15
M1288-0056
LN
2
Backup Units for Innova & Premium Freezers
User’s Guide
#
NOTES:
(1) When you install the backup system, note the weight or liquid level of
the LN
2
Dewar and the date of installation. At the intervals
recommended by the gas supplier, check the weight or liquid level of the
Dewar. LN
2
Dewars can lose gas over time (through the pressure relief
valve), even when they are not in use; replace them as needed.
(2) At any time, you can check the backup unit’s operation by setting its
temperature 10
o
C lower than the freezer temperature. The Valve Open
light should turn on and LN
2
should be injected.
3.1.4 Battery
Backup
The control unit is fitted with a battery backup in case of power failure. In
normal operation, with the external power supply available, the backup battery
is continuously being charged. If the external power supply fails, the internal
battery will power the backup unit for up to 48 hours, depending upon ambient
conditions.
With power off:
Should the battery voltage drop below 11.4 volts, the
battery low indicator will illuminate and the audible alarm
will sound.
3.1.5
Optional Remote Control
If remote control is desired, an RS-485 interface must be installed within the
control unit. If the RS-485 interface is installed, the remote control indicator on
the front panel (
see Figure 2
) will illuminate when the control unit is operating
under remote computer control.
3.1.6
Alarm System Monitoring Socket
The control unit is designed with a fixed socket at the rear labelled
Alarm Socket,
and a plug for external monitoring purposes (
see Figure 2 in Section 2.2.7 &
Figure 3 on the following page
).
Within the control unit, the alarm socket is connected to volt-free, switching
contacts rated at 24 volts, 1 amp. In normal operation, pin 1 (E) is in a closed
circuit with pin 2 (L) and in the alarm condition, pin 1 (E) is in a closed circuit
with pin 3 (N).
