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I would solve the problem with a Sonoff POW R3 reflashed with tasmota. Set the heatpump controller to always be ON and control when it receives power using the Sonoff.

I happen to have a parallel 5kw Multiplus setup like yours which I installed myself.

Well the GRID SETPOINT should not be ZERO. Grid setpoint This sets the point at which power is taken from the grid when the installation is in self-consumption mode. Setting this value slightly above 0W prevents the system from feeding back power to the grid when there is a bit of over-shoot in the regulation. The default value is therefore 50W - but should be set to a higher value on large systems. Do you have a ET112 grid meter giving you accurate results or are you using the measurements in the multiplus units?

Yes, get a geyserwala. It replaces the controller on the wall and allows you to connect to it via a webpage or a app. Cost less than a R1000. Easy diy fit.

My Victron Integration provides a grid power entity. I use it to determine if there is loadshedding. Remember to cater for hysteresis. Add a time condition to your trigger. This automation is currently disabled since it pre-dates my geyserwala setup. The geyserwala simply switches to solar only during loadshedding. The geyserwala+HA setup is simply brilliant.

That will work fine. I often buy from communica and they are legit. Another option if they don't have stock is to get one from Micro Robotics. Robotics.org.za https://www.robotics.org.za/cables/usb-cables/usb-converter/USB-SERIAL

Have you done the setup via VEConfig on the multiplus? If not your low voltage cut-off is still set to 48V. This is too high. Victon uses a low frequency switching design to create AC. This means that there is a big toroidal transformer that needs to charge up when you switch from bypass to on-line mode when the grid falls away. You get a big inrush current that the comparatively small battery can't provide. 1) setup the multi correctly via VEConfig. Use the portal and edit on a computer and re-upload. 2) Add another battery to bring the system in-line with what Victon reccomends should be the minimum battery size for a 8KW inveter.

Thanks Paul, didn't know it changed in the last update. Will have a look at it again. Last time was more than a year ago.

I run two Victron multiplus 2 5kW units in parallel. In the Victron guide for parallel setups they stress the point that your DC cables running from a busbar need to be of equal length. BUT the also state that your AC cables need to be of equal length as well and NOT be over sized. There needs to be a bit of resistance on the AC side for the units to correctly operate in parallel. I know you have 2x Sunsynk units but maybe this can help. To quote: Warning against over-dimensioning the AC wiring Note: Do not over-dimension the AC cabling. Using extra thick cabling has negative side effects. Technical background: for a properly working parallel system, the AC current should be evenly distributed between the paralleled units. The resistance in the cabling helps with that and is needed for that; to overcome small differences between one inverter/charger and another, for example in the AC contact on the AC input. When the resistance in the cabling is too low, such small differences in resistance of the current path in a unit itself can results in a large relative difference. This results in bad current distribution. An exaggerated example: Using 2 units (A and parallel and using too good cabling, one might achieve a total resistance for Unit_A of 0.0001Ω and a total resistance for Unit_B of 0.0002Ω. This results in Unit_A carrying twice as much current as Unit_B. Using the same 2 units in parallel with, for the sake of this example underdimensioned AC cabling one might end up with a total resistance for Unit_A of 15Ω and a total resistance for Unit_B of 16Ω. This results in a much better current distribution (Unit_A will carry 1.066 times more current than Unit_A) even if the absolute difference in resistance is much bigger than in the previous example (1Ω vs 0.0001Ω). A side effect of over dimensioning the AC cabling can be faulty Power Assist operation. Out of all units, the phase master is in control and measuring the AC input current. And in case that current is (grossly) unevenly distributed between the paralleled units, the resulting total AC input current can end up being too low (under charging the battery). https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

I've played around with it in the past and could not get it to work 'dynamically'. You are going to have to get NodeRed up and running to do what you explained above.

Sunsynk uses high-frequency switching to create a AC sine wave. This design is prone to dipping since it takes time for the control-loop to catch up and tell those mosfets to giddy-up. Your battery is a tad small for this size installation. You are barely over the 1C battery/inverter ratio. 1.5C is the minimum in my opinion. Funny enough I have friend with the same problem on a 8kw Sunsynk. Also dips and is undersized (1.275C) on the battery.

My CerboGX just continues on as if nothing is wrong. I have another installation at my office with a VenusGX that also just continues on when the internet drops. So this is rather odd. Both above running Multiplus 2. My home one has two 5kw units running in parallel.

Grid use for 2022: This year to date: Winter 2023 was a rather wet and cloudy affair compared to previous years. Since I do not export to the grid, as soon as the batteries are full the mppt units pull back. So Solar totals can be much higher if allowed to export. From the start of 2023 I've gotten a lot 'smarter' in managing loads with automation and scheduling. Home Assistant pulls data directly form the Victron Cerbo and now switches the geysers, pool pump etc on and off. This is where the savings happen. Switching your big consumers to times with ample sunlight and free power. More panels are going up over the summertime to help with generation in winter. Currently got 5760W on the roof and they have been there since 2014. Going to add another 4kW.

