Hello @CrankyCoder, looks like a nice project! Given that you have the data on the pi through an rs485 connection and are keen to avoid custom code, have you thought of using something like nodered? Nodered can be used to setup rules for controlling things in relation to input levels etc.
I would likely go for the custom code route myself but that’s not to say it’s the right way.
You might be interested in @danbates’s work on DC monitoring here too, although it sounds like you have the monitoring covered DCduo Board Update - #8 by danbates