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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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Craig1980

(@craig1980)

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Joined: 3 years ago

Posts: 146

Topic starter 30/11/2022 10:48 pm

Running

Stopped

Nothing particularly jumps up or down when pump restarts but you can see some figures have dropped when it stops.

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Derek M

(@derek-m)

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Posts: 4425

30/11/2022 11:14 pm

@craig1980

As you say, nothing appears to be changing dramatically. Though I fail to understand how your home is maintaining an indoor temperature of 18C, with an outdoor temperature of 6C.

Now try setting your system in fixed LWT mode with a setting of 35C.

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Craig1980

(@craig1980)

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Posts: 146

Topic starter 30/11/2022 11:23 pm

@derek-m I've no idea. 🤣

I turned the system off for the Octopus saving session at 17:30 room stats showing 18. Went out and came back at 20:30. Turned back on and room stats were at 17.5. Not sure if you need that info but just in case it's relevant.

I'll have to work out how to set fixed lwt mode. I'll do it tomorrow. Thanks again.

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Craig1980

(@craig1980)

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Topic starter 01/12/2022 8:53 am

@derek-m overnight it was 4 degrees and it has struggled to keep 18. The house is at 17.5 this morning. COP is down to 3.3 and it's using more power and running for longer. 15.6kw yesterday 13.3hours operation time (that's with turning off for 3hours)and a generation of 51.7.

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Craig1980

(@craig1980)

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Posts: 146

Topic starter 01/12/2022 8:53 am

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Craig1980

(@craig1980)

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Posts: 146

Topic starter 01/12/2022 9:58 am

I'm struggling to find where to switch to fixed LWT mode. 🙈

Although, whilst looking through the manual I found the page about removing the room stats from the system. Would this be an option? Thanks

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Craig1980

(@craig1980)

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Topic starter 01/12/2022 10:12 am

Is this what you mean?

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Derek M

(@derek-m)

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01/12/2022 10:31 am

Posted by: @craig1980

↑

Is this what you mean?

Yes, that would appear to be the correct method. Try running with a LWT of 35C and see how the system responds, and if it stops the 20 second off periods.

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Craig1980

(@craig1980)

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Topic starter 01/12/2022 11:31 am

Okay, that's done. It was already on standard temperature "water outlet". Could that have been an issue?

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Derek M

(@derek-m)

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Posts: 4425

01/12/2022 12:01 pm

@craig1980

How is the system operating now? Is it still running 8 mins on and 20 secs off?

What is happening with the room and radiator temps?

What are the flow and temperature readings etc?

Changing the way that the system is being operated is to try to find what is causing the 20 seconds shutdown.

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Craig1980

(@craig1980)

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Topic starter 01/12/2022 12:15 pm

So, it appears to run constantly but at quite high power usage of 1.9kw instantaneous power.

Rads feel warmer to the touch but room temp stays at around 18 according to room stats and thermometers that I used for radiator temps.

Outside temp is 6.0 according to wired remote.

Water outlet 35.4

Indoor 21.5 (remember, this is in the airing cupboard with the UVC).

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Derek M

(@derek-m)

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Posts: 4425

01/12/2022 12:34 pm

Posted by: @craig1980

↑

So, it appears to run constantly but at quite high power usage of 1.9kw instantaneous power.

Rads feel warmer to the touch but room temp stays at around 18 according to room stats and thermometers that I used for radiator temps.

Outside temp is 6.0 according to wired remote.

Water outlet 35.4

Indoor 21.5 (remember, this is in the airing cupboard with the UVC).

Now measure the top and bottom temperatures on two or three relevant radiators, and the flow rate and temperature readings from the information screens.

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