Multi-Channel Gas Alarm System
NV-520Instruction Manual for Installation

Keep this manual for easy reference.
Prior to use, carefully read this manual as well as the NV-520 instruction manual for operation (separate
document) for correct use.
This manual describes the standard model. If your unit has end-user-specific options, this manual will
be superseded by your delivery specifications.

Instruction Manual No.
GAE-174-00
July 2023

Related Manuals
The following documents have been prepared to guide your installation and use of this product.
(1) NV-520 Instruction Manual for Installation (this document), No. GAE-174-xx
This document is intended for supervisors and service personnel who are concerned with the
installation of this product. It provides the following information to ensure correct installation of
the product:● Safety precautions● Unit dimensions and components, and precautions for unpacking● Installation precautions(2) NV-520 Instruction Manual for Operation, No. GAE-175-xx
This document is intended for supervisors, operators and service personnel who are concernedwith the operation and maintenance of this product. It provides the following information toensure safe use of the product:● Unit dimensions and components, and power on/off● Operation modes and on-screen menus● Maintenance procedure, consumable replacement and troubleshootingiIntroduction
Thank you for purchasing the New Cosmos NV-520 multi-channel gas alarm system (“product” or“unit” hereafter).
Prior to use, please read this manual as well as the NV-520 instruction manual for operation (No.
GAE-175-xx) and follow the instructions provided for the correct use of the product.
This product is used in connection with multiple gas detectors at the site to form a multi-channel gas
alarm system (2 to 12 channels). Install gas detectors at a location that necessitates the detection of
the target gas and install this product at a location convenient for monitoring the gas concentrations.
This unit displays the gas concentrations detected by the corresponding gas detectors on its bar
graph displays. In the event that the detector detects a leak of the target gas exceeding the preset
limit, the unit will produce audio-visual alarms (e.g., LED, beep sound, voice message), thus helping
prevent incidents such as fire and gas explosions.
Periodic maintenance is essential to maintain the reliability of the product. Periodic maintenancechecks must be performed in the manner described in the NV-520 instruction manual for operation.
Keep this manual in a safe place for easy reference.
The following acts are prohibited without the prior consent of New Cosmos. Please note that the useof this product will be treated as your acceptance of these terms. If you do not agree to these terms,
do not use this product and immediately consult your local sales representative.
 Modification of this product and its related components
 Reverse-engineering of this product and its related components
 Analysis of this product and its related components including disassembly and reverse
compilation
 Transfer of this product and its related components to a third party Third-party use of this product and its related components for any reason, including lease andlicensing

Precautions
Unauthorized copying and replication of the contents of this manual, in whole or in part, are strictly
prohibited.
The contents of this manual are subject to change without notice.
This manual has been prepared with utmost care. If you come across any incorrect descriptions
please contact us for correction.

Symbols Used in this Instruction Manual
Symbols for Danger Levels
The safety symbols in this manual are divided into three categories: Danger, Warning and Caution.
These categories depend on the severity and magnitude of the risks. Operators’ safety has been put
first in designing this product. However, there exist some unavoidable risks due to the systemcharacteristics. Please read the contents related to the precautions carefully before beginning
operation and maintenance work.

iiThis manual uses Danger, Warning, Caution and Notice symbols to draw attention to procedures,materials, methods and processes that require particular attention.

Indicates an imminently hazardous situation that can result in death or serious injury.

Indicates a potentially hazardous situation that may result in death or serious injury.

Indicates a hazardous situation that may result in minor injury or property damage.

NOTICE
Indicates a hazardous situation that will not result in injury but may cause a product, facility or
related equipment damage or failure.

Other Signs and Symbols
This manual also uses the following signs and symbols.

NOTE

Provides supplemental or useful information on product handling.

Ref.

References for common procedure and/or related information.

Don’tsIndicates a prohibited action.
Mandatory
Indicates an action that must be done.
Electrical hazard
Warns of risk of electric shock under certain conditions.
Explosive hazard
Warns of a risk of explosion while handling explosive items.
Corrosive hazard
Contact with the skin or eyes may cause burns or loss of sight.

iii

Quick Index
This page lists parts that may be often referenced throughout the document.
Prior to use, please read the precautions in 1 “General Precautions”.
Unit Dimensions and Components
Pages 8 to 14

Installation
Pages 18 to 24

M6x20 mounting screws

M6x20 mounting screws

Wiring and Connection
Pages 25 to 34

iv

Table of Contents
Related Manuals........................................................................................................................................ i
Introduction ............................................................................................................................................... ii
Precautions ....................................................................................................................................... ii
Symbols Used in this Instruction Manual .......................................................................................... ii
Quick Index .............................................................................................................................................. iv
1

General Precautions ......................................................................................................................... 1
1.1 Before Work .............................................................................................................................. 1
1.2 Safety Precautions .................................................................................................................... 1
1.3 Labels Affixed to Product .......................................................................................................... 2
1.4 Disposal .................................................................................................................................... 3
1.5 Service Life ............................................................................................................................... 3
1.6 Definition of Supervisor/Operator/Service Personnel ............................................................... 3
1.7 Batteries (for Backup Power Type Only) ................................................................................... 4
1.7.1 Battery Location .............................................................................................................. 5
1.7.2 Battery Life ...................................................................................................................... 5
1.7.3 Battery Disposal .............................................................................................................. 6

2

Unit Structure .................................................................................................................................... 7
2.1 Package Contents ..................................................................................................................... 7
2.2 Unit Dimensions and Components ........................................................................................... 8
2.2.1 External Appearance ...................................................................................................... 8
2.2.2 Main Unit and Subunits ................................................................................................... 9
2.2.3 Internal Appearance ......................................................................................................10
2.2.4 Collective Terminal Block .............................................................................................. 11
2.2.5 Dedicated Terminal Block ............................................................................................. 11

3

HOME Screen (Gas-Monitoring Screen) ........................................................................................124

External Outputs..............................................................................................................................15

5

System Configuration ......................................................................................................................16

6

Preparation ......................................................................................................................................17
6.1 Tools ......................................................................................................................................17
6.2 Packing Material Disposal .......................................................................................................17

