air to air heat pumps work

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air to air heat pumps work
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Slim

Joined: 05 Mar 2006
Posts: 6614
Location: New England (In the US of A)

Posted: Mon Aug 01, 22 12:38 pm Post subject: air to air heat pumps work
Remember, the temperatures noted are in Fahrenheit... https://energynews.us/2022/07/27/in-maine-heat-pumps-are-proving-themselves-even-against-extreme-cold/

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28239
Location: escaped from Swindon

Posted: Mon Aug 01, 22 1:50 pm Post subject:
The question I would ask, is what are the insulation standards? There has been a lot of coverage in the UK saying heat pumps won't work here because the insulation of houses is so bad.

Slim

Joined: 05 Mar 2006
Posts: 6614
Location: New England (In the US of A)

Posted: Mon Aug 01, 22 1:56 pm Post subject:

Well, you need to address your insulation issues as well, regardless of the heating source. Your weather is only expected to get more extreme.

Still, heating systems need to be sized appropriately for the situation they're placed in. A 30k BTU/hr machine would never compare to a 500k BTU/hr machine, regardless of how the heat is sourced. But comparably rated machines will be equivalent heating potential. I think this is the source of some people's misunderstanding.

NorthernMonkeyGirl

Joined: 10 Apr 2011
Posts: 4630
Location: Peeping over your shoulder

Posted: Mon Aug 01, 22 4:58 pm Post subject:

I came across some heat pumps that were suspiciously cheap (£700 plus installation) given the costs for a full system (the ones eligible for the £5000 Boiler Upgrade Scheme).

I was less suspicious when I looked at them as a standalone air conditioner unit that happened to be reversible.

I'm wondering if - with insulation work etc - one standalone heat pump would suffice for most days in the year, leaving the gas central heating to take over for that odd week or two when things get grim.

I don't really know how to calculate and compare cost per degree C increase?

I do like this youtube channel though - in terms of helping me understand how a heat pump claims to be so much more efficient - it's because you're powering a compressor rather than making a wire glow red hot.
https://www.youtube.com/watch?v=43XKfuptnik

Slim

Joined: 05 Mar 2006
Posts: 6614
Location: New England (In the US of A)

Posted: Mon Aug 01, 22 5:09 pm Post subject:

Look to your current heater's BTU capacity, and look to the BTU capacity of the heat pump you're looking at, particularly at different outside air temperatures. We have a decently insulated 1,800-ish square foot house (but not without some serious air leaking from the basement that we hope to one day address), and if we wanted to rely on our one heat pump alone it would keep the house comfortable until the absolute coldest nights, and even then I don't think pipes would freeze!. If we were trying to heat with only heat pumps we would probably need a second unit.

Most folks here see them as supplemental heat, plus air conditioning, as you describe, which is the mindset that efficiency Maine is trying to move beyond in the linked article! I think it would work for you, though it can depend a bit on house layout (works best if the unit can blow air in a way that circulates more than just one room)

Mistress Rose

Joined: 21 Jul 2011
Posts: 16004

Posted: Tue Aug 02, 22 7:07 am Post subject:

I think one major difference between British and US systems is that British are designed to heat radiators and US to heat air. Heating radiators is not an efficient way to use heat pumps as the radiators need to be doubled up at least, and even then they don't work that well. The construction of British houses makes putting in air systems difficult in most cases. We are not used to air conditioning in houses, so I would think that putting a heat pump into that system would make it easier to install.

Nicky cigreen

Joined: 25 Jun 2007
Posts: 9887
Location: Devon, uk

Posted: Tue Aug 02, 22 9:37 am Post subject:

a lot of uk houses are old, and bringing insulation up to levels needed by air source heat pumps is not possible. Obviously new houses need to be built with that in mind, but the viability of knocking down old houses and rebuilding them is a whole other question.
Plus the noise factor is still an issue. A lot of our homes are squished next to each other. And the outside space to put equipment - not every home has it.

Slim

Joined: 05 Mar 2006
Posts: 6614
Location: New England (In the US of A)

Posted: Tue Aug 02, 22 9:48 am Post subject:
You're both ignoring my point about sizing units appropriately for delivery of BTU/hr.... This article was about air to air, but there are units to heat water. If sized appropriately, they will put the same BTUs through a radiator per hour as a boiler.....

