01441492R00 – REFVAC20/25 LB, PH, PD
17
Service - System Controls
The temperature controller and evaporator probe (P1-control) indicate when the refrigeration system is required to
turn on and off .
The refrigeration system removes heat from the cabinet and rejects it into the surrounding room air .
When the evaporator probe (P1-Control) reaches its predetermined cut-in value (Advanced settings, Viewable), the
probe signals the controller to turn on the refrigeration system . The controller sends a 12VDC signal to the normally
open compressor relay . The relay then closes, energizing the compressor and condenser fan .
When evaporator probe (P1-control) reaches its predetermined cut-out value (Advanced Settings-Viewable), the
controller interrupts the 12 VDC signal to the compressor relay, de-energizing the compressor and condenser fan .
The evaporator fan runs continuously .
Controller Operation
The controller displays product temperature in degrees C (default) or F to 1 decimal point .
The controller is pre-programmed with the following setpoint: 4 .4 C (40 F) . The controller allows for the set point to
be adjusted as low as 2 C (36 F) and as high as 10 C (50 F) to meet your desired product storage requirements .
All set points operate with a +2 .2 C (+4 F) differential offset along with a 10 C (18 F) differential . The differential
offset, in conjunction with the set point and differential, determine the cut-in and cut-out points of the cooling
system . For instance, a unit running with a defaulted set point of 4 .4 C (40 F) will have the cooling system cut-in
at 6 .6 C (44 F) and cut-out at –3 .4 C (26 F) according to the P1 control probe located within the evaporator coil .
Cut-in and Cut-out parameters are Viewable in via the Advanced Settings Menu .
ATTENTION
Cabinet temperature adjustments can be made by simply modifying the temperature control
setpoint. Modifications to the factory default settings for the control differential or evaporator
offset parameters will result in excessive compressor cycles that may lead to premature
compressor/start component failures. Component failures caused by adjusting these critical
control operating parameters may void the equipment warranty.
Sensor Readings/Temperature Display
The Touchscreen is defaulted to display the P4-Top probe which reads the solution temperature of your product
simulation bottle . For ease of troubleshooting, the Touchscreen can be toggled to display the P1-control probe to
view the refrigeration cycle . To toggle the display for your desired probe, Access Advanced Settings>Display Probe
and select the desired probe .
Note: After service is complete it is recommended to restore the display to the P4-Top Probe .
Heated door (option)
Heated doors are factory installed . An unheated door cannot be retrofitted to a heated door in the field . Factory
default for the heated door and fascia heater cycle is set to 10 minutes off and 10 minutes on .
Should the need arise, the door schedule can be changed in Advanced Menu>Door Heater .
