Should I ditch the installers and DIY my ASHP?

[jimseng]

I have had 3 quotes for my ASHP install on my new build. The cheapest was 10K for a 5k system but they have just come back with a re quote and it is now 12.7k, which is pretty much what the others came to. So I have got a bit fed up and decided to look at a DIY install. My plumber suggested he would do it last year and said I could get MCS sign off and claim the BUS grant and at the time I thought it was a lot of hassle for little gain. Since then I have established that the ASHP installation market is full of contradictions so I thought I should look at this again now I have more knowledge.
I am building an efficient 3 bed house with MVHR, UFH on both floors with very high insulation. Total heat loss circa 3.3kw. The latest heat loss survey showed the heat output of the floors to be between 150 - 200% of requirement at a flow temp of 35 degrees. 
So I have always planned to run the system completely open loop. Total UFH volume on both floors is 105 litres so I have been advised I don't need a volumiser, which is a good thing as space is tight in the plant room.
Now the thing is I have been quoted for a Samsung Gen 7 5kw unit and a Grant 4kw unit. I am planning on a 250l UVC. The thing is there are so many choices and brands so I thought I would ask you good people for some pointers as I don't know whether there is a huge difference between brands. Whether I should look at a kit etc. I am not actually going to do this myself, my plumber will but I am probably going to spec much of it myself. I am based in Somerset.
Thoughts?

[ProDave]

I recon from experience 2 days of electricians time and 2 days of plumbers time to install one on a new build.  And I am in the camp that does the sums on that plus materials cost and wonder just how most of the companies that quote get figures as high as they do.

 

If you are going for self install, then look at the other option, some companies will supply the kit for £0 using the grant for you to install.

 

MCS sign off for a heat pump is not mandatory, in fact I struggle to see what that expensive bit of paper will actually do for you.

[saveasteading]

28 minutes ago, jimseng said:

going to spec much of it myself

Your plumber may be limited in choices if they use a single merchant, as many do.

Best discuss with plumber ASAP.

 

Try talking to Trade Underfloor Supplies or similar. They supply the whole kit and I'm sure many plumbers get it done this way. But check you get the grant benefit.

[JohnMo]

Timings as @ProDave says is pretty real.

 

If your using a ToU tariff, I do and have the following 

4kW heat pump - Hiaer monobloc. 

Then a use a direct UVC, so is charged via immersion (have plenty of solar also). Heat pump is then not trying to do heating and DHW in a cheap period, they are independent of each other.

 

Going that route 

Heat pump under £2k when you claim the vat back.

Cylinder £600 incl vat. Drive via simple time switch. £20.

 

Plumbing very simple. You have loads of water volume.

[LaChab]

It's probably not very relevant to you, but I've just self installed a 5kw Samsung Gen 7 with a 300l Oso using the "umbrella" scheme for an overall "profit" of about £1000. Free heat pump!

If you do the course you can get a 7 year warranty for it.

Our build sounds rather different to yours, but as we're in North Somerset you're welcome to visit for a look.

[Square Feet]

Glyn Hudson on YouTube has some really good videos on DIY ASHP installs. Very technical and not flashy or clickbaitey.

https://www.youtube.com/@GlynHudson

[jimseng]

3 hours ago, ProDave said:

I recon from experience 2 days of electricians time and 2 days of plumbers time to install one on a new build.  And I am in the camp that does the sums on that plus materials cost and wonder just how most of the companies that quote get figures as high as they do.

 

If you are going for self install, then look at the other option, some companies will supply the kit for £0 using the grant for you to install.

 

MCS sign off for a heat pump is not mandatory, in fact I struggle to see what that expensive bit of paper will actually do for you.

I didn't fully understand this. Are you saying I can get the kit using the grant and don't need MCS sign off? I agree that MCS is a waste of time but don't the BUS grant people need it for the voucher?

[jimseng]

@LaChab
What is the umbrella scheme? Can you expand on that a bit?