[Richard]

I agree with Bill. Pull the access cover for the circuit board on the SCS. Look at the schematic printed on the back of the access panel. Put clamp on ammeter on each compressor, and also the evaporator and condenser blower motors. The compressors should be pulling 11 to 14 amps depending on outside temps. Each blower motor should pull around 2 amps.

A question to ask about the shutdown is, does the inside or outside blower motor quit before the breaker trips? reason being is tha either motor shutting down while the compressor is running will cause high head pressure in the compressor causing high amperage draw.

You could have a bad capacitor for either compressor or blower motor.

You could also have a compressor heading to failure. I have had one compressor failure in the SCS units and the early warning signs were sporadic breaker trips.