Nicky cigreen

Joined: 25 Jun 2007
Posts: 9887
Location: Devon, uk

Posted: Tue Aug 02, 22 10:52 am Post subject:

I take your point that you need the right size unit for the job required.

my point was if there is nowhere to locate said unit due to lack of actual space or the noise generated, or if it isn't possible to improve insulation to required standard, then even if it is proven to work, it isn't a viable option. I can see it could be great if you have a modern well insulated house with lots of space around it, but the vast majority of housing in the uk is not like that. Plus I suspect electricity costs a lot more here than there, which is another factor.

There is backlash against ASHPs in the uk because the gov has issued grants, for something that is largely attractive to those that are better off - and can afford that home with lots of outside space and potentially higher electricity bills, whereas perhaps that money ought to be spent on communal systems for terraced houses and blocks of flats.

Slim

Joined: 05 Mar 2006
Posts: 6614
Location: New England (In the US of A)

Posted: Tue Aug 02, 22 12:45 pm Post subject:
I take all your points, but don't think what you're saying and what I'm saying are mutually exclusive!

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28239
Location: escaped from Swindon

Posted: Tue Aug 02, 22 1:26 pm Post subject:

Nicky Colour it green wrote:

Communal makes a load more sense in general in the UK.
My house is hardly small, but even here I struggle to see where a heat pump would fit, and I can't think of any properties I have ever lived in where it would have easily fitted.

gz

Joined: 23 Jan 2009
Posts: 8962
Location: Ayrshire, Scotland

Posted: Tue Aug 02, 22 1:32 pm Post subject:
We have just had the leaflet in the post..but as we live in a 1940s scheme house, where the insulation is wrapped outside 5 years ago and 1970s roof insulation under a metal roof, single UPVC glazing and a solid concrete floor.... So even if the landlord was interested, the most sensible options are increased insulation of various kinds.

NorthernMonkeyGirl

Joined: 10 Apr 2011
Posts: 4630
Location: Peeping over your shoulder

Posted: Wed Aug 03, 22 10:36 am Post subject:

Insulation is the first line of attack (defence?), but that applies to any heating system.

The UK grant only covers air-to-water, the intention is to fully replace a normal heating and hot water system.

The "suspiciously cheap" unit I am looking at is air-to-air, looks like an air con unit, and if sized appropriately I could have the same level of heat produced as a gas boiler - and that heat would be lost through bad insulation no matter where it came from.

So the question is what is more expensive or worse for the environment out of a gas boiler with average insulation, or running the compressor of an oversized air-to-air heat pump compensating for average insulation?

If by next year I do give it a go (insulation upgrade first!), happy to share experiences. I would still have the gas boiler for hot water and topping up in the depths of winter so I wouldn't be getting the full benefit of disconnection.

tahir

Joined: 28 Oct 2004
Posts: 45676
Location: Essex

Posted: Wed Aug 03, 22 2:40 pm Post subject:
The only benefit of electric heating is if the grid is mostly renewable, which it currently isn't. Three things need to happen to make this worthwhile: 1. Improve building regs 2. Provide meaningful grants to get existing stock up to meaningful levels of insulation 3. Increase the amount of energy provided by renewables

Nicky cigreen

Joined: 25 Jun 2007
Posts: 9887
Location: Devon, uk

Posted: Wed Aug 03, 22 8:52 pm Post subject:

there was a feature on the pm program on R4 this evening on air source heat pumps - pro ASHP experts answering listeners questions. Unfortunately the answers came over (to me at least) as evasive and even dodgy in places.
eg when asked about the noise - the expert said you wouldn't be able to hear it above urban traffic. So.. for the rest of us without urban traffic? She said you could turn it off at night, which made me think 'oh you would need to turn it off because of the noise?' but without explaining the knock on on efficiency that would have.

and on the cost difference of replacing gas boiler with ASHP system - as there would be all new rads and pipes there would be warrantees built into those new items and that had a value. Don't think that would be a huge comfort when paying off that big debt..

On the cost difference running the system, the expert said with a well insulated house you might, at today's tariff, be paying £850 per year, and it would 'only be a bit more' at £1000 pa. that's 17.6% more - that's a noticeable bit more and will be worse when tariffs are higher.

So I sat down to listen to this feature, I need to learn about it, and I understand we need to move away from gas boilers... only to hear what sounds like a lot of glossing over, bending of truths etc. It doesn't make me want to rush towards it as a solution..

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