What happens
A wire or load fault, locked motor or other abnormal demand makes protection operate.
Typical symptoms
Immediate trip or a trip after an unsuccessful motor start.
Checks that distinguish this cause
Stop repeated resetting. Isolate damaged equipment and separate supply, wiring and load causes using the OEM test procedure; a grounded compressor is one possibility, not the only one.
What can look similar
Improper protection sizing or excessive connection heat may trip a circuit without a grounded motor.
Repair direction
Repair the verified cause before restoring operation. Never increase the protection rating to suppress trips.
Verify the repair
Verify circuit integrity and operating current against the approved design.
Equipment-specific limits
Use the nameplate maximum overcurrent protection, minimum circuit ampacity and installation instructions together. Breaker size is not selected from a single running-current reading.
Practice this diagnosis
This cause is a reference topic; it does not yet have a dedicated simulated call. Browse the practice board.
References and applicability
Original HVACSim explanations with manufacturer and instrument-maker references for further reading. These resources support the subject; their model-specific examples are not specifications for every system.
- Fluke: HVAC and industrial electrical testing applicationsElectrical measurement principles, including control-circuit voltage references.
- Carrier: HVAC installation and commissioning overviewSizing, airflow, charge and A2L installation considerations; obtain the exact unit manual.
Editorial review: 2026-09-29. Verify the current manual for the installed model.