NEW BRUNSWICK SCIENTIFIC LN2 User manual

LN2Backup System
for Innova®& Premium
Ultra Low Temperature Freezers
MANUAL NO: M1288-0056
Revision J
October 29, 2007
NEW BRUNSWICK SCIENTIFIC CO., INC.
BOX 4005 •44 TALMADGE ROAD •EDISON, NJ 08818-4005
Telephone: [phone] •1-800-631-5417
Fax: [phone] •Telex: 4753012 NBSCO
Internet: http://www.nbsc.com •E-mail: [email protected]

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New Brunswick Scientific Co., Inc. User’s Guide

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
INTERNATIONAL OFFICES:
BELGIUM
New Brunswick Scientific NV-SA
Stationsstraat 180/4
3110 Rotselaar
België/Belgique
Tel: [phone]
Fax: [phone]
E-mail: [email protected]
GERMANY
New Brunswick Scientific GmbH
In Der Au 14
D-72622 Nürtingen
Deutschland
Tel: [phone]
Fax: [phone]
E-mail: [email protected]
CHINA
New Brunswick Scientific Co., Inc.
A903, 904 Yin Hai Building
No. 250, Cao Xi Road
Shanghai 200235, P.R. China
Tel: [phone] or 5966
Fax: [phone]
E-mail: [email protected]
THE NETHERLANDS
New Brunswick Scientific BV
Kerkenbos 1101, 6546 BC Nijmegen
P.O Box 6826, 6503 GH Nijmegen
Nederland
Tel: [phone]
Fax: [phone]
E-mail: [email protected]
FRANCE
New Brunswick Scientific SARL
12-14, Rond Point des Champs Elysées
75008 Paris
France
Tel: [phone]
Fax: [phone]
E-mail: [email protected]
UNITED KINGDOM
New Brunswick Scientific (UK) Ltd.
17 Alban Park
St. Albans, Herts. AL4 0JJ
United Kingdom
Tel: [phone] or 0800 581331
Fax: [phone]
E-mail: [email protected]
Web: www.nbsuk.co.uk

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New Brunswick Scientific Co., Inc. User’s Guide
HEALTH AND SAFETY AT WORK ACT 1974
(For the United Kingdom)
New Brunswick Scientific, as manufacturer and supplier of laboratory equipment, is obliged under
the terms of the above act to provide our users with instructions on the safe installation, operation
and maintenance of our equipment.
Our equipment is designed to acceptable standards and does not entail any hazard if used as advised
in the attached instructions.
The following safety precautions should be observed by all personnel using this equipment:
1. Read and understand this guide to operations. If in doubt, contact one of the New Brunswick
Scientific Companies listed.
2. Do not remove any covers. There are no operable controls other than those referred to in this
manual. There are voltages in excess of 41.5 volts AC behind the covers.
3. This equipment maintains low temperatures in the freezers to which it is connected. These
temperatures are such that direct contact with the contents or the inside of the freezer can
burn unprotected skin.
4. Observe good housekeeping practices, at all times keeping the equipment, and the adjacent
areas, clean, dry and uncluttered.
5. Should any malfunctions occur or be suspected, immediately call a qualified service
engineer or supervisor to investigate.
6. This equipment uses high pressure gases. Observe the safety precautions recommended by
the supplier of the gas.
7. Always use this equipment in a well-ventilated area; the in-use gas could build up around the
equipment which, without proper ventilation, could cause suffocation.

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
CAUTION!
This equipment must be operated as described in this manual. If
operational guidelines are not followed, equipment damage and personal
injury can occur.
Please read the entire User’s Guide before attempting to
use this unit.
Do not use this equipment in a hazardous atmosphere or with hazardous
materials for which the equipment was not designed.
New Brunswick Scientific Co., Inc. (NBS) is not responsible for any damage
to this equipment that may result from the use of an accessory not
manufactured by NBS.

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New Brunswick Scientific Co., Inc. User’s Guide
Copyright Notice
New Brunswick Scientific Company, Inc.
Box 4005 44 Talmadge Road
Edison, New Jersey 08818-4005
©Copyright 2007 New Brunswick Scientific Co., Inc.
All Rights Reserved.
Reproduction, adaptation, or translation without prior written permission from
New Brunswick Scientific is prohibited.
Disclaimer Notice
New Brunswick Scientific Co., Inc. reserves the right to change
information in this document without notice. Updates to information in this
document reflect our commitment to continuing product development and
improvement.
Manual Conventions
#NOTE:
Notes contain essential information that deserves
special attention.
CAUTION!
Caution messages appear before procedures which, if
caution is not observed, could result in damage to the
equipment.
WARNING!
Warning messages alert you to specific procedures or
practices which, if not followed correctly, could result in
serious personal injury.
Bold Text in boldface type emphasizes key words or
phrases.
This particular Warning message, whether found in the
manual or on the unit, means HOT SURFACE–and
therefore represents a potential danger to touch.
CRUSH WARNING!
Crush Warning messages alert you to specific
procedures or practices regarding heavy objects which,
if not followed correctly, could result in serious personal
injury .

