FZR Undercounter Freezer
9
Operation –––––––––––––––––––––––––––––––––––––––––––––––––––––––––
The temperature controller and probe indicate when the refrigeration system is required to turn on and off.
The refrigeration system removes heat from the cabinet interior and rejects it to the surrounding room air. When the
cabinet interior temperature r2 C (+4 F) above the controller set point, the probe signals the controller to
turn the refrigeration system on. The normally-open controller contacts 2 and 3 close and energize the evaporator
fan motor, door heater, and control relay that energizes the condensing unit (condenser fan motor and compressor).
The snowflake and fan LEDs on the controller will light to indicate that the refrigeration system is on. The
compressor uses a current-style starting relay and a starting capacitor to start the compressor motor.
When the cabinet interior temperature falls to the set point, the probe signals the controller to turn the refrigeration
system off. The controller contact 3 reopens, which de-energizes the control relay and turns off the condenser fan
motor and the compressor. The snowflake LED will go out and the fan LED will remain on.
Any accumulated frost on the evaporator coils melts during the defrost cycle. The condensate drains to a drain pan
mounted along the condensing unit. The heat from the condensing unit evaporates any condensate in the drain pan.
Temperature Control
The temperature control system is preset by the factory to maintain a cabinet temperature of -23 C (-10 F). If
desired, the cut-out temperature can be raised as high as -15 C (5 F) by following the instructions on
page 7
for changing the temperature set point. The 2 C (4 F) cut-out differential will be maintained regardless of the
controller set point.
Defrosting
The FZR series undercounter freezers control frost accumulation on the evaporator through automatic timed defrost
cycles. The defrost cycle is initiated by the temperature controller every 6 hours. Contacts 2 and 3 on the controller
open and the refrigeration system is turned off. Contact 7 is closed and the defrost heater is energized. The melting
snowflake LED on the controller will light, and the temperature display will read “dEF” to indicate the freezer is in the
defrost cycle.
The heaters warm the evaporator coil and drain pan to melt the frost and drain the water to the condensate pan.
The temperature controller monitors evaporator temperature using a probe embedded in the coil. The controller
terminates the defrost cycle when the evaporator temperature r5 C (+41 F) or after 15 minutes of defrost
time, whichever occurs first. As the defrost cycle terminates, the controller de-energizes the heater and energizes
the control relay, turning on the compressor and condenser fan. The snowflake LED on the controller will light to
indicate that the refrigeration system is running.
There is a 5 minute delay before the evaporator fan motor is re-energized. The fan LED on the controller will
come on to indicate the fan is running and the temperature display resumes displaying cabinet temperature. A
defrost cycle can be initiated manually at any time by depressing and holding the melting snowflake button for
approximately three seconds. As a safety feature, a temperature safety switch mounted on the evaporator will turn
off the defrost heater if the temperature of the evaporator r27 C (+80 F) regardless of controller operation.
The FZR series freezers have been designed specifically for the storage of temperature–critical medications. Other
storage applications may require modifications of the factory-programmed defrost cycle settings. Please consult
Follett technical service if defrost modification is needed.
Note: Storage of products of very low volumes or mass may require additional product insulation.
Note: Serial numbers below C57095 were programmed with defrost cycles every 2-4 hours terminating at
+5 C (+41 F) or after 15 minutes, whichever came first. If you are experiencing problems with frost on any of
these earlier units, please call Follett’s technical service department at (877) 612-5086 or +1 (610) 252-7301
for a programming key to update your unit to the most current program settings.
