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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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Topic starter 29/11/2021 11:58 am

@derek-m my heat loss is very linear. So linear in fact the trendline is 93% accurate

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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Graham Hendra

(@grahamh)

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29/11/2021 1:04 pm

tbh if you guys are into this this much you should contact homely, they will sell you a device which hacks into the midea unit and tweaks the output as it learns the heat loss of your house giving the optimum curve. try it here, ive seen it work on the midea, it is very impressive, me i have a RED, it just gets on with it on its own. https://www.homelyenergy.com/

tell them i sent you

Heat pump builder

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batalto

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Topic starter 29/11/2021 1:09 pm

@grahamh I'll take a look - as a side note, what a terrible website. It doesn't say anywhere what they actually do, or how it works.

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Graham Hendra

(@grahamh)

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29/11/2021 1:23 pm

thats techys for you

Heat pump builder

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batalto

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Topic starter 01/12/2021 11:06 am

I will be on a heating measurement adventure in the loft in the next day or two. My aim? To discover what my low loss header is actually doing. Specifically I want to know which of the below scenarios represents my current system.

Potentially I might just buy one of these - LINK - as its basically disposable (£20) and will give me 4 temperature sensors I can just install and use the app to monitor, rather than camp in the loft.

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Kev M

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01/12/2021 1:37 pm

@batalto

I like the thermometer in the link and think I'll get one.

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batalto

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Topic starter 01/12/2021 1:56 pm

@kev-m its £16 after discount. As long as its mostly accurate its fine for my needs.

👍

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batalto

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Topic starter 02/12/2021 1:03 pm

@kev-m its arrived and I have to say I am impressed by the little device. I can do it all over the app and it provides me some graphs which I can use to track the readings from the monitor. It came with 4 probes, but can handle 6 - for my imprecise needs its ideal.

Now I just need to install the little guy in the loft

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batalto

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Topic starter 02/12/2021 2:01 pm

RESULTS - both my heating circuits are running (upstairs and down) and it would appear my low loss header is just that... low loss. In fact it seems to be operating almost perfectly. The numbers basically match at top and bottom. I cant see any evidence of mixing of water. One slight concern is that HP shows 41 degrees on its own curve, yet the temperature prior to the LLH is 37. There could be some losses on the way, but I doubt 4 degrees. However my measurements are just meat thermometers shoved inside the pipe lagging next to the pipe. Still the main concern was LLH losses causing in efficiency and this seems to be dispelled for me.

I am just going to leave it logging until the battery dies (apparently 200hrs, we shall see) and then I can review what might happen.

👍

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Kev M

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02/12/2021 4:42 pm

Good result. I've ordered one of the thermometers. It will be good for checking and collecting evidence that my ASHP's sensors aren't recording properly.

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batalto

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Topic starter 09/12/2021 11:26 am

Current total power purchased this month is at 532kW so far - from the heat pump hard monitor, its used 426kW, which is less than the internal app says its used. So far, given the cold, I am pretty happy. On track to use around 1.5MW in December @ a nominal 15p/kw (ignoring GO tariff) that would be approx £225.

My usual DD is £134 a month and December is supposed to be around 15% of your total heating bill (or two months worth of DD). I would say I am on track and so far pleased with my results. The house is a toasty 21 degrees all day and night.

For context last December I used 5,765kW of gas for heating and hot water.

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Jeff

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09/12/2021 12:23 pm

Posted by: @batalto

Current total power purchased this month is at 532kW so far - from the heat pump hard monitor, its used 426kW, which is less than the internal app says its used. So far, given the cold, I am pretty happy. On track to use around 1.5MW in December @ a nominal 15p/kw (ignoring GO tariff) that would be approx £225.

My usual DD is £134 a month and December is supposed to be around 15% of your total heating bill (or two months worth of DD). I would say I am on track and so far pleased with my results. The house is a toasty 21 degrees all day and night.

For context last December I used 5,765kW of gas for heating and hot water.

Sounding good.

As a comparison were you getting a toasty 21 degrees day and night when you were using 5765kw of gas?

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