EsiWelma Sensigas EW40 User manual

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CENTRALIZED GAS DETECTION
AND CONTROL SYSTEM
FOR INDUSTRIAL ENVIRONMENTS
Sensigas



EW40
INSTALLATION AND OPERATING
MANUAL

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CONTENTS
1GENERAL................................................................................................................................6
1.1 M EANING OF SYMBOLS .........................................................................................................6
1.2 H AZARDOUS GAS THRESHOLD ...............................................................................................6
2DESCRIPTION OF SYSTEM....................................................................................................8
3INSTALLATION .....................................................................................................................11
3.1 I NSTALLATION OF THE UCE 40… CONTROL UNIT ..................................................................11
3.2 I NSTALLATION OF THE DETECTORS ......................................................................................13
3.3 I NSTALLATION OF THE R ELAY MODULES , THE D ISPLAY MODULES AND THE A LARM MODULES ...15
3.3.1 Wall mounting..........................................................................................................15
3.3.2 Flush panel mounting .............................................................................................17
3.4 N UMBERING THE FIELD DEVICES ..........................................................................................18
4ELECTRICAL CONNECTIONS..............................................................................................20
4.1 T YPES OF CABLE ................................................................................................................20
4.2 C ONSUMPTION AND SIZING OF CABLES ................................................................................23
4.3 R ECOGNITION OF THE TERMINAL BOARDS ............................................................................25
4.3.1 Terminal boards on the control unit.......................................................................25
4.3.2 Terminal board of detectors ...................................................................................25
4.3.3 Terminal board of the display module...................................................................26
4.3.4 Terminal boards and configuration of the relay module ......................................26
4.3.5 Terminal boards and configuration of the alarm module.....................................27
4.4 S YSTEM STRUCTURE ..........................................................................................................28
4.4.1 Basic structure ........................................................................................................28
4.4.2 Extended structure..................................................................................................29
4.5 C ONNECTIONS OF THE CONTROL UNIT TO THE SYSTEM MONITOR ...........................................30
4.5.1 Point-to-point communication with RS232............................................................31
4.5.2 Multidrop connection with RS422 ..........................................................................31
5SYSTEM POWER SUPPLY...................................................................................................32
5.1 O PERATION .......................................................................................................................32
5.2 D ISPLAYS OF THE STATUS SCREEN ......................................................................................34
5.3 P OSSIBLE ABNORMALITIES ..................................................................................................36
6COMMISSIONING A NEW SYSTEM .....................................................................................37
6.1 F UNCTION OF THE KEYS AND OF THE LED S ..........................................................................37
6.2 C ONFIGURATION ................................................................................................................40
6.3 A SSIGNMENT OF THE SENSORS ...........................................................................................42
6.4 A SSIGNMENT OF THE ALARM MODULES ................................................................................45
6.5 S ENSOR OPERATION CHECK ...............................................................................................47
6.6 A LARM MODULE OPERATION CHECK .....................................................................................48
6.7 E RROR MESSAGES ON THE CONTROL UNIT ...........................................................................48
6.8 D ISPLAYS ON THE DISPLAY MODULE ....................................................................................48

