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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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Topic starter 24/11/2022 3:04 pm

@hughf well, that doesn't sound ideal. 😩

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HughF

(@hughf)

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24/11/2022 3:08 pm

Posted by: @craig1980

↑

@hughf well, that doesn't sound ideal. 😩

Whether it will make a whole lot of difference to your COP remains to be seen, but usually, with a modulating compressor (all modern ASHPs are inverter driven) and a modulating fan on the evaporator, you'd also want a speed controllable pump. This way when the ASHP modulates down, it can vary the pump speed to keep the delta-T within the optimum range.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.

👍

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Transparent

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24/11/2022 3:18 pm

That's a question to ask the installers.

Why did they suggest the Samsung unit?

Did they already have data to show that there was negligible increase in the COP by using an ASHP with the pump-speed variable?

Save energy... recycle electrons!

👍

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HughF

(@hughf)

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24/11/2022 3:38 pm

Samsung mono controller manual attached, this clearly shows the connection for external PWM pump control, Connection 10 on the main PCB.

It even says 'If you need an external inverter driven pump, make sure it is the same as that already installed' - then gives the grundfoss part number.

samsung-mono-controller-kit-manual.pdf

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.

👍

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HughF

(@hughf)

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24/11/2022 3:39 pm

Posted by: @transparent

↑

That's a question to ask the installers.

Why did they suggest the Samsung unit?

Did they already have data to show that there was negligible increase in the COP by using an ASHP with the pump-speed variable?

I doubt you'd get a meaningful answer from the installers.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.

👍

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Derek M

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24/11/2022 5:04 pm

@craig1980

Hi Craig,

PWM stands for Pulse Width Modulation, it is a type of control signal used quite often to vary the speed of pump motors and the like. If you Google PWM you may find a detailed explanation.

👍

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Craig1980

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Topic starter 25/11/2022 9:33 pm

@hughf looks like I should leave that alone.

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Craig1980

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Topic starter 25/11/2022 9:35 pm

@transparent I've had a chance to look through exactly what I have.

MCS certs for both.

NCIS certs for both.

Electrical installation certificate for both.

A copy of the G98 application.

No schematics or pre installation survey, I have asked for these so I'll see what I get.

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Craig1980

(@craig1980)

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Topic starter 25/11/2022 9:38 pm

@transparent I doubt they'd know. They fit Samsung or Vaillant but normally Samsung in larger properties. The Vaillant they fit is not a monobloc.

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Craig1980

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Topic starter 25/11/2022 9:39 pm

@hughf so, does this mean that had a different pump been connected we would be able to adjust pump speed? Thanks

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Craig1980

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Topic starter 25/11/2022 9:44 pm

Just as an update to this post yesterday's COP including water heating was very nearly 4. Electric usage was down at 11.1 with generation at 44. Happy with the numbers but still turning off for 20 seconds every 8 mins. I've turned the bedroom rad back on to see if more emitters would help but it hasn't.

Sat at between 18 and 19 all day except when solar gain took us above 21 degrees.

Also bled all rads today and got a decent amount of air out of 3 or 4 rads.

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HughF

(@hughf)

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Posts: 489

25/11/2022 10:04 pm

Posted by: @craig1980

↑

@hughf so, does this mean that had a different pump been connected we would be able to adjust pump speed? Thanks

If you wired it up with a pwm primary pump and used the samsung controller directly, I'd expect you'd see that COP up between 4 and 5 in the current weather.

If the Samsung controller had control of it's pump speed then it would be able to modulate all three components of the 'machine' - fan/pump/compressor.

I'm actually genuinely shocked that the Samsung monobloc isn't really very monobloc at all, and needs and external pump and flow switch. It makes me feel much more happy with my decision to go for an off-brand manufacturer for my own system (I went for a Cool Energy, made by SPRSUN in PRC, built on a complete Carel commercial refrigeration platform of parts)...

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.

👍

ReplyQuote