Thermal Protection: Built-in automatic reset thermal overload protects the motor windings from overheating during high-demand periods

the 220 series typically does not contain internal relief

the motor can be swapped by removing the power head cover and securing the new motor to the internal mounting plate

For very large ducts with high stratification

Tekmar Controls 356 Control 319847-401 Thermal Protection: Built-in automatic resetThe Tekmar Controls 356 Control is a sophisticated 24Vac Variable Speed Mixing Control engineered specifically for hydronic systems requiring precise outdoor temperature reset. A veteran tech knows that maintaining the right water temperature is non negotiable for radiant floor heating and commercial baseboard applications; this microprocessor based unit delivers exactly that by modulating the speed of a single permanent capacitor (wet rotor)