Operating instructions

TM 11574A-OI

2-54

(e) compressor and condenser fan motors. The cool light is also de-energized.

(f) The evaporator fan motors continue to run to circulate air throughout the container. The

in-range light remains illuminated as long as the supply air is within tolerance of set point.

(g) When the supply air temperature increases to 0.4 F (0.2 C) above set point and the three

minute off time has elapsed, relays TC and TN are energizes to restart the compressor

and condenser fan motors. The cool light is also illuminated.

(2) Sequence Of Operation – Perishable Mode Heating

NOTE

The unit will heat only when in the Perishable Mode, relay TH is electronically locked out

when in the Frozen mode.

(a) If the air temperature decreases 0.9 F (0.5 C) below set point, the system enters the

heating mode (see Figure 4-13). The controller closes contacts TH (see Figure 2-21) to

allow power flow through the heat termination thermostat (HTT) to energize the heaters

(HR). The HEAT light is also illuminated. The evaporator fans continue to run to

circulate air throughout the container.

(b) When the temperature rises to 0.4 F (0.2 C) 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 container.

open the heating circuit if overheating occurs.

Figure 2-20. Perishable Mode Cooling.