Robertshaw 780-790 HSI Module

For field techs dealing with intermittent ignition failures or flame sensing issues on gas-fired heating systems, the Robertshaw 780-790 HSI Module provides a reliable, direct replacement solution. This hot surface ignition control is engineered to drop into tight control cabinets, serving as the primary replacement for the HS780-17NL-304A as well as the 104A and 108A variants. Operating on a standard 120V AC ignition system, the module features a precise 17-second prepurge and an integrated 4-second valve trial for ignition. Its local flame sensing technology ensures stable burner operation by monitoring the flame rectification signal immediately after the ignitor de-energizes. Designed for intermittent pilot and main burner control, this Robertshaw 780 series module utilizes a small footprint and molded-in terminal barriers to simplify HVAC furnace repair and prevent cross-wiring. When a call for heat is received at the TH terminal, the 780-790 manages the full ignition sequence, ensuring the gas valve opens only after the ignitor reaches stable temperature.

• Universal Compatibility: Specifically designed as a direct replacement for HS780-17NL-304A and compatible with several OEM hot surface ignition modules.
• Precise Timing: Features a factory-set 17-second prepurge/warm-up and a strict 4-second safety trial for ignition.
• Field Reliability: Built with a robust mounting screw that establishes a positive ground connection, critical for accurate flame sensing.
• Compact Housing: Small form factor allows for easy installation in compact industrial and commercial furnace vestibules.
• Technical Architecture: Supports a 1.5 Amp main valve current and handles up to 5 Amps of maximum ignitor current.

• Does this module support remote flame sensing? No, the 780-790 is configured for local sensing applications only.
• How do I reset the module after a lockout? You must open the thermostat or system switch for at least 10 seconds to reset the internal lockout logic.
• What is the operating temperature range? This module is rated for performance in ambient conditions from -40°F to 176°F.

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.