Robertshaw 780-735 Ignition Module

The Robertshaw 780-735 ignition module is a universal hot surface ignition (HSI) control designed for reliable gas furnace repair and system troubleshooting. This 120V AC intermittent pilot lockout module features a critical 60-second trial for ignition (TFI) period, ensuring safe burner startup sequences in residential and commercial heating applications. As a direct 780-735 replacement for the OEM 62-22821-01 and SP735, this control manages the igniter and gas valve while monitoring flame rectification through a dedicated sensing circuit. For technicians working on HVAC part replacement, the 780-735 provides a robust solution for troubleshooting furnace ignition failure, specifically where moisture resistance and vibration durability are required. The module includes an intermittent pilot configuration, which saves energy by extinguishing the pilot during the off-cycle. Proper field installation requires verifying the existing wiring harness compatibility to ensure the integrated 60-second lockout safety timing functions correctly within the appliance's specific purge cycle requirements.

• Direct OEM Cross-Reference: Engineered as a drop-in replacement for the 62-22821-01 and SP735 modules, reducing field modification time.
• Enhanced Safety Timing: Features a 60-second lockout timer to prevent gas buildup during failed ignition attempts.
• Universal HSI Compatibility: Designed to work with 120V AC hot surface igniters commonly found in modern high-efficiency furnaces.
• Flame Sensing Technology: Utilizes high-sensitivity flame rectification circuits to monitor burner stability and prevent "nuisance" shutdowns.

What causes a 60-second lockout on this module?
A lockout typically occurs if the module fails to sense a flame signal within the 60-second trial period. Technicians should inspect the flame sensor for carbon buildup, check the igniter for proper ohms, and ensure the gas valve is receiving the correct voltage signal.

Can the 780-735 replace a 30-second trial module?
While the 780-735 is versatile, always verify the furnace manufacturer's original specification. Moving to a longer 60-second trial may be permissible depending on the heat exchanger's volume and the specific gas manifold pressure, but shorter trials are generally safer for smaller combustion chambers.

Does this module support local or remote flame sensing?
The 780-735 is designed to support both configurations. Ensure the sense lead is properly grounded and the probe is positioned within the outer three-quarters of the burner flame for optimal microamp signal strength.

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.