A 220v Circuit breaker that controls either AC or an inlet switch box

Question

I have a kill switch by my AC (40 Amps circuit breaker). I want this to be a selector to run AC or an inlet switch when there is no power (40 amp circuit) so I can plug in my generator to power the whole house.

Answer 1

This idea will be unsafe. You are trying to connect a double-throw switch between your AC and circuit panel so you can add a generator inlet. If you throw this switch to the inlet while the house has utility power, then the house power will be on the exposed inlet pins, and run the strong risk of electrocuting you and destroying your generator.

"OK, I'll just use an outlet instead of an inlet! Then the pins will be covered."

That won't be safe either. It prompts use of the usual "suicide cord" that folks try when back-feeding the electric dryer outlet. The cord is two male plugs with cable between, and is aptly named "suicide" because it will kill you sooner or later when the cord is unplugged from the house while the generator is running.

Either method is dangerous because there is a risk of running the generator while the main house circuit breaker is still accidentally connected. And, yes, one day you will accidentally forget to turn off the house breaker, and it only takes once to kill and destroy. The generator power will make it out to the utility workers, possibly through the utility's transformers that can make the generator's power size up to thousands of volts and kill the utility workers. You'll also be powering your neighbors unknowingly. And when the utility power comes back on it will very easily overpower and destroy/set afire your generator.

You should use a full approved interlock system or transfer switch, properly installed according to instructions, so there is a definite lockout between the main breaker and the generator input. Such interlocks or transfer switches will make it impossible to accidentally connect the generator and utility power at the same time. Note that a main panel interlock compatible with your panel can be relatively very inexpensive, and usually consists of a sliding piece of metal and an extra breaker in the correct place on the panel for the generator inlet.

Answer 2

If you want to install an inlet then it must be home run directly to the panel that it is going to power. That is the only way to ensure that you can properly lock out grid power while the inlet is providing power.

Otherwise you will end up with the situation where you have a generator running during a blackout and didn't turn off the main breaker and it's backfeeding to the power grid. This is dangerous for the people trying to repair the grid and can damage your generator when power is restored.