Went on a call last week and the outdoor fan was not running and the defrost board on a Ruud RQRM heat pump was flashing a high pressure trip. Checked out outdoor fan motor windings- O.K. , bearings O.K.
The main breaker 100 amp was tripped. The 100 amp breaker is wired into disconnect at the unit. The disconnect had 2 breakers one 30 amp breaker going to the Compressor/outdoor fan and another 55 amp breaker going to the heat strips. Checked out the dual run capacitor, the herm side was reading 45 uf which is what it is suppose to be. The fan side was reading 0 uf.
Just curious why the main breaker would trip and not the 30 am breaker going to the unit? I must have been asleep during at HVAC school that day they were discussing branch circuits.
I would seem that the smaller breaker feeding the compressor/fan would trip first. Wonder why it did not?
Replaced run capacitor and everything is fine, no more tripping.