Heat wave 2022 & th...
 
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Heat wave 2022 & the case for A2A ASHPs

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(@diverted-energy)
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Posted by: @batalto

@editor those are useful but very very inefficient as you are housing the compressor element in the house. Split is way better and more efficient.

You have solar, get AC, it's a no brainer and you can use for a burst of heat in the winter.

Completely agree:

Last Monday and Tuesday, house was 20.7 and 22.5 degrees with 'dry' non humid air. Upstairs 12,000BTU unit ran for 8 hours and a Portable 12,000BTU with pipe pushed through the Cat-Flap in Kitchen for 6 hours. Cats slept on bed all day so not upset at their door being sealed. Most of the time running the AC all days, leaves house dry and cool, only Tuesday did we need to run it again for an hour at 10pm.

Power Cost - completely FREE.

If nothing else, buy a Portable and cut a board the size of a window to pop pipe through. As per, my other posts, a Mini Split has many advantages of 120 days for supplemental Heating - 30 days cooling!!

Multi-Mini Splits are not ridiculous in pricing, £900 for 2 room and £1400 for 3 from one outside unit.


   
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(@kev-m)
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@diverted-energy 

I know they are your panels and therefore it's your free to you electricity but I feel just a little uneasy at running AC in UK homes.  Theoretically the energy you are not exporting while your AC is running may be generated by gas or other ffs, although I know that's a bit of a spurious argument.  And what you are doing is far better than importing the energy.  However I definitely wouldn't be happy about any funded scheme for PV using the power generated to run AC.  Or a swimming pool or hot tub. It's the same way I feel about how large, high performance EVs are subsidised so heavily. 

I'm currently in Athens and it's a normal cloudless 37C outside.  Night time temps are about 28C.  The flat I'm in is currently about 27.5C with no AC.  It's warm but still pleasant.  The 6 month old baby with us is perfectly fine too. The people we're staying with don't use the AC much, mainly if there are visitors. Having said that the houses here are built to withstand heat; white walls, shutters, awnings and tiled floors. 

Just a thought ...

This post was modified 2 years ago by Kev M

   
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Majordennisbloodnok
(@majordennisbloodnok)
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I must admit I'm also not entirely convinced about aircon in the UK as the norm.

Firstly, aircon needs power wherever it comes from, so if you're powering it from your own solar PV then it still isn't free; it's costing you what would have been paid if you'd exported those kWh to the grid. Moreover, any solar PV power you don't export as green energy is power others on the grid will consume at the prevailing CO2/kWh mix (in other words, you may not be adding to the problem, but you're reducing the amount you're part of making the problem better).

Secondly, and illustrated rather well by @kev-m above, is that for most of us prolonged exposure to higher temperatures just means our bodies will adapt. If aircon is installed, it just means you don't give your body a chance to adapt, meaning you either delay the issue or decide to live in an air-conditioned bubble only ever moving from air-conditioned house via air-conditioned car to air-conditioned office or air-conditioned shops/restaurants etc.

I'm certainly not going to suggest that aircon shouldn't be used, but I will say that for me and my family it's not the right choice. I would certainly and happily agree with aircon as an important and useful tool for anyone with a medical condition that is affected by the higher temperatures, but for anyone not in that bracket I'd urge a closer look at aircon's trade-offs before deciding whether or not to go down that route.

I hasten to underline here that I'm not suggesting aircon is a lazy fix or inappropriate. Everyone's situation is different, so all I'd like is that people make considered decisions rather than the admittedly tempting knee-jerk reactions that the current high temperatures can easily encourage.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and inverter
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; suus solum profundum variat"


   
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(@chickenbig)
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Posted by: @diverted-energy

Multi-Mini Splits are not ridiculous in pricing, £900 for 2 room and £1400 for 3 from one outside unit.

I just received a quote to add air-con to the whole of our 2 bedroom terrace house (to replace the central heating which operates on microbore); the setup would be 2 x 10kW Mitsubishi outdoor units (down the end of the garden) attached to 8 x 2.5kW indoor units. They would like just shy of £17,500 (with 0% VAT), and of course there is no BUS discount.

