Calculate current draw on unenergised circuit

[Firedancer]

Hi, I’ve got a 24v 10A power supply, fed from a 240v 6A breaker, that is breaking, it feeds three 6A type b circuit breakers, the first one I replaced was clearly struggling like it was overloaded and the second just gave up, before I fit the third I was wondering if I was to measure the resistance of the circuit straight from the power supply connections I could work out the current draw accurately to see if it’s faulty power supply or actually a short circuit or faulty component, I have already being doing the usual IR tests and resistance test of components in that circuit but wonders if I could save time by just measuring straight from the source the whole circuit or if this wouldn’t be accurate enough?
tia