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Shutting down heating when out for the day - data

jamespetts · 2024-11-04T23:59:47Z

Having just had a new heat pump (Vaillant Arotherm + 7Kw) installed, I wanted to test how the energy usage wold be affected by shutting the system down while out for the day. I have read and heard suggestions that, unless going on holiday for multiple days at a time, it is more efficient to leave the system running constantly, but that made me sceptical, since it makes implausible assumptions about how much power is consumed during a compressor restart. So, yesterday, I was out of the house from around 0830h to 1900h. I turned off the heating using the Vaillant app just as I was leaving and turned it on again just when I was about to start the journey home (about 1 hour door to door). The weather conditions in London yesterday were very similar to those to-day, with an average outdoor temperature measured by my heat pump of 12.3C compared to 11.5C to-day. Yesterday's overall power consumption was 2.1kWh with a COP of 3.2. To-day's, with me working from home all day, was 3.1kWh with a COP of 3.2. This does suggest that leaving the house for multiple hours at a time does indeed require the system to be shut down during the away periods to minimise power usage.

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jamespetts

(@jamespetts)

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Topic starter 08/11/2024 12:57 am

To-day's data: heating off between circa 1530 and 2230 outdoor temperature 10.7C, heat curve 0.50, 2.4kWh consumed.

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jamespetts

(@jamespetts)

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Topic starter 12/11/2024 1:11 am

Friday and Saturday's data are probably contaminated with confounding factors as I had builders in leaving doors open. But Sunday's and to-day's are instructive.

Sunday: heating on all day, average outdoor temperature 9.3C, heat curve 0.50, 4.3kWh consumed, reported COP 3.2

Monday: heating off from 1100h - 1700h, average outdoor temperature 9.9C, heat curve 0.45, 3.2kWh consumed, reported COP 3.3

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Mars

(@editor)

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12/11/2024 9:58 am

@jamespetts the one thing you’re not mentioning is the temperature inside the house. Is it uncomfortable or cool when you get back, and if yes, how long does it take to warm up?

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jamespetts

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Topic starter 12/11/2024 11:26 am

Posted by: @editor

↑

@jamespetts the one thing you’re not mentioning is the temperature inside the house. Is it uncomfortable or cool when you get back, and if yes, how long does it take to warm up?

So far, the house has been comfortably warm when I get home. The door to door journey is about an hour, although yesterday, I stopped to talk to some colleagues before I left work and after I had turned the heating on and then took a long walk before getting on the train, so the house had even longer.

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