Had a new alternator installed on my Phaeton. Plugged in to the same 15 amp circuit as usual when I got it back home. Noticed that the salesman switch was off and when I turned it on, the transfer switch made a banging noise and tripped the house panel breaker. Turned off the salesman switch, reset breaker, let the batteries charge completely, and same problem this morning. Inverter has a green light and appears to be working fine. If I disconnect from shore power, I can turn on salesman switch and all my 12 volt systems are good. Any thoughts?