[Richard]

I can just speak of the coaches with two house battery switches that I have laid hands on.

One of the house battery switches connected directly to the inverter. So the charger part of the inverter would be disconnected via this switch.
All six batteries were connected in parallel and fed the inverter and the 12V loads.
The second house battery switch was for all the 12V loads and also provided the connection to the engine charging.

This is where some explanation of the how the late nineties / early 2000 coaches were configured. In the engine bay, in the right rear electrical compartment the alternator wiring is run to TWO devices in parallel. One is a NOCO diode box that allows the alternator current to flow automatically to both the chassis and house batteries. Because it is a diode based system, it does not allow current to flow in the opposite direction, meaning the diode box will not allow the house and chassis batteries to connect with one another. The center post on the NOCO is from the alternator, it has one post for the chassis batteries and a second post for the house batteries.

In parallel with the NOCO is the merge solenoid that allows you to manually connect the house and chassis battery systems. If the batteries are merged, the battery banks are essentially one, meaning the alternator charges both, the inverter charges both, and any load drains both. So if you merge them, and run the inverter all weekend it will also drain the chassis batteries. The merge solenoid is UNLIKE the NOCO, it allows current to flow both ways. Newell routinely tells people to leave the batteries merged, I routinely tell them it’s a sure fire way to find yourself in a no start situation.

This setup gets a little more complicated if you have replaced your house batteries with Lithiums. It is complicated because the standard NOCO battery isolator does not play well with Lithiums because of the difference in charge voltage between Lithium and Lead Acid, and because the internal resistance of batteries using the two different technologies is very different. So, in my case the NOCO did nothing to charge the house batteries when I changed to lithium. However, the merge switch still works as it always did. There are differences of opinion on charging lithiums with the alternator. I am not going to do it except in an emergency with my standard Leece Neville setup. It’s a sure way to fry the alternator. If you have the monster 50DN, or you a device for limiting the charge interface between the two banks, then have at it.

I am not disputing what Orbit is saying about the way his bank is wired. Who knows how any of our machines are wired after a succession of owners. Someone may have wired it that way on purpose