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Thread: Evohome with Heatpump - Shortcycling Inefficiency due to limited boiler settings.

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  1. #1
    Automated Home Lurker
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    Mar 2018
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    Default Evohome with Heatpump - Shortcycling Inefficiency due to limited boiler settings.

    Running a fixed speed heat pump from Kensa. They have high starting currents and poor efficiency below 6 minutes.

    There is a very good report here on how inefficient it is to run the heat pump for < 10 minutes.
    https://assets.publishing.service.go...heat_pumps.pdf

    So with the Evohome, i have set the maximum # of starts per hour to 3. Which is fine doing a good job of limiting how many starts.

    Its the minimum run time to the heatpump(boiler) that is limiting my efficiency. The maximum allowed is 5 minutes. I would like to set it for 10 minutes to eliminate this shortcycling when all rooms are close to target (Most of the time at start/end of winter season).

    With underfloor heating in all rooms and a GSHP, 5 minute cycles is just too short. These systems need less but longer cycles to be efficient.
    These systems have expensive buffer tanks added to make sure the heatpump can run for its designed minimum period, but evohome is cutting it short, making most of that redundant.

    Any ideas how i can work around this limiting 5 minute on-time ?

    Example of 2 hours at low load (all rooms close to target). Evohome uses all of it maximum 3 x start per hour, and its maximum 5 mins per start. So 15 mins / hour, or 25% run time.
    It needs more flexibility: 1 x 10 minute run or even 1 x 15 minute run. My hands are tied by Evohome and its frustrating.

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    Last edited by ecoheated; 5th November 2019 at 08:44 AM.

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