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Mitsubishi Ecodan R290 10kW performance

Air Source Heat Pumps (ASHPs)

Last Post by Ecoste 49 minutes ago

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Ecoste

(@ecoste)

Active Member Member

Joined: 8 hours ago

Posts: 5

Topic starter 27/10/2025 5:09 pm

I have just had a Mitsubishi Ecodan R290 10 kW heat pump system installed. The system performance is excellent in most aspects, the house is warm, the temperatures are evenly distributed. An internal temperature of 22C at a flow temp of 35C and an external temp of 7C. Flow rate is 18 litres per minute and the delta T is 3C. However, under these circumstances the COP is 1.4.

There is no buffer tank.

It takes about 45 minutes to heat the 180 litre hot water tank to 50C, the COP for this is 1.2.

Does anyone have any suggestions why the performance is so poor.

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GrahamF

(@grahamf)

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Joined: 6 months ago

Posts: 84

27/10/2025 9:19 pm

It may be cycling on and off a lot. Do you have any graphs of the compressor frequency, water outlet/inlet temperature, other relevant data... over say a 24 hour period?

Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation

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JamesPa

(@jamespa)

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Joined: 3 years ago

Posts: 3196

27/10/2025 9:32 pm

I cant remember what Ecodan reports but some heat pumps report energy consumed and environmental gain. In this case cop = energy consumed/(energy consumed + environmental gain). Still not good, just not so bad if it is that that the Ecodan reports.

Have you got any thermostats or TRVs operational which might cause forced cycling

Is there a LLH (low loss header) included in a Mitsubishi pre-plumbed cylinder which might cause system distortion. How many water pumps are there?

Whats your house floor area and construction which might indicate an oversized heat pump causing excessive cycling.

FWIW BUS requires a min SCOP of 2.8 so as it stands the system is not compliant and installer has to fix it. Probably worth understanding whats happening though,

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Ecoste

(@ecoste)

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Posts: 5

Topic starter 27/10/2025 10:41 pm

@grahamf

It is not cycling, it ran constantly for 5 hours and then only dipped by 2 or 3 degrees for 10minutes. See attached report

Heat Pump Performance.pdf

This post was modified 38 minutes ago by Ecoste

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Ecoste

(@ecoste)

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Joined: 8 hours ago

Posts: 5

Topic starter 27/10/2025 10:50 pm

Posted by: @jamespa

↑

I cant remember what Ecodan reports but some heat pumps report energy consumed and environmental gain. In this case cop = energy consumed/(energy consumed + environmental gain). Still not good, just not so bad if it is that that the Ecodan reports.

Have you got any thermostats or TRVs operational which might cause forced cycling

Is there a LLH (low loss header) included in a Mitsubishi pre-plumbed cylinder which might cause system distortion. How many water pumps are there?

Whats your house floor area and construction which might indicate an oversized heat pump causing excessive cycling.

FWIW BUS requires a min SCOP of 2.8 so as it stands the system is not compliant and installer has to fix it. Probably worth understanding whats happening though,

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Ecoste

(@ecoste)

Active Member Member

Joined: 8 hours ago

Posts: 5

Topic starter 27/10/2025 10:55 pm

I am using my Powervault electricity monitoring App to monitor the electrical power, and I have calculated the heat transferred from the heat pump using the Mitsubishi data which gives flow rate, flow temp and return temp. See attached

Heat Pump Performance.pdf

There is no low loss header, I don't have the Mitsubishi cylinder. There are 2 pumps, in series - 1 on the flow and 1 on the return, see attached.

The floor area is about 200m2, in a well insulated 1930s house.

Ecodan R290 Schematic.pdf

This post was modified 36 minutes ago by Ecoste

This post was modified 35 minutes ago by Ecoste

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