Technicians should look for visible burn marks on the PCB

ensuring a seamless fit for technicians performing field retrofits or repairs

confirm the cut-off temperature rating and mounting footprint match the existing heater assembly or plenum housing to maintain UL compliance and system safety integrity

a mechanical internal failure is likely

it offers a more compact footprint than its predecessor

AERCO Boiler and Water Heater 18557-1 Tstat 321702-401 Technicians should look for visibleThe AERCO 18557 1 Pneumatic Bulb Thermostat is a critical OEM replacement part designed specifically for AERCO boiler and water heater systems. This RA 20 240 thermostat utilizes advanced pneumatic sensing technology to ensure the precise temperature regulation required for commercial heating environments. By providing dependable sensing through its bulb style design, the 18557 1 Tstat maintains peak efficiency and prevents the energy waste associated