7

Installation .......................................................................................................................................18
7.1 Installation Location ................................................................................................................20
7.1.1 Installation Conditions ...................................................................................................20
7.2 Installation Procedure .............................................................................................................21
7.2.1 Wall-Mounting Procedure .............................................................................................21
7.2.2 Panel-Mounting Procedure ...........................................................................................23
7.3 Wiring and Connection ............................................................................................................25
7.3.1 Cable Work ...................................................................................................................25
7.3.2 Wiring for Power/Signal Cables ....................................................................................29
7.3.3 Ground Connection .......................................................................................................30
7.3.4 Wiring Connection to Gas Detectors ............................................................................31
7.3.5 Wiring Connection to External Equipment ....................................................................32
7.4 Power-on Check......................................................................................................................35

8

Glossary ..........................................................................................................................................38v

（This page intentionally left blank）

vi

1 General Precautions

1 General Precautions
1.1 Before WorkTo ensure safe use of the product and prevent unexpected accidents, please read the precautions inthis manual carefully before turning on this product. New Cosmos is not responsible for any accidents
resulting from any usage other than that outlined in this document.
This chapter provides a general description for safe use of this product, as well as safety and caution
information related to this product.

1.2 Safety Precautions
Please read the following precautions carefully for correct use.

 Operation check using actual gas is extremely dangerous and requires special
attention, because combustible gas may have a risk of explosion. It must be
performed by qualified personnel or a New Cosmos-authorized technician.
 This product is not explosion-proof and should not be installed in hazardous areas.

 Ground the product to prevent electric shocks.

 In the event of a gas leak alarm, follow safety procedures in accordance with yourcompany’s regulations.

 This product is heavyweight. Handle it with care not to drop it. Failure to do so may
cause injury or property damage such as damaged floor.

 Use this product in accordance with the applicable laws and regulations.
 Wiring and installation should only be performed by a qualified electrician with
sufficient knowledge of wiring/installation procedures, in accordance with theapplicable technical standards.
 New Cosmos assumes no responsibility or liability for any injury or damage resulting
from the use of this unit's output signals to control external devices such as interlocks.
 This product is not drip-proof and should be kept away from water or rain.
 Do not use radio wave-emitting devices (e.g., cell phones, wireless devices) within
30 cm of the product.
 Do not disassemble, modify, or alter the structure of the product or its electricalcircuits. Doing so may compromise product’s performance.

NOTICE
 Do not use organic solvents for cleaning the product. Organic solvents may
negatively affect the product’s exterior as well as internal components.

1

1 General Precautions

1.3 Labels Affixed to ProductWarning and Caution labels are affixed to the areas or surrounding parts that are potentially
dangerous and require special attention. Please read the contents of the labels carefully prior to use.

Do not relocate the labels affixed to the product.
If Warning and Caution labels are missing, damaged or illegible, please contact New
Cosmos or its authorized representative for replacement or new labels. It is very
dangerous to leave the Warning and Caution labels dirty or obscured.

Item
1
2

Description
Serial number label
Indicates the serial number of this product.
User guide label
Describes switch/button operation.
Power rating label

3

Indicates the model, power source, target gas, month of manufacture, serial
number, and precautions to be adopted while handling this product.

21 General Precautions

1.4 Disposal
Used products, components and/or batteries should be disposed of in accordance with the applicablelaws and regulations.

1.5 Service Life
The service life of this product is 10 years. The unit can operate for up to 10 years with standard
installation and operation in accordance with the NV-520 instruction manuals for installation andoperation. When the service life has expired, replacement is essential for continued reliable
performance and other purposes. The 10 year service life is only an estimate and not guaranteed.

Ref.

Refer to 12 “Maintenance” of NV-520 instruction manual for operation for the
replacement parts, which may require replacement before this product’s service life (10years) expires.

1.6 Definition of Supervisor/Operator/Service Personnel
This manual is intended for personnel concerned with the use/installation/maintenance of thisproduct. Concerned personnel are divided into three categories according to safety level, skills andexperience. This manual specifies the name of the applicable category and shows that the
information or instruction given below applies to that category only.
Manages product operation.
Supervisor

Fully understands the product operation method, the gas alarm facility,
and the gas/fault alarm clearance method.
Should carefully read this manual and familiarize themselves with thesystem characteristics and relevant work activities.
Operates the product.

Operator

Servicepersonnel

Understands the product operation method, how to address gas/fault
alarms, and daily work activities for the product under the supervisor’s
instruction.
Carries out installation, failure cause investigation, maintenance andrepair work for the product.
Requires special knowledge and skills.
Acts as New Cosmos authorized technician in principle.

3

1 General Precautions

1.7 Batteries (for Backup Power Type Only)
This product uses two lead storage batteries.
The batteries need to be replaced periodically.
The replacement cycle changes depending on the frequency of use and environmental conditions.
Follow the precautions listed below for proper operation.

Batteries may short-circuit, resulting in electric shock or burns.
Follow the precautions listed below:
 Avoid thermal, electrical and mechanical impact on the batteries.
 Do not disassemble the batteries. Do not insert metal objects in the battery
connections and their power/signal cables. Doing so may result in electric shock,excessive heat, ignition or injury.
 To prevent rapid battery discharge, protect the battery’s electrodes from directcontact with other electrodes or metal objects. Battery discharge may cause heat orbattery leaks.

 Do not place tools or other metal objects on the batteries.

 Do not mix new and old batteries.

 Do not use other than specified batteries. The use of unspecified batteries may cause
device failure.
 Dispose of used batteries in accordance with the applicable laws and regulations.
 If abnormal odor, noise or smoke is observed during operation, cease the operation
immediately and disconnect the power to the product. Continued operation undersuch circumstances may cause a fire.

 Replace the batteries periodically. Using expired batteries may cause a battery leak,
which will then result in a secondary disaster such as an electric leak, electric shock,smoke or ignition.

 Battery replacement must be performed by qualified personnel. Please contact New
Cosmos or its authorized representative for replacement.

