Fenwal 35-705700-005 Control

The Fenwal 35-705700-005 is a 120VAC Direct Spark Ignition (DSI) control module designed for precise gas valve sequence management in commercial and industrial heating applications. This microprocessor-based gas ignition control features a 10-second Trial for Ignition (TFI) period and is configured for a single ignition attempt (1Try) without a prepurge (NoPP) cycle. Engineered for intermittent duty gas burners, this unit facilitates reliable flame sensing via the high-voltage electrode, utilizing the flame rectification principle to ensure safe operation. The Fenwal 35-70 series architecture provides robust resistance to vibration and thermal cycling, making it a standard replacement in commercial cooking equipment, forced air furnaces, and water heaters. As a 120V system, it leverages on-board diagnostics to streamline HVAC troubleshooting, allowing technicians to verify flame signal strength and power supply stability during the ignition sequence.

Key Technical Benefits

• 10-Second TFI: Provides a dedicated window for flame establishment, ensuring reliable light-off in high-output burner configurations.
• Integrated Flame Sensing: Utilizes a single electrode for both high-voltage discharge and flame monitoring, reducing wiring complexity.
• Compact Enclosure: The potted design protects internal solid-state circuitry from moisture, dust, and mechanical stress in harsh boiler rooms.
• 120V DSI Logic: Eliminates the need for a standing pilot, significantly increasing seasonal energy efficiency and reducing gas consumption.
• Multi-Mount Capability: Standardized footprint allows for straightforward retrofitting in existing control cabinets and burner assemblies.

Common Installation Questions

What is the difference between this model and a 24V DSI control?
The Fenwal 35-705700-005 operates on a 120VAC line voltage input. Substituting a 24V module in this circuit will result in immediate board failure or an inability to power the gas valve solenoids. Always verify your primary transformer output before installation.

Can I use this module for a liquid propane (LP) burner?
Yes, provided the gas valve and burner orifices are correctly sized for LP. This direct spark ignition control manages the timing and electrical sequence regardless of gas type, though the 10-second TFI must meet your specific appliance’s safety requirements.

How do I troubleshoot a 'No Spark' condition with this board?
Ensure the 120V input is stable and the ground connection is a zero-ohm path to the burner chassis. If the board receives power but fails to generate a high-voltage spark across the electrode gap, inspect the high-tension lead for insulation breakdown or carbon tracking before replacing the module.

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.