Rheem-Ruud 42-25105-02 Start Relay

The Rheem-Ruud 42-25105-02 Start Relay is a precision-engineered potential start relay designed for single-phase compressor motors in HVACR systems. Rated for 395 VAC, this component is essential for increasing starting torque by temporarily introducing a start capacitor into the circuit. It operates via a voltage-sensitive coil that monitors the Back EMF (Electromotive Force) generated by the compressor motor, effectively disengaging the start capacitor once the motor reaches approximately 75% of its rated speed. This prevents internal winding damage and ensures reliable startups under high head pressure conditions. This specific HVAC start relay is a direct OEM replacement for various Rheem, Ruud, and WeatherKing condensing units. Its robust construction handles inductive loads reliably, making it a critical compressor start component for technicians addressing hard start issues or failed potential relays in the field. Utilizing an OEM Rheem start relay ensures exact electrical specifications are met, maintaining the integrity of the motor's starting cycle.

• Precise Voltage Sensing: Calibrated to 395V to ensure accurate capacitor cutout, protecting the motor from prolonged high-torque exposure.
• OEM Compatibility: Replaces Rheem-Ruud 42-25105-02, ensuring terminal alignment and mounting footprints match original equipment specifications.
• Heavy-Duty Contacts: Designed to withstand the high inrush current typical of AC compressor startup cycles without pitting or sticking.
• Enhanced Motor Longevity: Reduces heat buildup during the start cycle, effectively extending the service life of the hermetic compressor.

Is this relay compatible with other 395V applications?
While this relay is rated for 395V, it is specifically calibrated for Rheem and Ruud equipment. Always verify the continuous coil voltage and pick-up/drop-out ratings before attempting use in non-OEM applications.

What are the symptoms of a failing 42-25105-02 start relay?
Common indicators include the compressor humming without starting, tripped circuit breakers on startup, or a burnt odor from the control box. Resistance testing across the coil and checking for fused contacts can confirm failure.

Does this replace a standard hard start kit?
This is a potential relay component often used in conjunction with a start capacitor. It provides more reliable and motor-specific timing than a generic two-wire PTCR hard start device.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.