I have 4 1875 Watt hair dryers wired on a board which has a so cord and a plug at the end. I plug it in turn it on full blast and trips a 15A breaker in no time and a 20Amp breaker in less than a minute. And if it does not trip within a minute i know the breaker is higher than a 20. It could also be used to test GFCI under normal load condition.
