The optional back up system is designed to inject CO2 or LN2 into the
freezer compartment if the temperature rises above back up system set
point. To set the BUS set point:
1. Press the Mode key until the Set Temperature and Backup indicators
light.
2. Press the up or down arrow key until the desired BUS set point is
displayed.
3. Press Enter to save the setting.
4. Press the Mode key until the Run indicator lights for Run mode.
If no control keys are pressed, the freezer will automatically return to Run
mode after 5 minutes.
Caution Changing the operating temperature set point can affect the BUS
set point. The BUS set point will self adjust to maintain a temperature of
at least 10°C above the operating temperature set point.
s
Caution The BUS set point cannot be set any colder than the high
temperature alarm set point (see Section 1). If the back-up system is
installed with CO
2, then -65°C is the coldest BUS set point that can be
used (if the cabinet set point is -75°C or colder). s
After the freezer has stabilized and both batteries are fully charged, the
BUS can be tested to verify proper operation.
1. Disconnect the AC power to the freezer by turning the power switch
off.
2. As the freezer warms up, verify the BUS injects at the desired
temperature. Displayed temperature may vary by a few degrees from
inject temperature due to the differences in probe locations.
Routinely check the vent stack for frost or ice build-up. The type of frost
that forms in the vent stack is generally very soft and may be easily
removed with a bristle brush or soft cloth. If ice build-up has occurred, a
complete defrost may occasionally be required. See Section 4 for freezer
defrost instructions.
5-6 Isotemp Basic Fisher Scientific
Section 5
Factory Options
Clean the Vent Stack
Test BUS Operation
Set Optional BUS Set
Point
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