Why aren't A2A ASHP more popular

[Gone West]

2 hours ago, joe90 said:

However, I think 8% losses through the floor is minimal and in my case (as I have UFH) worth the small cost to not have (what I consider) ugly radiators or “indoor units”. My heating costs are so low that 8% of very little is very very little ?‍♂️. My heating is yet to come on yet this year. I do however have a new well insulated house and existing housing stock is not this fortunate so I think there is a market fir the A2A units.

You're lucky, as I was, to have a very low energy house. I found my house was very comfortable without any conventional heating. Most of the people the government are pushing to have ASHP and hence UFH don't have low energy houses. When you try to fit UFH in an unsuitable house the 8% goes up because the temperature gradient is steeper as a result of needing higher water temperature. That combined with limited under floor insulation means a significant amount of the heat is lost.

[shuff27]

I'm guessing (without knowing the split) that most on this forum are doing new builds rather than renovations/extensions.  AFAIK the A2A variety of heat pump won't provide DWH, while A2W will.  If that's the case the latter would be a more obvious solution for most of us here; it certainly gets a lot more coverage.

[RomyD]

43 minutes ago, shuff27 said:

I'm guessing (without knowing the split) that most on this forum are doing new builds rather than renovations/extensions.  AFAIK the A2A variety of heat pump won't provide DWH, while A2W will.  If that's the case the latter would be a more obvious solution for most of us here;

Mines a renovation and with only 75mm floor insulation it seems UFH is probably wasteful so A2A or rads. Really don't want rads. Quite like the idea of A2A. HW is the next problem. 

[saveasteading]

20 hours ago, SteamyTea said:

Marginal improvements in the insulation, and the brick material

I salvaged the bricks from some old storage heaters. Incredibly heavy for their size, and I am guessing there is a lot of iron in there.

Why, you ask?

They are in the greenhouse as plant stands as they absorb (a lot of)  heat in the day and keep the plants a little bit warmer for a little bit longer.

 

I have come across ironstone in excavations and the weight and heat absorption are similar, although the bricks were clearly manufactured to a precise shape

[severnside]

1 hour ago, shuff27 said:

I'm guessing (without knowing the split) that most on this forum are doing new builds rather than renovations/extensions.  AFAIK the A2A variety of heat pump won't provide DWH, while A2W will.  If that's the case the latter would be a more obvious solution for most of us here; it certainly gets a lot more coverage.

DHW can be solved separately with ASHP integrated Water Cylinders like Dimplex Edel or Ecocent.

We are also doing renovation and I quite like the idea of A2A heatpump but first level discussion with installer suggest 3-4 external units (It's a 5 Bed House, 9 rooms). Also Tiles without UFH will not be comfortable 

[saveasteading]

The other factor is that a warm floor provides warm feet and a better comfort level than the air-temperature might suggest.

Whereas ducted warm air rises straight to the ceiling.

The higher the ceiling the more energy benefit.

 

This will be especially the case in situations such as children playing on the floor, watching telly with the legs  stretched out, and bare feet situations.

 

Impossible to evaluate I expect.

[Gone West]

1 hour ago, shuff27 said:

AFAIK the A2A variety of heat pump won't provide DWH, while A2W will.

 

31 minutes ago, RomyD said:

HW is the next problem. 

There are small A2W heat pumps that heat just a water tank. There might be more than these.

 

https://www.ariston.com/en-uk/products/air-source-heat-pump-water-heater/air-source-heat-pump-water-heater/

 

https://www.earthsaveproducts.com/products/ecocent

 

[Gone West]

3 minutes ago, saveasteading said:

The other factor is that a warm floor provides warm feet and a better comfort level than the air-temperature might suggest.

Whereas ducted warm air rises straight to the ceiling.

The higher the ceiling the more energy benefit.

 

This will be especially the case in situations such as children playing on the floor, watching telly with the legs  stretched out, and bare feet situations.

 

Impossible to evaluate I expect.

We had a tiled ground floor in our PH without UFH. We heated the house with three towel rails in the bathrooms, supplemented with warm air from an EASHP, and kept the air temperature at 23C. The floor never felt cold and I measured the floor temperature and it was always between 22C and 23C. Warm air only rises to the ceiling because of the temperature gradient. If the house is well insulated and the ducted warm air came in at floor level at a low enough temperature it wouldn't rise straight to the ceiling.