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
Every Instrument manufactured by the New Brunswick Scientific
Co., Inc. is warranted to be free from defects in material and work-
manship. This apparatus with the exception of glassware, lamps and
electrodes (where supplied), is warranted for 1 year against faulty com-
ponents and assembly and our obligation under this warranty is limited
to repairing or replacing the instrument or part thereof, which shall
with-in 1 year after date of shipment, prove to be defective after our
examination. This warranty does not extend to any NBS products
which have been subjected to misuse, neglect, accident or improper
installation or application; nor shall it extend to products which
have been repaired or altered outside the NBS factory
without prior authorization from the
New Brunswick Scientific Co., Inc.
W A R R A N T Y

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New Brunswick Scientific Co., Inc. User’s Guide
NEW BRUNSWICK SCIENTIFIC CO., INC.
CERTIFICATE OF CONFORMITY
THIS IS TO CERTIFY THAT THE
CO2– LN2 BACKUP SYSTEM
manufactured by NBS Cryo-Research Ltd
conforms with the protection requirements of
Council Directive 89/336/EEC, relating to Electromagnetic Compatibility
by application of the following standards:
EN50081-1 : 1992 Emission Standard
EN50082-1 : 1992 Immunity Standard
BS EN 55014-1 : 2001
BS EN 55014-2 : 1997
BS EN 61000-3-2 : 2001
BS EN 61000-3-3 : 1995
FCC Part 15, Class B
Approved by _____________________ on this 3rd day of December 2001
D J Minister, Executive Designer
New Brunswick Scientific Co., Inc., 44 Talmadge Road, Edison, NJ 08818, USA
New Brunswick Scientific (UK) Ltd, 17 Alban Park, St. Albans, Herts. AL4 0JJ UK
New Brunswick Scientific BV, Kerkenbos 1101, Nijmegen 6546 BC, NL

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
TABLE OF CONTENTS
1INTRODUCTION..............................................................................................................................................1
1.1 SCOPE OF MANUAL .....................................................................................................................................1
1.2 DESCRIPTION OF EQUIPMENT ......................................................................................................................1
1.3 PRODUCT SPECIFICATIONS ..........................................................................................................................2
1.3.1 Dimensions ............................................................................................................................................2
1.3.2 Weight....................................................................................................................................................2
1.3.3 Performance ..........................................................................................................................................2
1.3.4 Gas Consumption ..................................................................................................................................3
1.3.5 LN2Supplies ..........................................................................................................................................4
1.3.6 Electrical Supply Requirements.............................................................................................................4
1.3.7 Fuses......................................................................................................................................................4
1.3.8 Operating Environment.........................................................................................................................4
2INSTALLATION...............................................................................................................................................5
2.1 INSPECTION .................................................................................................................................................5
2.2 INSTALLING INDIVIDUAL PARTS..................................................................................................................5
2.2.1 Installing the Temperature Sensor.........................................................................................................5
2.2.2 Installing the Insulated Transfer Hose ..................................................................................................7
2.2.3 Installing the LN2Valve/Injector Assembly...........................................................................................7
2.2.4 Installing the LN2Supply.......................................................................................................................8
2.2.5 Testing for Gas Leaks............................................................................................................................9
2.2.6 Installing the Magnetic Door Sensor.....................................................................................................9
2.2.7 Installing the Control Unit...................................................................................................................11
3OPERATION ...................................................................................................................................................13
3.1 GETTING STARTED ....................................................................................................................................13
3.1.1 Testing Gas Flow & Door Switch Operation ......................................................................................13
3.1.2 Testing Injector Valve & LED Operation............................................................................................14
3.1.3 Testing Backup System Operation.......................................................................................................14
3.1.4 Battery Backup ....................................................................................................................................15
3.1.5 Optional Remote Control.....................................................................................................................15
3.1.6 Alarm System Monitoring Socket.........................................................................................................15
4MAINTENANCE.............................................................................................................................................17
4.1 LN2SUPPLIES............................................................................................................................................17
4.2 TRANSFER LINES &MANIFOLD.................................................................................................................17
4.3 CONTROL UNIT &ELECTRICAL CONNECTIONS .........................................................................................18
4.4 CLEANING .................................................................................................................................................18
4.5 BATTERY...................................................................................................................................................18
4.6 ROUTINE PERFORMANCE CHECK...............................................................................................................18
4.7 RETURN AUTHORIZATION POLICY.............................................................................................................18
5SPARE PARTS ................................................................................................................................................20
6SCHEMATICS.................................................................................................................................................21
6.1 LN2CIRCUIT DIAGRAM/SCHEMATIC.........................................................................................................21