4

1 General Precautions

1.7.1 Battery Location

Item
1

1.7.2

Description
Lead storage battery x 2 pcs

Battery Life
If this product is to be kept unused or stored for an extended period of time, the batteries must be
removed. Leaving the batteries inside while the product is not in use or being stored for an extended
period of time may impair/reduce the performance/life of the batteries and cause their terminal
corrosion.
The battery life is three years (when used at 25C) after being shipped out. After three years, replace
the batteries even if they pass the battery voltage test.
“Three years” is only an estimate and not guaranteed. The replacement cycle may change depending
on several factors including frequency of use, temperature and usage or storage conditions.

To prevent serious secondary disasters such as a broken battery case or ignition,
replace the batteries periodically. Using expired batteries will cause internal battery
degradation, which may prevent the product from operating for the designed hours withbackup batteries after a power outage, or may result in an abnormal appearance suchas a swollen battery case, battery leak or electric leak.

5

1 General Precautions

1.7.3

Battery Disposal
Used batteries must be disposed of as hazardous waste in accordance with theapplicable laws and regulations.
The Waste Electrical and Electronic Equipment (WEEE) directive (2012/19/EU)
is intended to promote recycling of electrical and electronic equipment and theircomponents at end of life. This symbol (crossed-out wheeled bin) indicatesseparate collection of waste electrical and electronic equipment in the EU
countries. This product uses batteries. Batteries must be recycled or disposedof properly. At the end of their life, batteries must undergo separate collection
and recycling from general or household waste. Please use the return andcollection system available in your country for the disposal of the batteries.

Do not heat or throw batteries into a fire. Improper handling may lead to an explosion.
Do not open or disassemble batteries. Battery electrolyte is harmful, and any contact
with eyes and skin is dangerous.

62 Unit Structure

2 Unit Structure
2.1 Package Contents
A standard package consists of the following items. If any items are missing or damaged, pleasecontact New Cosmos or its authorized representative for replacement.
Item

Quantity

Description
250 V, 5 A Φ5.2 × 20 mm
Mounting screw (M6 × 20) x 4 pcs
Mounting bracket
x 2 pcs
Mounting screw (M6 x 20)
x 4 pcs*2
Panel-mounting kit
1
Used to attach the brackets to NV-520 unit
Tension screws (M6 x 40)
x 4 pcs
Used to attach the NV-520 unit to the panel
Hex wrench set
1*5
Used to install a gas detector
Testing connector (test jig)
1
Used to check the voltage of the input power
A set of labels indicating the installation locations ofLocation label sheet*3
1
the gas detectors (location is printed on each label)
Usage: Affix the labels to fill the table label
A set of labels with a gas name printed on each label
Gas name label sheet*4
1
Usage: Affix the labels to fill the table label
Table label for gas
A label of a blank table for channel/gas name/location1
name/location
Usage: Affix it onto the product’s front panel, etc.
NV-520 instruction manual
Instruction manual for installation (GAE-174-xx) x 1 pc
1*5
set
Instruction manual for operation (GAE-175-xx) x 1 pc
Inspection certificate
1
*1. Provided when “wall-mounting” was specified at the time of order.
*2. Provided when “panel-mounting” was specified at the time of order.
*3. If the exact location name is not found, please manually enter the name of the location ina blank label, and use it.
*4. Feel free to use blank labels if needed.
*5. One set is provided per order, not per unit.
NV-520 unit
Replacement fuseWall-mounting kit*1

1
2
1

7

2 Unit Structure

2.2 Unit Dimensions and Components
2.2.1

External Appearance

Refer to 15 “Specifications” of NV-520
Instruction Manual for Operation for the width

Front View

Side View(Dimensions are in mm)

Bottom View

2-channel
without
backup power

Item

2-channel
with backup power,
or 4-channel

6-channel
or 8-channel

Component

10-channel
or 12-channel

Description

1

Case

－

2

Front panel－

3

Main unit and subunit(s)Show the gas concentrations and alarm statuses.
System can be operated using the buttons and jog dial on them.

Cable grommet(s)Used to cover the cable entry located on the bottom. Split open
the grommet as needed. The number of cable entries changes
depending on the case type.

48

2 Unit Structure

2.2.2

Main Unit and Subunits
It is possible to create a gas alarm system with up to 12 detection points using a combination of theMain Unit (U1) and Subunits (U2/U3). U1 displays gas concentrations sent via Channels 1 to 4, U2
displays gas concentrations sent via Channels 5 to 8, and U3 displays gas concentrations sent via
Channels 9 to 12, in bar graph form.

Item

Unit Type
Main Unit (U1)Main Unit (U1)
Subunit (U2)
Subunit (U3)

Specifications
Backup power typeNon-backup power typeMain Unit (U1)

Subunit (U2)Component

Model
NVM52-1A
NVM52-1C
NVM52-2A
NVM52-3A

Subunit (U3)

Description

5

Jog dial

Turn to select an item or increase/decrease parameter value.

6

MENU/CANCEL button

Press to switch to the Main Menu, or to cancel the current operation.

7

ENTER button

Press and hold/Press to confirm the selection or setting.

8

BZ STOP/RESET button*

Press to mute the audio alarm (beep sound and voice message).

9

Audio vents*

Opening for audio. A gas leak or device fault alarm will be issued by beepsound and voice message.

10

LCD

Shows gas concentrations in bar graph form (refer to 3 “HOME Screen”).

11

Green POWER LED

12

Yellow FAULT LED*

13

Red ALARM LED*

14

Red MAINT LED*

15

Red BATT LED*16

Red alarm status LED*

Indicates operation status:
Off when the unit is off.
Blinks when warm-up is in progress.
Lights up when the unit operates normally.
Indicates operation status:
Off when the unit operates normally.
Blinks when a fault is detected.
Indicates alarm operation status:
Off when warm-up is in progress or the unit operates normally.
Blinks when 1st stage gas alarm activates.
Blinks rapidly when 2nd stage gas alarm activates.
Lights up when an audio alarm is muted.
Indicates maintenance mode status:
Off when the unit is in normal operation and not in maintenance mode. Blinks
when the unit is in maintenance mode 1.
Lights up when the unit is in maintenance mode 2 or in aging mode.
Indicates backup power operation status:
Off when the unit operates normally and backup batteries are not being used.
Blinks when backup batteries are being used.
Lights up when a backup battery failure is detected.
Note: This LED is always off for non-backup power type.
Indicates alarm status:
Off when the unit operates normally.
Blinks when a gas or fault alarm is detected.
Lights up when an audio alarm is muted.

