Hi,
It would be easy and simple to have two receptacles side by side, then wire one to the shore power, the other to the inverter. Then plug in the refrigerator to the desired receptacle.
Another way is to always leave the refrigerator on inverter power, and leave it on 24/7. Then while on shore power, the charger will supply 45 - 65 amps of DC power to the batteries and inverter, powering everything. . .
Using a three way switch 'might' work and 'probably' will not explode. . Yet it "CAN" short across the terminals. . . When I worked for a large city, they used 3 way switches on the lights in the radio transmitter room. One side was 'on' with generator power, the other 'on' with shore power. When they test the generator, all the lights that had been off (because they did not get power from the generator when not running) would turn on for the duration of the test.
Sometimes the circuit breakers from shore power to the light switches would trip. I don't know why, my guess is a short circuit? Many times the 3 way switch will not shut off before making contact with the other wire. So if you want to chance back feeding 120 volt shore power into the output wires of the inverter, and cause it to explode, try this. . .. If you want it to be safe, then a proper automatic transfer switch, or manual transfer switch is the SAFE way to make sure that the power is off, and that the shore power will never feed into the output wires of the inverter. . Most inverters will burn up or melt something internally when 120 volts is applied to the output wires. Some will synchronize with the incoming shore power, but not many.
Try the two plugs, it is safe.
Try just leaving the inverter on, and let the charger feed power to it. That is safe too, not not as energy efficient.
Also are you using a modified sine wave inverter or a pure sine wave inverter? Most motors require pure sine wave power, because they have high torque motors that will require PSW power, or they will tend to draw to many amps, or not start at all.
Fred.
