Struggling with performance of Samsung Heat Pump

Timbones · 2024-02-08T16:25:39.501Z

My heat pump was installed with a TPI-only thermostat, and fixed flow temp. The only way to disable TPI was to move the setpoint 1.5° higher than I wanted, then it would call for heat continuously. Then I could play around with weather compensation, and use other methods to turn off the heat pump when the house was warm enough. I made it work, but it wasn’t reliable.

markocoheat · 2024-02-08T17:53:18.530Z

Timbones:

My heat pump was installed with a TPI-only thermostat,

Awww. MCS at it’s finest.

Madsen68 · 2024-02-09T09:05:36.929Z

johnfresh:

I use a EPH Controls thermostat, it was about £50-00 there are options on which to have depending if you want timed on/offs or not.

Hi John

By any chance - do you have a model or partnumber. Need to have one…

Thanks

Arne

johnfresh · 2024-02-09T09:20:25.000Z

Hi

This is the programmable one

Mine is just the stat version non programmable
Regards

John

Screenshot_20240209_091902_Chrome.jpg1080×2408 202 KB

Michal_S · 2024-02-15T10:54:59.166Z

SarahH:

I use a Honeywell T3R which works OK with my 8kW Samsung Gen 7, thou

Hi Sarah,

So what’s type is Samsung wired controller roomstat integrated in the display? It’s not intelligent at all and it’s pure on a off. If I set 22C on it then it waits until temperature raise to 23C and then switch off. Wait until in goes down to 22C and switch off. This is just stupid 1C hysteresis. Or am I missing something here?

I’ve bought this external thermostat COMPUTHERM B300RF where I can set sensitivity from 0.1 until whatever I need and it works just fine. Much better comfort and at 0.4C hysteresis pump starts 3x in 24h if there is warm outside. Maybe I will reduce it to just 0.2C…

So what these modern TPI are doing ? How can this help me with comfort. Drop of 1C is just too much for me for Samsung indoor thermostat integrated in the display.

SarahH:

PS I just noticed a reference in the Gen 7 Installers Manual to a maximum ASHP design cycle rate of 4/hour. I’m speculating that provided your roomstat cycle time is longer than this (e.g. 3/hour) then it should work OK with the MIM controller.

What do you mean? For me the issue was that in “water outlet” mode it cycled 6x in one hour which was unbearable. So not sure if it followed this max. 4 cycle per hour. But OK, found out this mode is not suitable for me so I’ve switched to Samsung roomstat indoor temperature control which of course works with MIM controller but it’s just stupid. There is no intelligence behind with a fixed hysteresis of 1C as I’ve described above… Also many other guys confirmed it has hysteresis of 1C.

Timbones:

OpenTherm would be better, so that the heat pump can make its own decisions about run times based on the room temperature.

What is exactly this OpenTherm ?? Now I use this I stated above with hysteresis of 0.4C (maybe will lower) and it’s pretty much better than this Samsung’s indoor temp sensor with 1C hysteresis.

SarahH:

Can you say which heat pumps (if any) are compatible with OpenTherm? (I was under the impression that this communication platform was mainly - albeit increasingly - available only for gas boilers.)
As far as I know, Samsung ASHPs are not compatible, so those owners wishing to incorporate roomstat control may have no option but to select TPI.

I read about Homely which is compatible via modbus but how it would work for me in my use case scenario I have no idea.

Ian_Calderbank:

with an old-school simple stat (as per marko reply) that has some known variation between on and off . not sure if you can get “configurable” variation though.

This is right and it works like that but hysteresis which you can’t control and is set to 1C is pointless. But as you said fore some stupid reason they won’t allow you to modify water law temp by +/- 5C which is a problem.

There are so many stupidities programmed with this pump that the person who is responsible for this should be fired and they should employ Sarah or other guys here to tell them how it should behave lol.

I’m really thinking to implement my own control using modbus…

SarahH · 2024-02-15T11:36:37.220Z

Hi Michal,

Glad you’ve discovered a good solution (the 3rd party roomstat).

Couple of points:

Majority of wired roomstats offer only on-off control (most with a preset hysteresis like the Samsung, though I recall seeing a couple with adjustable hysteresis). Almost all (all?) wireless roomstats operate on TPI to minimise overshoot. Here’s a brief summary of TPI (though it doesn’t help you with cycle magnitude): https://support.salus-tech.com/portal/en/kb/articles/tpi
Some TPI roomstats offer you the ability to programme the TPI cycles/hour and the minimum “off” time (most likely hidden in the factory settings).
Forget Opentherm. This applies only to gas/oil fired boilers. ASHP vendors have not adopted this yet (to my knowledge).

I think you’ll learn to like the Samsung controller once you have finished tweaking it.

Sarah

Michal_S · 2024-02-15T12:26:57.681Z

SarahH:

think you’ll learn to like the Samsung controller once you have finished tweaking it.

This is interesting, howerver, not sure if it’s good enough for hetpumps ? Maybe if you can controll off time and cycles then yes, but not sure it would be good for those where you can’t.

Also what benefit it could have in comparison with hysteresis set to +/- 0.1C ? E.g I set temperature to 22C. Now system is on until 22.1C is reached and then it waits until it drops util 21.9C and starts again. So this is 0.2C hysteresis.