*Provided on Main Unit (U1) only.

92 Unit Structure

2.2.3

Internal Appearance㉑ Channel LEDs
(e.g., CH1-CH4)⑳ CH.SWITCH button

Item

Component

Description

17

ZERO button

Press and hold to enter the one-touch zero adjustment mode.

18

SPAN button

Press and hold to enter the one-touch span adjustment mode.

19

TEST button

Press and hold to enter test mode.

20

CH.SWITCH button

Used to select the channel to be set or adjusted.

21

Channel LED

The LED corresponding to the selected channel lights up in green.

22

Battery (2 places)*

Supplies backup power to the unit In the event of a power outage.

23

Battery case*Houses two batteries.

24

Battery lid*

Remove the battery lid for battery replacement.

25

AC-DC power supply unit**

Used to convert AC power to DC power.

26

Power switch

27

Collective terminal block28

Backup power switch LED

Used to turn the unit on/off.
Provided for multiple channels and used for external wiring (refer
to 2.2.4 on next page).
Lights up in red when the backup power switch is set to on.

29

Backup power switch***30

Dedicated terminal block

31

Fuse holder (2 places)

Used to set the backup power supply to on/off.
One block is provided for each channel and used for external
wiring (refer to 2.2.5 on next page).
Houses a fuse.

* Provided for backup power type only.
** Provided for AC type only.
***Enabled for backup power type only.

10

2 Unit Structure

2.2.4

Collective Terminal Block
Terminal

No.

ID

Function

1st stage gas
alarm

1

A1

1st stage gas alarm
contact output

3

C1

Common with A1

2nd stage gas
alarm

5

A2

2nd stage gas alarm
contact output

7

C2

Common with A2

9

BZ

Audio alarm contact output

AC Type(Thread size: M3)

DC Type

Audio alarmCollective voltage
output(Thread size: M3)

Power (input)

External switch（Earth terminal）

2.2.5

11

BC

Common with BZ

13

L

Voltage output ()14N

Voltage output ()

2

R
(P)

AC type: 100-240 VAC
DC type: 24 VDC ()

4

S
(N)

AC type: 100-240 VAC
DC type: 24 VDC ()

6

E

Earth

8

AR

10

AS

12

N

External switch input
Used for grounding the unit
Thread size: M3 (2 places)*

Dedicated Terminal Block
Terminal
Dedicated voltage output
2nd stage gas alarm

ID

Function

L
N
ZC2

Voltage output ()Voltage output ()Common with ZA2
2nd stage gas alarm
contact output
Common with ZA1
1st stage gas alarm
contact output
Power for pump 24 V ()Power for pump GND ()

ZA2
ZC1

1st stage gas alarm
Pump

Detector

ZA1
PA
PB
A
B
C
D

Gas detector**

Used for grounding the unit
Thread size: M3 (2 places)” is printed next to the PCB-mounting screw (2 places).
** As per delivery specifications.

(Earth terminal)*“(Thread size: M3)
Dedicated terminal blocks

Ref.

Refer to 4 “External Outputs” for the functions of the collective/dedicated terminal block.

11

3 HOME Screen (Gas-Monitoring Screen)

3 HOME Screen (Gas-Monitoring Screen)

HOME Screen
Item

Component

Description
Displays gas concentration in bar graph form. The bar graph andbackground color change depending on the alarm level. They
turn green during normal operation, yellow when 1st stage gas
alarm activates, and red when 2nd stage gas alarm activates.

1

Gas concentration bar graph2

1st stage gas alarm set value

Displays the 1st stage gas alarm set value as a yellow line.

3

2nd stage gas alarm set value

Displays the 2nd stage gas alarm set value as a red line.

4

Lock icon

This icon appears when the button/dial operation is locked toprevent unintended operation.

5

Warm-up icon

This icon appears when the unit is in a warm-up cycle.

Maintenance 1 icon
6This icon appears when the unit is in maintenance mode 1/2.
Maintenance 2 icon

7

Beep sound icon

This icon appears when the audio alarm is unmuted.

Voice unmute icon
8This icon appears when the voice message is unmuted/muted.
Voice mute icon

9Enter icon

10

Unit number (U1/U2/U3)

11

BAON/BAOFF*

Press and hold the ENTER button to confirm the setting while
this icon appears.
U1: Main Unit, Channels 1–4
U2: Subunit, Channels 5–8
U3: Subunit, Channels 9–12
Indicates on/off status of the backup batteries.

This icon appears when an internal process is in progress.
It replaces the Enter icon during internal processing.
*Displayed for Main Unit (U1) of backup power type only.
12

Internal process icon

12

3 HOME Screen (Gas-Monitoring Screen)

Setup Details Screen

Test Mode Screen

Invalidated Channels

Item

Component

14

F.S.*

Description
This icon appears when a setting is being saved. You cannot open
the setting screen being saved. It replaces the Enter icon whilesaving.
Displays the full-scale value.

13

Save icon

15

AL1*

Displays the 1st stage gas alarm set value.

16

AL2*

Displays the 2nd stage gas alarm set value.

17

Unit of measurement*

Displays the unit of measurement for gas concentration.

18

Gas sensor type*

Displays the connected gas detector’s sensor type (Ci or Cv).

19

20

21

Test icon
Increase/decreaseby small step
Increase/decreaseby medium step
Increase/decreaseby large stepT (test mode indication)

This icon appears when the unit is in test mode.
This icon appears when the unit is in test mode.
Select from 3 options (S/M/L) for bar graph increment/decrement
unit. “S” allows to increase or decrease by 1 bar with 1 turn of thejog dial, “M” by 3 bars, and “L” by 10 bars at one time.

“T” appears for the channel that is in test mode.
The channels set to be invalidated are displayed in solid color (no22
Invalidated channels**bar graph) as shown in the figure above.
* See the setup details on the screen by pressing the ENTER button while on the HOME screen. You canreturn to the HOME screen by pressing the ENTER button again. If you do not do so, the screen willautomatically return to the HOME screen after 30 minutes if the unit is left idle.
**CH1 will never be invalidated.