[saveasteading]

2 hours ago, Gone West said:

it wouldn't rise straight to the ceiling.

Are you sure? If ever Ii have to get on steps so my head is near the ceiling, it feels much warmer there.  If there is lots of movement and a lowish  ceiling, then not so much.

[joe90]

51 minutes ago, saveasteading said:

Are you sure? If ever Ii have to get on steps so my head is near the ceiling, it feels much warmer there.  If there is lots of movement and a lowish  ceiling, then not so much.

If a house is well insulated and no draughts with warm(er) incoming fresh air (mvhr) then yes as @Gone West says the whole structure is the same temperature.

[SteamyTea]

4 hours ago, saveasteading said:

children playing on the floor

Should be illegal.

 

https://www.bbc.co.uk/programmes/m0011lf7

[Gone West]

12 hours ago, saveasteading said:

Are you sure?

Yup, well in a PH. If you're not pumping loads of heat in low down, how is it getting to the ceiling. The heat has to be coming from somewhere. If the UFH is only a degree above room temperature the gradient is shallow. If you have hot radiators there is a steep temperature gradient and the hot air travels upwards quickly, cooling as it goes, until it drops down for the cycle to be repeated continuously.

[RomyD]

22 hours ago, Gone West said:

 

There are small A2W heat pumps that heat just a water tank. There might be more than these.

 

https://www.ariston.com/en-uk/products/air-source-heat-pump-water-heater/air-source-heat-pump-water-heater/

 

https://www.earthsaveproducts.com/products/ecocent

 

 

Thanks for the tips. I've had a look at these. They sound great but i don't like the idea of sacrificial anodes as a consumable that will get forgotten about. The Dimplex Edel which looks like the best of the bunch doesn't use such a thing but still only has five year tank warranty. Is a 5yr tank warranty a bit stingy or does it sound about right? 

 

And then there's the COP. Dimplex claim 3.21 which from their spec sheet isn't the sum of the power out divided by power in which is 1650/700=2.36 

Have i got that bit right? 

 

And why cant a multi split system do A2A internal units and DHW somehow?

 

Sorry for all the questions, I am still getting my head round all of this.

 

 

 

Edited November 17, 2021 by RomyD

[PeterW]

11 minutes ago, RomyD said:

And why cant a multi split system do A2A internal units and DHW somehow?

It can but will be inefficient. A2A will have a setup to support coil evaporators and not a gas / water heat exchanger. Those tend to need a slightly higher gas flow rate, and having a mix of multi splits on the same condenser will be a challenge. 

[Gone West]

1 hour ago, RomyD said:

Thanks for the tips. I've had a look at these. They sound great but i don't like the idea of sacrificial anodes as a consumable that will get forgotten about. The Dimplex Edel which looks like the best of the bunch doesn't use such a thing but still only has five year tank warranty. Is a 5yr tank warranty a bit stingy or does it sound about right? 

 

And then there's the COP. Dimplex claim 3.21 which from their spec sheet isn't the sum of the power out divided by power in which is 1650/700=2.36 

Have i got that bit right? 

I would prefer a stainless steel or copper tank and not have an anode. I had a Genvex Combi 185L unit which had a 585W EASHP which heated the tank. The tank was enamelled steel and had an anode. The warranty for the unit was only two years. COP is P out/P in, so I don't know how Dimplex have done their calculations.

[SteamyTea]

1 hour ago, Gone West said:

don't know how Dimplex have done their calculations

Possible SCoP.

Dividing max output by Max input does not really work out the CoP.

[Onoff]

@Gone West, I can't remember, what happened to your blog, why is it gone?

 

You should write a book of the build btw, I'd buy it!

 

This is a bit of an aside to the OP's thread (apologies) but was was your daily energy requirement for heating the old place including running the Genvex & heat recovery?

[Gone West]

2 hours ago, SteamyTea said:

Possible SCoP.

Dividing max output by Max input does not really work out the CoP.

I've always read that COP was P out/P in which is why SCoP is supposedly more accurate. Is that wrong?

[Gone West]

19 minutes ago, Onoff said:

@Gone West, I can't remember, what happened to your blog, why is it gone?

 

You should write a book of the build btw, I'd buy it!

 

This is a bit of an aside to the OP's thread (apologies) but was was your daily energy requirement for heating the old place including running the Genvex & heat recovery?

