Reznor 121275 Block and SV9501 series

and SV9501 series

Installing this in a natural gas system will result in improper combustion and potential safety hazards

Using a tube that is too short will result in inadequate air sampling and potential code violations

or 45-second hot surface ignition (HSI) control systems

Reliable Ignition: Supports proper flame impingement on thermocouples and flame sensors to reduce system downtime

Reznor 121275 Block and SV9501 seriesThe 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