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New Brunswick Scientific Co., Inc. User’s Guide
7INSPECTION FORM .....................................................................................................................................22
7.1 LN2BACKUP PRESSURE SYSTEM CHECKLIST............................................................................................22
8INDEX...............................................................................................................................................................23

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
1
1 I IN
NT TR RO OD DU UC CT TI IO ON N
1.1 Scope of Manual
This manual provides the user with the necessary information for the installation and
operation of the LN2backup system for New Brunswick Scientific’s Innova®and
Premium ranges of Ultra Low Temperature Freezers.
1.2 Description of Equipment
The LN2backup 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 LN2low-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 0o C and -90o C. When the temperature within the freezer rises above the
selected backup temperature, the injector switches on and LN2is continuously injected
into the body of the freezer.
The injector continues to inject LN2 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.

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New Brunswick Scientific Co., Inc. User’s Guide
When the door or lid of the freezer is opened, the proximity switch is activated to prevent
additional gas injections while the freezer is open. This keeps the freezer user from
being burned by the very cold gas stream.
WARNING!
The LN2back-up unit must always be used in a well-ventilated area. In
use, the freezers fill with inert odorless gas that eventually spills out into
the surrounding area. Ventilation is essential to keep a person who enters
the area from possible suffocation.
1.3 Product Specifications
1.3.1 Dimensions
Control Unit
Control Unit
Width 203 mm 8.0 in
Depth 342 mm 13.5 in
Height 86.5 mm 3.4 in
Other important dimensions:
Power Cord, Cable & Hose Lengths
Power cord 3.0 m 9.8 ft
Temperature sensor cable 2.75 m 9 ft
Control unit to injector cable 0.9 m 3 ft
Magnetic door sensor cable 1.2 m 4 ft
Insulated Hose, LN2Dewar to
injector 2.0 m 6.6 ft
1.3.2 Weight
The control unit weighs 5.6 kg / 12.3 lbs.
1.3.3 Performance
The LN2backup system is capable of maintaining a maximum internal
temperature of –80º C in an ambient temperature of +32º C.

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
The LN2backup unit can maintain the internal temperature of a 410-liter (14.5
cu ft) or smaller upright freezer at -85o C maximum in an ambient temperature of
+30o C, if it is switched on when the internal temperature of the freezer is already
-85o 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 LN2
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: LN2Consumption 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

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New Brunswick Scientific Co., Inc. User’s Guide
1.3.5 LN2Supplies
Consult your local gas supplier for suitable LN2supplies. A low-pressure liquid
nitrogen storage Dewar (or other suitable storage tank) with a liquid
withdrawal port is required to properly utilize the cooling properties of the liquid
nitrogen. The liquid withdrawal port must have an adjustable valve with a
pressure gauge. The withdrawal pressure should be set to between 6 to 8 psig
(0.44 to 0.55 bar).
1.3.6 Electrical Supply Requirements
Single phase, 100/240V, 50/60Hz, 1.0 Amp.
1.3.7 Fuses
The control unit input power socket is fitted with two fuses, Live and Neutral.
They are both 2-amp, 250-volt, 20mm ceramic T fuses (see Section 5 for
replacement part numbers).
1.3.8 Operating Environment
The LN2backup system is designed for and tested to the CE/UL specifications
listed below:
•Indoor use
•Altitude up to 2000 M
•Ambient temperature 5o C to 40o C
•Maximum relative humidity 80% for temperature up to 31o C, decreasing
linearly to 50% relative humidity at 40o C
•Power supply voltage fluctuations not to exceed ±10% of nominal voltage
•Installation category II
•Pollution degree 2

