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What is the maximum output of the Vaillant 7kW Arotherm Plus

Air Source Heat Pumps (ASHPs)

Last Post by Judith 1 year ago

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AdamK

(@adamk)

Reputable Member Member

Joined: 1 year ago

Posts: 211

Topic starter 01/03/2025 10:11 pm [#2156]

what is the max this HP can output? are they under the rating or over?

heat loss on my property is 5.58kw-6.8kw depending on surveyor.

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Mars

(@editor)

Illustrious Member Admin

Joined: 5 years ago

Posts: 4516

01/03/2025 11:56 pm

Data badges are performance labels for heat pumps that show how much heat they can produce at different outdoor temperatures. For example, a heat pump might output 8 kW at 7C but only 5 kW at -3C. These numbers are crucial because they tell you how well your heat pump will perform in different weather conditions.

Since you have a Vaillant 7 kW Arotherm Plus. At 7C, it should output around 7 kW, which is its rated capacity. At -3°C, the output drops to about 5.5–6 kW, depending on settings.

Your heat loss is 5.58–6.8 kW, so the Arotherm Plus should be able to handle most of your heating needs. However, during extreme cold (e.g., below -3C), it might struggle to meet the upper end of your heat loss (6.8 kW), and you might need to rely on backup heating during those cold snaps.

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JohnR

(@johnr)

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Joined: 1 year ago

Posts: 106

02/03/2025 9:33 am

According the the Vaillant app, my 7kW Arotherm+ produced 7.6kW when the outside temperature was -7C.

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JamesPa

(@jamespa)

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Joined: 3 years ago

Posts: 4714

02/03/2025 9:58 am

Posted by: @adamk

↑

what is the max this HP can output? are they under the rating or over?

heat loss on my property is 5.58kw-6.8kw depending on surveyor.

There is a table here showing figures generally well above 7kW

PROFESSIONAL.VAILLANT.CO.UK "https://professional.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/arotherm-plus-installer-quick-guide-2848532.pdf"

However there has been recent speculation that these figures are gross output and do not take into account defrost cycles (which, if it is the case, is rather misleading).

https://community.openenergymonitor.org/t/vaillant-maximum-output-capacity-testing/27221

https://community.openenergymonitor.org/t/vaillant-maximum-output-capacity-testing/27221/62?page=4

It might be wise to ask the question explicitly of Vaillant Tech support if you are marginal. They are generally very helpful at least in my experience.

My heat loss is 7kW (or 16kW if you believe two surveyors!); the 7kW Vaillanthas worked for me in practice, Ive only had it since November though, design OAT-2.

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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AdamK

(@adamk)

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Joined: 1 year ago

Posts: 211

Topic starter 02/03/2025 3:18 pm

Thanks all. Think it should be ok. If not I’ll start upgrading rads in cold rooms.

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Judith

(@judith)

Prominent Member Member

Joined: 2 years ago

Posts: 519

02/03/2025 4:26 pm

On the Vaillant app our 7kW showed9.1kW at ~+2C. I suspect that is a bit on the high side of the measurement accuracy though.

@adamk your surveyor may suggest radiator changes for some rooms, but but you can decline.

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with SCOP 4.7) open system operating on WC

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