The kit wires in parallel with the run capacitor and, for a fraction of a second at startup, boosts starting torque so the compressor can start against unbalanced pressures. It helps systems with TXVs that don't equalize, long or high-resistance supply circuits, and aging compressors that are starting to struggle. On a compressor with mechanical problems it only delays the inevitable.
Compressor's tripping on LRA every few starts, throw a hard start kit on it to buy the customer a season while they price a new unit.
Also heard as
- hard start
- start kit
Related terms
Cap
Short for capacitor, the part that gives compressor and fan motors the phase shift they need to start and run.
LRA
Locked rotor amps: the current a motor draws at the instant of starting, before it turns, listed on the nameplate.
Compressor
The pump that raises refrigerant vapor from evaporator pressure to condenser pressure and keeps it circulating.
Contactor
A heavy-duty relay that uses a 24 volt control signal to switch line voltage to a compressor and condenser fan.