it is not recommended for thermostats using triacs or solid-state switching without further isolation

always verify your dip switch settings and parameters against the original WH155 control to match the specific site requirements

When you're troubleshooting a system lockout or inefficient compressor cycles

you know that brittle or corroded HVAC wiring leads to intermittent flame signal loss (microamps)

you know that reliability in high-limit safety is non-negotiable

Reznor 122990 Limit 321894-706 it is not recommended forFor service technicians and commercial contractors, the Reznor 122990 Manual Reset Limit Switch is a critical OEM safety component designed for heavy duty gas fired unit heaters. Engineered to open at 180F, this high limit control acts as a fail safe against heat exchanger overheating. Unlike automatic switches, the manual reset design requires a physical inspection of the system before resuming operation, ensuring that common failure pointssuch as