Amount of space required for airsource heatpump

Slinky

We are about to start a large project which will include replacing our ancient gas boiler with a modern gas boiler which will be going into a full floor to ceiling height cupboard in a first floor bedroom. We are conscious that at some point in the future we may have to go down the ASHP front, so we are planning on having new pipework and radiators installed that will be compatible with a pump when the time comes. We plan on installing a new hot water cylinder in the airing cupboard which directly adjoins the cupboard where the boiler will be going, and there's the possibility of pinching some space from the airing cupboard to make the boiler cupboard larger if required. How much more space do we require for all the 'gubbins' associated with an ASHP than would be required for a gas boiler, so we know how much space to steal off the airing cupboard? It makes sense to move the internal partition of the cupboards to allow for the space required now, rather than having to muck about moving the cylinder at some point in the future. We definitely want a water cylinder, not a small radiator in the airing cupboard.

TIA

ComicGeek

The simplest way to do the future installation is to use a pre-plumbed cylinder for a monobloc ASHP condenser unit - something like https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_EHPT15-30X-UKHDW_Product_Information_Sheet#page-1

That means you don't need to allow space for any separate hydrobox between the heat pump and cylinder/heating system - the downside is that you have to replace the cylinder at the same time, but if that's 10-20 years down the line then that's probably not a big issue. So the airing cupboard would need to be 750mm x 750mm on plan.

If you definitely want to retain the existing cylinder when you come to install the ASHP (and you would want it to be a heat pump compatible cylinder to keep it), then the gas boiler gets replaced with a hydrobox - like https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_FTC5_-_EHPX-VM2C_Monobloc_Packaged_Hydrobox_Product_Information_Sheet#page-2. This is probably a very similar size to the gas boiler being replaced.

The key thing though is how to get the pipework from the external condenser unit to the pre-plumbed cylinder or hydrobox, given that the cupboard is at first floor - and how to get the electrical cabling to the external condenser. You don't need to install it now (probably best not to, as regs change over time), but you need to have an accessible route available. I replaced our boiler recently, and moved it to a position on an external wall where the ASHP could sit on the opposite side - then it's a very simple retrofit install once I've made some minor mods to a couple of radiators.

Belenus

Here are some of my thoughts on this subject.

Is it still correct that gas boilers will be banned from new builds by 2025, and new gas boilers will no longer be for sale by 2035?

That may well change. I think the 2035 date is more likely to get pushed further into the future than staying the same or being brought forward although there is great uncertainty about the security of gas supplies (Putin?).

There is also uncertainty about the viability of ASHPs for many homes.

If I understand you correctly, you are planning to create space that will not be used for many years, if ever, and also to install larger radiators than needed as they will need to be larger for use with a ASHP.

I am 69 years old so my thinking may be different to yours. If I needed to replace our gas boiler now I would get another gas boiler and worry about ASHPs in 15 to 20 years time. I would not want to have to have very large radiators in expectation of some unknown event in the fairly distant future.

You could buy a gas boiler now and buy another one in 13 years time, thus deferring ASHP for maybe as much as 30 years. By that time the technology may have changed and you may need less space than you need now to install a ASHP.

I post all this purely as food for thought as I am not particularly well informed on the matter.. I hope it helps.