I am upgrading my sons van and we had a Blue Seas ACR in the van that we used for sending a charge to his AGM batteries it worked great.
We are now installing a Victron system with a Multi Plus, XS 50 dc to dc Orion and removing the old system.
My question is can we leave the ACR in place and use it like a switch to turn the XS50 on and off when not needing to charge house system?
You can try it. I have one between 2 lead acid batteries and then an Orion to lithium. My alternator is 65amps and the Orion is 18 amps I can measure 20amps going into the Orion which exceeds the idle charge current from the alternator. You may need to adjust the charge current. If the relay is opening and closing often it will heat up and burn out. You might be able to use it to send a signal to the remote on the Orion to switch it on and off so there is no current flowing through the switch. If you do decide to keep it there will be some adjustments to be made.