Your meter has now been updated with two key change reset tokens. https://infrastructurenews.co.za/2023/01/25/24-months-to-go-if-not-reset-prepaid-meters-will-stop-working/

My father used to own a metering company with a few thousand meters. Yes you get flagged for no usage by the system and then get inspected. You also get flagged if your consumption drops more than 80% over a period of 6 months. There is no way to tell if the prepayment meter is consuming electricity other than tracking the amount and interval at which units are purchased. In short there is no communication with the prepayment meter. Its all tracked on the vending side. By buying small amounts at regular intervals is the best way to beat the system. This drags your long term average down without triggering the system. Just be aware that these prepayment meters will run down and consume units if you export to the grid. They only 'spin' one direction.

Geyserwise + Geyserwala

Thanks @Thingwala. I waited a bit before replying here to see if any bugs pop up. No issues whatsoever. Really happy with your product and can't recommend it enough. Thank you again. Now for the next project.... ITS heatpumps....😉

@Ken I buy the geyserwala. The guys are willing to work with you if you have problems and its simply a superior product. I'm very happy with mine.

Get a geyserwise system installed with remote access via their own tuya implementation or get the even better geyserwala unit. Then you can remotely or via timers switch your geysers as needed.

Issues encountered. The following problem is unique to my home network setup but isn't out of the ordinary. I run a extensive Ubiquity Unifi network setup at home. UDM pro, several switches, several unifi security cameras and more than a handfull of APs. Each AP has two SSIDs one for secure devices and one for IOT devices (things that don't need to get to my NAS or talk to my secure network). IOT is on a seperate vlan. Both SSIDs are dual band. 2.4ghz and 5ghz. This is the backgound to my issue. I had trouble getting the geyserwala connected to the IOT network. I know its a ESP and can only run on 2.4ghz. But up to now all my other ESP sonoff or other 2.4ghz only devices had no issue connecting to the IOT dual band network. What made this frustrating is that I had no way of getting the info out of the geyserwala unit nor a place to look in to work out why its not connecting. This is also due to the way the geyserwala connects to the network. It requires you to input all the network values before hand instead of getting it to look what wireless networks are available and then select one to connect to. I had to input network adresses and DNS addesses manually. Things my DHCP should do for me and the geyserwala. Its how all my tasmotas or any other device did it. I suspected that the issue lies with the dual band nature of the IOT SSID. The ESP can only do 2.4 and maybe it gets dropped or drops because of this. Unifi didn't even show any attempt at joining the network. So to solve the problem I had to create a 2.4 only network and set the closest AP to this SSID GW_IOT2.4. Only then did the geyserwala join the network. Not happy with a seperate network for just one device I tried to get it to now join the original IOT network. Changed the SSID value on the GW. Now it had no trouble connecting to it. It still is. This was a very long way of saying that if you have issues with your GW joining your network, change it to 2.4ghz. Get it to join then change the network back to a dual setup. I'll update this thread if there are any other issues.

Some thoughts, issues encountered and where I think there is room for improvement. 1) Add a user defineable max thermostat value. Suds has a 75C one, mine is a 65C. The installer/user should be able to set this via the settings page on the geyserwala. 2) On the timers screen add a disable/enable radio button for each timer. Sometimes I want to disable a timer for a while. Now I'm forced to delete and recreate it every time I need to disable it. 3) Info, info, info. I'd like a single page telling me what version is running, what my current mqtt details are etc. Tasmota does this perfectly. Example below: This helps a lot with fault finding and debugging. 4) When on timer mode if you press the red power button it now changes it to boost mode. On the original it would cancel the timer and stop heating. If you pressed the power button again it would turn on the boost and only heat until the end of the current timer period. It no longer does that. This was very handy during loadshedding and cooking hours. I could just press the physical button a few steps away, cancel the current timer and continue cooking without a additional 2kw draw on the batteries. When done with cooking press the button again, trigger boost which will stop at the end of the next timed slot.

5) If your entire house/load is on the essential side of the Inverter, do not allow geyser to deplete batteries during extended power outages/loadshedding. This was one of the major requirements for me at the start of this whole thread. I ended up installing a Sonoff POW R3 (tasmotized) on the geyser circuit to cut off power if the SOC dropped below 30%. With the geyserwala unit I no longer need the Sonoff POW R3 which cost about the same as the Geyserwala. I plan to remove it and use it somewhere else. Not sure where else I'm going to need to be able to switch 25A...

4) The ability to set an independent max temperature for each power source: 30C for grid, 75C for PV. This is covered by explanations 1) and 2). Automation, pull data, set triggers and conditions, done.

3) Some way to connect the Geyserwise element relay directly to my grid source, but still keep the keypad powered by the inverter, so that I always have my temperature display, even when there is loadshedding or when the Inverter AUX port is off. I want to get the connected version of the Geyserwise, as I'm interested in plotting geyser temperature over time so that I can better understand usage patterns and whatnot. Since I have my geyser on the essentials side this requirement is met. HA captures and plots the data of every entity out of the box. Getting that entity into the box is done with the Geyserwala HA integration.

2) Set the temperature on the Geyserwise to a safe minimum, say 40C. So that if the temperature drops below this, the grid kicks in to boost the temperature. Similar to 1) use automation to read the geyser temperature value and trigger a change in the setpoint value when it drops below 40C and is not on solar mode or on a timer. I make use of the built in timers to manage this to a degree and still leave room for the sun to warm the water via the collector. Since its just me and my wife for the time being (subject to change) with fairly simple predictable shedules a simple set of timer based slots is fine.