I changed the settings back to Water Law mode and the on/off behaviour of the primary pump and heat pump has stopped. The only usage I am now seeing is the two hot water heating events
I wired in an octocoupler to see when the primary, secondary, downstairs radiators, upstairs radiators and underfloor pumps were running. The weather has been mild for the last few days so the zone pumps have been off most of the time but primary pump has been cycling 3 mins on and 7 mins off almost constantly (apart from the peak electricity period of 17:00 - 19:00 where the heat pump is turned off and hot water cycles at 04:00 and 15:45). The heat pump has been cycling approx 5 mins on and 50 mins off also (when the heat pump cycle runs, the primary pump runs for an 8 min cycle instead of 3 mins).
The outside temperature was very similar in the two time periods so I think heat demand would also have been similar.
With the behaviour that I have seen, I don't see any advantages in turning off Water Law? The next avenue of investigation might be to see if the manual temperature offset which can be set on the controller when in Water Law mode (+/- 5°C) can be controlled via modbus?
Thank you very much for all the useful information here. I have a (maybe very stupid) question.
I bought a Samsung EHS Mono HT Quiet 8kW and the MIM-B19 module. When opening up the side of the outdoor unit I can't seem to find the designated space where the MIM-B19 Module is supposed to go. There is a video on YouTube of somebody installing it on the previous version but on the Mono HT Quiet things look different (see attached picture).
I think I'm overseeing something very obvious and I would really appreciate any help 🙂
@redzer_irl I think I've just twigged what might have been wrong with version 1.0 of your design.
you had it set to simply give a fixed LWT (which the value being calculated from the WL curve). AT ALL TIMES. That would make the system keep coming on, just to keep the LWT at the value thats targeted. There is no way for it to know that there is no demand. If the system was running full time in winter, you wouldn't have noticed what you have, but because its mild, it still always runs, to keep that LWT that you've asked it to target.
you need to implement something else in your logic along the lines of:
If the there is no heat demand , then set the target LWT to a very low number. Or perhaps set the "CH active" binary register to Zero (off).
as you've put the samsung controller back in charge, it would seem that it knows there's no demand, so its being off when it should be.
@betaphi not sure if anyone on here has the HT quiet, most are Gen6. two suggestions
a) ask samsung (you can register on their partner portal pretty easily)
b) don't worry about it. the MIM module is small and light and only needs simple low voltage wiring, so mount it anywhere that looks safe and convenient.
in my case, the MIM didn't want to fit into what other pictures / video's that I'd seen said was the suggested space, and the wires weren't long enough to reach there either. So I put the MIM inside the plastic case that the MIM came with, and securely cable tied that case to what I seemed to me a suitable spot away from other components.
@iancalderbank Thank you very much for your swift response.
Any chance you can provide me with directions to the said partner portal? I'm not situated in the UK and over here in mainland Europe it is practically impossible to get registered with Samsung as an individual.
@iancalderbank Thanks Ian, I think your idea is sensible.
Since I do not have smart thermostats, I previously had no way of telling if any particular zone was calling for heat. Now with the optocoupler I can get this data in home assistant and use that to make a decision on what action should be taken in relation to the LWT or Heating on/off status.
@betaphihttps://partnerhub.samsung.com/ or email Tech.Aircon <tech.aircon@samsung.com> even if your not registered I'd hope they'd answer a simple factual email query such as yours of "where should I mount it"
@iancalderbank This system was designed by Joule and installed by the plumbing contractor so I will lay out my understanding. I have 3 of these regular thermostats, one for each zone and they run on mains voltage.
The switched live from the thermostats feed into this Joule board which is located under the main Samsung board on the DHW tank.
I raised the target room temperature on the downstairs radiators thermostat and this caused the associated circulation pump, the secondary circulation pump and the primary circulation pump to all turn on and the heat pump started to use about 1kW of power.
@redzer_irl interesting! so there must be something from the joule board that leads to the samsung control board to tell it to be "on". A guess: is there a wire from the joule board to B22 on the samsung board, that goes live when any zone wants heat?
so, I've finally resolved my difficulty with being unable to "write" modbus commands to the HP. It was a physical layer one - I mistakenly wired the heat pump side of the MIM-19 to terminal F1/F2 on the outdoor unit, rather than R1/R2. Interesting in its own way that it does work - but only as a readonly device - when connected to F1/F2.
I am now able (via modbus , from HA) to control the target LWT directly and turn the flow on/off (@redzer_irl - just set register 52). The system itself takes care of whether to run the compressor or not. So I have the necessary outputs of a control system! test and experimentation to follow as it gets cooler...
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