Hello all,

I came across a product from a company named Plentify that basically let's your inverter en geyser talk to each other. However it rather expensive.

These are the main functions I would want to try and replicate from there system:

1. To switch your geyser off as soon as you pick up that the grid power goes down from the inverter. Without having to run wire to your inverter to create an non essential circuit.

2. This is the more tricky one. I want to try and prevent my inverter from tripping due to overload. Now a normal inverter has a max power output just above it's rated power output however it has a peak power output it can sustain for about 10s of about 2x it rated power output. What my thinking is if you can use Solar Assistant to give live power output information from your inverter to Home Assistant. You would then theoretically be able to use Home Assistant to swith of your geyser using a IOT breaker before that 10s runs out and your inverter trips. Then after 10 or so minutes of the output power being lower then some threshold you can switch the geyser back on.

Now the problems I can see is as follows. Solar Assistant not being able to give the correct information to Home Assistant for this to work thus live info regarding grid power (On/Off) and power output number for inverter. The second thing is that 10 seconds is just not enough time given Solar Assistant will have a delay Home Assistant will have a slight delay and switch the breaker will also have a slight delay.

Now at this stage everything is theoretically as I don't have Solar Assistant to check what is going on (don't want to spend money on something that might have already been proven impossible).

My backup power setup consists of a 5kw Sunsynk and 5kwh Greenwich battery. My geyser is currently not connected to the inverter but want expand my system by adding PV in the future and also my geyser.

Thanks in advance for all the feedback and ideas

Edited March 13, 20251 yr by Abri_de_Beer

Solar Assistant is at most 2-seconds delay to get the data to home assistant - and this is over wifi. If cabled it will likely be a consistent 1 second.

1 - In Home Assistant you can setup the loadshedding notifications and then an automation will kick in based on what you want to do, so for e.g. if you know LS is hitting your area in an hour you can charge your batteries to 100% from the grid as a precaution. You have access to all these sensors so what you do with them is up to you

2 - Again this is possible though not fool proof - SA will get the load data from the inverter and then send it to HA where you can the decide to turn off certain circuits etc but again you have that 1-2 second delay in getting this done.

5 minutes ago, mzezman said:

Solar Assistant is at most 2-seconds delay to get the data to home assistant - and this is over wifi. If cabled it will likely be a consistent 1 second.

1 - In Home Assistant you can setup the loadshedding notifications and then an automation will kick in based on what you want to do, so for e.g. if you know LS is hitting your area in an hour you can charge your batteries to 100% from the grid as a precaution. You have access to all these sensors so what you do with them is up to you

2 - Again this is possible though not fool proof - SA will get the load data from the inverter and then send it to HA where you can the decide to turn off certain circuits etc but again you have that 1-2 second delay in getting this done.

Thanks for the insight mzezman. As you might know due to living in the East of Pretoria we regularly get unexpected power cuts so on point one I cannot just work off the load-shedding schedule. I will edit my topic to be a bit more clear in that regard. Looking for a way to use the described setup to cut power to the geyser as soon as grid power goes down.

Edited March 13, 20251 yr by Abri_de_Beer

44 minutes ago, Abri_de_Beer said:

Thanks for the insight mzezman. As you might know due to living in the East of Pretoria we regularly get unexpected power cuts so on point one I cannot just work off the load-shedding schedule. I will edit my topic to be a bit more clear in that regard. Looking for a way to use the described setup to cut power to the geyser as soon as grid power goes down.

Ah hello fellow PTA East sufferer 🤣

Heres a screenshot of one of my HA sections - - the red icon shows there is no grid at the moment - so again you can have an automation that says: If the grid thingy switches to off then switch off geyser (unless batteries are full and load is less than 1000w) etc etc

15 minutes ago, mzezman said:

Ah hello fellow PTA East sufferer 🤣

Heres a screenshot of one of my HA sections - - the red icon shows there is no grid at the moment - so again you can have an automation that says: If the grid thingy switches to off then switch off geyser (unless batteries are full and load is less than 1000w) etc etc

Power just got back so the same section now looks like this -

I made a custom geyser controller based on the Geyserwise thermostat (which you can get for about R260), and a Sonoff THR320 (about R400). I also changed the element in my geyser to a 2kW from the 3kW it had orignally. I was actually fortunate enough to have my geyser pack up, and get replaced by insurance at the time, so I got the installers to fit the new element before it was even installed in the roof.

I have an 8kW Sunsynk, and 10kWh battery. Geyser is on the AUX section of the Sunsynk, though in hindsight, I'd be happy to move it to the essential loads, freeing up the AUX for a generator at some future point.

