I designed and built my own.. So perhaps I can help Two sets of directions.
My RV is a 50 amp Rig with NO Intelletec Energery Management System. So it was easy
I disconnected the wire from the breaker for the REAR A/C and also the assoicated white and bare wires.. THey went to a junction box I added nearby...
I ran new 12 ga Romex out to .. in your case the PSRV box in my case an outlet box.
I ran new 12 ga from the junction box. connected to the original romex. out to the same area. Added a plug. the remote plug/outlet (20 amp type by the way) are in an compartment protected. A 20 amp breaker is included in the PSRV in the "inlet" half
On the PSRV the flexible line is the outlet. and the fixed is an Inlet. I did it the other way around. which way does not matter.
IF you have a 30 amp RV with a generator.. When the Generator is running one cirucit on the Genny powers JUST the rear A/C.. So the generator connection box becomes your "Break out" point instead of the main circuit breaker panel as on mine.
Does this help??? I may have the orignal schematic on another machine but not sure.