13

3 HOME Screen (Gas-Monitoring Screen)

NOTICE The alarm status cannot be checked while the setup details are displayed on
the screen. After checking the setup details, press the ENTER button again to
return to the HOME screen.
 Do not turn off the unit while saving is in progress, i.e., while
is displayed).

(save icon)

Aging Mode Indication

Alternately
displayed
at 3 secintervals

Gas-Monitoring Screen

Item

Component

23

Aging mode icon

Ref.

Aging Mode

Description
This icon appears during the sensor’s aging process.

Refer to 9 “Aging Mode” of the NV-520 instruction manual for operation for more
information.

14

4 External Outputs

4 External Outputs

Operation
External output

Collective
terminal
block

Dedicated
terminal
block

Terminal

1st stage gas alarm
contact output

A1-C1

2nd stage gas alarm
contact output

A2-C2

Audio alarm
contact output

BZ-BC

Voltage output

L-N

1st stage gas alarm
contact output

ZA1-ZC1

2nd stage gas alarm
contact output

ZA2-ZC2

Voltage output

L-N

Pump power output

PA-PB

Description

Contact(s) will activate
in response to a gas
alarm that occurs in any
channel.
Contact will activate in
response to an audio
alarm that occurs in any
channel.
Voltage will be output
depending on the alarmstate of the NV-520 unit.
L: Positive ()N: Negative ()Contact(s) will activate
in response to a gas
alarm that occurs in therelevant channel.
Voltage will be output
depending on the alarmstate of the relevant
channel.
L: Positive ()N: Negative ()Power supplied to thegas detector’s pump.

(No alarm)

Normal

Gas
alarm

Fault
alarm

Open

ClosedOpen

ClosedOpen

ClosedClosed

6 VDC

12 VDC

0 VDC

Open

ClosedOpen

Closed

6 VDC

12 VDC

0 VDC

24 VDCThe contacts use mechanical relays, which may falsely activate if exposed to excessive
impacts or vibration, or magnetic force. Install the product free from impacts, vibrationand magnetic force.

15

5 System Configuration

5 System Configuration
This NV-520 unit is connected with gas detectors (sold separately) to form a gas detection system.
All the parts are connected with cables. The NV-520 unit displays the gas concentrations detectedby the connected gas detectors and produces audio-visual alarms when the gas concentrations
reach preset limits.
Non-hazardous area

Hazardous area

NV-520Power source
100-240 VAC(24 VDC)

3-wire/4-wire cable

Diffusion typegas detector

6-wire cable

Extractive typegas detector

Typical System Configuration

NOTE Diffusion or extractive type gas detectors can be connected to the NV-520 unit. Usea protective cover (sold separately) for each gas detector for outdoor installation.
Refer to the gas detector’s instruction manual for details.
 Wiring differs depending on the type of the connected gas detector.

16

6 Preparation

6 Preparation
6.1 Tools
The below tools required for installation are not included, and should be prepared by the user: Phillips screwdriver #3: Used for M6 screw installation

6.2 Packing Material Disposal
Packing materials (e.g., corrugated cardboard, plastic bags) used for the product and its accessories
should be disposed of in accordance with the applicable laws and regulations.

17

7 Installation

7 Installation
This chapter describes the installation flow and procedures.
Refer to the product specifications for proper installation.
7.1 Installation Location

7.1.1 Installation Conditions

7.2 Installation Procedure

7.2.1 Wall-Mounting Procedure
7.2.2 Panel-Mounting Procedure
7.3.1 Cable Work

7.3 Wiring and Connection

7.3.2 Wiring for Power/Signal Cables
7.3.3 Ground Connection
7.3.4 Wiring Connection to Gas Detectors
7.3.5 Wiring Connection to External Equipment
7.4 Power-on Check
Installation Flow Do not touch the battery terminals. Short-circuited terminals may become a possible
source of ignition.

 This product is not explosion-proof and should not be installed in hazardous areas.
 Ground the product to prevent electric shocks. Class D grounding is mandatory.
 In the event of a gas leak alarm, follow the safety procedures in accordance with yourcompany’s regulations.
 The contacts use mechanical relays, which may falsely activate if exposed toexcessive impacts or vibration. Install the product in a place free from any impacts
and vibration. Set a delay time greater than one second for external devices
connected to this product.
 Avoid installing the product in the vicinity of equipment that can generate highfrequencies. High frequencies may cause malfunction.
 This product is heavyweight. Handle it with care not to drop it. Failure to do so may
cause injury or property damage such as damaged floor.

NOTICE
 Do not use organic solvents for cleaning the product. Organic solvents may
negatively affect the product’s exterior as well as internal components.

18

7 Installation



Install the product in a place free from corrosive gas, high temperature and/or highhumidity. Failure to do so may cause product damage or malfunction.

Adding a ferrite core to the power cable is recommended, in case the product needs
to be installed in a place exposed to electrical noise, such as in the vicinity ofequipment that is a source of electrical noise, such as a boiler or a motor.

The power cable and the detector cable must be wired separately; they should not
be bundled together.



Take care not to damage the surface of the product (e.g., scratches) during
installation.



Install the product in a place where it can easily be accessed for maintenance orinspection.

This product is not drip-proof. Install it indoors and keep it away from water or rain.

Do not install the product in a place exposed to direct sunlight. Sudden temperaturechange inside the unit may impair the product’s performance.

This product needs to be periodically checked and maintained. Do not install the
product in a place that may pose a danger during maintenance or inspection.



Do not install the product in the following conditions:- Ambient temperatures beyond the specified operating temperature range- Condensation prone area
- Exposure to sudden temperature/humidity changes- Exposure to water spray- Presence of corrosive gas- Proximity to equipment that can generate high frequencies or magnetic fields- Proximity to heat or an ignition source- Exposure to vibration- Installation on a ceilingRef.

For the gas detector’s installation procedure, refer to its instruction manual.

19

7 Installation

7.1 Installation Location
7.1.1

Installation Conditions
Install the product in a place where, in the event of crises such as a gas leak alarm, it can be easily
notified and addressed. The required space for installation is explained below.

