T-354 5–105. When the calculation reaches -250, contacts TC and TN are opened to de-energize compressor and condenser fan motors. The cool light is also de-energized.6. The evaporator fan motors continue to run to circulate air throughout the container. The in-range lightremains illuminated as long as the supply air is within tolerance of set point.7. When the supply air temperature increases to 0.2C (0.4F) above set point and the three minute off timehas elapsed, relays TC and TN are energizes to re start the compressor and condenser fan motors. Thecool light is also illuminated.5.10.2 Sequence of Operation - Perishable Mode HeatingNOTEThe unit will heat only when in the Perishable Mode, relay TH is electronically locked out when in theFrozen Mode.1. If the air temperature decreases 0.5C (0.9F) below set point, the system enters the heating mode (seeFigure 5.3). The controller closes contacts TH (see Figure 5.6) to allow power flow through the heat termi-nation thermostat (HTT) to energize the heaters (HR). The HEAT light is also illuminated. The evaporatorfans continue to run to circulate air throughout the container.2. When the temperature rises to 0.2C (0.4F) below set point, contact TH opens to de-energize the heaters.The HEAT light is also de-energized. The evaporator fans continue to run to circulate air throughout the con-tainer.3. A safety heater termination thermostat (HTT), attached to an evaporator coil support, will open the heatingcircuit if overheating occurs.Figure 5.6 Perishable Mode HeatingCONTROL TRANSFORMERPOWER TOCONTROLLERSIGNAL TOCONTROLLERSIGNAL TOCONTROLLERENERGIZEDDE-ENERGIZEDFOR FULL DIAGRAM ANDLEGEND, SEE SECTION 7
