Thermo Scientific TDE Series Manual page 28

Problem
Unit compressors run
continuously.
Cabinet temperature reached
an alarm condition, but
suitable alarm is not
activated.
Problem with temperature
validation/calibration.
Unit is constantly alarming.
Unit cycle on-percentage is
increasing (Compressors are
running more often than
before).
Difficult to close/open the
outer door.
Outer door alignment issues.
Difficult to close/open the
sublid.
Thermo Fisher Scientific ULT Freezers
Cause
Freezer set point is low.
Frost build up.
Dirty condenser.
Gasket damage.
Alarm setpoints may be
changed.
Cabinet temperature
displayed doesn't match
with actual temperature.
Exterior lid is closed but
not sealed completely.
Door open alarm, exterior
door not closing
completely.
Door open alarm, lid is
closed but not sealed
completely.
Alarm set points may have
changed.
Ambient conditions.
Warm load (or) over load.
Frequent and prolonged
lid openings.
Unit is not level.
Frost accumulated on lid
gasket.
Frost accumulated around
inner sublid.
Solution
Check whether the setpoint is in operating range. Change
the setpoint if necessary.
Defrost the unit. Refer Defrosting the Freezer in user
manual.
Clean the condenser and condenser filter.
Check for punctures or tears on gasket. If replacement is
necessary, call service. Refer Gasket Maintenance in
user manual.
Check the present setpoints for temperature alarm
conditions. Change the setpoints if required.
Customers performing on-site temperature calibration
may observe as much as a 2°C variation when an external
probe is placed next to the freezer control probe. This
variation is normal due to optimisation of the control
system to ensure temperature uniformity throughout the
cabinet.
Clean any ice build-up on gasket and/or cabinet surface.
Check for punctures or tears on gasket.
Open door completely and immediately close and latch it.
Defrost exterior lid gasket and make sure the door is
completely sealed.
Change the set points as required.
Unit performance is directly impacted by these causes
mentioned. Try maintaining ambient conditions, reducing
load, reducing door openings.
Once temperature is stable, cycle dynamics should return
to normal range. If not call service.
Make sure the unit is level.
Refer Leveling in the user manual for levelling procedure.
Wipe with a soft cloth or cryo-gloved hand.
Do not puncture gasket.
Remove frost or ice build-up from sublid assembly.
Troubleshooting Guide | 23