@spare do not use an extension cord is number 1. Number 2 is that your breaker at 16amps is underrated since you most likely have other things on that particular branch of your circuit. Number 3 would be to clean the AC properly since a dirty AC will attempt to continuously run to keep up with the workload. Since we do not know what AC unit you have, it is difficult to figure out the BTU of the unit compared to your room size. If your AC output is to small for the area you are trying to cool down, your AC will try to cool it down but wont keep up with it. This can cause the compressor to run all the time and it will draw maximum amperage. There is nothing touching the plug and it is not the plug that is at fault here.