The D21-T electronic controller has been designed to take full advantage of our patented Air-Flow Sensor which modulates the heater’s capacity according to the quantity of air flowing through the heater by responding to the radiant heat of the elements even at very low CFMs. With normal airflow the controller will operate at full power. When the airflow drops below the minimum airflow, the controller will still operate but at reduced power. It will also safely shut down the heater in case of a total loss of airflow. The D21-T has a single output and the D22-T is equipped with two outputs effectively doubling the capacity of the D21-T. In cases with even larger loads, a D21-TS may be used instead to drive up to 4 SSRs. The maximum load is then limited to the capacity of the Solid State Relays. The ‘T’ versions of controllers such as the D21-T are exclusively controlled by a thermistor type thermostat such as our RT (room thermostat) and DT (duct thermostat) as well as our integrated Duct Sensor. Thermolec’s RTs and DTs are available in a variety of temperature ranges. Please order the proper range for your application.

• controlled by Thermolec’s RT, DT and integrated Duct Sensors
• compatible with electronic Air Flow Sensor
• works with 24 VAC control voltage
• single Triac output up to 240 VAC