Trying hard not to steal a thread...but...
Nomad.. thanks will check out the wiring under the cover...it is my understanding that both 120v lines are disconnected by the main breaker...
What you will find (probably) are two very heavy wires each going to a switch. They are not two sides of the circuit, but one side each of two circuits that feed your house. Together they give you 220v. However the switch breaks only one side of each circuit.
Not being opened are the neutral and ground.
If the backfeed is wired wrong (very easy to make a mistake here) you can still put power back onto the grid, even if these are open. I am not sure how that can happen and seek understanding here.
Now back to your regularly scheduled thread...
Nomad