Long delay change Fronius WMaxLimPct (Power limit)

Configuration
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1

One year ago, I created script for change WMaxLimPct by modbus registers on my Fronius solar invertor. It worked perfectly.
During winter I didn’t use it (because was not so much sunlight). During this time I did a lot of upgrades home assistant and Fronius firmware.
Now when I start the script, it has very long reaction time to change WMaxLimPct (delay is between 20s-60s) .
I dont understant why. Is it because some firmware upgrade maybe?

My script:

sequence:
  - if:
      - condition: state
        entity_id: input_select.rezim_omezovani_vyroby_fronius201
        state: Manual Power Limit
    then:
      - action: modbus.write_register
        metadata: {}
        data:
          hub: Fronius201
          address: 40236
          slave: 1
          value: 0
      - action: modbus.write_register
        metadata: {}
        data:
          hub: Fronius201
          address: 40232
          slave: 1
          value: "{{ states('input_number.maximalnivykonfronius201') }}"
      - action: modbus.write_register
        metadata: {}
        data:
          hub: Fronius201
          address: 40236
          value: 1
          slave: 1
        enabled: true
alias: Fronius_nastaveni_max_vykonu
description: ""
2

Hey Jiri.
Your post is already 9 years ago…:wink:
I am strugling with my fronius symo5 and searching for a solution to limit the power by automation.
Did you find a solution?
regards
Stephan

3

Hi,
My post is from 16.3.2025 :slight_smile: . Not from 2016 :smiley: …
Anyway, I ddin’t find any solution. Today I tried to contack technical support of Fronius with request for help, because I have still no solution for that.
It looks to be some problem in communication between Home Assistent and Fronius, because modbus communication between Home Assistent and Victron works without any problem.

We will see, what they will answer me …

4

I’m also fighting with my fronius to get some control.
I noticed I can"t find any descent info about what register to use.
Like 40228 is defined as “A well-known value 123. Uniquely identifies this as a SunSpec Immediate Controls Model”
I can’t find 123 there but I find it at 40237, So my guess is they are shifting register around…

And for your problem, have you set / read WMaxLimPct_WinTms Time window for power limit change. (should be on 40234)

5

Hey my friends.
here is my Update.
I got my symo running with Modbus TCP and can control the power with home assistant.
I created a 7 pages how to for this and i do not know, how to put this PDF here to the community.
So, if you need this information, just send me a PN and I can send it to you by e-mail

6

I also noticed this effect where the address are always one number less in home assistant and node red, I dont remember exactly the reason. If you are using a fronius inverter, you can use the integration GitHub - CJNE/ha-sunspec: Home Assistant customcomponent for SunSpec modbus devices for read only values. Im currently doing something to get the registers in node red and writing them to homeassistant using mqtt and also getting writing access.

I stopped using the homeassistant modbus because it was too limited compared to working in modbus, specially considering if you are using int values with scale registers.