I think some part of this cost may be due to using 4-way mini-splits which will increase the total pipework length; my preference would have been for a mini-VRV/mini-VRF. Another part of the cost is the over-specing of the outdoor unit (20kW heating/cooling, whatever that means) and indoor units (2.5kW is approximately the heat output of a kettle).

I'm not sure there is enough common ground to even start to negotiate the system specification and price.


   
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(@derek-m)
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@chickenbig

20kW of heating for a 2 bedroom terraced house I suspect is way over the top. Do you have no insulation and keep the windows open throughout the year? Who is offering such a large system?

I installed a 2.6kW single outdoor unit / single indoor unit which is more than adequate to heat our 3 bedroom bungallow down to temperatures of +5C. It provides any heating we require from Spring through to Autumn and also helps for some of the heating during the Winter.

How many rooms do you have? I suggest you get at least two further quotes from other companies.


   
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(@chickenbig)
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Posted by: @derek-m

@chickenbig

20kW of heating for a 2 bedroom terraced house I suspect is way over the top. Do you have no insulation and keep the windows open throughout the year? Who is offering such a large system?

I installed a 2.6kW single outdoor unit / single indoor unit which is more than adequate to heat our 3 bedroom bungallow down to temperatures of +5C. It provides any heating we require from Spring through to Autumn and also helps for some of the heating during the Winter.

How many rooms do you have? I suggest you get at least two further quotes from other companies.

I filled in the MCS calculation spreadsheet by myself and came to a figure of around 7.1kW for this 2 bedroom Victorian terrace (two up, two down) with extension. We have double glazing, loft insulation, capped chimneys along with cavity wall insulation in the more modern extension; however we do have uninsulated suspended floors and solid walls.

I believe the heating capacity is driven by the cooling capacity (according to this Graham Hendra article one should at least double the heating capacity), so I feel 14kW or 16kW cooling capacity should have been adequate, leading to using 1.5kW (or 2kW in the larger rooms?) wall mounted units across the 8 locations we currently have radiators.

Of the two other air-con suppliers I could get hold of, one withdrew from making a bid after I outlined what I wanted (as I let slip I was in contact with another air-con company) and a fortnight ago the other one promised to give a budgetary quote and then decided they needed to see the site before quoting but has not yet contacted me to see the site.

I get the impression that, like heat pumps and solar panels, there is a very limited pool of talent and they are already busy. I should probably buy shares in oil and gas companies rather than spend it on energy saving measures!


   
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(@kev-m)
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Posted by: @chickenbig
Posted by: @diverted-energy

Multi-Mini Splits are not ridiculous in pricing, £900 for 2 room and £1400 for 3 from one outside unit.

I just received a quote to add air-con to the whole of our 2 bedroom terrace house (to replace the central heating which operates on microbore); the setup would be 2 x 10kW Mitsubishi outdoor units (down the end of the garden) attached to 8 x 2.5kW indoor units. They would like just shy of £17,500 (with 0% VAT), and of course there is no BUS discount.

I think some part of this cost may be due to using 4-way mini-splits which will increase the total pipework length; my preference would have been for a mini-VRV/mini-VRF. Another part of the cost is the over-specing of the outdoor unit (20kW heating/cooling, whatever that means) and indoor units (2.5kW is approximately the heat output of a kettle).

I'm not sure there is enough common ground to even start to negotiate the system specification and price.

That seems very expensive.  I also understand you will need planning permission for two AC units.  Are your neighbours going to be OK with what you're doing?

I know central heating needs a radiator in each room but do you need so many indoor AC units?     


   
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(@chickenbig)
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Posted by: @kev-m

I also understand you will need planning permission for two AC units.

Indeed, but I'm not sure air conditioning counts as a heat pump for planning purposes. At least the air-con engineer who visited site did not think planning permission was required. Also see the end of the Graham Hendra blog post

The unit on the left is an air-conditioning unit, (air to air Heatpump) it doesn't use water at all, the installer just installed it, no grant, no paperwork, no DNO, no planning permission and it cost under half of the one on the right. Oh and it heats too.

