Thanks, Dave. This makes sense. I was thinking that the main bus would see voltage on it (solar or other) even with the house switch open but that shouldn’t happen if the controller is working properly.
My next question to all and to Ward’s point about my alternator wiring to the main bus (that seems pretty common) what happens in the following situation with my proposed setup:
1. House battery is off.
2. DC+ in on position (not combine).
3. I start the engine
Power comes from start/reserve battery. Positive bus bar should have no voltage because house is open and DC+ is not in parallel. ACR wouldn’t be combining because no voltage on main bus. What does the alternator do immediately after starting? I would think it would be outputting even just momentarily but would the ACR respond quickly enough to allow current to the start/reserve battery or would the alternator output have nowhere to go and burn the diodes? Or, am I going way down a rabbit hole with this that isn’t needed.
Thanks again for all the comments. I want to make sure I get this right the first time and fully understand how to operate the system.
Good question and I can't give you a definitive answer. I think it will depend on where the source of the regulator's power and the location of the regulator's sense circuit.
A regulator needs power to operate, if the power source for the regulator is turned off then the regulator cannot provide power for the field and with no power to the alternator's field it can't generate electricity.
If the regulator sees the battery as being fully charged (i.e, the voltage above a certain level) through the sense wire, then the regulator should (?) reduce the field current so that it does not produce electricity.
I can't even speculate about how this would work on an internally regulated alternator.
The very basics of generating electricity is to pass a coil of wire through a magnetic field. At least in the old school (when I learned about this) the magnetic field was supplied by permanent magnets and the current produced was DC. As I understand alternators, the magnetic field is provided by electromagnets, the presence and strength of that field is determined by the field current produced by the regulator. Thus, if there is no field current there is no electricity being generated and our worries about frying diodes and rectifiers is unwarranted. (there are also issues about how the strator is wound and the number of poles on the armature, but I think bringing those up would distract from the core issue).
To answer your question, I think it depends. It depends on how your alternator is regulated and wire. I suspect it is a slightly different situation than the classic situation where the alternator is producing electricity and then the load is suddenly cut off cause the diodes to blow. But I can't be 100% confident.
