Single pole or double pole for main circuit breaker on AC distro panel

[vanwilder]

I am trying to find out if it is ok to use a 40 amp single pole circuit breaker as my main circuit breaker from the inverter to the AC distro panel. I will be using a 4000w inverter to feed my 120v AC loads. I have read that single pole circuit breakers should only be used for 15 to 20amp and double pole circuit breakers should be used for 240v 20 - 60 amp. I was planning to get a Blue Sea AC distro panel and get a Blue Sea 40 amp single pole circuit breaker for the main circuit breaker. Can anybody tell me if that will work?

 

[Bud Martin]

The number of pole on the breaker has to do with the Hot lines, the 240VAC for US home you get power from L1 and L2 so you need to break both lines thus double pole ganged breaker is required.
Is your inverter allowed you to bond the Neutral to safety ground?