3
M1288-0056
LN
2
Backup Units for Innova & Premium Freezers
User’s Guide
The LN
2
backup unit can maintain the internal temperature of a 410-liter (14.5
cu ft) or smaller upright freezer at -85
o
C maximum in an ambient temperature of
+30
o
C, if it is switched on when the internal temperature of the freezer is already
-85
o
C or lower.
1.3.4 Gas
Consumption
The consumption of gas is very difficult to specify because it is dependent on the
operating conditions.
Gas consumption is affected by several factors. Consumption
increases
with:
•
An increase in ambient temperature
•
Increasing age of freezer
•
Increasing age of door or lid seal
•
A colder temperature set on the backup
•
Frequent opening of door or lid.
We highly recommend that the user decide, prior to full operation, what
temperature conditions the backup unit should maintain. The user should then
install the system, switch the freezer off, and record the time it takes for the LN
2
Dewar to empty while the system maintains the desired temperature. This
precaution will enable the user to select the Dewar size best suited to providing
the degree of protection required. As a guide, the following chart can be used to
calculate consumption:
Table 1: LN
2
Consumption Rates
Gas consumption was measured at the indicated temperatures,
in the center of the cabinet and in an ambient temperature of 23ºC.
Consumption in kg/hr (lbs/hr):
at –60ºC
at –70ºC
at –80ºC
Upright freezers (empty)
U725 Innova
2.62 (5.76)
2.75 (6.05)
3.0 (6.6)
U535 Innova*
2.05 (4.51)
2.16 (4.74)
2.11 (4.63)
U101 Innova*
1.13 (2.49)
1.38 (3.03)
1.79 (3.93)
U410 Premium
2.0 (4.4)
2.2 (4.84)
2.6 (5.72)
U570 Premium
2.25 (4.95)
2.7 (5.94)
3.3 (7.26)
Chest freezers (empty)
C760 Innova
2.85 (6.3)
3.0 (6.6)
3.2 (7.0)
C585 Innova
2.6 (5.72)
2.85 (6.3)
3.1 (6.82)
C660 Premium*
2.67 (5.86)
2.83 (6.22)
3.03 (6.63)
C340 Premium*
1.99 (4.37)
2.07 (4.58)
1.84 (4.04)
*estimated figures
