Fenwal 35-665725-121 is a 24VAC microprocessor-based hot surface ignition (HSI) control module designed to manage ignition sequencing and flame sensing in compatible gas-fired equipment. It’s not position sensitive (mounts vertically or horizontally) and is commonly used in pool/spa heaters, gas furnaces, water heaters, and other 24VAC gas burner systems under 400,000 BTU.
Product Specifications
- Part Number (MPN): 35-665725-121
- Type: Ignition Control Module / Ignition Module
- Ignition Type: Hot Surface Ignition (HSI)
- Control Input Power: 18–30 VAC, 50/60 Hz (Class 2 transformer)
- Line Voltage Capability (L1/L2 only): 24 / 120 / 240 VAC (model-dependent wiring)
- Control Current: 300 mA max @ 24 VAC (with relays energized; control only)
- Gas Valve Output Rating: 2.0A max @ 24 VAC
- Hot Surface Igniter Output Rating: 5.0A max @ 24/120/240 VAC
- Operating Temperature Range: -40°F to 176°F (-40°C to 80°C)
- Flame Sensitivity: 0.7 µA minimum
- Fuel Types: Natural Gas, LP (Propane), Manufactured Gas
- Mounting: Not position sensitive; vertical or horizontal mounting
- Typical Timing for This Model: 15-second pre-purge, 4-second trial-for-ignition (TFI)
Applications
- Pool and spa heaters
- Gas furnaces
- Water heaters
- Any 24 VAC gas burner application under 400K BTU
What’s Included
1 √ó Fenwal 35-665725-121 Ignition Module (Control Board)
