CSLB C-20 HVAC ContractorControls, Electrical and SafetyMedium
Before removing a run capacitor from a de-energized air conditioning condensing unit, a technician should first do which of the following to prevent injury?
- AWrap the capacitor in electrical tape before handling
- BMeasure the capacitor's microfarad rating with an ohmmeter
- CReconnect the disconnect switch to verify power flow
- DDischarge the capacitor terminals using an insulated resistor or approved discharge tool
Show answer & explanationAnswer & explanation
Correct answer: D. Discharge the capacitor terminals using an insulated resistor or approved discharge tool
Run and start capacitors can retain a dangerous electrical charge even after power is removed, so they must be safely discharged across their terminals with an insulated resistor or discharge tool before handling. Using an ohmmeter to measure capacitance is done after discharging, and reconnecting power defeats the safety purpose entirely.
Why the other options are wrong
- A. Tape does not discharge stored electrical energy.
- B. An ohmmeter measures resistance/capacitance, not a safe discharge method.
- C. Reconnecting power reintroduces the hazard being avoided.
Capacitor Discharge Safety
Capacitors store electrical energy even when disconnected from power and must be safely discharged before handling to prevent shock injury.
- Use an insulated resistor, not a screwdriver, to discharge
- Capacitors can hold charge for hours after power-off
- Always verify zero charge with a multimeter before touching terminals
- Shock hazard exists even with the disconnect open
Memory trick: Power off doesn't mean charge is gone — discharge before you carry on.