Set Optional Bus Set Point; Test Bus Operation; Clean Vent Stack - Thermo Scientific 902 Operating And Maintenance Manual

Section 5
Factory Installed Options
Set Optional BUS Set

Test BUS Operation

Clean Vent Stack

5-8 Model 900 and 5900 Series
The optional back up system is designed to inject CO
freezer compartment if the temperature rises above back up system set
Point
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 to
RUN mode after 5 minutes.
Warning 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.
Note The BUS set point can not be set any colder than the high
temperature alarm set point. (See Section 1, Set High Temperature
Alarm). If the back-up system is installed with CO
coldest BUS set point that can be used (if the cabinet set point is -75°C or
s
colder).
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 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.
3. Preventive Maintenance - Monthly maintenance action to check CO
or LN back-up system operation, and battery voltage.
2
- Check for fault codes on the BUS probe per Table 5-1. Also verify
solenoid operation by performing a Press-To-Test.
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.
or LN into the
2 2
s
, then -65°C is the
2
Thermo Scientific
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