A2A basics

[Crofter]

Researching A2A as a form of heating.

E.g. slap one of these right in the middle of the house:

https://www.appliancesdirect.co.uk/p/iqool24/electriq-iqool24-air-conditioner

 

Seems too good to be true given the price.

 

Any thoughts?

[JohnMo]

If sounds too good, normally is. Like most things there can be huge performance and life expectancy difference.

 

This is a good source of information, I would go for a unit that is A*** for both heating and cooling.

 

https://www.eurovent-certification.com

 

 

[S2D2]

Some thoughts on the DIY unit here:

 

I've been happy with mine and offset whole house gas heating with the single unit. It's been working very well in combination with the PV since installation in March, but hasn't had a full winter to test it to its limits yet, though we did have negative temperatures in March.

 

There are downsides (see thread) but overall no huge catches, it will pay for itself.

[Crofter]

41 minutes ago, S2D2 said:

Some thoughts on the DIY unit here:

 

I've been happy with mine and offset whole house gas heating with the single unit. It's been working very well in combination with the PV since installation in March, but hasn't had a full winter to test it to its limits yet, though we did have negative temperatures in March.

 

There are downsides (see thread) but overall no huge catches, it will pay for itself.

That's a great thread, thank you. I did skim it previously when starting to investigate this.

 

I see you're finding it worthwhile despite being on gas. I'm on direct electric (storage heaters) so should see an even bigger benefit. Very encouraged that your COP figures are so high.

 

I'm in NW Scotland which is not exactly tropical. But one advantage is that we don't actually get many frosts.

 

What would your thoughts be on fitting one big central unit vs several smaller ones?

[S2D2]

Yes compared to direct electric it's very good. You may find a humid climate slightly above zero worse for defrosting cycles, but even still the CoP will stay favourable compared to direct electric.

 

1 hour ago, Crofter said:

What would your thoughts be on fitting one big central unit vs several smaller ones?

 

This one is probably personal preference. I wouldn't want the internal unit on when in a bedroom, it's not quiet enough. More expensive units will be better I'm sure. I'm able to overheat the room the unit is in for most of the day when it's empty and leave internal doors open, which is the only way it can heat more of the house. There are still rooms it doesn't reach, hence the boiler still being on. If you can't overheat the central space I'd be very worried about a 7kW system cycling too much, depending on heat loss/size of the space. The other obvious disadvantage is if you choose to shut a door to a room, the room will get cold.

 

Long term I'm likely to fit an A2W ASHP to get stable temps in all rooms. The A2A will do the large room it's in and provide whole house cooling if required.

[Crofter]

@S2D2 just in case you didn't see it in the other thread I've attached the rough floorplan with the central A2A in red. It would be in a hallway so how well it works will depend mostly on whether doors are opened or not.

 

One complication we have is we can't really say who is going to be in the house. It is our family home, but it's currently used as a holiday let whilst we're living elsewhere. We're likely to come back and live there again, but equally there's a good chance we may let it out again in future.

 

The holiday lets are mainly over summer, so a somewhat undersized A2A might manage to cover the summer heating needs, and be far cheaper and more responsive than the storage heaters.

 

I think the simplicity of a central unit might win out. We have a woodburner in the living room too which should help a lot in colder weather.

[JohnMo]

The trouble with a single unit, it recycles the air, sucking in the air close to it and then throwing it out. It may find it difficult to migrate the warm or cool air around the rooms.  You may end end with a warm or cool corridor and room doorways, but rooms not comfortable.

 

You may be better with a two or three outlet A2A, one unit in the kitchen doorway, that will throw conditioned air towards the bedrooms, the other unit on bedroom 3 wall throwing air towards kitchen and lounge. Or with a 3 outlet a dedicated outlet in lounge and kitchen. The more outlets you have more doors that can be shut and it doesn't matter.

 

Single outlets are good for a single room or open plan, not so good for whole house with dedicated rooms.

[S2D2]

9 hours ago, Crofter said:

@S2D2 just in case you didn't see it in the other thread I've attached the rough floorplan with the central A2A in red. It would be in a hallway so how well it works will depend mostly on whether doors are opened or not.

 

One complication we have is we can't really say who is going to be in the house. It is our family home, but it's currently used as a holiday let whilst we're living elsewhere. We're likely to come back and live there again, but equally there's a good chance we may let it out again in future.

 

The holiday lets are mainly over summer, so a somewhat undersized A2A might manage to cover the summer heating needs, and be far cheaper and more responsive than the storage heaters.

 

I think the simplicity of a central unit might win out. We have a woodburner in the living room too which should help a lot in colder weather.

One thing to note with this plan is that you would end up with an internal join due to the length of pipe, ruling out a DIY R290 install. If I had paid the heavy premium for a professional install (despite 0% VAT...) I would probably have gone the whole way with a multisplit.

 

I do think you'll get short cycling with a unit that size in that space, perhaps aim for a smaller unit and run for longer. I'm no expert though, just a hunch based on what I've seen from mine.

 

Summer lets will 100% turn on the air con, so that may also offset savings!

[Crofter]

2 hours ago, S2D2 said:

One thing to note with this plan is that you would end up with an internal join due to the length of pipe, ruling out a DIY R290 install. If I had paid the heavy premium for a professional install (despite 0% VAT...) I would probably have gone the whole way with a multisplit.

 

I do think you'll get short cycling with a unit that size in that space, perhaps aim for a smaller unit and run for longer. I'm no expert though, just a hunch based on what I've seen from mine.

 

Summer lets will 100% turn on the air con, so that may also offset savings!

The distance between the outside and inside units would be about 2.5m, maybe a little less. The specs mention a 5m pipe length so I thought I'd be ok- am I misunderstanding something?

 

And that's a good point about AC! Ideally I'd like a system where I can 'lock in' certain parameters but I'm not sure if that's possible.

[Crofter]

2 hours ago, JohnMo said:

The trouble with a single unit, it recycles the air, sucking in the air close to it and then throwing it out. It may find it difficult to migrate the warm or cool air around the rooms.  You may end end with a warm or cool corridor and room doorways, but rooms not comfortable.

 

You may be better with a two or three outlet A2A, one unit in the kitchen doorway, that will throw conditioned air towards the bedrooms, the other unit on bedroom 3 wall throwing air towards kitchen and lounge. Or with a 3 outlet a dedicated outlet in lounge and kitchen. The more outlets you have more doors that can be shut and it doesn't matter.

 

Single outlets are good for a single room or open plan, not so good for whole house with dedicated rooms.

That makes sense.

I'd prefer to keep the outside unit(s) on the back wall of the house where nobody can see them. That would mean a minimum 4m run to put an outlet in the living room.

[S2D2]

10 minutes ago, Crofter said:

The distance between the outside and inside units would be about 2.5m, maybe a little less. The specs mention a 5m pipe length so I thought I'd be ok- am I misunderstanding something?

 

And that's a good point about AC! Ideally I'd like a system where I can 'lock in' certain parameters but I'm not sure if that's possible.

The unit you linked is R32 so legally must be installed by an fgas installer. R290 units don't have to be, but the DIY unit I got has 1.5m of pipe on the indoor unit then a 3m extension. If the joint is internal it has to be brazed but outside it's just mechanical. Unsure if you can DIY braze an R290 line, someone else will know the appropriate regs.