Multi-Split Air-to-Air heat pump - DIY?

[Ivor Windybottom]

Is fitting a multi-split heat pump a reasonable job for a fairly well experienced DIYer? I realise it needs a dedicated power feed to the outdoor unit, but other than that?

Access is really good - it's a concrete floored bungalow with a big loft. There's no existing system at all. So fitting pipes to radiators would involve drops down into each room, which is the main reason I'm looking at an Air-to-Air system. I'm thinking the pipes/cables to the outdoor unit would drop from the soffit directly above. Pipes to the indoor units would just need a short length of trunking up to the ceiling. No need for any core drilling at all.

Is the refrigerant gas even obtainable? I'm wondering if it's restricted, as it is a greenhouse gas.

I've seen lots of US-based YouTube videos indicating DIY is a sensible option. I understand I need a vacuum pump and torque wrench for the fittings.
Does anyone have experience of fitting one of these? I get the impression they're pretty popular in lots of the world but not very much in the UK, although they seem to be getting more attention recently.

I know there are low cost pre-filled DIY kits, but I'd worry about reliability and parts availability. I'm hoping I could buy a posh Daikin system and fit it myself, obviously after much more research and buying of tools.

Alternatively, I wonder if there are hybrid DIY/Pro options, e.g. I fit everything then a HVAC engineer and sparky visit to do their bits.

By the way, we don't have mains gas so that isn't an option. I don't want solid fuels or oil due to the fumes, mess and many other issues. Please no conspiracy theories about heat pumps being a big con or whatever!

Has anyone else done similar?

 

[Old Salt]

I have just had one fitted 2 months ago. Ex marine engineer, used to working on ac and refrigeration. You need specific certification to be working with refrigerant gases hence the pre filled systems. The additional cost of fitting was about a grand over and above the cost of a similar sized diy option. Now take into account the cost of the vacuum pump, all the brazing of connections and the hassle of crawling around in the loft.

I personally would not diy in this instance.

 

[Ivor Windybottom]

Thanks for the info. I suspected there were restrictions around the supply of the gas. I'll approach open-minded, for a difference of a grand I'd happily pay someone else to do it, but I was expecting a bigger difference as they're the latest thing.

If the prices are really silly then I may look at the option of me doing the install then someone else doing the vacuum and fill. I do know there are various risks to doing this, among them the risk of a kinked pipe. It seems weird that apparently fitters just hand-bend the copper tubes from what I've seen, due to them being within a wrapped up cluster of pipes and cable. No elbows, joints or even pipe bending springs. Perhaps the wrapping kind of acts like a bending spring?

I'm still at an early stage of working things out, I know very little at the moment.

I'm half about saving money, the other half is I like things doing carefully and I'm a bit of a perfectionist. With other projects I've usually regretted getting someone else in, but I'll do my best to let go!

What system have you got, and are you happy with it so far?

 

[Old Salt]

Mitsubushi, 5kw outdoor unit, 1 x 3 kw and 1 x 2.5 kw indoor. I live in a bungalow and only have it supplying the lounge and 1 bedroom.