Robertshaw 780-785 HSI Module

The Robertshaw 780-785 HSI Module (780-34NL306A) is a universal hot surface ignition control designed for gas furnace and boiler applications utilizing 120V HSI systems. This non-lockout module replaces obsolete Johnson Controls and Honeywell ignition modules, simplifying truck stock by consolidating multiple part numbers. Engineered for intermittent pilot or direct spark conversions, this Robertshaw replacement module operates on a 24V AC thermostat circuit. It features a specific 34-second trial for ignition period, ensuring reliable flame rectification and gas valve synchronization. For technicians troubleshooting intermittent ignition failure, this unit offers robust diagnostic capabilities and works with both natural and LP gas systems. The 120V HSI output provides consistent voltage to the igniter, reducing premature component wear. When performing a Robertshaw 780-785 wiring installation, ensure proper grounding to the burner assembly to maintain signal integrity during the flame sensing cycle.

• Universal Compatibility: Replaces a wide range of OEM HSI ignition control boards including several competitive 120V furnace control modules.
• Non-Lockout Operation: Provides continuous retry attempts for ignition, making it ideal for systems in harsh environments where signal drops may occur.
• Streamlined Installation: Designed with standard spade terminals and a mounting footprint that matches legacy Robertshaw ignition components.
• Field-Proven Reliability: Solid-state construction resists vibration and heat-stress common in high-cycle residential and light commercial HVAC units.

What does the non-lockout feature mean for my service call?
Unlike lockout modules that require a manual reset after failed ignition attempts, this direct replacement HSI module will continue to cycle the ignition sequence until flame is established or the thermostat is satisfied.

Is this unit compatible with 80V or 24V igniters?
No, the 780-785 is specifically engineered for 120V hot surface igniters. Using this with lower voltage igniters will cause immediate component failure.

Can I use this for a 3-wire sense system?
Yes, this module supports remote flame sensing through the burner ground circuit or a dedicated sensor rod, ensuring accurate flame rectification feedback.

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.