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Low COP on Samsung 16kw Gen6

catapult · 2023-01-23T18:03:37Z

TLDR: Improved the WC, but COP still bad at 2.1. What can I try next? I've been trying to learn about our Samsung Gen6 16Kw ASHP that was installed in April 2022 as the electric bills got scary when the weather finally turned cold, as we were running the ASHP like a gas boiler.... Thanks to this forum (and @craig1980 for asking all the questions!) I am now running the ASHP 24/7 with WC and the house is finally at a lovely constant 19 degrees (bedrooms at 16). WC was set up as outside temp +15/+2, water temp 37/55 (with +5 manual setting). Now it is +20/-10 and 25/50 (0 on the manual setting)(so approx 43 degrees water at -2 outside). Still fine tuning a little, but I don't think I can really go much lower. I will start reducing the room temp overnight for maybe 4 hours to see if that drops Kw usage a bit, but the house might not recover well. House has 11 radiators downstairs and 9 radiators upstairs, individual pipe to each radiator. All TRVs wide open except bedrooms. External Honeywell thermostats set to 21 degrees 24/7 and room temp holding at 19 degrees. But our usage today will be about 64 kW with a COP of 2.1, outside temp approx -4 to +3 degrees. Our COP was a median of 1.8 before I started fiddling, so it's definitely improved, but I was hoping there'd be a bigger improvement in COP and reduction in kW. Is it just a case of "suck it up buttercup, it's cold outside", and there'll be big improvements when it gets warmer? It's lovely having a consistently warm house, but I'd also like lower electric bills! My next step was to look into the hot water settings, but they don't seem too outrageous. Is there a way to make the hot water heat once in the morning only? We only really need it for 3 showers in the morning.

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Craig1980

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23/01/2023 10:01 pm

@catapult just on flow rate I believe the aim is 2 x the KW of your system so 16 x 2 =32 so you are thereabouts. Although I've actually turned my flow rate down to around 20lpm (I'm all rads btw) and I get a better delta T. Although my system, as you have likely already read, wasn't installed all that well.

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catapult

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Topic starter 23/01/2023 10:04 pm

@craig1980 ha, are any of them?

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Craig1980

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23/01/2023 10:08 pm

Well ours was on an Eco4 grant so they definitely just slapped it in and legged it. 😩🙄

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catapult

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Topic starter 23/01/2023 10:08 pm

@william1066 thanks for sharing. All makes sense. Nice to know others are going through the same tinkering, though I'm jealous of your graph! How do you take the readings, daily off the monitor, or do you have a remote system?

We have the hot water at 50 at the moment. Might be a mutiny if I tried 48. I'm tempted to just turn it off after the morning showers and see what happens to the kw....

Water flow in the rads is currently at 38 degrees and using 1.8kw according to the "instantaneous" reading on the monitor. Not sure how accurate that is, but would be 43kw/day which seems more reasonable.

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Craig1980

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23/01/2023 11:06 pm

@catapult my flow temp is 28-31 normally and that sits me at 18-19 degrees 24/7 all on rads. I'd imagine you should be much lower than that with underfloor heating. Unless you're aiming for higher room temp but I'd still expect lower flow temps.

I'd bet £5 you could turn the water down to 48 and no one would notice. I'm a long, hot shower guy and didn't think 48 would cut it. There's no way I could turn the shower to full hot.

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robl

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24/01/2023 1:13 am

@catapult

I’m pretty sure that black thing in your pic is a magnetic water trap. Strong magnets inside pick up bits of circulating rust flaking off from inside radiators - a good thing, as otherwise they get stuck in a heat exchanger, making it less efficient. The magnetic waste can generally be easily removed every now and then.

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Craig1980

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24/01/2023 8:19 am

@robl it definitely is.

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william1066

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24/01/2023 8:32 am

Posted by: @catapult

↑

How do you take the readings, daily off the monitor, or do you have a remote system?

For now off the controller UI, manually put it in a spreadsheet. I have installed the modbus adapter in the unit outside, just not had a chance to connect it up yet it is on the todo list.

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catapult

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Topic starter 24/01/2023 1:23 pm

I worked out the COP and usage/generation for the last few days. The weather turned on Jan 14 (from 10-12 degree high to 0-4 degree high), so perhaps that explains some of it. I changed the WC on Jan 19 (and also bled the rads).

Not as great as @william1066, but improving.

I tried turning down the thermostat last night from 11pm to 4 am by one degree. It took 7 hours to regain that 1 degree.... but Kw did go down quite a lot in total. House needs to be warm at 8am to stop people putting fan heaters on, so I'll try out a set back from 10pm to 1am next.

Also turned the hot water down to 48 degrees (shhhh). Let's see if anyone notices...

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catapult

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Topic starter 24/01/2023 2:18 pm

I found the heat loss calcs. House size 230sqm.

For space heating the house requires 26,479 kwh/yr. The HP is expected to consume 7,653kw/yr with a SCOP of 3.46.

For hot water the demand is 3,496kwh/yr. HP is expected to consume 1748kwh/yr (plus 515 from immersion) for SCOP of 1.75.

Is this good or bad? Any other numbers I need to find?

Edited: that's at a flow temp of 55 degrees and outside air temp of -1.8 degrees.

This post was modified 3 years ago by catapult

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catapult

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Topic starter 24/01/2023 6:10 pm

Posted by: @craig1980

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@catapult I'm not really sure if you can see how often the hot water turns on. Mine has always been on a schedule.

Schedule is dead easy to set up. Probably worth a try.

Does using the schedule override DHW heating the rest of the time? Or do you change the "temp to start heating" so low that it never heats, until the schedule comes round again? We only really need 3 showers between 7 and 10am. Not bothered about the temp the rest of the time as it's just for hand washing.

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Craig1980

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24/01/2023 6:26 pm

@catapult schedule overides the water heating. Mine heats up once for 1.5 hrs (often doesn't take that long) at 3am on our cheaper rate electric. When we get up the hot water is usually at least 48 degrees. We both have showers and there is still enough to wash up later and other small jobs with hot water through the day. You can set several on/off schedules.

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