Attached are 2 files. One is the schematic on a PSI 20KW gen. The other is on your SE350VR. The VR senses the main gen output on L1 and l2. There is a metal cover over the main breakers. Please remove for testing. Now ensure nothing is touching the CB connections, and start the gen. Measure from N to L1 on both sides of the CB8 closed.
Now measure on both sides of L2 on CB8. If they read the same on both sides of CB8 closed it is good, and they should read about the same between phases; and now on the regulator there is a voltage adjustment under a tamper resistant plastic cover. Set the r1 in the middle (on the control panel) and adjust for 120VAC L1 to neutral. Now monitor the AC swing.
With no load because everything else is open , see if the swing is livable. if steady, then it is time to one at a time check the load banks, or the other breakers as they do go bad. The difference from power in to out should be very low, like nothing to 1.5 VAC difference on the breakers. You can also just measure across the breaker phase to see the voltage drop. If not and you still swing 20VAC, you may require a new SE350 VR if the swing is too great.
These are sections of the Proprietary manual that does not say they are proprietary as they were sent to me about 25 years ago. Not many 20KW sets were sold to units as they usually went for the 35KW sets. The turbo charged LP engine is a very good engine.
