A “Super Boost” relay + hard start kit (often under Supco’s Super Boost / SPP series) is an accessory used with single-phase compressors (especially in HVAC systems) to assist the compressor during startup. The kit typically combines:

A start capacitor sized to give extra starting torque, and

A relay or PTC / EPR (Positive Temperature Coefficient / Electronic Potential Relay) to remove the start capacitor from the circuit once the compressor is up to speed.

The purpose is to help “hard start” or “weak start” compressors, especially under low-voltage conditions or when the motor is under load (e.g. high ambient temperature). The Super Boost kits are marketed to provide high torque boost (for example “500 % torque increase” in some models).

Edmondson Supply

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supco.com

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They are designed for “two-wire” installation (across the run capacitor terminals) in many PSC (permanent split capacitor) motors, and are UL-recognized.