Thermo Fisher Scientific ULT Freezers
Troubleshooting Guide | 23
Unit compressors run
continuously.
Freezer set point is low.
Check whether the setpoint is in operating range. Change
the setpoint if necessary.
Frost build up.
Defrost the unit. Refer
in user
manual.
Dirty condenser.
Clean the condenser and condenser filter.
Gasket damage.
Check for punctures or tears on gasket. If replacement is
necessary, call service. Refer
in
user manual.
Cabinet temperature reached
an alarm condition, but
suitable alarm is not
activated.
Alarm setpoints may be
changed.
Check the present setpoints for temperature alarm
conditions. Change the setpoints if required.
Problem with temperature
validation/calibration.
Cabinet temperature
displayed doesn’t match
with actual temperature.
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.
Unit is constantly alarming.
Exterior lid is closed but
not sealed completely.
Clean any ice build-up on gasket and/or cabinet surface.
Check for punctures or tears on gasket.
Door open alarm, exterior
door not closing
completely.
Open door completely and immediately close and latch it.
Door open alarm, lid is
closed but not sealed
completely.
Defrost exterior lid gasket and make sure the door is
completely sealed.
Alarm set points may have
changed.
Change the set points as required.
Unit cycle on-percentage is
increasing (Compressors are
running more often than
before).
Ambient conditions.
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.
Warm load (or) over load.
Frequent and prolonged
lid openings.
Difficult to close/open the
outer door.
Outer door alignment issues.
Unit is not level.
Make sure the unit is level.
Refer
in the user manual for levelling procedure.
Frost accumulated on lid
gasket.
Wipe with a soft cloth or cryo-gloved hand.
Do not puncture gasket.
Difficult to close/open the
sublid.
Frost accumulated around
inner sublid.
Remove frost or ice build-up from sublid assembly.
Problem
Cause
Solution
