the day of installation.  If you are unconvinced by the Daikin unit offered, or the proposal they're offering, is it worth you speaking to local, reputable installers (non-Heat Geek branded ones won't necessarily carry the 'premium' pricing) and/or some of the other energy companies to see if they can offer an alternative option, even at this late stage?

I've just gone through a quotation and installation process, during which I spoke to a lot of companies.  Of the big energy suppliers, EDF were very helpful in my discussions on difficult technical challenges (in my case a conservatory with a large calculated heat loss), even though I didn't ultimately use them.  When you call them you're actually speaking to a company called CB Heating, who are a heat pump specialist company that was purchased by EDF to do this work under their name.  It might be worth a phone call, at the very least.

Does your installation require a large number of radiator changes?  This was where I found that the local companies were less able to 'bundle' them into the cost, as the larger suppliers were.  If you have relatively few, this might not make as much of a difference in price.

Regardless of anything, I wish you the best with your plan to have an installation carried out.

@sheriff-fatman sorry for the delayed reply. We had few quotes from other local installer but some wanted a non refundable deposit for the survey and other had very long lead time. With regards to other energy company we like Octopus ethos and how they operate and would struggle a lot having an installation from a company that still invest a lot in Gas ( but this is personal preference)

At the end we had the installation completed from Octopus two week ago and to be honest it was hassle free, aside from a moment where it appears we had to get rid of everything gas related to get the grant( I posted another thread on that) which got solved. The engineers were really helpful and as far I we know they have done a neat job. 

I attach photo of the install. We have only used for DHW at the moment and find it amazingly quiet compare to what we expected.

Not sure how the buffer is working as it has been plumbed only top to bottom. I read numerous post on how bad buffer tank are for the heat pump, but find strange how in Italy are considered essential. 

@rikiarn 

Delighted to hear that the install went well.  It looks neat.

Posted by: @rikiarn

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Not sure how the buffer is working as it has been plumbed only top to bottom. I read numerous post on how bad buffer tank are for the heat pump, but find strange how in Italy are considered essential. 

That buffer tank looks like its got only 2 connections, which is also what you appear to be saying.  In this case, provided both connections are either in the flow or in the return (not one in each), its a volumiser not a buffer.  These are just fine, unlike 3/4 port buffer tanks - which in principle can also be fine if correctly installed and controlled, which is rarely the case.

Fancoils are more popular in Italy than here and, they have very little volume of water in them compared to radiators.  This may be why extra system volume is considered essential in Italy.  Both a 2 port volumiser and a 3/4 port buffer tank add to system volume, the thing about a volumiser is that its almost installer-proof unlike a buffer which definitely is not. 

@rikiarn It's a not a buffer it's a volumiser which is not the same thing. It helps keep the system on its toes during defrosts in the winter, for example. It has no impact on efficiency. So no worries. 🙂

Oh I just read James' post. 🫢

Anyway, I have the Daikin 6kw and have been very pleased with it. It was excellent last winter. Octopus have been good too and quick to respond when I needed help briefly.