Can an air source heat pump work in an urban property?

The short answer I’m finding is NO!

I booked an engineer for a heat loss survey in preparation for the install of a heat pump and have been shocked by the first point mentioned by the surveyor/installer. From what I have been told you have to have a one metre boundary between the heat pump unit and any door/window/drainage. As far as I am aware this is because of potential leaking of noxious gasses from pump and the gasses used having a lower density (hence could block drainage) than air.

You are also not allowed to install a heat pump within one metre of the boundary of your property without planning permission.

These two issues combined mean that I would need to have a heat pump in the middle of my (limited because town/terraced house) garden which is both unsightly and would require a lot of work digging up of existing work.

In short I cannot see how this then becomes financially viable for people in my situation (a lot of people live in terraced housing)? Am I missing something?!

see image below of rear of my property…no one metre (radius) gaps anywhere!

This is all news to me. I’ve had an Air Source Heat pump installed in January 2020. It’s a few inches from the wall of my house between the kitchen window and the bathroom window. I was assured no planning permission was needed - and I checked that out for myself*. Not long after it was installed, some council workers came round to have a look (unofficially) and ask me about it, because they were going for training themselves. Most of the properties around here are council owned and many are terraced. They are planning to install them in all properties, or so I was told. The pump does have to be one metre from the property boundary, though, so I can see that being an issue in some places.

As for the gas issue - surely the gases used are the same as (or similar to) those used in fridges and freezers?

Interesting! If having it on a terrace house is a potential issue, I wonder how/if it would work on a block of flats!

The one meter away from the window bewilders me as this makes it very difficult to make the install. I wonder when these regulations came in?

Hi Libby and all Jumping in very late here! Can anyone advise re how noxious these gases are? What are the dangers?

Hi Stuart

One of the gasses used as a propellant in the heat pumps is Radon. Radon is 7.5x heavier than air so it is dangerous to have near a drain as it can block them. I don’t know about propellants/issues that can affect door or window openings.

My Grant ASHP uses R-32(Difluoromethane)

I had it installed in January 2021, not 2020 (as I mistakenly said above). It’s close to a drain - there have been no problems.

Thanks for this response. I think this is going to be problematic for us due to multiple drains and openings. A bit more research here needed I think…

Thanks Libby.

Hi all.

So here’s my understanding after some research:

UK regulations state that an ASHP should be placed 1) 20cm from a house wall, outside, 2) the other side, expelling air, should be at least 1m from the home exterior window or door, and 3) this side needs to be again another 1m from neighbouring properties.

These regulations, I have been told, are in place due to noise. These are not in place for pollution where an ASHP may give off noxious gases.

I have been told that the only way noxious gases may escape an ASHP could be if they become damaged. This is unlikely. They are designed to hold in the refrigerants that could cause health issues etc. Further, these are contained within the pump in small amounts, within a cylinder. Once this cylinder is empty, it will not emit further gas. The gas contents will empty into open air and dissipate, being unlikely to enter a house, drain or cause problems at all.

The type of system installed may keep all gas containing parts of an ASHP outside. But alternatively may pump them within a house interior. The installers vary in how they wish to install. As with a refrigerator, these gases should not escape.

I phoned a few installers today. The advice above is mostly based on the most coherent chat I have had - with H2Eco in Poole. They seemed quite on the ball. The man I spoke with unfortunately also informed me that although the RHI is available until end-March, that I should avoid anyone who states to fit us in before that date. All trusted traders in this area will 99.9% be fully booked up.

Hope this is useful. Stuart

I just want to add - that I am sure I read on here somewhere about a new scheme for training heat pump installers, running at a national level.

If anyone can point me in the direction of this info, this would be greatly appreciated?

AFAIK it depends on the unit.

The Mitsubishi Ecodan, specifically, is classed as “ultra-quiet”, which avoids some of the planning requirements. They state:

Low Sound = Heat Pump Placement Flexibility

One of the regulations under Permitted Development, is that the sound pressure level of an air source heat pump must not exceed 42dB(A) 1m from the neighbour’s nearest room (Assessment Position).

With class-leading sound power levels of just 58dB(A), the Ultra Quiet Ecodan air source heat pump can be located much closer to the assessment position and pass planning.

This ultra-quiet performance means you can now choose the most convenient location for your Ecodan, causing no disturbance to neighbours.

It’s the one I had installed in our terraced house, no planning permission and no issues. It’s also quite a smart unit and I would recommend it :grinning:

You can read more about it in their product spec sheet.

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I know Octopus are doing something like that. Also look on Heatgeeks website for list of fully trained installers.

Thanks for the info. It would seem that British Gas don’t know what they are doing.

I spoke to @omantench the other day and he had had another quote for Mitsubishi install and they said the issue was associated with external heat pumps with toxic refrigerant - it was a Valliant installer who had given this advice (obviously didn’t recognise that other brands wouldn’t have same issue!).