air to air heat pumps work

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air to air heat pumps work
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dpack

Joined: 02 Jul 2005
Posts: 46244
Location: yes

Posted: Wed Aug 03, 22 11:38 pm Post subject:
at the risk of oversimplifying things, does fire work? if you are in a place with a decent sustainable fuel supply, burning wood makes sense

NorthernMonkeyGirl

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

Posted: Thu Aug 04, 22 6:26 pm Post subject:

NorthernMonkeyGirl wrote:

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

So, pour a glass of your preferred beverage and behold my Crap Maths With Assumptions

- assume 30 kW gas boiler
this converts to around 102300 BTU

- this says 24000 BTU at 1.9kW
https://www.appliancesdirect.co.uk/p/iqool24/electriq-iqool24-air-conditioner

So, let's say this particular ASHP gives off a quarter of the heat energy of the gas boiler. Ignore the cooling function for now.

My current tariff is 29.6p / kWh electricity and 7.4p / kWh gas. Ignore the standing charges.

So, an hour of ASHP would be 1.9 * 29.6 = 56.24p
An hour of gas boiler would be 30 * 7.4 = 222p

222 / 56.24 = 3.9 i.e ASHP is a quarter of the price of the gas

Which implies the cost per BTU is very roughly the same at this point.

So the questions are
- can the slow and steady ASHP maintain a suitable temperature?
- (noting that if only the gas boiler can reach the desired temp, you will be losing that heat and paying for it anyway, so would benefit from insulating)
- noise
- maintenance commitment and costs (and risks of poor maintenance, I guess)
- future utilities price changes
- future installation of domestic solar panels?
- better to spend money on insulating?
- worth having for the bonus air con?

Air-to-water heat pumps are a different beast again, with the probable need for bigger radiators (or switch to underfloor heating or something).

My two-doors-down neighbour has a heat pump of some variety and I occasionally notice it, but not really.

Please feel free to correct the maths!

Mistress Rose

Joined: 21 Jul 2011
Posts: 15993

Posted: Fri Aug 05, 22 7:08 am Post subject:

Our next door neighbours are installing a heat pump so we will see what their experience is. Dpack, I think that wood for heating is a very good idea, and one that we use. Unfortunately wood is being painted as worse than gas because of the particulate matter and so the sales are being regulated. Apparently the particulate matter given off by wood is evil and will kill you etc. although the carbon dioxide released is not 'fossil' so if it comes from local sustainable forestry will be absorbed again quite quickly.

NMR, if it comes out more expensive than gas heating, I can't see most people wanting to pay out more for heating with current costs. I also don't see how we can convert to electric cars and heating unless the electricity infrastructure is there to supply it. If a person has solar panels and can supply their own, or most of their own needs, it makes a lot of sense of course.

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Aug 05, 22 10:26 am Post subject:

Other thoughts - I thought the UK grid was getting an awful lot more wind power these days? Seems like you're heading in the right direction: https://www.nationalgrid.com/stories/energy-explained/how-much-uks-energy-renewable

The noise comparison to urban traffic does help give you a real world example of the decibels. My heat pump in a rural setting is not very bothersome, but as you've pointed out, UK homes need to be better insulated.
Unless I'm right next to the outdoor unit, or it's an absolutely quiet winter evening, I typically need to look to see if the fan is moving to tell if it's running or not. (You can hear it on quiet mid winter nights when there's no animal noises, no background traffic noise, etc). The indoor unit is practically silent.
As I've said previously, I've been woken up by older fossil fuel furnaces or boilers more than a great pump (they certainly don't have that same rumble of the old gas in-floor furnace in my older less insulated last house)

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Aug 05, 22 11:18 am Post subject:
Okay, I'm standing about 10 feet from my outdoor unit, which is running to cool the house. If I concentrate I notice the noise over the cacophony of the crickets this morning. More so if I'm facing towards it versus away... Mostly my brain can't filter out much other than the crickets, but I'm in a rural area, so there's a lot of them....

Nicky cigreen

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

Posted: Fri Aug 05, 22 11:20 am Post subject:
it is true that the noise factor is partly what you are used to - and boilers do have a noise, and we accept that. Also we are a country that typically does not have AC so not used to the concept of an outside unit fan whirring. I can see - as a nation of homes squished next to each other, disputes between neighbours as people place them thoughtlessly.

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Fri Aug 05, 22 10:04 pm Post subject:

Try this one for an accurate account of energy generation,
https://l.facebook.com/l.php?u=https%3A%2F%2Fgrid.iamkate.com%2F%3Ffbclid%3DIwAR3DFATkrO_bEeyYP-DxjgRrujS561pa6XLo-mD3oD1R-qYKG5WnELuAGik&h=AT3XoBWfLlq7eF1uFHEZzdU5jsBtIqY8DZgUKczpOSIUfx7mqstUmB0wxgivC-YPe9MuTyCUn3aGCEsTa4zbCnoNqSTH8QR66W1RYfmdQ-BQyov2-lCwnVKNlo3GmayQykv2&__tn__=-UK-y-R&c[0]=AT35FIqmE7-zjxh4xYQsfEWLu1qOsMMVwtj-Ox1atB-YcFjUoHDw_C-jn-OYNFiz17kzkZP0tObnnfZzbDR15QNKVwchvfXUCBpZBEv91JPJ-ZStQ4N-hGwsvU8vePUo6p2FiFM_gHvUvNHX--VlAgO1ADcwueNJvd0_c3u-lp2YZzyNiAkuOUxrqL3BdHrvgDWBvGzR0BOIfW46awDMS8fZ81KMxrs66AkTxOoPv3M

dpack

Joined: 02 Jul 2005
Posts: 46244
Location: yes

Posted: Sat Aug 06, 22 4:34 am Post subject:

