I Ian,
Like Gary, I wonder what the ring main is...assuming it's the 220 outlets on the boat that run on the inverter unless there is 220 power coming into the boat, in which case they get power directly from the 220 source???
 
It sounds to me like there's a problem with the automatic switch that shuts the inverter off when you are connected to 220v power.  It may be shutting the inverter off and not allowing the 220 power thru to the 220v receptacles and microwave.  I know there are some breakers and fuses in my Hart Interface charger/inverter, but I'm not on the boat and don't know if these are designed to specifically for the automatic switch mechanism.  Have you looked at the breakers and fuses?
 
I look forward to hearing what the real experts have to say...I'm just shooting from my position in the dark.
Kent
S/V KRISTY
SM 243
 

 

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