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.

[FelixtheHousecat]

On 30/01/2023 at 10:19, mike2016 said:

Considering this question for my own house - it's going to be a new build, quite small only 100m2 and I can get a Daiken with a 90l/120l hot water cylinder water heating option too. I think A2A works best in a retrofit though. Another primary benefit is direct cooling. I could live with the slight noise and draught, in an ideal world I'd get A2A for the bedrooms / office and A2W for the ground floor! 

Still heavily leaning on A2W for my house as it's a 3 bedroom with a bath and I'm not sure the smaller A2A tanks would work well on the hot water side and take too long to recharge. An A2W is better suited for my situation. The other con though is cost, the A2W is closer to 20K all in with the underfloor heating loop. An A2A would be much cheaper. 

Treated floor area 101.0 m²

Heating demand 14.91 kWh/(m²a)

Heating load 11.06 W/m²

I could run refrigerant pipe, Electrical & Drains to all the proposed locations so it's easy to retrofit later but would I ever use it? 

https://www.daikin.ie/en_gb/product-group/air-to-air-heat-pumps/multiplus.html

 

What do people think about using the heat pump manufacturers integrated cylinder vs getting a separate one? Any advantages / benefits there? Thanks! 

 

Look at the Samsung TDM plus Climatehub model.

 

Multi-split with A2W hydro box plus 2 extra indoor A2A units.

So you could have A2W heating circuits and hot water, plus two A2A wall or ducted units for shoulder season heating and summer cooling.

200L or 250L tank, BUS grant certified.

It's R410A, which wouldn't be my preferred option, and isn't as efficient as some of the latest models, but it'll do what you want.

 

https://samsung-climatesolutions.com/gb/b2c/our-solutions/home/heat-pump-solutions/heating-cooling/tdm-plus.html

[Iceverge]

On 18/11/2024 at 11:34, ReedRichards said:

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? 

 

 

Pretty happy with this so far. The WiFi app makes schedules etc pretty straight. 

[Iceverge]

On 18/11/2024 at 11:51, SteamyTea said:

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.

 

These units are the wrong way around in my view. 

 

They should be outside the house with the heated air going through the ducts into the house. 

 

They'd be much quieter then as they wouldn't be trying to push too much air through too small a hole. 

 

[mike2016]

On 08/12/2024 at 00:03, FelixtheHousecat said:

 

Look at the Samsung TDM plus Climatehub model.

 

Multi-split with A2W hydro box plus 2 extra indoor A2A units.

So you could have A2W heating circuits and hot water, plus two A2A wall or ducted units for shoulder season heating and summer cooling.

200L or 250L tank, BUS grant certified.

It's R410A, which wouldn't be my preferred option, and isn't as efficient as some of the latest models, but it'll do what you want.

 

https://samsung-climatesolutions.com/gb/b2c/our-solutions/home/heat-pump-solutions/heating-cooling/tdm-plus.html

 

Thanks - am currently looking at separate DHW and A2A solutions from the same company for the new house. 

[joth]

On 08/12/2024 at 00:24, Iceverge said:

 

These units are the wrong way around in my view. 

 

They should be outside the house with the heated air going through the ducts into the house. 

 

They'd be much quieter then as they wouldn't be trying to push too much air through too small a hole. 

 

For ground floor install that makes sense but I think a lot of attraction on the DIY install is that can be done on any story of a building with no external works needed. (I'm struggling to remember how the external grill is installed and made good from inside, but pretty sure I saw video of it being done)

Then just plugs into a wall socket. 

[Iceverge]

32 minutes ago, joth said:

For ground floor install that makes sense but I think a lot of attraction on the DIY install is that can be done on any story of a building with no external works needed. (I'm struggling to remember how the external grill is installed and made good from inside, but pretty sure I saw video of it being done)

Then just plugs into a wall socket. 

 

True, I didn't think of multi story apartments. 

 

I like the idea of a "monoblock" a2a as anybody can install one. 

 

I've seen claims of a COP of 3 but I'm not sure if it's accurate. 

[JohnMo]

1 hour ago, Iceverge said:

I like the idea of a "monoblock" a2a as anybody can install one.

Should be able too, as there are no breaks in the system.

[Beelbeebub]

I looked at some monoblock a2a. Units where you just drill 2x.160mm holes in the wall. Powermatic make one plustthere are some Italian units (olympia splendid or something)

 

The two big issues are prices - a couple of grand each and efficency. CoPs of about 3 tops. I can only guess this is down to the size limitations.

 

Some US companies are looking at updated versions of the old window mounted AC systems. Unfortunately those are only really viable with sash windows which are standard in the US but not common over here except in period properties. They are ugly but do have the advantage of being very easy to fit.

 

The best bet would be if we could get a refrigerant that has the low GWP of r290 (or similar) without the flammability issues.  That way we could have DIY installs with precharged linesets using some sort of push fit connection.  You just buy an outdoor unit, an indoor unit(s) and a premade lineset in an appropriate length from B&Q etc and away you go.

 

If they could make air to water boxes that mimic the inside unit then you could provide DHW too.