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ASHP in Hampshire

batalto · 2021-04-22T13:28:11Z

Hi all, Just wanted to talk you through our upcoming ASHP installation. We live on the south coast, just outside of Portsmouth. The house is a detached home of around 260m2 in footprint. The bottom floor was an extended bungalow and we added a second floor. The first floor is standard construction, brick cavity that's filled and double glazed. The upper floor is made of Structurally Insulated Panels (SIPs) with triple glazing. We had to use SIPs because they are lightweight and so wouldn't affect the shallow bungalow foundations. As an upside SIPS are also extremely efficient in retaining heat and have a very low U value, 0.18. The loft has 200mm of insulation in the middle beneath the floor and 400mm of insulation for everywhere else. We have 8.4kW of solar PV on the roof and 7kWh of battery storage (Pylontech batteries). We also have a Solic solar PV heat controller, which will dump excess solar power into the tank before we export. We've just had our EPC done and we scored very highly A (93) that also provided a heat demand of 34w/m2 which tallies with our ASHP assessment of 36w/m2. The ASHP is a 12kw Midea with a stated SCOP of 3.36 supplied and installed by J A Rees, sourced from Freedom Heat Pumps - total cost just under £10k. We will be replacing our current 32kW gas system boiler and hot water cylinder and using the green homes grant for £5k of the cost and I will paying the other £5k. We qualify for the highest RHI so would expect to get roughly £7200 back over the next 7 years. The boiler will be retained as a backup heating system and isolated from the ASHP system. We have been told this is fine with the RHI as its a backup and not hybrid. The heating is currently set to 45 degrees and we have had no problems. Our main living area has a large bifold door system and west facing. This means we have significant heat loss in the winter and for 2 months its very cold and this makes the room chilly, but not cold. All the other months the solar gain is significant, heating the room and the rest of the house. With the conventional boiler the room is chilly, so I am expecting issues in January heating up the room. We might need to come up with a plan for this room, possibly some thick curtains. The install will be next week and should be very straightforward. The ASHP will go on the drive next to the current power intake. The pipework will go straight through the wall into the current boiler room and tap into the current pipework. The tank will need replacement for one with a larger coil, but more or less everything else will remain the same. The aim is 2 days. Currently our gas is 2.5p and electricity is 14p and the current boiler is 58% efficient (according to the boiler) - this leads to a bill of around £1250 for both gas and electricity for the year. With the ASHP, boiler efficiency and assuming a worse SCOP of 2.7 on the current tariff we expect the bill to fall to just under £1,000 (34,000kw of gas to 7,000kw of electricity). This cost includes a standing charge for gas even though we wont be using it. My plan after we have got used to the ASHP is to upgrade the batteries and add 7kw extra, then move to a new tariff. Agile GO is very interesting as I could fill my batteries at night and expend them during the day. The batteries would store 11.4kw (14kW @ 80% Depth of Discharge). I have estimated this would further drop my bills down to £780

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Air Source Heat Pumps (ASHPs)

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batalto

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Topic starter 09/12/2021 12:36 pm

@jeff no, it was 21 with a set back. Probably to 18, I can't remember exactly

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE

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batalto

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Topic starter 09/12/2021 1:15 pm

@jeff just checked and it was 2.44p/kw for gas and we spent about £140 for it. At our current gas tariff of 4p it would be £230 so that's my comparison target (for the heat pump).

Electricity wise, we used 416kw last December without a HP at a price of 14p/kw - Approx £58. Dual fuel we had a higher electricity tariff as we used so little in a year. Only 1.4MW due to our solar and batteries. This year so far we've purchased 2.7MW and we didn't have the heat pump at the start of the year.

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batalto

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Topic starter 22/01/2022 2:35 pm

I've finally received my bill for the 21st of November to the 20th of January. Why they billed two months together I have no idea.

Long and the short of it £423 for the two months.

3481kw @ 11.33p once the tariffs were blended plus standing.

1214kw at 5p - £57

2267kw at 15p - £336

Octopus Go and batteries seem to be keeping me in business for the moment

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batalto

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Topic starter 27/01/2022 2:51 pm

News update from me. The scaffold next door is finally coming down and my solar panels are now back in the sun... after 3 months. At least it was the darkest time of the year that it was up. Hopefully now the solar can start to make a dent into our costs now the full 8.4kw is available to us again.

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batalto

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Topic starter 09/02/2022 2:01 pm

looks like today might be somewhat of a landmark day for the year. If things continue I think we may well avoid buying any significant "peak power"

Current battery status is 84% so another 3kwh of storage left to fill. It'll be interesting to see if this gets us to 00:30 when the off peak rates kick back in!

👍

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batalto

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Topic starter 10/02/2022 9:30 am

I was so close - died just before midnight

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IanJRW

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10/02/2022 9:43 am

@batalto Hi batalto, newbie here (so cant DM you) - wondered if u could advise please....We're being offered a 8kW Midea that can be installed in time to catch the last of the RHI. Our home is much smaller than yours but just wondered how you're finding your Midea? Do you have an on/off thermostat (lots of voices on here saying it shouldn't have one) or do you just use the controller? I'm looking at your helpful COP tracker spreadie and just checking i'm reading it right - e.g. 25/1 : total power in 69kWh, power delivered 179kWh when ambient was ave 4degs with a COP of 2.59? Thanks for any feedback.

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batalto

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Topic starter 10/02/2022 9:54 am

@ianjrw I guess I find it fine. The app is a bit crappy and buggy, for example at the moment its not logging data for some reason - no idea why. House is plenty warm now we have the weather compensation nailed.

On your questions, I am using a nest thermostat. If I was to install again I would use the controller. I will swap to the controller at some point, but its a job that's a bit of a hassle so I'll get round to it at some point.

Yes I think you are correct - its worth remembering that ambient is an average of the whole days temperature. So it would have had a terrible COP overnight when its very cold and a much better one during the day hours. Better to look at the analysis tab which will show the "spread" of power and COPs for every temperature

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IanJRW

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10/02/2022 5:03 pm

@batalto thanks, thats great. So no combined COP under 2.5. Any idea why somedays you get better COP on the water, other days on the heating?

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batalto

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Topic starter 10/02/2022 5:11 pm

@ianjrw it can only be due to ambient temperatures when we are using the heat pump. I imagine there is a bit of an error bar in there too (in terms of measuring power used and heat delivered). However it will be broadly correct.

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IanJRW

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10/02/2022 5:29 pm

@batalto nice. I see you have set up your Current weather compensation: 50@-3 and 25@17. Is that easy to do with the Midea - a curve or straight line?

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batalto

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