Aprilaire 4740 Relay

The Aprilaire 4740 Relay is a critical replacement component engineered specifically for Aprilaire 700 series humidifiers, including the 700A and 700M models manufactured after 2008. As a genuine AprilAire humidifier part, this fan relay is responsible for powering the circulator fan when the humidistat signals for moisture. Unlike older "Series One" versions that utilized the 4238 control board with an integrated transformer, this modern 24V humidifier relay is designed to work in conjunction with an external transformer to manage the HVAC blower activation and solenoid valve operations. Featuring a compact 10A design and a 24 VAC coil, the 4740 ensures your whole-house humidifier maintains optimal humidity levels by providing reliable switching for the unit's high-output fan. Whether you are performing routine maintenance or a humidifier fan relay replacement, this authentic OEM component offers perfect mechanical fitment and restores the system's ability to distribute humidified air throughout your home efficiently.

• OEM Compatibility: Specifically designed for Aprilaire 700A and 700M power humidifiers.
• Enhanced Efficiency: Precisely activates the circulator fan to ensure consistent moisture distribution.
• Direct Replacement: Replaces the Aprilaire 4740 relay in newer Series Two units.
• Reliable Performance: Features a durable 24 VAC coil rated for 10A for long-term cycling.

• Will this relay work for my pre-2008 model 700? No, older "Series One" models typically require the 4238 control board; this 4740 relay is for "Series Two" units with external transformers.
• What tools are needed for installation? Most technicians use a Phillips screwdriver and needle-nose pliers to complete the swap.
• Does this part control the water valve? Yes, the 24V signal is routed through this relay to both the solenoid valve and the fan.

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.