High Stage System Failure; Probe Failure Alarm; Voltage Compensation Alarm - Thermo Scientific 700 Series Operating And Maintenance Manual

Section 3
Alarms
High Stage System

Probe Failure Alarm

Compensation Alarm
3-2 Model 700 Series
The "high stage system failure" condition is created when the high stage
compressor and fans run for 30 minutes and are not capable of cooling the
Failure
interstage heat exchanger to the proper temperature. Under this condition,
the high stage compressor and fans turn off after 30 minutes and an
audible and visual alarm occur. The audible alarm can be silenced and will
ringback every 15 minutes.
The microprocessor in Model 700 Series freezers continually scans all
probes including the control probe, heat exchanger probe and condenser
probe to ensure that they are operating properly. Should an error be
detected, the "Probe Failure" alarm will occur as shown in the table above.
If an error is detected with the control probe, the high and low stage
compressors will run continuously. As a result, the cabinet temperature
will decrease until it reaches the lowest temperature that the refrigeration
system can maintain. If an error is detected with the heat exchanger probe,
the freezer will cycle properly at its temperature set point using a 5 minute
step start between the high and low stage compressors. If an error is
detected with the condenser probe, there is no impact on the performance
of the freezer; however, the hot condenser alarm may also occur. Contact
the Technical Services department (1-888-213-1790) or your local
distributor.
Voltage
In addition to the alarms listed above, another condition detected by the
controls will result in an audible and visual alarm. If the freezer is
compensating for high or low line voltage, the system will measure the
compensated AC voltage. If the voltage is incorrect, the unit will stop
attempting to compensate, and the compressor will run on direct line
voltage. Under this condition, there will be a visual and audible alarm that
can be silenced with a ringback period of fifteen minutes. This alarm
condition is unlikely to occur, and as such, there is no LED alarm
indicator for this condition.
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