Samsung Gen 6 water law - compressor stops always for 3 minutes no matter what

[marko (Marko Cosic)]

@Ian_Calderbank

As soon as it goes to an off part of the cycle, this water cools down. because its outside, it cools quickly. So then it detects the drop and restarts, after not long. It is an entirely useless mode unless you have some other control input as well. Such as a 3rd party thermostat, or a modbus controller.

Or you have external control over the pump and are circulating water through the unit.

[marko (Marko Cosic)]

@Ian_Calderbank

strongly suggest you don’t do a relay to actually power down the unit, thats a really bad idea IMO

Seconded!

Could also sell it to somebody else who doesn’t care and fit a unit that does run at low temperature/output with decent sCOP

I Might Have Pushed My Heat Pump Too Far...

There are some.controls not dumb as a rock when it comes to heating.

[Michal_S (Misiak)]

@Ian_Calderbank

As soon as it goes to an off part of the cycle, this water cools down. because its outside, it cools quickly. So then it detects the drop and restarts, after not long. It is an entirely useless mode unless you have some other control input as well. Such as a 3rd party thermostat, or a modbus controller.

You are right with this but what this water law is good for then ?? I can’t get it I’ve posted this in another forum for one guy strugling as well but this is insane behavior in WL mode?!

Look at these two screens. One is with water law, the other is indoor thermostat.

Water law… no comment:

It always heat to 35C, then stop, pump off after a minute, within another 3 minutes temperature drops to 33C and it starts again ?! What is this shit and then it’s running for 5 minutes and the same shit again.

This is in indoor mode. Continual work… Ignore those cyan spikes, it’s my electric boiler So WL completely ignored here and it’s off only by thermostat.

Zoom:

Now tell me this is normal… This WL seems to me completely screwed up. You can see it start with high power input around 2KW then it goes down slowly but this heats up water very quickly in warm water so the pump is running for 3 minutes. I simply don’t understand.

I’ve tried all the 3 WATER PUMPS modes and all behaves the same. Water pump is always switched off one minute after compressor then it’s off for 3 minutes and always compressor starts. There is no waiting of another 7 minutes like in manual. Can’t get this…

@Ian_Calderbank

I strongly suggest you don’t do a relay to actually power down the unit, thats a really bad idea IMO. turn it off in software.

Definitely. It’s really a bad idea, especially if this is done in freezing temperatures.

@marko

Or you have external control over the pump and are circulating water through the unit.

Marko, this HP should work like that but it’s simply not… I don’t know why but there is a mode @2093-3 where the PWM pump should circulate the water. But it does not follow this settings. After a minute the pump shut off and the water get cold of course, so I guess this is the reason for cycling. I don’t know.

[Timbones (Tim)]

@Michal_S

what this water law is good for then

I think that when installed on a well designed system and correctly sized for the property, this heat pump will work well with water law mode. If the radiators are undersized or the heat pump is oversized, then water law just doesn’t work.

We see the same across other manufacturers too. Pure weather compensation only works when the whole heating system has been designed properly. Room thermostat mode is what many owners have to resort to in order to get reasonable performance.

Some better models have “weather compensation with room influence”, which is somewhere in the middle, and may work for some systems.

Looking at the 110 systems listed on HeatpumpMonitor.org, only 46 are using Pure weather compensation, no room influence. Half of those are Vaillant Arotherms. Average COP is 3.8.

Of the rest:

• 20 Weather compensation with simple set point control (dumb thermostat) (COP 3.6)
• 17 Weather compensation with a little room influence (mostly Vaillant) (COP 3.7)
• 11 Weather compensation with significant room influence (mostly Daikin) (COP 3.3)
• 8 Room influence only (e.g Auto adapt) (mostly Mitsubishi) (COP 3.5)

Only 1 Samsung is using pure weather compensation, others are using some kind of internal thermostat, and getting better performance:

[Michal_S (Misiak)]

@Timbones

I think that when installed on a well designed system and correctly sized for the property, this heat pump will work well with water law mode. If the radiators are undersized or the heat pump is oversized, then water law just doesn’t work.

Yeah, seems we can agree on this now. Definitely my system is not optimal with those radiators I have. But it’s a nice finding that this pump can go as low as 2KW by varying fan speed…

Here one other guys uses an external thermostat and the compressor can be turned off only by this. It has hysteresis of only 0.4 which would be great for me. As a bonus if external thermostat is used you can use water law temperature offset directly on Samsung controller (instead of ability to change only temperature in roomstat mode).

Every day something to learn.

I regret a bit I did not find this site sooner and those comparisons on heatpump monitor. Maybe I would choose something else. But I’m not disappointed (yet) with this Samsung

@Timbones

Only 1 Samsung is using pure weather compensation, others are using some kind of internal thermostat, and getting better performance:

Yes this inner thermostat… 1C hysteresis not great and you can’t change water temp offset. So I guess will try external one instead. Some wifi model or what.

I can see my HTQ has pretty much worse performance in comparison with older gen6 model But could be because the leaders are smaller units. Now I’ve realized the title of this board is wrong. It should be gen 7.