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
2
2 I IN
NS ST TA AL LL LA AT TI IO ON N
WARNING!
Ensure that all equipment is switched off and disconnected from the power
supply. Personnel are responsible for familiarizing themselves with the
equipment owner’s safety policy and regulations.
Note, too, that maintenance adjustments and repair should only be carried
out by qualified and experienced personnel who have been approved to
undertake such work by New Brunswick Scientific or its authorized agents.
2.1 Inspection
Carefully unwrap the backup unit and retain the packing materials for possible future use.
Check that all the items listed on the packing list are present. Inspect all items for
damage that may have occurred in shipping. Report any damage and/or deficiencies
within 14 days to your nearest New Brunswick Scientific Company (using Customer
Satisfaction Form 6300), or to the agent who supplied the equipment. Also report
damage to the carriers within their specified time limit.
See Section 4.7 for details on NBS’ return authorization policy.
2.2 Installing Individual Parts
WARNING!
The LN2back-up unit cannot be fitted to a freezer that is operating.
Before installation, empty the freezer, switch it off, and disconnect it from
the power outlet. Open the door or lid and let the whole freezer reach
ambient temperature.
2.2.1 Installing the Temperature Sensor
The temperature sensor is fitted to the freezer through the hole that has a nylon
plug. The hole is located (a) on Upright models, on the top panel, in the rear
right-hand corner (except for the Model U101: see NOTE on the following
page), or (b) on Chest models, inside the compressor compartment.

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New Brunswick Scientific Co., Inc. User’s Guide
#NOTE:
On the U101 Innova freezer, the temperature sensor port is located on the
left-hand side wall.
For Upright Freezers:
1. The temperature sensor is fitted through one of the two plugged holes.
2. Remove the plug that is not surrounded by four screws and set it aside.
3. Using the replacement plug provided (black for Innova models and clear for
Premium models), insert the sensor through the hole in the plug and seal it by
pressing the rubber grommet located on the sensor cable into the hole.
4. Insert the temperature sensor through one of the insulation tubes provided and
push the sensor and insulation tube into the cabinet port. Install the nylon
plug by pressing it into the hole.
5. Inside the freezer cabinet, position the sensor next to the existing freezer
temperature sensor, located halfway down the rear right-hand corner of the
cabinet. (For the Model U101, skip now to step 9. For all other models,
complete steps 6 through 8 only.)
6. Remove the freezer probe cover inside the freezer cabinet and position the
two sensors side by side. Fasten with the cable ties provided.
7. Replace the probe cover.
8. Using two more cable ties, secure the probe cable to the two fixing points
(plastic clips) attached to the cabinet of the freezer.
9. For the Model U101 freezer, complete Steps 9-12: the temperature sensor cable
should pass under the fixed shelf and be located on the right side of the internal
cabinet. The probe should be attached directly next to the existing freezer
temperature probe.
10. Remove the freezer probe cover inside the freezer cabinet and position the two
sensors side by side. Fasten with the cable ties provided.
11. Replace the probe cover.
12. Using two more cable ties, secure the probe cable to the two fixing points
(plastic clips) attached to the cabinet of the freezer.
For Chest Freezers:
1. Remove the right side cover of the freezer exposing the compressor
compartment.
2. Looking into the compressor compartment, at the top left-hand corner, the
freezer temperature sensor can be seen passing into the freezer cabinet. The
LN2backup temperature sensor should be fitted through the same port. This
can be accomplished by creating a hole through the insulation next to the
freezer cabinet probe by inserting a length of ¼-inch or ~6mm metal rod or
tube through the insulation to create a passage for the probe (be sure to keep
the rod or tube perpendicular to the cabinet wall when you insert it through the
insulation).

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
3. After creating the new hole, push the probe through the hole and pull enough
probe cable through the hole to reach the freezer temperature probe, located
approximately halfway down the front right corner, inside the freezer cabinet.
4. Remove the freezer probe cover inside the freezer cabinet and position the
two sensors side by side. Fasten with the cable ties provided.
5. Replace the probe cover.
2.2.2 Installing the Insulated Transfer Hose
The Insulated Transfer Hose consists of a two-meter hose that is surrounded by a
tube of thermal insulation.
For Upright Freezers (including Model U101):
1. Attach the smaller fitting of the insulated transfer hose to the solenoid
valve/injector assembly.
2. Tighten the fitting by turning it clockwise.
For Chest Freezers:
1. Remove the compressor housing panel if not already removed.
2. Remove the 2-inch blanking plug from the rear panel of the freezer.
3. Insert the smaller fitting of the insulated transfer hose through the port; pull
enough hose through to attach to the solenoid valve/injector assembly.
3. Attach the free end of the insulated transfer hose to the solenoid valve/injector
assembly.
4. Tighten the fitting by turning it clockwise.
2.2.3 Installing the LN2Valve/Injector Assembly
The injector is fitted to the freezer through the hole fitted with a nylon plug and
surrounded by a ring of four screws. The hole is located (a) on Upright models,
on the top panel in the rear right-hand corner (except for the Model U101: see
NOTE below), or (b) on Chest models, inside the compressor compartment.
#NOTE:
On the U101 Innova freezer, the injector port is located on the left-hand side
wall.

