Rheem-Ruud 42-21571-08 Relay

The Rheem-Ruud 42-21571-08 Relay is an essential 24V SPST Normally Open control relay specifically engineered for high-cycle reliability in residential and commercial HVAC equipment. As a genuine OEM Rheem replacement part, this relay provides a precise match for voltage requirements and mechanical mounting within Rheem and Ruud air handlers, furnaces, and condensing units. It handles switching for internal fan motors, compressors, and auxiliary control circuits, ensuring seamless command response between the thermostat and high-voltage components. Built to withstand 50/60 Hz frequencies, its Single Pole Single Throw configuration ensures a clean break or connection in the 24 VAC control circuit, preventing erratic system behavior or contact welding under standard inductive loads.

Key Benefits for Technicians:

• Universal Terminal Compatibility: Equipped with standard 1/4 inch quick-connect terminals for rapid field installation and secure electrical paths.
• Optimized Electrical Ratings: Supports 12A FLA at 120V and 8A FLA at 230V, providing the overhead necessary for demanding blower and motor starts.
• OEM Integrity: Eliminates the guesswork of mounting footprints and coil resistance common with generic 24 volt switching relays.
• Heavy-Duty Construction: Rated for up to 60A LRA at 120V, ensuring the contacts can handle the high inrush current typically seen in HVAC compressor relays.

Common Questions:

Can this relay replace a 2-pole SPDT relay?
No. This is a Single Pole Single Throw (SPST) relay with a Normally Open (N/O) contact. If your circuit requires a changeover contact or a normally closed position, you must use the manufacturer-specified relay to ensure proper sequence of operations.

Is this relay compatible with 50Hz power systems?
Yes, the 42-21571-08 is rated for both 50Hz and 60Hz, making it suitable for standard North American grids and international applications requiring a 24V HVAC control relay.

What causes an OEM relay to fail prematurely?
Common causes include pitted contacts from excessive arcing, coil burnout due to low voltage/brownout conditions, or vibration-induced mechanical failure. Using a genuine Rheem-Ruud 42-21571-08 ensures the coil resistance is matched perfectly to the transformer output.

Important Installation Notice: This HVAC relay should only be installed by qualified service professionals. Improper installation or use may result in electrical hazards, including fire, electric shock, or equipment damage. Always consult the product manual and adhere to manufacturer guidelines.

California Proposition 65 Warning: This product contains materials known to the State of California to cause cancer and reproductive harm. For more information, visit P65Warnings.ca.gov.

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.