CSLB C-20 HVAC ContractorCooling and RefrigerationMedium
A technician installs a hard start kit consisting of a start capacitor and relay on a single-phase compressor that struggles to start under high head pressure. What is the primary purpose of this device?
- ATo reduce amperage draw during steady-state running conditions
- BTo continuously improve running power factor during normal operation
- CTo provide additional starting torque so the compressor can overcome high starting load
- DTo permanently replace the run capacitor in the circuit
Show answer & explanationAnswer & explanation
Correct answer: C. To provide additional starting torque so the compressor can overcome high starting load
A hard start kit adds a start capacitor momentarily in parallel with the run capacitor during startup, boosting starting torque so the compressor motor can overcome high head pressure or a hard-starting condition. The relay then disconnects the start capacitor once the motor reaches running speed, so it has no effect on steady-state efficiency.
Why the other options are wrong
- A. Hard start kits don't affect running amperage since the start capacitor disengages after start-up.
- B. The start capacitor is disconnected after startup and does not affect continuous running power factor.
- D. The run capacitor remains in the circuit; the start capacitor only supplements it briefly at startup.
Hard Start Kit
A device (start capacitor + relay) added to a single-phase compressor circuit to boost starting torque during startup, then disengage automatically.
- Used for compressors with high starting loads (e.g., high head pressure restarts)
- Relay disconnects start capacitor after motor reaches running speed
- Does not affect normal running performance or capacitance
Memory trick: Hard Start = Extra Push, then Steps Away