extending the operational life of the primary control board

making it a reliable choice for commercial and heavy-duty residential furnaces

reducing nuisance service calls while maintaining strict safety parameters

check the specific terminal unit submittal to ensure signal compatibility

it provides critical boiler overpressure protection for legacy and modern steam systems

Maxitrol TD121B Temperature Selector R-410A extending the operational life ofThe Maxitrol TD121B Temperature Selector is a critical component for Selectra Series 21 and 31 electronic gas flame modulation systems. Specifically engineered for indirect fired make up air units, this remote selector provides precise setpoint control within a 120 170F temperature range. For a stable discharge air temperature, it must be paired with a TS121B sensor to ensure the resistance curves match the A1010 or A1011 amplifier logic. This