Reznor 121275 Block Direct Compatibility: Engineered as the

Direct Compatibility: Engineered as the official successor to multiple legacy parts

secondary output to ensure stable operation of thermostats

and elbows without the need for additional fasteners or adhesives

Precise Pressure Calibration: Factory-set at 0

Reznor 121275 Block Direct Compatibility: Engineered as theThe Reznor 121275 Stack Flue Block is a high limit safety component engineered specifically as an Energy Cutout Device (ECO) for commercial and industrial gas fired heating units. Designed to monitor the integrity of the ventilation system, this blocked vent switch acts as a critical failsafe by measuring exhaust temperatures at the flue. If the sensor detects a restriction, backflow, or overheating condition where temperatures reach the 275F trip