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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

(@batalto)

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Joined: 5 years ago

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Topic starter 29/06/2021 12:26 pm

I just stuck with the normal one. The company wouldn't provide a guarantee with tanks that aren't already tested by them and they have knowledge of installing. Currently they are trying to work out my plumbing and heating system. Always fun to watch others rate someone else's work - "where does this go?" "Why did they do that?"

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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Kev M

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29/06/2021 1:23 pm

@batalto, good luck, hope it all goes well. 👍

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JulianC

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29/06/2021 5:41 pm

@batalto 😊. I know what you mean. There don’t seem to be any standards

Daikin Altherma 3H HT 12kWh ASHP with Mixergy h/w cylinder; 4kW solar PV with Solic 200 electric diverter; Honda e and Volvo EX30 Ultra Twin Performance electric vehicles with Myenergi Zappi mk1 & Ohme chargers

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batalto

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Topic starter 29/06/2021 7:50 pm

First day over. The pump is in and the lines into the house are done. Tomorrow the electrician will come and do his bit including surge protection for the whole house.

For the tank, it looks like we are going to have to wait a few days for the proper one to come. In the meantime we'll stay on gas and we'll just have to wait it out.

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batalto

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Topic starter 01/07/2021 3:37 pm

Everything is now done, bar swapping the tank. Currently the old boiler is disconnected, so no heating (not an issue right now) and the hot water is being done on a heating element which is on for 3 hours a day at mid day. For some reason my Solic200 main board has failed, I can either return it to them and they'll fix it in around 4 weeks, so they'll sell me a new one for half price.

Need to wait for the new tank and then we can switch over fully to the ASHP. Also I have the option of getting a load of batteries which aren't needed anymore at a reasonable price. So I might bulk out my current 7kwh meaning I can better use my solar in the shoulder season and winter. Also means moving to Octopus GO or even agile might represent even better value for me.

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JulianC

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01/07/2021 4:16 pm

I’d go with the free replacement board for the Solic

Otherwise you are still using solar to run the immersion. It’s just not operating dynamically when you boil a kettle.

Im glad the install went well. Shame they measured the tank incorrectly or did they send the wrong one?

Photos please 👍

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batalto

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Topic starter 01/07/2021 7:34 pm

@julianc I might take it out, but the lazy person in me just thinks take the half price replacement. Luckily the batteries balance it out at the moment.

Supplier sent the wrong tank. 510mm on the box, 560mm in the box!

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JulianC

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01/07/2021 9:03 pm

I know what you mean - easy replacement

Shame on the wrong tank. Is your installer ok to return and fit? Mixergy sent the wrong part for my tank - some resistor. The replacement turned up very quickly

👍

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batalto

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Topic starter 01/07/2021 10:07 pm

@julianc yeah they are fine and just waiting on the replacement to come in. For the time being we are just waiting but no rush given the temperature of our house. In the summer we don't need heating and our batteries/PV mean we aren't short of electrical power to deal with water.

👍

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batalto

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Topic starter 08/07/2021 11:28 am

Tank is now in stock and will be installed next Tuesday. The installer stated he didn't want it to be a "Friday" or "Monday" job. Given the weekend and the football I am inclined to agree.

As another note, I also picked up 7.5kwh of storage today for £1,150 from someone who didn't need it. Once installed it will take usable storage to just under 12kwh. Given our normal daily use is about 12-16kwh (pre ASHP) I think this is a great deal. Planning on moving to Octopus Go in the autumn and topping up all my storage overnight in the winter months for 5p a kW - At 2.8COP that brings my energy cost down to 1.75p per kw, half the price of my current gas tariff

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JulianC

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08/07/2021 11:39 am

Fantastic job. That is really good cost of battery storage.

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batalto

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Topic starter 08/07/2021 11:51 am

@julianc all in I think the total battery cost is about £2,500 for 14.2kwh. I don't include the inverter as I needed that anyway to make the solar work!

As a side note, a powerwall is £7.5k for 15kwh including the inverter, however it can output at 5kw and I can only output at 3.5kw and a powerwall has a power cut switch which allows you to keep running in the event of a power cut. However I'm not sure that's worth £5k to me.

👍

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