That’s the problem I don’t like that Samsung temperature controller because of 1C hysteresis. There is no way around so I can like it ? I can like it (partially) only when external thermostat is connected since it allows me to set water temperature by +/-5C. Also not perfect but better than nothing.

My main issue is I would need this heat pump to work flat at 45C water temperature from +3C and above. Otherwise it’s running with very low power input which is inefficient. And I would need to set my own hysteresis from +3C and bellow. But this is simply not possible because those Samsung controls are so stupid. There are useless limits on temperatures which don’t help. Think sooner or later I will end with modbus and my own code once I figure out how to do it. Then I will monitor outside temperature every few minutes and set my own water outlet temperature at given outside temp. If sun is shining I will decrease it proportionally.

william1066 · 2024-02-16T17:55:28.017Z

matt-drummer:

Samsung have probably allowed some sort of load compensation in room thermostat mode so that it can modulate lower, it sounds sensible. no?

Is this documented anywhere? I would be interested in understanding a bit more about this theory.

SarahH · 2024-02-17T09:31:36.855Z

Hi William,

I’ve scoured all the available manuals, and I have found nothing to suggest that the hysteresis either in the Samsung standard roomstat, or in the weather-compensated ASHP exit temperature, is adjustable by the user.

Indeed on the latter, Samsung UK Tech Helpline wrote the following to me last year:
“Morning Sarah,
Your understanding seems correct, system will start to back of (sic) within 2K of set point target WL.
Minimum turn down for the 8Kw is 4Kw so your 50% reduction seems correct.
I’m not aware of any SW update currently available to change the hysteresis unfortunately.”

The last point was in response to a rumour posted on this forum that a firmware update was available for the Gen 7 which fixed this hysteresis constraint.

Sarah

william1066 · 2024-02-17T09:58:29.039Z

Hi Sarah

SarahH:

Minimum turn down for the 8Kw is 4Kw so your 50% reduction seems correct.

That is strange. I have the 16kW and the compressor speeds I have seen are min 15Hz and max 75Hz.

@15Hz I can get down to 4kW output - though today when my CoP was 6.4 @ OAT 11 degC and flow temp at 32 degC @18Hz the output was 5.4kW. On colder days I have got down to under 4kW output though.

I have not installed the controller thermostat, just controlling on/off via HA.

I would expect the 8kW also to be able to get down to about 25%, so 2kW … but what do I know about heatpump compressors!!

William

matt-drummer · 2024-02-17T10:08:39.300Z

Hi William,

By all accounts the 8kW has the same compressor as your 16kW so it turns down to exactly the same values that you are seeing.

Hence the problems owners of the 8kW are experiencing.

You have made the same assumption that lots of us have made about heap pumps and heat pump manufacturers, that they design and build heat pumps with similar ranges of outputs based on the highest nominal output, they don’t.

They make one heat pump and then limit it at the top end and sell it as a smaller heat pump for smaller homes.

Not all of them do this and the knowledge of this is now starting to spread.

I suspect we will all be far more mindful of this as time goes by and it will influence our buying decisions, just as it should.

SarahH · 2024-02-17T10:10:33.368Z

@william1066
All three Gen 7 ASHPs (8/12/14kW) have the same compressor, so presumably the same turndown of ~4kW.
(I guess you have the Gen 6 AE160RXYDEGEU, and I don’t know what their rated turndown is.)

william1066 · 2024-02-17T10:19:10.431Z

Yup, that is my model. Just looked back a bit in my data, have been able to get as low as 600w input, for 3.8 output @15Hz.

History – Home Assistant.pdf (138.5 KB)

SarahH · 2024-02-17T11:37:12.557Z

william1066:

just controlling on/off via HA

Sorry William, what is “HA”?

william1066 · 2024-02-17T11:55:43.453Z

SarahH:

Sorry William, what is “HA”?

Sorry … Home Assistant via modbus.

SarahH · 2024-02-17T12:46:27.617Z

Thanks for clarifying. (It could have been Hand Actuator - i.e. switch - as used in the chemical industry.)

billt · 2024-02-17T22:17:29.298Z

For information, my gen 6 8kW heatpump will modulate down to just over 400W input power, 2.5kW heat output. Peak heat output is about 9kW.

The 12kW and 16kW Samsung heatpumps are considerably bigger than the 5 and 8kW models, so at the very least they have bigger heat exchangers. I think claiming that the models are the same but with software limitations is a bit of a stretch

Madsen68 · 2024-02-17T22:55:27.282Z

billt:

The 12kW and 16kW Samsung heatpumps are considerably bigger than the 5 and 8kW models, so at the very least they have bigger heat exchangers. I think claiming that the models are the same but with software limitations is a bit of a stretch

Hi Bill

Gen. 7 Heatpumps use the same Scroll Compressor in 8, 12 and 14 kw - that is not the case in Gen. 6 - so big difference in compressor size in Gen 6 and 7 - 8 kw. Besides in gen 6 it is not a Scroll comprssor but a… cant remember that though…

Michal_S · 2024-03-03T08:49:19.913Z

I have gen 7 8kw and from my experience it can go as low as ~2kw output by reducing the outdoor fan speed to a bare minimum and consuming 600-700W of energy.

Timbones · 2024-12-07T10:12:55.069Z

A post was split to a new topic: Samsung controller measures higher indoor temperature