Ocean HVAC Lab

Quick Summary

System had a cooling call, but the outdoor unit would not stay on.
After resetting the breaker, the compressor started briefly and immediately tripped the breaker again, pointing strongly to compressor failure.

System Info

• System: Heat Pump
• Location: Outdoor Unit
• Outdoor Temp: Not Recorded
• Delta T: Not Recorded
• Subcooling: Not Recorded
• Superheat: Not Recorded

Customer Complaint

No cool air from the system.
Warm air was blowing from the indoor unit, and the outdoor unit appeared not to be running.

What I Found

• Thermostat was calling for cooling (cooling demand present, but no actual cooling)
• Suction line was checked by touch indoors (large line should typically feel cool during cooling operation)
• Liquid line condition was also considered during the indoor check (no clear indication of normal active cooling)
• Condensate pump was not full (no visible overflow or safety shutoff)
• No immediate sign of a drain-related shutdown was found
• Outdoor unit was not running at time of inspection
• System was confirmed to be a heat pump
• No high voltage was present at the outdoor unit board initially
• No voltage was found at the disconnect at first (suggesting possible upstream power issue rather than immediate equipment failure)
• Breaker was found tripped at the panel
• Breaker was reset
• After reset, 240V was confirmed at the outdoor disconnect (power supply to the unit was restored)
• After reconnecting the disconnect, the compressor started briefly for about 1 second
• Breaker tripped again immediately on compressor startup
• Repeated breaker trip during compressor start is a strong sign of compressor-related failure (possible high inrush current or internal compressor issue)
• Wiring was checked for contact or shorting
• Wires were adjusted and separated
• System was retested after wiring adjustment, and the same result occurred (breaker tripped again after compressor start)
• Wiring issue became less likely based on repeated identical result
• Compressor wires were isolated for further testing
• Terminal check was performed
• No clear continuity to ground was detected (this is normal)
• Reading between terminals was about 253 MΩ (this does not resemble typical low winding resistance and increases suspicion of internal compressor issue)
• With the compressor disconnected, the breaker held and the outdoor unit remained powered
• This strongly suggests the breaker trip is tied to the compressor itself
• A kinked suction line was observed during visual inspection
• A kinked suction line can create long-term refrigerant restriction and may have contributed to compressor damage

Diagnosis

This is most likely a compressor failure, not a simple wiring or drain issue.

Primary causes:

• Breaker trips immediately when compressor tries to start
• Breaker holds when compressor is isolated
• Kinked suction line may have caused long-term compressor stress or damage

Recommended Action

• Replace compressor
• Repair or replace the kinked refrigerant line
• Flush the system
• Check for possible acid contamination
• Replace the filter drier
• Perform a deep vacuum
• Verify final operation after repair using pressure, amp draw, and temperature readings

Study Note

Compressor Starts, Then Breaker Trips

If the breaker trips right when the compressor tries to start, the problem is often inside the compressor rather than in the thermostat or drain system.
When the breaker holds with the compressor isolated, that becomes a strong diagnostic clue that the compressor is the main load causing the trip.