Air-to-air vs air-to-water

[Kelvin]

6 hours ago, Kelvin said:

Coming back to the question of you’ll find it hard to get someone to fit it. These guys do a complete purchase and install service for not a lot of money. It’s unclear if they cover Scotland though as despite their map saying they do the person I spoke to said they don’t but is checking for me. 
 

https://www.appliancesdirect.co.uk/content/air-conditioner-installation

 

My slight issue is the size of the space at 10.5x6x4.2 (ridge height) so to size it for the space would likely require two units. My plan is to create an office within the garage anyway so will likely just size it for that. 

 

Closing this point off. They don’t cover Scotland (despite their coverage map saying they do) Happy to sell me the unit but I need to provide them with the fGas installers details. However for the rest of you in England this seems like a reasonable way to get an A2A unit installed for a reasonable fee.  They’ll zero rate the VAT if doing supply and install. 

[MechanicalBuilder]

Just to bring this thread back up for anyone who finds it, I’ve just installed 2 daikin ASHP’s on my new build. One 8kw for the ufh and dhw with a 7.5kw split for the three bedrooms (large) upstairs. The a2a is quiet and the Daikin Stylish wall mounts are aesthetically pleasing to be fair. All set via the onecta app and very quiet at night. 

Didn’t bother with the grant as I’m fortunate enough my best mate is a HP engineer.

[Garald]

I thought the COP of A2A, while improving, is still clearly below that of A2W, and so it's more of an option for places where there are about as many air-conditioning days (to the extent that there is such a thing) as heating days? I'd think the set of places in the UK falling under that category is empty (unless you count Gibraltar or something).

[Crofter]

3 hours ago, Garald said:

I thought the COP of A2A, while improving, is still clearly below that of A2W, and so it's more of an option for places where there are about as many air-conditioning days (to the extent that there is such a thing) as heating days? I'd think the set of places in the UK falling under that category is empty (unless you count Gibraltar or something).

What do you think the COP of A2A is? Some units I was looking at were around 5.5.

 

By the way, I've recently completed the installation of a Panasonic system. The clever bits were done by an f-gas engineer, then I finished it off myself. 

Because I had several rooms to heat, I chose a ducted system. We installed it under the floor and I ran the 200mm ducts to grilles just above skirting height. 

Early days but so far I'm delighted. The response speed is amazing. You only notice a draught if you stand right next to a grille. The noise is definitely detectable, although any background noise whatsoever will drown it out.

Total installation cost was £4200, no grants.

[Garald]

5 hours ago, Crofter said:

What do you think the COP of A2A is? Some units I was looking at were around 5.5.

That’s remarkable. The ones advertised around here tend to be between 2 and 3 (with some saying that 3 is not really attained in practice).

 

Actually (and this shows I am not talking from actual experience) to what temperature does an A2A generally heat air?

[Crofter]

2 hours ago, Garald said:

That’s remarkable. The ones advertised around here tend to be between 2 and 3 (with some saying that 3 is not really attained in practice).

 

Actually (and this shows I am not talking from actual experience) to what temperature does an A2A generally heat air?

In mine, you can set it between 17⁰-24⁰C. On the lower settings in particular you can't really tell that the air is any warmer than ambient. But due to the volume of air flow it does very quickly heat up the room. 

I was actually worried that something was wrong when I first installed it, because I expected the air to feel much hotter coming out of the vent.

[Beelbeebub]

A2a has a theoretical advantage as the target temperature (and hence pressure) for the compressor to reach can be lower than with a water based system *for a given emitter surface area*. 

 

A2W can gain an advantage if it uses underfloor as the surface area can be huge.

 

I think a2a has potential as it can usually be fitted alongside any existing heating system. This negates any fear of "will I be cold" or "will it cost more to run" as the owner can use whichever system is most appropriate at the time. 

 

They tend to be cheaper to install too. 

[Garald]

1 hour ago, Crofter said:

In mine, you can set it between 17⁰-24⁰C. On the lower settings in particular you can't really tell that the air is any warmer than ambient. But due to the volume of air flow it does very quickly heat up the room. 

I was actually worried that something was wrong when I first installed it, because I expected the air to feel much hotter coming out of the vent.

 

Wait, so it's recyling air, right? (Or maybe it need not if you also have MVHR?) Don't the same health concerns (which may or may not be reasonable) as for AC apply?

[Crofter]

1 minute ago, Garald said:

 

Wait, so it's recyling air, right? (Or maybe it need not if you also have MVHR?) Don't the same health concerns (which may or may not be reasonable) as for AC apply?

Yes, it takes in air from inside the house and warms it slightly. Way more efficient than pulling air from outside and having to heat it up all the way. 

 

What health concerns?

[Garald]

38 minutes ago, Crofter said:

Yes, it takes in air from inside the house and warms it slightly. Way more efficient than pulling air from outside and having to heat it up all the way. 

 

What health concerns?

 

People in France (well, Paris, or the northern half of France perhaps) are generally of the opinion that AC moves germs around and around (with a seasoning of things that grow in ducts or filters, but that's just improper maintenance). Might make sense in some contexts (restaurants, or other crowded spaces).

[SteamyTea]

7 hours ago, Garald said:

Wait, so it's recyling air, right

Radiators and UFH reheat the same air.

 

6 hours ago, Garald said:

People in France

Are generally a bit bonkers, I think I can say that as half my family are French descendants.

Ask a French person what happens to their nuclear waste.

[Crofter]

6 hours ago, Garald said:

 

People in France (well, Paris, or the northern half of France perhaps) are generally of the opinion that AC moves germs around and around (with a seasoning of things that grow in ducts or filters, but that's just improper maintenance). Might make sense in some contexts (restaurants, or other crowded spaces).

Perhaps that's why my A2A has some sort of fancy nanoscale filtration system, that supposedly cleans the air as it passes through? I thought it was just marketing guff.

[SteamyTea]

3 minutes ago, Crofter said:

thought it was just marketing guff

It almost certainly is.

 

I was told once that filling my bedroom with elevated levels of O₃ would cure my hayfever.

Nearly (expletive deleted)ing killed me.

[Archer]

I've just fairly recently installed a ducted A2A system (mostly retro fit of existing 70's gas warm air). I can confirm that it's virtually silent in the bedrooms, haven't noticed a major difference in comfort from the radiator/ wet systems that we've had in other houses but with the benefit of the option of cooling. The supply air is still "warm" but not as hot as that coming from the gas warm air system it replaced. If anything this is an advantage - you get a much longer, gentler heat and it modulates the fans up and down as it nears the target temperature. Our system is a 2 zone VRF - which is overkill, but was done for noise reasons and the outside unit is very quiet most of the time - barely audible from 5 metres, despite having a Sound Power rating of 70db. 

 

Biggest negative is the amount of space the fan units and plenum's take up; also the lack of grant and general wild west nature of AC installers. There are plenty around but trying to find a good one...

[joth]

On 08/11/2024 at 01:42, Crofter said:

What do you think the COP of A2A is? Some units I was looking at were around 5.5.

 

Remember this is best-case COP and A2W (thanks to MCS) generally quote SCOP not COP

 

[ReedRichards]

My OH has a small studio tacked on to the back of our garage, which is external to the house.  I've been thinking I should get an A2A heat pump to heat that room; it's only 10 square meters in floor area, although being a garage the walls are not insulated.  Any recommendations for a make/model? 

[SteamyTea]

11 minutes ago, ReedRichards said:

Any recommendations for a make/model

Not really, but you can get them that only require a couple of 150mm holes cut though the wall.  A tiny bit nosier I am told, and does take up some floor area, but no F-Gas, so easy to DIY.