ahh, i dont hand data to facebook

re noise, gas boilers are a mixed family, some make horrible noises

more importantly they can be badly sited and blast combustion products directly into your or your neighbours' spaces, some even blast onto public pavements

and burning fossil fuels is a bad idea we should abandon quicker than asap

retrofit is usually more difficult than make a new one that works but it can be done

every little helps, if it will be "cheaper" to run for a similar "comfort" level chances are it is "greener" as well

this is a slight tangent from energy supply etc but it is related

good clothes make turning it down or off an option, frugal shopping for good clothes might look"odd" but even a few degrees off the thermostat settings is less fuel and money
a £5 hat is better value than a £5 of fuel

when i had a choice of cold or hat, guess which seemed best

Mistress Rose

Joined: 21 Jul 2011
Posts: 15993

Posted: Sat Aug 06, 22 7:30 am Post subject:

As far as biomass is concerned, I was talking to a forester yesterday and we discussing this. Where there are large amounts of commercial forestry, the biomass people are paying a premium for the timber, which means it is too expensive for other users such as small firewood suppliers and in some cases small manufacturers of treen and furniture. Using it for the latter uses would tie up the carbon rather than chip perfectly useable wood for burning.

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Sat Aug 06, 22 9:44 am Post subject:

Around here the valuable tinder goes to lumber, etc, some lower quality hardwood go to cordwood, and in big operations the slash and low quality stuff go to wood pellets, and occasionally chips. With of course a diversity in harvest styles between different land managers. My neighbor let a company come and clear out any trees of value, and huge swaths of low quality stuff as well via feller bunchers. I haven't walked over there in a couple years, so it would be interesting to see how the regrowth looks. While the harvest was dramatic, they did at least leave lots of slash down on the ground, and lots of young trees for regrowth.
The folks who owned our land before us have clearly had it logged, but very selectively, likely via skid steer, so the impact has been less, and we definitely still have some 100+ year old oaks, pines and hemlocks.
Plantation style forestry was tried in this region on small scales about 100 years ago, and you can still see some of them if you pay attention looking for straight rows, but they're very rare up here. They didn't really make sense for our climate, geography, etc, so most of the region is natural regrowth.

Nicky cigreen

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

Posted: Sat Aug 06, 22 12:34 pm Post subject:

dpack wrote:

good clothes make turning it down or off an option, frugal shopping for good clothes might look"odd" but even a few degrees off the thermostat settings is less fuel and money
a £5 hat is better value than a £5 of fuel

when i had a choice of cold or hat, guess which seemed best

yep - wearing another jumper is the first line of action - it seems a recent idea that people expect not to have to wear layers. To me it is as natural as opening the door on hot days. I worry that Europe will go the way of US and Canada and expect cold houses in summer too... when you are in the situation of having to remember to take a jumper to the cinema or shopping mall because it will be too cold, in summer... then things have gone wrong.. and this is the normal for so many already

Mistress Rose

Joined: 21 Jul 2011
Posts: 15993

Posted: Sun Aug 07, 22 8:53 am Post subject:

Slim, if there are big parcels a lot goes to the sawmills, but it is uneconomic for small parcels. There is also very little coherent thinking on timber here either. Our beech plantation was put in about 1969. It has a final felling date of about 2049-69, and it has already been repurposed twice since planting. It was intended for the pulp mills, but we don't have any taking virgin hardwood now. We repurposed it for firewood, but that is currently 'evil' so we are repurposing again for charcoal. Sadly most of it isn't of good enough form for sawmilling, but any good trunks may go that way in our own sawmill.

Most of our wood is natural woodland and we get a variety of species out of that for a lot of different uses. It has been managed for possibly millennia though, as our part of the UK was inhabited virtually since man got this far north. There have been stone age artifacts found not far away, and we have Bronze Age field systems and tumuli under the woods, and Saxon boundary ditches, About 2000 BC and from about 400 AD respectively.

Nicky, yes, air conditioning can be a pain, as can places built for a specific climate. I was in Avignon one autumn on business, and it was so cold at night I had to wear a jumper in bed.

NorthernMonkeyGirl

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

Posted: Mon Aug 08, 22 8:25 am Post subject:

Agreed that a woolly jumper is the first approach, sadly that doesn't help keep the house itself dry (my tenancy contract actually gives minimum temperatures for the house to be kept at, and I did dip below those occasionally)

Re. heat pump noise, assuming that's what my neighbour had running the other night, it sits about 7m from my back door with a quiet road about 10m away, a car passing was louder than the hum. Can;t hear anything from the front of the terrace. I would compare to a slightly noisy extractor fan, perhaps? My own extractors are definitely noisier but they are a bit rubbish! I could see that if it were a certain tone or pitch, it would drive someone potty.
I wonder if there are showrooms for different models, I would hate to be That Neighbour who buys cheap and awful.

waerloga

Joined: 11 Sep 2011
Posts: 9

Posted: Sat Sep 10, 22 1:17 pm Post subject:

I have an air-to-air heat pump that is combined into a forced ventilation heat recovery system. The idea is to extract heat from the (still warm) air leaving the building rather than from the cold air outside the building.
This is easiest installed in a bungalow as the pipes are large (120mm plus insulation).
https://www.totalhome.co.uk/ventilation/index.asp

I am unaware of any other system that combines heat recovery ventilation and heat pump as a single unit like this.

dpack

Joined: 02 Jul 2005
Posts: 46244
Location: yes

Posted: Sat Sep 10, 22 1:57 pm Post subject:
i have come across heat exchange ventilation with a small fire heating a large bungalow it did have scandi spec insulation but that worked well a heat pump exchange rig might harvest a fair bit from inside and some from outside which makes sense

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