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M1288-0056
LN
2
Backup Units for Innova & Premium Freezers
User’s Guide
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1.1
Scope of Manual
This manual provides the user with the necessary information for the installation and
operation of the LN
2
backup system for New Brunswick Scientific’s Innova
®
and
Premium ranges of Ultra Low Temperature Freezers.
1.2
Description of Equipment
The LN
2
backup system is designed to provide a means of maintaining the contents of the
NBS freezer at a preset temperature, should a power failure or mechanical problem with
the main refrigeration system occur.
The freezer is fitted with an injector unit, a proximity switch, and a platinum resistance
thermometer (referred to as a
temperature
sensor
) to measure the internal temperature.
A freestanding control unit and cables are provided. Transfer lines and connectors are
supplied to connect between the injector and the LN
2
low-pressure storage Dewar.
Dewars, however, are
not
provided.
#
NOTE:
A low-pressure liquid nitrogen storage Dewar with a pressure-regulated
liquid withdrawal port is required. Liquid nitrogen must be used to ensure
proper operation.
The backup control unit is plugged into the power supply and a temperature selected
between 0
o
C and -90
o
C. When the temperature within the freezer rises above the
selected backup temperature, the injector switches on and LN
2
is continuously injected
into the body of the freezer.
The injector continues to inject LN
2
until the temperature within the freezer drops below
the preset value selected on the backup unit. If a power failure occurs, a battery within
the unit will continue to operate the backup system for up to 48 hours
.
