CSLB C-20 HVAC ContractorHeating SystemsMedium
A heat pump system is experiencing frequent trips of the circuit breaker for the outdoor unit. The technician finds that the compressor draws excessively high amperage during startup attempts. Which of the following is the most likely cause?
- AA faulty compressor start capacitor.
- BAn undersized circuit breaker.
- CA low refrigerant charge.
- DA clogged outdoor coil.
Show answer & explanationAnswer & explanation
Correct answer: A. A faulty compressor start capacitor.
A faulty compressor start capacitor can prevent the compressor from starting efficiently, causing it to 'lock rotor' or struggle to start. This results in the compressor drawing extremely high amperage (LRA - Locked Rotor Amps), which will quickly trip the circuit breaker.
Why the other options are wrong
- B. While an undersized breaker could trip, the question implies a sudden change in behavior ('frequent trips') and high amperage *during startup attempts*, pointing to a component failure rather than an installation error (unless it's a new installation).
- C. Low refrigerant charge would lead to low suction pressure and reduced capacity, not typically extreme high amperage at startup that trips a breaker.
- D. A clogged outdoor coil would lead to high head pressure and reduced efficiency, potentially causing high running amps, but less likely to cause immediate, high startup amperage trips.
Compressor Hard Starting
A condition where a compressor struggles to initiate rotation, often due to a failed starting component, leading to excessive current draw and potential circuit breaker trips.
- Often caused by a failed start capacitor or relay.
- Results in high locked-rotor amperage (LRA).
- Can damage compressor windings if not addressed.
Memory trick: Breaker goes 'snap,' if the start cap's a trap.