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Replacing Worcester oil boiler with an ASHP

JulianC · 2021-03-30T18:15:26Z

I am replacing my 25/32 Worcester oil boiler with an ASHP Had discussions with many suppliers, a lot of whom wouldn't quote because we have 10mm pipe drops to each radiator, from 28mm loft pipes. Anyway: 201m2 bungalow. Built 2001. EPC rating of B after triple glazing, 300mm of loft insulation. We currently use between 1220-1500L of oil per annum. 100A incoming circuit. ASHP approved by DNO (Western Power). 20,500kWh of heating energy required. 3000kWh of hot water demand from the EPC. An energy loss calc and room by room heat demand has been undertaken. This has lead me to select Ecobubl from Winchester to undertake the work. They have proposed a Daikin Altherma 3H HT 18kW ASHP. Also a Mixergy 150L H/W tank - but we are also considering a standard cylinder with a large internal coil, to maximise the ASHP. And a 3kW immersion to use my 4kW of PV and Solic 200 electric diverter. Simple control system, using my current Nest. Had wondered about the Homely Energy control system, but I wonder if this adds complexity. Price is £13,700 for ASHP + Mixergy + buffer tank + installation and support for RHI. I should get back about £10k through RHI. I will take photos before, during and after installation which should be 12 April

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Air Source Heat Pumps (ASHPs)

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JulianC

(@julianc)

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Topic starter 31/10/2021 2:20 pm

Hi @kev-m our installer, Ecobubl did a hear loss and heat demand calc (required by MCS). He then used the Daikin ASHP tool to plug the data into, to come out with a heat demand and electric usage curve per month across the year. So I am just comparing my metered ASHP usage to this. I don’t know how much is supplied by my solar PV.
My solar PV does provide all of the hot water over the summer months. Meaning ASHP does run.

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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JulianC

(@julianc)

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Topic starter 31/10/2021 5:16 pm

@jeff yes both. Coming to about 21k kWh per year for both

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batalto

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31/10/2021 5:42 pm

@julianc the ASHP used 560kw in October, last year on gas we used 3,000kw. So all together not too shabby in terms of use. I get that as a cop of 5.3 (if demand was broadly the same) however I've been running the house overnight at 20 and at 22° between 00.30 and 04.30 due to the go tariff. So the house is probably far warmer than last year.

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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Mars

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31/10/2021 5:47 pm

@batalto, that's brilliant. Great to hear it's been such a success.

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Derek M

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31/10/2021 5:56 pm

@batalto Hi Batalto,

I am pleased to see that at least someone has been listening. Well done on your efforts to reduce your energy consumption.

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batalto

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31/10/2021 6:02 pm

@derek-m not sure I've been listening lol. My minimum temperature is set to 37° and the house is much more comfortable than it was with the water temperatures in the 20s. That said the radiators in our main room are far colder, so I think they need balancing.

As a note, I've never seen the ASHP use more than 3kw at any point yet. It's a 12kw pump, so it's performing admirably as far as I can see.

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batalto

(@batalto)

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31/10/2021 6:16 pm

From the data I have October should be roughly 6% of your annual demand. 565/6% = 9,416kw for the year. Last year we used 34,683kw. So if we can get by with 9.4MW I get an annual COP of 3.68

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(@heacol)

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31/10/2021 6:58 pm

@batalto 37 Deg C is vey high at this time of the year, I would expect to be running at least 10 Deg lower than that, however, it you have buffer tanks, system seperation, TRV's and thermostats, that is why you have to keep it that high with a resulting reduction in performance and increased electricity bill.

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(@heacol)

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31/10/2021 7:27 pm

Just for intersts sake, this is how a heat pump should be installed. It is exactly the same as a system gas boiler but with bigger pupes, valves and no control on the under floor or radiators (except in the bedrooms).

Mars, you can move this wherever you want.

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batalto

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31/10/2021 7:41 pm

@heacol less than that just doesn't warm up our main room - which is where we have the most heat loss. There is no way to fix it without changing a huge area of glass; the bi folds are more than 12m2. I think there is also an issue with radiator balance as they are coldest in the house. Once that's fixed I might be able to lower the temperature. However my current price per KW is 10p averaged, so I'm doing pretty well.

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(@heacol)

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31/10/2021 7:46 pm

@batalto Are you heating the whole house or just the main room?

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batalto

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31/10/2021 7:50 pm

@heacol the whole house, however that room would seem to have it's own climate. You can feel a difference in the doorway. The thermostat lives in the main room