Air Sourced heat pump

[Theblacksheep]

Less efficient. Define "so cold". There's still a lot of energy in the air at 273K.

 

Coefficient of Performance of 4 at 7c and 2 at -5 (1kwh = 4 or 2 kwh of heating depending on the temp). At very low temps the aux electric heater will come on to boost it (set per heatpump) and it'll also come on once a week to get the temps over 60c because of legionella.

Edited May 25, 2021 by Theblacksheep

[mavhc]

Less efficient. Define "so cold". There's still a lot of energy in the air at 273K.

 

"the time you want the heating most is" [when] "the heat pump is least efficient."

[Andrew_C]

Yeeeesss... My question was really "how much less efficient - anything in real-world terms"?

[mavhc]

https://en.wikipedia.org/wiki/Coefficient_of_performance will be your starting point.

 

Weirdly gas isn't carbon taxed, but electricity is, even though electricity is 50% green, so there's a bias towards gas currently.

 

The question is what to do with the excess solar you generate, you can heat water in a storage tank, stays hot for about a week, but that's not going to get you through a month of cold cloudy weather. However you more you can generate the less you need gas, and eventually the fixed network costs will make it cheaper to get rid of gas. Of course as more people do that the fixed network costs on the remaining people will increase, causing a tipping point.

[jmak]

 

It would help if teh government gave out incentives to convert over time - I have seen some mutterings (can you see a muttering???) but nothing concrete

 

There is currently quite a generous incentive, but it's not easy to access and the consumer has to provide the funds up front.

 

There was the green homes grant, but that was such a shambles it was discontinued. The RHI is worth more money, but it's more complicated and paid over 7 years. The obvious solution (to me anyway) would be a 0% government loan. That way it is more useful to consumers and it doesn't go on the government books as spending.

[Theblacksheep]

Yeeeesss... My question was really "how much less efficient - anything in real-world terms"?

 

I just posted an example of two temperatures and the COP difference which related to the KWH in/out.

 

The obvious solution (to me anyway) would be a 0% government loan.

 

Tax gas 25%, fund green investment bank, 0% loans for high-efficiency panels, drop tax on batteries and solar panels to 5%.

Edited May 25, 2021 by Theblacksheep

[mikeprice]

I was hoping the last Election would be quite close and that the Green party would get enough seats to be able to have some influence

 

And we would get some proper incentives to install Green energy

 

But, as we know, that didn't happen

 

If I was in charge the above ideas would be at the top of my list.

I would aim for a situation where every house with a suitable roof has an incentive to install solar panels - although I think there might be problems with the distribution but all that can be worked on

[Andrew_C]

Start with EVERY new house has to be built with solar of some sort (with caveats re orientation etc) and/or GSHP / ASHP. No excuses for big developers who might give big party political donations to one party....

[mikeprice]

Start with EVERY new house has to be built with solar of some sort (with caveats re orientation etc) and/or GSHP / ASHP. No excuses for big developers who might give big party political donations to one party....

 

I would agree - and unless there are problems with protected trees or existing buildings - then orientation shouldn't be a problem if the site is planned with this in mind

 

also - ground source heating should be far simpler if planned in and installed when the building is being first built - so no reasons not to do that as well!

[mavhc]

Well, there's one reason, houses are already handmade expensive things, adding more expense won't help.

 

Make everyone pay for their pollution, and then offer interest free loans to get things to reduce it, paid back at the amount you're saving, so they cost you nothing. You were paying £x for heating/petrol/electricity, now you're still paying £x

 

Your £100k house cost £20k more to build, but saves £100/month in running costs, so you pay £100/month back on your loan for 200 months

[jmak]

Has anyone switch to a Air Source heat pump? What has your experience been?

Not quite a necro-thread, but revisiting....

 

Reason for updating now instead of waiting for a full year is that if you're still interested, the grant from April is a lot less generous unless you already have a very efficient house. Partner's mother has just had an estimate for a 1980s 3 bed detached house with oil fired heating and should be eligible for about £9000 RHI payments. Downside is that it's paid in installments over 7 years after you install it rather than an up front grant, but if you can take out a loan, you'd be better off.

 

Our ASHP was installed in June, but it hasn't really been tested until now. We live in exactly the type of house that's cited in some newspapers as totally unsuitable: Victorian, solid walls, windows double glazed, but 20 year old wooden frames, oil fired boiler running at 70°.

 

Relieved to report that the house is warm, which was our biggest concern - in fact we're struggling to get used to it. The installers were adamant that it was a case of designing a suitable system and setting an expectation that it's not just a drop-in replacement for a traditional boiler and so far it seems they're right.

 

 

More technical stuff only worth reading if you have an interest in ASHPs...

 

At -1° this morning when it was working to raise the inside temperature from 16° to 19° the flow temperature was 40°. That's giving a scop of just over 3 for 12 hours when average temperature has been 0°. Average scop to date is about 4.6. The ASHP can automatically adjust the flow temperature up to 65° (at which point it won't be efficient, but I'm now very confident it will keep the house warm even on very cold days) and there are two built in auxiliary heaters if even that isn't enough.

It was an expensive installation, but we had to have an EPC which scored an E and came with recommendations for spending at least 50% more than the ASHP system to save up to 35% of our heating needs and would still have left us needing to replace the broken boiler.

 

You can hear it - it's louder the harder it works, but today standing near it, the oil boiler 2 doors down is louder. We can't hear it inside except in the room it's next to - so again quieter than the old oil boiler.

