This single-pole single-throw (SPST) inductive switch is factory-calibrated to a set point of -0

The MARS 39004 is a professional-grade 390 Series SPDT Changeover Switch designed for automatic seasonal transition in hydronic heating and cooling systems

The higher volt-ampere rating provides more overhead for additional HVAC accessories like humidifiers or electronic air cleaners without overloading the circuit

Noise Reduction: Properly seats the motor to dampen mechanical resonance and vibration during operation

Ensure the mounting surface is clean and the disc has direct contact with the heated air or surface for accurate thermal response

Robertshaw 41-408 Hot Surface Ignitor This single-pole single-throw (SPST) inductiveThe Robertshaw 41 408 Hot Surface Ignitor is a high performance silicon carbide furnace igniter engineered for precision in HVAC gas ignition systems. Built with high purity recrystallized silicon carbide, this 120V HSI replacement offers superior thermal and physical strength, maintaining stable electrical properties even under extreme cycling conditions. Featuring a Norton 271N factory configuration, it is designed for a rapid 17 second heat up time