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12kW Samsung gen 6 short cycling

Craig1980 · 2022-11-23T23:30:08Z

Good evening. Welcome to my life staring at my ASHP and scratching my head. I've had a Samsung gen 6 12kw ASHP fitted with all new pipework and rads on an eco4 grant so you can guess that I was just handed the room stats for each of the two zones and told to adjust with the stat.The system was set at 55 and no WC. No legionella either (although I've turned this off and will run manually as and when). The house is a medium 5 bed, cavity bead insulation, loft insulation and double glazing. It's a 60s house but modernised and well insulated for its age. It is in West Wales so fairly mild climate. I like to run the house at 18 degrees max so I've set the WC pretty low at 20 and -3, 20 and 31. I'm getting a good COP at around 3.7 although that has dropped to 3.4 today. Using around 16kw including water heating for up to an hour. Temp today is 8-9 degrees and the pump runs for around 7-8 mins, turns off for 18 seconds then runs again for 7-8 mins. It starts at 100w and peaks at 800w. House is sitting at around 19 degrees. Water law is set up on Floor, should it not be set on Fcu and rad? What diffeference would that make? External thermostat #1 and #2 and remote controller room temp are all set on "room temp on/off or WL interlink on/off (water pump 3)". Is that correct? My question is how can I stop the short cycling and how can I improve efficiency? Sorry for all the questions but I've driven myself mad staring at that screen. 🙈🤣

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Derek M

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30/11/2022 5:03 pm

Posted by: @craig1980

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@derek-m outdoor temp remains the same through cycling process at 6.7 degrees

Is that the temperature indicated on the controller?

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Craig1980

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Topic starter 30/11/2022 5:04 pm

@derek-m yes. It's 6.4 now though.

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Craig1980

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Topic starter 30/11/2022 5:25 pm

I've just watched the outside temp on the display for the whole 8 min run. It starts at 6.6 degrees then by around 4 mins it's dropped to 6.3 degrees then in the last minute or so it climbs back to 6.6 where it cuts out for 20 seconds but starts again when still on 6.6.

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Derek M

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30/11/2022 5:31 pm

@craig1980

I'm looking for something changing, during the 20 second period, from the heat pump switching off, to it restarting.

Correct me if I am wrong, that your heat pump runs for 8 minutes or so, switches off for 20 seconds, then runs for a further 8 minutes or so, etc. etc.

A further thing that I find quite surprising is how low are the temperatures of your radiators, your home must be very well insulated.

The next test to try would be to change the controller mode from WC to a fixed LWT of say 35C, and see what effect this has on how your heat pump operates, and what changes occur to the radiator temperatures and room temperatures.

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Craig1980

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Topic starter 30/11/2022 5:37 pm

Yes, that's correct. 8 mins on, 20 seconds off then 8 on ad infinitum. There is no change in the outside temp during the 20 seconds.

I'm not sure if it's that great on insulation. Cavity wall beads, loft insulation, large double glazed windows but heating sits at 18-18.5 all day. Heat pump is on 24-7.

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Derek M

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30/11/2022 5:43 pm

Posted by: @craig1980

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Yes, that's correct. 8 mins on, 20 seconds off then 8 on ad infinitum. There is no change in the outside temp during the 20 seconds.

I'm not sure if it's that great on insulation. Cavity wall beads, loft insulation, large double glazed windows but heating sits at 18-18.5 all day. Heat pump is on 24-7.

The temperatures measured on your radiators would indicate that there is very little heat energy being transferred into your home.

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