 

Posted by: @kev-m

That seems very expensive.

Indeed; during the site inspection I did point out that installing a heat pump and renewing the radiators would be approximately £16,000 before the BUS grant takes it down to £11,000. Factoring in perhaps £3,000 to install a Vaillant aroSTOR with the air-con option, results in the air-con route being £9,500 more expensive.

Posted by: @kev-m

do you need so many indoor AC units

Perhaps not, but the cost appears to be around £2,200 per indoor unit, so even cutting the units in half results in a barely competitive quote.


   
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(@derek-m)
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@chickenbig

Obviously I don't know the exact details so I am having to make some assumptions.

Your assessment of 7.1kW would seem fair for your property and of course this would be the probable heating demand when the outside temperature is in the order of -2C to -3C. A 10kW or 11kW heat pump I think would be more than adequate to meet your need, unless you choose a Midea unit which appear to be underpowered compared to other manufacturers.

What system do you have at the moment and what is the size of the microbore pipework? Can it easily be replaced?

There are pro's and con's for installing A2A (Air to Air) ASHP's rather than A2W (Air to Water). Experience with my own A2A heat pump has shown that it can heat a room much quicker than via A2W and radiators/UFH. It is probably slightly more efficient in that you are directly heating the air rather than via water heated radiators. A2A can provide cooling during hot Summer days. The heating and cooling capacity is about the same.

Unless you can get reasonable good airflow from room to room you would require an indoor unit in each room, there is also noise from the fans to consider. The temperature control may not be as accurate as an A2W system. An A2A system cannot provide hot water. A2A heat pumps do not qualify for the £5000 grant.

I think that some of the forum members have installed A2W systems with microbore pipework that have worked quite successfully, so maybe you should also consider an A2W system. I think that I have also seen some manufacturers information that had a combination A2W and A2A system.

 

 

 


   
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(@diverted-energy)
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think this needs rethinking..

1) planning permission is not needed, unless building is grade listed.

2) don't try to Air Condition every room in your house  if communal landing, put one there and blow into each room.

Downstairs, just the lounge or living area and justeave doors open to each additional room you need cooler.

I have a three bedroom detached and two, a 12,000 BTU and an 18,000BTU is plenty. For heating smaller rooms with Solar, use portable oil heater in discreet location in conjuction with A/C. Consider it mass heating or cooling.

Paid less than £900 for both. Buy them yourself and pay an engineer to install by ringing around.

This post was modified 2 years ago by Diverted.Energy

   
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(@chickenbig)
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Posted by: @derek-m

What system do you have at the moment and what is the size of the microbore pipework? Can it easily be replaced?

The pipework is at best 10mm microbore, but with sharp turns everywhere the effective flow will be much less. Also the pipework is totally uninsulated (save for layers of emulsion and gloss paint). The boiler itself is an Ideal Logic Max Combi C24 (24kW) although I calculated that the existing radiators will struggle to dissipate about 12kW without going to very high temperatures. I've had two quotes for radiator replacement costing around £3,000 (including 20% VAT) plus the cost of the radiators (perhaps another £2,000 including 20% VAT). The reason I looked at going down this road was to make the house more heat-pump ready, and allow renovation of the rest of the house to proceed independently.

Posted by: @derek-m

A2A heat pumps do not qualify for the £5000 grant.

I suspect that grants do little to reduce the price paid by the consumer. However A2A prices look to be on the increase too.


   
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(@derek-m)
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@chickenbig

Have a look on the Appliances Direct website where you can purchase an 8.8kW 3 indoor / 1 outdoor A2A system for just under £1300, and they can provide an installation service at additional cost. I purchase my A2A system from them, which I ordered in the afternoon and it was delivered the following morning. They also have a quite useful technical help department.

They have so many different units available that you are spoiled for choice.

Do you have solar PV?


   
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