Hi All,

I have been working on a heat pump package unit that keeps tripping out the main c5o amp 3 phase circuit breaker, and I am struggling to find out why.

It only happens usually when on full demand for a couple of hours, its not over load its going out on short circuit because I monitored my clamp meter while it did it.

I first suspected the bearings in one of the motors were getting hot and ceasing up but I have observed most of the fans and they all seem to be spinning freely just before it trips.

I think the most logical explanation would be maybe a cable is chaffing somewere? and the fact when it is on full load vibration speeds it all up.

I will megger the cable from the unit back to the board as a next precaution but any help shared would be very gratfefully recieved!