(a) Required Space for Installation
Top: Keep a distance of 5 cm or more above the product.
Sides: Keep a distance of 5 cm or more between each side of the product and any other object.
Front: Keep a distance of 60 cm or more between the front of the product and any other object.
The product needs to be operated from the front during maintenance or inspection.
Bottom: Keep a distance of 40 cm or more below the product. This space is required for
opening/closing the front panel.

(b) Installing the Product in a High Location
The installation of the product in a high place is not recommended; however, if you need to
install it in a high place, leave space below the product for maintenance and inspection work
which may require a stepladder.

Ref.

For the gas detector’s installation procedure, refer to its instruction manual.

20

7 Installation

7.2 Installation Procedure
There are two installation methods: wall-mounting and panel-mounting.

Turn off the product by setting the POWER switch to OFF before starting the installation.
For the backup power type, set both the POWER and backup power switches to OFF.
Failure to do so may cause a device failure.

7.2.1

Wall-Mounting Procedure
This product can be installed directly onto a wall using the four screws.
(1) Cut four mounting holes in the wall by referring to the figure and table below.

Mounting holes on wall
(4 places)

Wall cut

Case type2-channel without backup power
2-channel with backup power/
4-channel
6-channel/8-channel
10-channel/12-channel

NOTE

Width a(mm)
152

Width b(mm)
212

Width c1(mm)
35

Width c2
(mm)
35

230

290

90

90

417
565

487
635

119
157

177
251

This product has cable openings on its rear and bottom. When using the bottom cable
opening(s), it is not necessary to cut a hole in the wall for cable entry. When using therear cable opening(s), a wall cut (c1 + c2 width) must be made. Also, cables can be
hidden when using the rear cable opening(s).

217 Installation(2) Install a female threaded wall anchor or wall plug or wall plug into each of the four wall-mounting
holes, and tighten two mounting screws into the two top wall anchors.
(3) Hang the case on the two top screws (Step 2) by sliding these screws through the case’s upper
mounting holes. Tighten two mounting screws into the two lower anchors. Firmly tighten all fourscrews to fix the case to the wall.

M6x20 mounting screws

M6x20 mounting screws

NOTE

To prevent the product from falling in the event of an earthquake, etc., use female
threaded wall anchors or wall plugs to ensure that the product is firmly secured to the
wall.

22

7 Installation

7.2.2

Panel-Mounting Procedure
This product can also be installed on a panel (1.6 to 6 mm thick).
(1) Remove the cable grommets from the case bottom so that the case can be smoothly engaged
into the panel.
(2) Cut a square cutout in the panel by referring to the figure and table below.

Panel Cutout Size

Case type

Width d (mm)2-channel without backup power

215±12-channel with backup power/4-channel

293±16-channel/8-channel

490±110-channel/12-channel

638±1(3) Insert the case through the square cutout.

23

7 Installation(4) Attach the two mounting brackets to the case by tightening the four M6x20 mounting screws(provided).
(5) Secure the mounting brackets to the panel by tightening the four M6x40 tension screws(provided).

NOTE

Screw type

Recommended tightening torqueM6×20

100 cN・m

M6×40

50 cN・m This product can be installed on a 1.6–6 mm thick panel.
 Refer to the table above for the proper tightening torque.

In case of replacing a NV-500 unit with a NV-520 unit, place a cover plate (sold separately)
to conceal the gap around the unit.
Mounting bracket(2 places)
Cover plate（Optional）

M6x20
mounting
screw

M6x40
tensionscrew(4 places)(4 places)

Tighten the screws with the proper tightening torque. Excessive tightening may deformthe case or damage the mounting brackets.

(6) Install the cable grommets back into the case bottom.

24

7 Installation

7.3 Wiring and Connection
7.3.1

Cable WorkBe careful not to damage the cable surfaces. Keep them free from any damage.

 To prevent electric shocks, turn off the product by setting the POWER switch to OFF
before installation/wiring/gas detector replacement. For the backup power type, setboth the POWER and backup power switches to OFF.

 Ground the product and gas detectors to prevent electric shocks.



Refer to the terminal markings on the product and the gas detector to ensure thatthe wires between them are correctly connected. Incorrect wiring may cause adevice failure.

Keep the connection cables (power and signal cables from this product and its
connected gas detectors/external equipment) away from other power cables.

While wiring, avoid excessive stress on the cables.

Gas detectors must be installed by qualified personnel or a New Cosmos-authorized
technician. Please contact New Cosmos or its authorized representative for the
installation of additional gas detectors. Incorrect wiring and setup may cause adevice failure.
Collective Terminal Block
Terminal

1st stage gas alarm
2nd stage gas alarm
Audio alarmCollective voltage output

Power (input)

External switch

ID

Cable type

A1
C1
A2
C2
BZ
BC
L
N
R
（P）
S
（N）
E
AR
AS
N

CVV cable with 0.75 mm 2 to 2.00 mm2 wires

CVVS cable with 0.75 mm2 to 2.00 mm2 wires

CVV cable with 0.75 mm 2 to 2.00 mm2 wires

25

7 Installation

Dedicated Terminal Block
Terminal
Dedicated voltage output
2nd stage gas alarm
1st stage gas alarm
Pump

Detector

ID
L
N
ZC2
ZA2
ZC1
ZA1
PA
PB
A
B
C
D

Cable type
CVVS cable with 0.75 mm 2 to 2.00 mm2 wires

CVV cable with 0.75 mm 2 to 2.00 mm2 wires

Refer to the instruction manuals for gas detectors.
CVV cable with 0.75 mm 2 to 2.00 mm2 wires*Refer to 7.3.4 “Wiring Connection to Gas Detectors”.

 Use a rubber, plastic or metal sheathed cable appropriate for the installation environment.
The cable should have a circular cross-section and its outer surface should be smoothand even. For protection, the cable(s) should be sheathed in a protective casing, such asa metal conduit or a carbon steel pipe. Other protective structures such as metal orconcrete ducts are also acceptable.
 It is not recommended to connect a cable with another cable; however, if you need toconnect cables, direct or branching connections of cables should be done inside theflameproof enclosure.
 When using a flameproof cable gland with a gasket, use a cable whose outer diametermatches the inner diameter of the gasket by referring to the table below or gas detector’s
instruction manual. Fully tighten the cable gland to prevent the formation of a flame pathfor explosive gas or fire.
KD-5A (B)-N Detector
Cable outer dia.(mm)Gasket inner dia. (mm)Washer inner dia. (mm)Φ10-Φ10.9

Φ11

Φ12

Φ11-Φ11.9

Φ12

Φ12

Φ12-Φ12.9

Φ13

Φ14

26

7 Installation

Explosion-proof (flameproof enclosure) wiring using metal conduits
Explosion-proof (flameproof enclosure) wiring is required for installation of the connected gas
detectors in hazardous areas.

