Fenwal 35-655910-991 Module

The Fenwal 35-655910-991 is a robust 24 VAC Hot Surface Ignition (HSI) control module engineered for precise sequencing in gas-fired furnaces, boilers, and commercial heating equipment. This micro-processor-based control manages the combustion blower, ignitor, and gas valve while providing continuous flame monitoring. Designed for field replacement and OEM applications, it features a 45-second prepurge and interpurge cycle to ensure the combustion chamber is clear, followed by a critical 4-second trial for ignition (TFI). With a flame sensitivity of 0.7 microamps, it maintains reliable operation even in demanding environments. The rugged gray Noryl enclosure is conformally coated, protecting internal circuitry from moisture and contaminants in temperatures ranging from -40°F to +176°F. This module is compatible with 120/240 VAC silicon carbide ignitors and supports natural, LP, and manufactured gases, making it a versatile solution for high-recovery heating systems.

Key Benefits for HVAC Contractors

• Enhanced Troubleshooting: Diagnostic LED provides instant feedback on internal hardware or flame sensing issues, reducing time on the job site.
• Multi-Voltage Compatibility: High-voltage output ratings support 120/240 VAC hot surface elements up to 5.0A.
• Superior Moisture Resistance: Conformal coating allows for operation in up to 95% relative humidity (non-condensing) environments.
• Standardized Timing: Fixed 45-second purge and 4-second TFI provide a consistent safe ignition sequence for industrial burners and ovens.
• Universal Mounting: The compact footprint and mounting design allow for easy integration into existing control cabinets.

Common Questions about the Fenwal 35-655910-991

How do I test the flame signal on this module?
Technicians should measure the DC microamp signal in series with the flame sensor. A minimum of 0.7 microamps is required for the 35-655910-991 ignition control to maintain the gas valve circuit.

Can I use this to replace a 120V ignition system?
The control itself requires an 18-30 VAC input from a Class 2 transformer, but it is capable of switching 120 VAC or 240 VAC for the inducer blower and the ignitor element.

What does it mean if the gas valve shuts off after 4 seconds?
This typically indicates that the module did not sense a flame during the 4-second trial for ignition. Check the flame rod position, ceramic insulator for cracks, and ensure the module has a solid burner ground.

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.