I am monitoring my Sunsynk using the KellerZA/sunsynk integration in Home Assistant, and the Sonoff is flashed with ESPHome firmware, exposing the geyser as a generic thermostat (heating only).

I also have some automations that monitor the state of the grid (based on Sunsynk grid power, which normally idles at 30W to prevent backfeeding, but obviously drops to zero when the grid disconnects), the state of charge of the batteries, and the rate of charge of the batteries, and apply automations to turn off the geyser whenever load shedding is active after 16:00 and before 9:00 (i.e. when the solar is not producing). If the geyser thermostat changes to heating overnight (i.e. 16:00 to 9:00), it turns off the inverter timer, and sets the battery charge current to 0A. This runs the whole house from the grid while the geyser is heating, but doesn't charge the batteries. This change gets undone when the geyser stops heating, or if the time crosses the thresholds.

One of my best automations checks the battery State of Charge (>70%), and rate of charge (>2500W), and then sets the thermostat to 70C, or back to 45C if it goes below 70% or charge power goes negative for 5 minutes (i.e. discharging from the battery to run the geyser). This can be quite effective at absorbing an additional 4kWh from the panels as hot water, which would otherwise just get discarded when the batteries are full.

To answer your questions more directly, it depends on the size of the element in your geyser as to whether this will be feasible for you, and what other loads you expect to handle. Trying to run a 4kW element on a 5kW inverter, with other loads as well is asking for trouble, obviously. If you can downgrade to a 2kW (which just means that the water takes longer to heat up), then the impact on the inverter will be a lower magnitude, but require a longer run time to get the same result. If you can install a heat pump, the energy requirements drop significantly too. Roughly 1kW for a 4kW equivalent heat output. That becomes a lot more reasonable to put onto a 5kW inverter, but is obviously a lot more expensive.

Edited March 13, 20251 yr by RoganDawes

Just a question RoganDawes,

With KellerZA/Sunsynk what is the latency like? Also can you measure output of the inverter using KellerZA/Sunsynk?

As mentioned in the original post I would have about 10s to monitor output and switch of the geyser.

Edited March 13, 20251 yr by Abri_de_Beer

Regarding option 2 and the fact you want to prevent the inverter from tripping due to overload might I suggest investing in some smart switches that can provide power readings and add a couple of them to the big-ticket items like the stove, microwaves, ac’s, pool pumps ect.  The key is the switches must be able to be integrated into HA, That way you can identify what is pushing you over the limit and then turn them off one by one to bring the power to below the limit with minimum disruption.  Monitoring just the geyser and pulling in solar assistant to HA is a start but might be inadequate for what you want to do.

Obviously this is subject to what you consider expensive whether this is a viable option but at a quick glance what Plentify offers is what I achieved on my own in HA with some automations at the cost of just the smart switches and wiring and some time to identify and setup most of the automations.

E.G.

This effectively monitors these appliances and switches them off if it is on one by one until the load is below the threshold. So the AC's will get turned of but the Stove and Geyser will be left on if the combined load is below 5100.

28 minutes ago, Abri_de_Beer said:

Just a question RoganDawes,

With KellerZA/Sunsynk what is the latency like? Also can you measure output of the inverter using KellerZA/Sunsynk?

As mentioned in the original post I would have about 10s to monitor output and switch of the geyser.

I've setup my KellerZA to give me effectively live readings at the cost of a big database file but storage is less of an issue for me.

30 minutes ago, -cK- said:

I've setup my KellerZA to give me effectively live readings at the cost of a big database file but storage is less of an issue for me.

Hello CK,

Any good links that show how to set up HA and KellerZA with your Sunsynk inverter?

https://powerforum.co.za/topic/22145-kellerza-integration-installation-video

This should get you on the right track.

You will need a RS485 converter, setup your MQTT and the KellerZA integration but think it is all covered in the video.

https://www.diyelectronics.co.za/store/serial/2808-usb-to-rs485-converter-module-industrial-grade.html for ease of reference.

Also your inverter MODBUS and the one in the config must match, generally unless your running a parallel setup or something this should be set to MODBUS_ID: 1

By default if you haven't fiddled on that menu on the inverter it will be 0 and when I helped setup my neighbors one I had to change it to 1 to work (fair warning I believe this do trip the inverter Alarm when you change it for a minute or so and needs to be restarted if I recall correctly, its been a while since I've done this so do this in the day and not 12 o'clock at night during loadshedding, it will get dark and quite real quick with a oh 💩 did I just F-up my inverter moment 😅)

Edited March 13, 20251 yr by -cK-

8 hours ago, Abri_de_Beer said:

To switch your geyser off as soon as you pick up that the grid power goes down from the inverter.