 This product is not explosion-proof and should not be installed in hazardous areas.

 Prior to wiring or opening any part of the gas detector, set the POWER switch of thisproduct to OFF to eliminate s possible source of ignition. For the backup power type,set both the POWER and backup power switches to OFF.

NOTE



Wiring and installation of explosion-proof gas detectors (flameproof enclosure)should only be performed by a qualified electrician with sufficient knowledge of
explosion-proof wiring/installation procedures, in accordance with the applicablestandards/guidelines.



Select the appropriate rubber, vinyl or polyethylene insulated cable by considering
the ambient humidity and temperature, and the presence of corrosive substances.



Sheath all cables in rigid steel conduits (JIS C 8305). To prevent the formation of aflame path for explosive gas or fire inside the conduits, use conduit sealing fittings
and fill the joints with putty (refer to the figures on next page).

When flexibility is required, use explosion and water proof flexible conduits. The
entry of rain or other liquids inside the gas detector may cause function loss ormalfunction of the detector.



Waterproof the joints between conduits, fittings and joint boxes. The entry of rain orother liquids inside the gas detector may cause function loss or malfunction of thedetector.
 Natural disasters such as an earthquake could result in a secondary disastersuch as a broken cable. To prevent this, the cable may have slack (tension
relief spot) when installed.
 Use parallel pipe threads (JIS B 0202) for connections between conduits,
fittings and joint boxes. The New Cosmos product comes with PF3/4 (G3/4)
female threads. Engage at least five threads per connection and then, firmly
tighten with a lock nut.

27

7 Installation

Partition
Non-hazardous area

Hazardous area
No joints should be madePutty
Conduit sealing fitting
may be used here

Conduit sealing fitting

Pipe fixture

フィッチングFlexible conduit

Rigid steel conduit

Slack

Union coupling

Diffusion typegas detector

Coupling

Typical Connection for Diffusion Type Gas Detector

Partition

Non-hazardous area

Hazardous area

Extractive typegas detector

No joints should be madeフィッチングフィッチング

Putty
Conduit sealing fitting
may be used here

Conduit sealing fitting

Pipe fixture
Slack

Flexible conduit

Rigid steel conduit
Coupling

Typical Connection for Extractive Type Gas Detector

28

Union coupling7 Installation

7.3.2

Wiring for Power/Signal Cables
 If needed, use a dedicated breaker for the power cable going to the product.
 Ensure that the power voltage supplied to the product is within the specifications.
 Ensure that the load resistance of the signal cable (voltage output), including theresistance of the wire, is 1.2k– 50k ohm.
Use ring wire connectors to connect the wires to the terminals inside the product toprevent unintended disconnection of the wires from the terminal block in the event ofan earthquake. In addition, the wires should have sufficient length to allow them to fully
travel without tension on the terminals.

NOTE

How to install a ferrite core to the power cable
Install a ferrite core to the power cable as shown in the figure below.

When installing a ferrite core to the power cable, ensure that the cable does not getcaught in the core.

When installing a ferrite core to the power cable, it is recommended to loop the cablearound the ferrite core. However, if it is difficult, install it without a loop.

When installing a ferrite core without a loop, add a cable tie to tighten the ferrite coreto the power cable, if it is loose.

Install a ferrite core as close to the NV-520 unit as possible.

Ferrite core
Power cablewithout loop

Ferrite core

Cable tie

Power cablewith loop

Ferrite Core Installation29

7 Installation

7.3.3

Ground Connection

Wiring and installation should only be performed by a qualified electrician with sufficientknowledge of wiring/installation procedures, in accordance with the applicablestandards/guidelines.

NOTE

Single-point grounding (grounding at a single point) is mandatory. When the external
equipment or NV-520 unit is grounded, do not connect the shield cable to the terminal
inside the gas detector (). Doing so would create a 2-point grounding.

(a) Typical wiring connection when the external equipment is grounded

External
equipment

Gas detector
Shielded cable

Shielded cable

ShieldGrounded(Class D)

Do not groundDo not ground

Grounded(b) Typical wiring connection when the NV-520 unit is grounded
External
equipment

Gas detector
Shielded cable

Shielded cable

ShieldGrounded(Class D)

Do not ground

Grounded30

7 Installation

7.3.4

Wiring Connection to Gas Detectors
For wiring between this product and a gas detector, use a cable with 0.75mm 2 to 2mm2 wires suchas a 600V vinyl insulated cable (1V), VCT cable, or CVV cable. The cable length should be as
specified in the table below.
Wire cross-section

Cable length

0.75 mm2Max. 200 m

1.25 mm2Max. 600 m

2.00 mm2Max. 1 km



Refer to the terminal markings on the product and the gas detector to ensure thatthe wires between them are correctly connected. Incorrect wiring may cause adevice failure.

Keep the connection cables (power and signal cables from this product and its
connected gas detectors/external equipment) away from other power cables.

31

7 Installation

7.3.5

Wiring Connection to External Equipment



New Cosmos assumes no responsibility or liability for any injury or damage resulting
from the use of this unit's output signals to control external devices such as
interlocks.

This product’s external alarm contacts should be used for controlling an external
gas alarm/indicator (e.g., alarm horn, signal tower).



The load current/voltage should not exceed the contact’s rating.



If a relay contact is used with a very low current load (e.g., used as a digital input toa PLC), it may result in insufficient contact of this relay contact. To avoid insufficient
contact, ensure that the load current going to the relay contact is 100 mA* or higher.
Perform operation test before use.
Typical configuration when the relay contact (normally open) is used with a very low
current load
Relay contact usedwith a very low current
load

PLC,
etc.

