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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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Derek M

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15/11/2021 1:14 pm

@batalto

I am considering using the controller - but at this moment I don't see the advantage. I am sure @heacol will come along and tell me it has many advantages I am not yet aware of.

The advantage is that you should get more precise control of the indoor temperature, without fluctuations that may be caused by solar gain and the like. Having more accurate control may then make it possible to lower the desired temperature setting slightly, which would give the benefit of reduced energy consumption.

Having said that, it is your choice at the end of the day.

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batalto

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Topic starter 15/11/2021 1:17 pm

@heacol the thermostat is set above the temperature in the room - so the system is just "on". Its not switching on and off at all

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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15/11/2021 1:38 pm

Posted by: @batalto

@heacol the thermostat is set above the temperature in the room - so the system is just "on". Its not switching on and off at all

same as I'm doing. My 'stats are set to 30C, house never more than 22C

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Brendon Uys

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15/11/2021 1:48 pm

@batalto As a trial, that is fine, however if you want to get the best performance, you need to optimize the entire system, not only the controller. You are only doing 1/4 of the job if you are just turning the thermostat up.

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batalto

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Topic starter 17/11/2021 9:24 am

So far so good in terms of heating - house is plenty warm. Annoyingly my app isn't working so I cant see power used vs heat delivered. I'll be calling them later to try and find out what's going on with things. It was very very helpful to understand that data

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batalto

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Topic starter 23/11/2021 9:49 am

Tweaked my curve last night. Went to 50@-3 and 25@17 down from -4 and 18. House is warmer today. The back room remains my largest issue, as its the hardest place to warm up. The rest of the house is very house. My child and wife also don't help matters; the former turning off one of the radiators and the latter covering everything with washing and then complaining the room isn't warming up.....

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batalto

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Topic starter 25/11/2021 7:37 pm

The app is still not delivering COP or any other data. @grahamh do you have any idea why the app might stop showing this? I'm not sure if it's me, or the app. Do you know anyone else who might have a Midea unit they could check? Otherwise I'm going to have to put in my own monitoring system, which is fairly costly in parts and a plumber

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batalto

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Topic starter 26/11/2021 10:40 am

And the app is suddenly working again. Nothing logged since the 17th, but... At least it's working again

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Graham Hendra

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26/11/2021 1:43 pm

speak to the guys at freedom who supply all the mideas in teh country. Paul is the midea app guy he will fix it. I no longer work for freedom so cant really assist, i am not an app guy tbh. to complex for me .

Heat pump builder

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batalto

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Topic starter 26/11/2021 2:13 pm

@grahamh I just know you have a lot of experience with the units themselves. The app is working again now. I don't think FHP will be much use, it seems to be a data/server issue from Midea. I imagine only they/the app development team can really fix the issue.

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Graham Hendra

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26/11/2021 2:15 pm

yep the app was written by freedom, well one of them was, worth checking. im more a mechanicla and electrical guys, fluid flows my thing. i still have a honeywell mechanical stat onmy heat pump, i dont need an app. if my house is cold my wife will call me

Heat pump builder

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batalto

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Topic starter 26/11/2021 2:18 pm

@grahamh I have both the MSmart app and the Comfort Home app. From what I can see, they are identical. The Comfort home seems to just be a reskin of the Midea (or vice versa) - even the images are even the same in the background. The setup is also the same, it just seems to redirect data to the other app. However both had the same data retrieval fault, which leads me to believe this is a Midea server issue - the place where the data is stored.