11
Reprinted with permission from Dixell.
3.
C
oolers
Air Defrost Sequence of Operation
for Coolers
Air defrost units are preprogrammed for 3 hours of
compressor run time between defrosts. These periods are
not reprogrammable. After 3 hours, the temperature control
will turn the compressor off. When the coil temperature
reaches 38°F, the control will terminate the defrost cycle.
Room Thermostat Settings:
• Approximate dial settings of control
0 = Unit off (not an electrical disconnect)
1 = 52°F (11°C)
2 = 49°F (9°C)
3 = 45°F (7°C)
4 = 41°F (5°C)
5 = 38°F (3°C)
6 = 34°F (1°C)
Cooler Defrost Control
Cooler units utilize an electronic temperature control.
The temperature may be adjusted by setting the dial. This
control is preset to provide 3 hours of compressor run time
between defrost cycles. Defrosts are temperature terminated
and cannot be reprogrammed. The temperature control
is programmed for minimum on cycle of one minute and
minimum off cycle of four minutes.
Maintenance
The evaporator section of a
system should be checked
at least once for proper defrosting because the amount
and pattern of frosting can vary greatly. The frost build-up
is dependent on the temperature of the room, the type of
product being stored, how often new product is brought
into the room and percentage of time the door to the room
is open.
System Standard Maintenance Guidelines
After first year of operation and under normal usage,
maintenance should cover the following items at least once
every six months:
1. Check and Tighten
ALL
electrical connections.
2. Check all wiring and insulators.
3. Check contactors for proper operation and for worn
contact points.
4. Check all fan motors. Tighten motor mount bolts/nuts
and tighten fan set screws.
5. Clean the condenser coil surface.
6. Check the operation of the control system. Make
certain all safety controls are operating properly.
7. Check that all defrost controls are functioning properly.
8. Clean the evaporator coil surface.
9. Clean the drain pan and check the drain pan and
drain line for proper drainage.
All Cooler Models
NOTE:
If power is interrupted to the unit during the
refrigeration off-cycle (system at temperature setpoint,
compressor off), the thermostat will initiate an extra defrost
period approximately one hour after power is restored.