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New Brunswick Scientific Co., Inc. User’s Guide
For Upright Freezers:
1. Remove the nylon plug and the four screws surrounding the plug, retaining
the screws for reuse.
2. Remove the protective cap from the end of the injector tube attached to the
solenoid valve assembly
3. Holding the LN2valve/injector tube, slide one of the short insulation tubes
provided over the copper injection pipe.
4. Push the injector and insulation tube into the exposed port in the freezer
cabinet.
5. Align the Z-shaped bracket attached to the solenoid valve body over the four
mounting holes and, using the four screws previously set aside, secure the
bracket to the body of the freezer.
6. Tighten the screws equally to lock the injector and LN2valve into position.
For Chest Freezers:
The port for the solenoid assembly is located inside the upper right-hand side of
the compressor compartment.
1. Make sure the manifold-to-injector hose assembly passes through the port in
the rear panel of the freezer and the solenoid valve cable to the control unit
passes through the grommet on the upper rear panel.
2. Install the solenoid valve/injector assembly to the port inside the compressor
compartment as described in steps 1 through 6 for Upright Freezers.
2.2.4 Installing the LN2Supply
1. Position the LN2Dewar within one meter (3.3 ft) of the freezer. To prevent
injury or equipment damage, secure the Dewar to make sure it cannot fall or
roll.
2. Connect the insulated transfer line to the regulated liquid withdrawal port of
the LN2Dewar.
#NOTE:
The transfer line connector is ¾ inch - 16 UNF, female union. Two transfer
line adaptors are also supplied, ½ and ⅜inch NPT, to adapt the transfer line
to the supplied Dewar if necessary. Before installation, verify, with your
local gas supply company, the correct adaptor to use with the supplied
Dewar.

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M1288-0056 LN2Backup Units for Innova & Premium Freezers User’s Guide
2.2.5 Testing for Gas Leaks
1. Test the assembled joints for leaks: be sure all fittings are tight before
continuing.
2. Turn on the LN2supply and test each joint (including the LN2Dewar
connection) for leaks by using a liquid soap solution. Bubbling or foaming
will identify a leak.
3. If any leak is found, retighten the fitting(s), then retest.
4. After verifying that there are no leaks, continue installing the system.
WARNING!
Failure to properly check for leaks can result in failure of the system due to
lack of LN2supply.
2.2.6 Installing the Magnetic Door Sensor
The magnetic door sensor is composed of two separate items and is installed:
(a) on Upright models (except model U101), on the top left-hand surface of the
door
(b) on the U101 Upright model, on the top right-hand surface of the door
(c) on Chest models, on the rear, right-hand surface of the lid.
#NOTE:
For Innova Freezers, use the two, small metal adapter plates supplied. Install
the magnet and magnetic sensor to the adaptor plates using the attached
fittings.
Figure 1 (on the following page) shows the magnetic sensor assembly
attached to an Innova model freezer. When attaching to a Premium freezer,
the adaptor plates are not used and the magnetic sensor assembly is
attached directly to the freezer cabinet and door.

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New Brunswick Scientific Co., Inc. User’s Guide
Figure 1: Installing the Magnetic Door Sensor
Gap must be
between 1mm
and 3mm
Freezer
Case Freezer Case
D
o
o
r
D
o
o
r
Attachment Nuts
Magnetic Sensor
VIP Adapter Plates
Attachment Screws
Gap must be
between 1mm
and 3mm
Freezer
Case Freezer Case
D
o
o
r
D
o
o
r
Attachment Nuts
Magnetic Sensor
VIP Adapter Plates
Attachment Screws
1. Remove the two existing screws on the lid or door of the freezer, then fasten
the door switch magnet (the portion of the sensor that has no wires) in place
using the screws you removed. The magnet should face toward the freezer
case.
2. Remove the screws on the freezer case and, opposite the magnet, fasten the
part of the switch that has the electrical cable attached, using the screws
provided.
CAUTION!
Failure to adjust the magnetic door switch correctly will result in the system
failing to operate correctly.
3. Close the lid or door to check that the two parts of the switch do not touch.
There should be a gap of no more than 1 to 3 mm (0.04 to 0.12 inches)
between both parts.
4. If the gap is greater than 3 mm (0.12 inch) or less than 1 mm (0.04 inch),
loosen the screws and adjust the magnet in the slots provided until the gap is
correct, then retighten the screws.
Magnetic Door Sensor components,
uninstalled
Magnetic Door Sensor, installed