I removed both copies of the blog when I sold the house.  The 13kWh/m2a was for space heating only but I can't remember for sure whether the energy for running the Genvex was included in that. I would have thought the PHPP would have included the Genvex energy used and the heat recovery though because I bought a version upgrade for PHPP from 2007 to 2010 that included built in compact unit data which included the Genvex Combi.

[SteamyTea]

44 minutes ago, Gone West said:

I've always read that COP was P out/P in which is why SCoP is supposedly more accurate. Is that wrong

Coefficient of Performance is just Power Out / Power In.

But it needs to be within fixed bounds i.e. output temperature 35°C, external temperature 7°C.

SCoP is a method to try an mimic real life conditions, so will have a weighted average for different output temperatures and different external temperatures.

So a SCoP in maritime Cornwall will be different from maritime Newfoundland, which will be different from the Swiss Alps, which are different from Idaho's Snake River Plain.

 

I would rather see an isothermal chart.  But then I understand them.

[puntloos]

On 17/11/2021 at 15:15, PeterW said:

It can but will be inefficient. A2A will have a setup to support coil evaporators and not a gas / water heat exchanger. Those tend to need a slightly higher gas flow rate, and having a mix of multi splits on the same condenser will be a challenge. 

 

Strange how I looked into exactly this, this weekend. 

 

A heating guy (also called Peter.. ) I am working with suggested the multi-split too - A2A, and I'm certainly wondering if there is no useful way to just use 1-2 of the gas lines into a 'water heater'. Not sure about the flow rate but surely that wouldn't at least cost money, it'd just heat the water somewhat slower?

 

I would imagine from the same brand, as long as they have split A2W and split A2A devices these hoses should somewhat connect seamlessly?

 

Frankly I'm debating both, a smallish A2W ASHP next to a smallish A2A ASHP with 3-4 FCUs in strategic locations. But it feels overkill to do so.. 

Edited November 28, 2021 by puntloos

[Iceverge]

https://www.ebay.co.uk/itm/Air-source-heat-pump-water-heater-air-conditioning-and-heating-/224649548830?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=710-127635-2958-0

 

It's been done. 

 

[puntloos]

6 minutes ago, Iceverge said:

https://www.ebay.co.uk/itm/Air-source-heat-pump-water-heater-air-conditioning-and-heating-/224649548830?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=710-127635-2958-0

 

It's been done. 

 

That sounds.. decidedly like cheap Chinese stuff. But yes, looks like in theory it could work then. 

 

The reverse is more common, I believe, a A2W heat pump with water (not coolant) driven FCUs.. 

 

Am I correct that coolant-based FCUs are better, or is there no major downside to feed cold water - perhaps somewhat higher speed - through a FCU? (I realise the device design will be somewhat different, can't just feed anything through any device, but the principle seems similar)

[Iceverge]

14 minutes ago, puntloos said:

decidedly like cheap Chinese stuff.

Yes. 

 

14 minutes ago, puntloos said:

Am I correct that coolant-based FCUs are better

 

No idea. 

 

I wouldn't overthink it. A properly speced  A2W with cooling is the best bet for a new build with a good budget. Provision for upstairs UFH (and cooling) and forget the A2A. Get as large a UVC as you can manage and run the DHW as cool as possible and you'll have a good COP. 

 

Something like this. 

 

https://www.daikin.ie/en_gb/products/edlq-bb6v3.html

 

 

 

 

[puntloos]

1 minute ago, Iceverge said:

Yes. 

 

 

No idea. 

 

I wouldn't overthink it. A properly speced  A2W with cooling is the best bet for a new build with a good budget. Provision for upstairs UFH (and cooling) and forget the A2A. Get as large a UVC

 

UVC? A google search says Ultraviolet - to clean air, desinfect?

 

1 minute ago, Iceverge said:

as you can manage and run the DHW as cool

as possible and you'll have a good COP. 

 

Something like this. 

 

https://www.daikin.ie/en_gb/products/edlq-bb6v3.html

 

This one is heating only though. Did you intend that?

 

FWIW because my "bloc" needs to be pretty far away from the house I probably need a split.

 

My current plan is a split reversible one, something like https://www.daikin.eu/en_us/products/eabx-d6v.html (not 100% settled on a brand/type/size yet) but I've been told that water-based FCUs are a bit ancient technology compared to proper multi-split.