3-Phase system with DC solar power and 1-phase hot water boiler: Configuration of Assistants (off-grid)

Q&A and troubleshooting
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1

While setting up a AC Thor hot water boiler in an off-grid system, we found ourselves in a situation where we could not derive all the necessary information from the documentation.

The system is off-grid and consists of 3 MultiPlus 5kVA, and about 5kW of solar power is connected on the DC side only.
A hot water boiler (AC Thor) with 3kW power is installed and connected to one of the phases to use the excess energy.

According to https://www.victronenergy.com/live/actor_offgrid, the PV Inverter support assistant should be added without further clarification. According to all other Victron docs, the assistants, particularly the PV Inverter support assistant, must be added to all inverters.

It is the setup of the assistant where the questions arise:

  • Is the Total installed PV inverter power 3kW or 1kW (if it is calculated per phase, it will result in 3kW)?
  • Is the Total installed PV panel power only the solar power or, in this case, the solar power plus power of the heating element, so that the ratio (total power to reducible power) is correct?
  • And also related: The MyPV AC-Thor uses the frequency range 50.1Hz to 51Hz by default, while Victron uses 50.2Hz to 52.7Hz. Is this deviation intentional?
2

Do you have an AC-Thor?
If not you are looking in the wrong document.

The easiest would be the “programmable relay” assistant.
Just as example: close the relay if SOC is over 99% and open it if SOC drops below 95%.
Maybe you have to combine the OFF assistant with a load condition to kick out the boiler if another big load is turned on on the same phase.

3

Yes, it is. Added it to the components list of the first post.

So, is the frequency mode - as advertised and documented by both MyPV and Victron - not the way to go?

For a relay (or any other non-frequency control), we’d need additional wiring that we haven’t planned for.

4

As your system does not have any AC coupled generation this will not work, as per that guide you linked in the first post.

The PV inverter support Assistant will only regulate the frequency if there is AC coupled generation on the ACout.