Fenwal 35-705500-501 Control

The Fenwal 35-705500-501 is a microprocessor-based Direct Spark Ignition (DSI) control engineered for 120V gas-fired systems. This 120V ignition module provides a fixed 5-second pre-purge to clear the combustion chamber and a 4-second trial for ignition (TFI) to ensure safe burner startup. Designed for compatibility with both natural gas and LP applications, this replacement furnace control board utilizes Detect-A-Flame technology for precise flame sensing, maintaining a minimum 1.0 µA signal. The single-try ignition sequence simplifies local code compliance in specific commercial and residential configurations. For field troubleshooting, the unit features on-board diagnostics with LED indicators and accessible flame current test pins, allowing contractors to verify performance without breaking the circuit. This rugged HVACR control module is polarity insensitive, reducing the risk of miswiring during installation in demanding infrared burner or crop dryer environments.

• Enhanced Safety: Internal microprocessor control provides repeatable timing sequences and immediate lockout if flame sensing is not verified within the TFI window.
• Efficient Diagnostics: Integrated LED error codes and dedicated test pins allow for rapid identification of ignition failures or hardware faults.
• Versatile Application: Suitable for a wide range of gas-fired appliances, including commercial cooking equipment and industrial heaters.
• Robust Design: Operates in extreme temperatures ranging from -40°F to 175°F, ensuring reliability in unconditioned spaces.

What does the single-try ignition lockout mean for system resets?
As a single-try model, if the burner fails to light during the 4-second TFI, the control enters a hard lockout. The system must be reset by cycling the thermostat or 120V power input.

Can this module replace 24V DSI controls?
No, the Fenwal 35-705500-501 is strictly a 120VAC ignition control. Always verify line voltage at the L1 terminal before installing to prevent board damage.

How do I test the flame signal on this board?
Use a DC micro-ammeter connected to the FC+ and FC- pins. A stable reading of at least 1.0 µA is required for reliable flame rectification and continued operation.

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.