Why not have a contactor/relay that feeds power to the HWC/geyser, and let the contactor or relay be powered from the commercial supply side... as soon as commercial supply side dies, the relay drops and disconnects the HWC...

The good point of doing it this way, is, it cannot fail and there is no reliance on inverter/solar assistand/home assistant or anything else, except the grid being there or not...

Edited March 13, 20251 yr by Kalahari Meerkat
The good point of...

23 hours ago, Abri_de_Beer said:

Just a question RoganDawes,

With KellerZA/Sunsynk what is the latency like? Also can you measure output of the inverter using KellerZA/Sunsynk?

As mentioned in the original post I would have about 10s to monitor output and switch of the geyser.

Latency can easily be sub 10-second, although you can control the polling frequency for the parameters that are super-important. I actually have two different systems polling my inverter, because I'm a bit ridiculous :-) I originally set up the KellerZA RS485 integration, and then subsequently figured out how to reprogram the Sunsynk dongle as well. That is now running ESPHome, and I'm happy to share that procedure and config if you want it. I'm happy not to have the Sunsynk dongle talking to the cloud, since their clock sync foulups resulted in my inverter discharging at the wrong times. Although I do recognise that it may be useful to have vendor firmware available in case I ever need a firmware update. I took a backup so I can restore that if necessary.

However, the kellerza integration is actually still the primary source of data for me. And yes, all the figures that you see in their diagram on the inverter itself are available, and more. You can get an idea of what is available here: https://github.com/kellerza/sunsynk/blob/main/src/sunsynk/definitions/single_phase.py

Those that have RW in their class are read-write, i.e. can be changed.

On 2025/03/14 at 6:30 PM, RoganDawes said:

Latency can easily be sub 10-second, although you can control the polling frequency for the parameters that are super-important. I actually have two different systems polling my inverter, because I'm a bit ridiculous :-) I originally set up the KellerZA RS485 integration, and then subsequently figured out how to reprogram the Sunsynk dongle as well. That is now running ESPHome, and I'm happy to share that procedure and config if you want it. I'm happy not to have the Sunsynk dongle talking to the cloud, since their clock sync foulups resulted in my inverter discharging at the wrong times. Although I do recognise that it may be useful to have vendor firmware available in case I ever need a firmware update. I took a backup so I can restore that if necessary.

However, the kellerza integration is actually still the primary source of data for me. And yes, all the figures that you see in their diagram on the inverter itself are available, and more. You can get an idea of what is available here: https://github.com/kellerza/sunsynk/blob/main/src/sunsynk/definitions/single_phase.py

Those that have RW in their class are read-write, i.e. can be changed.

Good day RoganDawes,

I think I would go the KellerZA. Not feeling brave enough to flask the Sunsynk dongle.

So if you have nice instructions on how to set up KellerZA that would be very helpful.

24 minutes ago, Abri_de_Beer said:

Good day RoganDawes,

I think I would go the KellerZA. Not feeling brave enough to flask the Sunsynk dongle.

So if you have nice instructions on how to set up KellerZA that would be very helpful.

Probably better to not flash your dongle, I agree!

There are two ways to connect to your inverter: RS485 and RS232. I'm tempted to say that RS232 is simpler than RS485, as I have seen a bunch of people struggling with the RS485 dongles specific requirements. Some dongles work better than others, some need a resistor to be added or removed, etc. There is a lot of documentation on the kellerza wiki on that approach, and I won't repeat it here. There is less on the wiki about RS232, which is how the sunsynk dongle itself connects to the inverter.

If you decide that you don't need the sunsynk app on your phone for remote access to data and control, you can simply connect your Home Assistant box using a USB-RS232 adapter, and a DB9 serial cable. Unscrew the dongle, plug in your DB9 cable, and connect it to the USB-RS232 adapter plugged into the Home Assistant box. Install the kellerza/sunsynk addon according to the instructions on the wiki, configure it using the appropriate single phase/3 phase sensors for your inverter, and you should be good to go.

It can be a bit more complicated if your inverter and your Home Assistant server are too far from each other to connect directly with a cable. In that case, you have two options. RS485 is designed for longer runs than RS232, so it might end up being necessary to go that route. Alternatively, you can use mbusd (Modbus Daemon aka server) on a raspberry pi or other small linux computer (even a Pi Zero is enough), to make either the RS232 or RS485 port accessible via wifi. i.e. instead of a long cable, you substitute with a computer conveniently located close to the inverter, and use wifi instead. Let me know if you need to go down this route.