Relay power* 100 mA is only an estimate and not guaranteed.
(a) Wiring connection to external control unit/annunciator
This product has dry contacts (normally open or normally closed) for the 1st stage gas alarm, 2ndstage gas alarm and fault alarm. Each contact will activate when its own threshold is exceeded.

Controlunit

Annunciator

Fuse

Control power

Typical Wiring Connection to External Control Unit or Annunciator (Normally Open)32

7 Installation(b) Wiring connection to external buzzer (e.g., alarm horn, siren)
This product has a dry contact (normally open) for an external buzzer. The contact will activate
when its own threshold is exceeded. For an electromagnetic buzzer, the buzzer rating should notexceed half of the contact’s rating. Add a fuse to the buzzer’s electronic circuit.

BuzzerRelay

BuzzerFuse

Fuse

Buzzer power

Relay power

Wiring Connection to Low Capacity Buzzer

Buzzer power

Wiring Connection to High Capacity Buzzer

Typical Wiring Connection to External Buzzer(c) Wiring connection to external reset switch
This product is equipped with external switch terminals for “AR” (alarm reset) and “AS” (alarmsilent). Closing the AS and N terminals and the AR and N terminals will reset an alarm.
For the semi-lock type, which mutes and resets an alarm simultaneously, connect the AS terminal
to the AR switch on the external instrumentation panel or the operator console. The alarm can
now be reset using the external switch on the external instrumentation panel or the operator
console.
For the full-lock type, which mutes and resets an alarm separately, connect the AS terminal to theAS switch and the AR terminal to the AR switch on the external instrumentation panel or theoperator console. The alarm can now be muted and reset using the external switches on theexternal instrumentation panel or the operator console.

For the alarm reset switch, use a dedicated circuit which is independent from othercircuits.

AR switch

AS switch

AR switch

Semi-lock Type

Full-lock Type

Typical Wiring Connection to Alarm Reset Switch

33

7 Installation(d) Wiring connection for voltage output
The voltage (0/6/12 V) will be output from the terminals “L” and “N”, depending on the alarm status(0V: fault alarm, 6V: no gas alarm, 12V: gas alarm). These terminals can be connected to arecorder, PLC, etc.

When wiring this product to a PLC, separate the PLC’s power from this product’s.
Add a noise filter near the PLC power.

Ensure that the load resistance of external equipment is 1.2k– 50k ohm.

Recorder,
PLC, etc.

Noise filterPowersourceGrounded

Typical Wiring Connection to Recorder, PLC, etc.

34

7 Installation

7.4 Power-on Check
Upon the completion of the installation, check that the product starts up normally.



Do not connect the product’s external alarm contacts to a load exceeding theircapacity.

Turn on the product while no gas is present around the connected gas detectors.

Check that all wiring is correct before turning on the external devices (e.g., signal
towers, alarm horns, etc.) connected to this product.

Check that all wiring is correct before turning on the product. Ensure that the terminal
markings on the product and gas detectors match.



If the sensor is unstable, the external relay contacts may be activated upon thecompletion of a warm-up cycle. Release the interlocks of external devices, as
needed, to prevent their possible activation.

A gas alarm is inactive and a fault alarm is active, when in the warm-up cycle.



If a broken sensor wire is restored during the warm-up cycle, the warm-up cycle may
be completed before the sensor becomes stable. Release the interlocks of external
devices, as needed, to prevent their possible activation.



If the sensor output is unstable during the warm-up cycle, the product operation may
also become unstable. To prevent possible activation of gas alarm/contact, set the
product to maintenance mode 2, as needed. Refer to 8 “Maintenance Mode” of theNV-520 instruction manual for operation for information on the maintenance mode.

Check Procedure

Hold the front panel with your hand while opening/closing it.
Flinging the front panel open may cause injury or product damage.
Flinging the front panel close may cause unintended activation of the alarm
contacts.

Ensure that the latches are in the lock position after closing the front panel. If thelatches are not in the lock position, the front panel will loosen or open over time byvibration, etc., which may cause injury or product damage such as a broken LCD.

(1) Pull the two latches down to the unlock position. Pull the front panel open.
Latch (2 places)

Unlock

Lock

Latch

35

7 Installation(2) Ensure that the power switch is in the off position.

Power switch(3) (Backup power type only) Check that the backup power switch is in the off position.
Backup power switch(4) Disconnect the connector from the AC cable harness connector.

AC cable harness connector(5) Connect the testing connector (provided test jig) to the AC cable harness connector to prevent
short circuits.
Connect the testing connector here36

7 Installation(6)

Set the power switch to the on position to turn on the unit.
Power switch

Backup power switch(7)

Measure the voltage between the test points with a digital multimeter. Check that the measured
value is in the specified range (100 to 240 VAC±10% or 24 VDC±10%).

Test points(8)

Set the power switch to the off position, and disconnect the testing connector.

(9)

Connect the connector removed in Step (4) back to the AC cable harness connector.

(10) Set the power switch to the on position again.
(11) (Backup power type only) Set the backup power switch to the on position.
(12) Check that the NV-520 unit normally turns on.

37

8 Glossary

8 Glossary
Term
Backup power type andnon-backup power typeDefinition
There are NV-520 units with and without attached backup batteries. They arecalled “backup power type” and “non-backup power type,” respectively.

Gas detector

Device used to detect the presence of a target gas and provide its
concentration information in the form of an electrical signal.

Diffusion typeGas sampling method using convective diffusion while placing a gas detector
at a detection point.

Extractive typeGas sampling method using a pump.

Hazardous area

An area in which an explosive atmosphere is present, or may be expected to
be present, in quantities such as to require special precautions for theconstruction, installation and use of electrical apparatus.

Non-hazardous area

An area in which an explosive atmosphere is not expected to be present inquantities such as to require special precautions for the construction,
installation and use of electrical apparatus.

38

（This page intentionally left blank）

（This page intentionally left blank）

Document No.

Revision History
Date

Revision

GAE-174-00

July 2023

00 (Initial issue)

Additional copies of this instruction manual may be purchased. Contact New
Cosmos or its authorized representative for ordering.

Authorized representative:

Manufacturer:
NEW COSMOS ELECTRIC CO., LTD.
2-5-4 Mitsuya-naka, Yodogawa-ku,
Osaka 532-0036, Japan
www.newcosmos-global.com