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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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Morgan

(@morgan)

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Joined: 5 years ago

Posts: 698

04/11/2021 9:39 am

Posted by: @editor

@batalto, we changed our distribution pump and it made a world of difference. And you’re right, radiator balancing is extremely important.

@editor

I will probably need to research how to do the juggling act that is called radiator balancing.

Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.

2 ESS Smile G3 10.1 batteries.
ESS Smile G3 5kw inverter.

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batalto

(@batalto)

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Posts: 1092

Topic starter 04/11/2021 9:54 pm

So, after several days I am there. All of the rads are lovely and warm - ALL of them. So I've taken this moment to lower the weather compensation by 5°. We'll see how that goes over the next couple of days and then lower it again.

For background it's now 32° @ 16° ambient and 55° @ -2° ambient.

These figures are now subject to change until I get the system dialled in. But I can tell you, before ALL else balance your damn radiators. What a difference. Trial and error are 100% your friend. In fact I've still got one rad which I would consider too warm so I might dial it back some more to push more water where I need it.

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 04/11/2021 10:01 pm

@editor today's haul of filter crap. Considerably less than yesterday's

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Mars

(@editor)

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Posts: 4550

04/11/2021 10:25 pm

@batalto, much better. In a few days' time you'll have no more rubbish in your filter. Where is your filter located?

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batalto

(@batalto)

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Topic starter 04/11/2021 10:27 pm

@editor it's right next to everything else in the "plant cupboard". It's where the old gas boiler still resides with the solar batteries, inverter, consumer units, ASHP control, some coats and my son's collection of scooters. Being in the house and a 5 second walk from the sink makes checking it a 1 minute job.

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Derek M

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04/11/2021 11:20 pm

@batalto Shame on you Batalto, your radiators should not be lovely and warm, they should be lovely and cold!!!!!!

Joking apart, it may take some time to get there, but it will be worth it in the end.

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batalto

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Topic starter 05/11/2021 10:59 am

@derek-m using the MSmart APP I found I can see my power use and heat delivered! Its not perfect as it just gives you a number for the day, not hour by hour, however its a start.

Today so far we used 23kw for heating and 8kw for hot water. It delivered 68kw for heating and 13kw for hot water. With average hot water at 55 degrees and average heating at 41 degrees

Heating: 68/23 = 2.95 COP

Hot water: 23/8 = 2.87 COP

Given the hot water was this morning when it was warmer, that accounts for the higher COP. Last night we got down to 2 degrees, so I am fairly pleased with that COP. Also we use a lot of heating overnight due to the 5p tariff, so this is very deliberate. I run the system to get heat into the house. I might play with lowering this, as I am not sure I am seeing much benefit.

Yesterday as a whole

heating: 111 kw / 37 kw = 3 COP

hot water: 23kw / 11kw = 2 COP

Heating water setting average 44 degrees

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Kev M

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05/11/2021 1:24 pm

@batalto,

do you need your HW at 55? Unless you're having a lot of baths, you could maybe get away with less. Ours is 50 and even that's too hot for a shower or handwashing on its own so I might dial it down a little. It might not save many ££ but every little helps.

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batalto

(@batalto)

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Topic starter 05/11/2021 1:54 pm

@kev-m we found at 50 we started to lose the heat after morning showers. 55 seems to be the sweet spot

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Mars

(@editor)

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05/11/2021 3:35 pm

We've set out hot water to 44C - ideal for us, but it will vary on peoples' preference. Always interesting to see.

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batalto

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Topic starter 05/11/2021 9:45 pm

@editor I think for us it's a function of having a very high flow rate rain shower. All that extra cold water into the tank cools it fairly rapidly. Maybe we should be less decedent and get a normal shower... But I suppose there is a line between living and surviving

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batalto

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Topic starter 06/11/2021 12:08 am

This evening's update. Cleaned out the filter again, more crap in there. Hopefully I won't need to do this many more days now. Amazing how much rubbish was floating around in the central heating before the gauze was installed. I've also adjusted the heating schedule to remove the 00.30-04.30 heating push I've been doing for the last few weeks. I don't think it's making any difference in the scheme of things, so I've axed it. I imagine it'll cut power use, but at 5p over that time it'll make limited difference in the grand scheme.

I've adjusted my weather compensation down again. Now at 50° @ -2° and 30° @ 15°

The rads were all nice and warm today and that was 55 and 33. So let's see what impact this will have. I cannot stress enough how important balancing the radiators has been to this whole thing.

Finally I'm now extracting COP data from the app that can access my HP. No idea how accurate it is, but it's a start!

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