As to "Can we run generator while plugged in to shore power"
Two answers: First yes you can but PLEASE .. do it right.
There are several devices you should shut OFF before starting the generator. Or better yet.. Turn off all big ticket items and THEN: Trip the MAIN circuit breakers on your 120 volt panel, then wait 2 minutes before starting the generator, wait at least one more minute before restoring the main breaker to the ON position.
YOu need not set foot outside to do this
Returning to shore power
Turn off the big ticket items again (A/C, Microwave, Water heater) and shut off the MAIN breakers.
Then shut off Generator
Wait 3 minutes
Turn on main breakers and restore re-activate other things as needed.
WHY:
This is epically true of the Air Conditioners but all power suckers contribute
When power is interrupted motors and other inductive loads tend to keep current flowing. This can create one "Heck" of a voltage spike, in fact it is why you should have spike suppression on delicate stuff like TV and computer. (I have a lot of it here). This spike can cause the contacts on your automatic transfer switch to ARC OVER, welding the contacts so the switch no longer switches.. Happened to me when the rig was new.
Shutting down before transfer, eliminates this inductive spike and minimizes the change over arcing.. The 3 minute wait is for Air conditioners only.. If shut them off the water heater can be brought up soon as transfer is completed.