 

It does need to run all the time as our house loses heat pretty quickly(thermostat set to 19°in the day and 16°at night), but that does mean the house is much more comfortable. We used to run the oil heating for 1.5 hours in the morning and about 6 hours in the evening (on at 4.30 to take the chill off by the time we got home and off at 10.30. Despite that, we're spending less than we would on oil (costs are higher than the estimates, but oil has gone up more than electricity).

Edited November 29, 2021 by jmak

[mavhc]

How many kWh of electricity does it use daily?

[nicholab]

Start with EVERY new house has to be built with solar of some sort (with caveats re orientation etc) and/or GSHP / ASHP. No excuses for big developers who might give big party political donations to one party....

 

I don't know why two new house built in the village had oil heating they should have had heat pumps!

[Andrew_C]

Because the Building Regs haven't caught up. If a builder can get away with something on the cheap, he will.

[mavhc]

Also they'll build houses in the same way we did 200 years ago so they're really expensive to modify later, and who do you pay to modify them?.....

[jmak]

How many kWh of electricity does it use daily?

It's complicated and varies a lot...

 

October looks like 11.2kWh/day

November looks like 27.5kWh/day, but yesterday it was more than 60kWh and today will only be about 18kWh

 

The system provides lots of data, but not in the way that I would like. It seems to focus on kWh of heat produced which takes varying amounts of electricity depending on relative temperatures. The electricity usage information for individual days resets at midnight, but yesterday I estimate it says it produced 200kWh of heat and when I was looking during the day it was running at a scop of about 3.2, so about 62.5kWh electricity. Today we're using much less heat and it's warmer; so far it's produced 75kWh heat from 15kWh electricity, so much more efficient at a scop of 5.

 

This is a graph showing heat generated over the last month:

 

 

To try and get an idea of how much electricity we're using for heating, I'm comparing our monthly usage against a month when we didn't have the central heating turned on (September).

 

Our electricity usage in October was 347kWh more than September.

November was 825kWh higher than September. Not all of the increase is heating - obviously we use lights more and cook more hot food. I do have the equipment to monitor all of it properly, but it needs to be wired into the consumer unit. While I could do that, it's very much against regulations and I have been trying to get an electrician to come for months.

 

I appreciate these amounts are high, but for context we were buying between 3500l and 4000l of heating oil per year.

Edited November 30, 2021 by jmak

[woodham]

you raised an intresting point about noise , i wonder what its going to be like when they are more common and people have to live with the constant drone of heatpumps its the one bit that im concerned most about

[mikeprice]

I wonder what the regulation say about putting them in spaces that are shared and has walls from both houses

 

e.g. my sister-in-law's house has a passageway between the houses with a 'flying freehold' over the top of it - both houses need access down the passageway but there may be room for an air source thing on each side

 

but the room over the top could becoem rather noisy maybe

 

and also - as there are walls on each side and a roof above - the rooms on each side would also get more noise than normal

 

 

 

probably an extreme case - just wondering

[StevieM]

I wonder what the regulation say about putting them in spaces that are shared and has walls from both houses

 

e.g. my sister-in-law's house has a passageway between the houses with a 'flying freehold' over the top of it - both houses need access down the passageway but there may be room for an air source thing on each side

 

but the room over the top could becoem rather noisy maybe

 

and also - as there are walls on each side and a roof above - the rooms on each side would also get more noise than normal

 

 

 

probably an extreme case - just wondering

 

 

My house is the same and I wouldn't even consider putting one in the passageway (let alone two). Apart from accessibility, it wouldn't be a suitable location as it is too enclosed.

[Rob_D]

I wonder what the regulation say about putting them in spaces that are shared and has walls from both houses

e.g. my sister-in-law's house has a passageway between the houses with a 'flying freehold' over the top of it - both houses need access down the passageway but there may be room for an air source thing on each side

but the room over the top could becoem rather noisy maybe

and also - as there are walls on each side and a roof above - the rooms on each side would also get more noise than normal

probably an extreme case - just wondering

 

Maybe I'm a cynic, but if they become a requirement or standard for new builds you know that's exactly the kind of thing the planners/builders would do.

[jmak]

I'm guessing it will depend on what is determined to be The Boundary. Regs say at least 1m from the boundary and you usually need 300mm clearance behind.

 

When a surveyor visited my OH's mother, he mentioned 4m from a neighbouring house, but I can't find any mention of that anywhere. He also recommended against using an alcove type space as it can make them noisier. I suspect the passageway with a roof might create the same problem.

 

In terms of noise, mine is against my study wall underneath the window. I can hear it hum - until I turn my PC on which completely drowns it out. Realistically, I wouldn't want it on my bedroom wall, but anywhere else is fine. My parents live in a modern development set around a square with an extra row of houses in the middle. On their side of the square there are three sets of four house terraces. The only obvious place to put them on those buildings is on the front wall. One or two wouldn't be noticeable above the background noise level, but I suspect 12 might be annoying.

 

The ASHP I have also comes in a version you can install indoors - sounds illogical, but you use ducts to draw in warm(er) air and exhaust cold air. It's intended for plant rooms and they make big systems which are popular for blocks of flats in Germany, but I can't see why you couldn't put one in the loft and use a lot of soundproofing.

[Andrew_C]

Having lived in Texas, with the huge A/C compressors outside - yep, it will be noisy. However, in Britain, most of the noise will be in the winter, and evenings, when we are less prone to be outdoors.