All I can say from a very quick look, the first issue that hits me is space.  If you are considering siting your ASHP in that alley outside the window in your picture you will experience serious issues.  That site looks totally unsuitable.

Posted by: @samiebon1

↑

Hi all (first post),

I've had a survey and quote for an ASHP in our retrofitted 1907 house. 

Two different companies have spec'd 5kW size heat pumps. 

The challenge I'm having at the moment is locating the heat pump, given that they need maitenance/performance clearances, and R290 needs safety clearances. There are sub floor vents in places and multiple drains.

I've sketched up the outside area I had envisaged it going, though I'm struggling to find an R32/R290 ASHP that would suit. (Images attached).

Thought i'd use the forum hive mind to get any reccomendations or considerations.

Cheers!

-- Attachment is not available -- -- Attachment is not available --

I would be asking my installer (both installers) to tell me where they would install it since they are quoting. 
Then take them to task on why they would put it where they recommend.

Regarding limitations on position of R290… this is an outdated law which urgently needs to be reviewed. It’s because the gas inside a R290 is propane so it falls into gas safety requirements of any high volume outdoor gas appliance which might spring a leak near an opening window or door. However there is such a small and finite amount of gas in the heat pump that it doesn’t really match the reason for the law.

however there are all sorts of environmental and performance reasons why the R290 is more superior. It’s just that you are an early adopter with specific site limitations so you are breaking new territory.

post edit

Another major consideration is your access to your own garden without a cold blast of air in the area you like to occupy. Decide what you don’t want to compromise on. Convenient and comfortable access to your outdoor space is, or should be an important consideration. 

At a quick glance @samiebon1 I would be inclined to put the heat pump at the end of the alley (as far away from your window as possible), or even around the corner that we can’t see in the photo, where the air movement will be greater.

The R290 law as SUNandAIR says needs urgent changing, but that doesn’t help you.

Did your prospective installers not give you any siting suggestions?

Maybe consider a first floor wall mounted design. Check out Glyn Hudson’s self install on YouTube which looks like a similar position. 

@bontwoody Our installation has similar restrictive drains, doors and windows which was a pain; we went for daikin ASHP and that uses R32; with this, the restrictions no longer applied. Regards, Toodles.

@morgan Thanks - are you thinking air flow / noise issues or others? Definitely isn't the most ideal but its a common arrangement around me (Manchester) so someone going to have to find a solution at somepoint! Attached a better photo - had thought about the end of the wall but the bu-folds are next to it, also don't think my partner would accept it being there...

@editor copying you in as you raised similar questions. 

Looking at some Vaillaint installation documentation, one bit says 1000mm clearance out the front of the ASHP, some say 600mm. If its was 600mm, then I could technically make it work.

@sunandair both installers kind of were a bit flippant about location saying 'yeah it should be ok there' but something seems like its not been taken into account.

They've spec'd either a Vaillant aeroTherm Plus 5kW (R290) or EcoDan 5kW (R32) with the EcoDan specificed to address the clearance issues of R290. It has lower clearance figures required for maitenance but is quite tall and wouldn't fit under the window at the end (see image in response to Morgan at the top of thread).

I've heard about the outdated Propane limitation - hopefully gets sorted and allows more uptake.

Thanks @toodles do you have any photos of your install location that could help with my context? Just looked at your profile and looked up the spec of you Daikin ASHP. Its clearances and dimensions look like they would be suitable for one location i'm thinking (where the bins are in the image).

@samiebon1 I’ll take a few photos tomorrow and post them for you to see - sun has put its’ nightcap on now though. Regards, Toodles.

@samiebon1 If you are to site the ASHP in that alley I can guarantee you will have serious issues with air flow. A guaranteed 'cold well'.  If your installer is suggesting that as a viable site, I would recommend you look for advice from a different installer.

I doubt it could go in the alleyway anyway as it’s going to be within 1m of the boundary so won’t meet permitted development requirements