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7OPERATING MODES ............................................................................................................50
7.1 A LARM OPERATING MODE ...................................................................................................50
7.1.1 Direct mode..............................................................................................................50
7.1.2 Parking mode...........................................................................................................50
7.2 A LARM DIGITAL INPUT OPERATING MODE ..............................................................................52
7.3 A LARM DIGITAL OUTPUT OPERATING MODE ...........................................................................54
8SYSTEM STATUS..................................................................................................................56
8.1 F AIL STATUS ......................................................................................................................56
8.2 A CTIVATED STATUS ............................................................................................................56
8.3 D EACTIVATED STATUS ........................................................................................................56
8.4 R ESIDUAL LIFE ...................................................................................................................57
8.5 D ISPLAYING AND CHANGING THE PARAMETERS OF A FIELD DEVICE .........................................57
9AUXILIARY FUNCTIONS.......................................................................................................64
9.1 L IST OF SENSORS ...............................................................................................................64
9.2 D IAGNOSTICS ....................................................................................................................64
9.3 D ISPLAY ADJUSTMENT ........................................................................................................65
9.4 A LARM MODE .....................................................................................................................65
9.4.1 Manual restore.........................................................................................................65
9.4.2 Automatic restore....................................................................................................66
9.5 A LARM RESET ....................................................................................................................67
9.6 A LIGNING ALARM THRESHOLDS ...........................................................................................68
9.7 M ODBUS ADDRESS .............................................................................................................69
9.8 M ODBUS B AUD R ATE .........................................................................................................70
9.9 M ODBUS PORT ...................................................................................................................71
9.10 T RANSFERRING DATA .........................................................................................................72
10 CHANGES TO AN ALREADY OPERATING SYSTEM .......................................................73
10.1 N EW CONTROL UNIT ...........................................................................................................73
10.2 D ELETING FIELD DEVICE .....................................................................................................74
10.3 C HANGING A FIELD DEVICE .................................................................................................75
10.4 A DDING A FIELD DEVICE ......................................................................................................76
10.5 S YSTEM RESET ..................................................................................................................77
11 TECHNICAL SPECIFICATIONS.........................................................................................79
11.1 C ONTROL UNIT ...................................................................................................................79
Arrows to scroll up and down the screen................................................................................80
11.2 F IELD DEVICES ...................................................................................................................80
11.2.1 Detectors (UR.40..)...................................................................................................81
11.2.2 Relay module (MAR40)............................................................................................82
11.2.3 Display module (MDD40).........................................................................................83
11.2.4 Alarm module (MID40).............................................................................................84

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12 DIMENSIONS .....................................................................................................................87
12.1 UCE40… CONTROL UNIT ...................................................................................................87
12.2 MAR40 RELAY MODULE , MDD40 DISPLAY MODULE AND MID40 ALARM MODULE ...................88
12.3 D ETECTORS (UR.40.E, UR.40.I)........................................................................................88
12.4 UR.40.S DETECTORS .........................................................................................................89
12.5 UR.40.L DETECTORS .........................................................................................................89
13 ELECTRICAL DIAGRAMS..................................................................................................90
14 SYSTEM TABLE (FACSIMILE) ..........................................................................................92
15 INSTALLATION DATA........................................................................................................93
16 ROUTINE CHECKS............................................................................................................94

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1 GENERAL
This chapter provides some information on the characteristics of the gases and on the
installation criteria for gas detection devices before the description of the EW40 system.
It is not essential to read this chapter to install and commission the system described in
this manual. Readers who already know the subject can skip this part.
1.1 Meaning of symbols
The symbols used in this manual have the following meaning:
• ppm: Parts Per Million of concentration of gas in the air
• L.E.L%: Lower Explosive Limit
• %VOL: concentration of gas measured in percentage by volume
• D: Detector
• RM: Relay module (MAR40)
• DM: Display module (MDD40)
• AM: Alarm module (MID40)
• t: threshold limit value
• Pr: pre-alarm threshold
• 1t: alarm threshold one
• 2t: alarm threshold two
• FA: fail
1.2 Hazardous gas threshold
For gases and for combustible vapours, the hazardous conditions begin from a threshold
called "Lower Explosive Limit" (LEL) that is the lowest concentration (percentage) of a gas
in air capable of producing a flash of fire in presence of an ignition source. This threshold
changes from gas to gas. The Lower Explosive Limits for some of the most common
gases are shown in the table below.
LEL (100%)
GAS ppm %VOL
METHANE (CH4) 50.000 5%
ISOBUTANE (iso-C4H10) 18.000 1,8%
BUTANE (C4H10) 18.600 1,86%
LPG 19.000 1,9%
HYDROGEN (H2) 40.000 4%
Table 1.1

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For toxic gases such as carbon monoxide (CO), the hazard level must be considered also in
relation to the duration of the person's exposure in the polluted environment.
The table below shows risks from exposure to carbon monoxide (CO). Carbon monoxide is
generated wherever combustion occurs and the lungs rapidly absorb it and spread it
through the pulmonary alveolus where it reversibly binds with the haemoglobin as
“carboxyhaemoglobin” (COHb). It is also colourless and odourless so it is not naturally
detected. This is why CO-specific detection devices are necessary.
COHb in the bloodstream has the following effects on healthy adults.
% COHb EFFECTS
0,3-0,7 Normal amount in non-smokers from the endogenous production of
CO
0,7- 2,9 No detectable symptoms
2,9-4,5 Cardiovascular disorders in patients suffering from heart disease
4-6 Usual levels in smokers, some physical impairment in psychomotor
tests
7-10 Ailments in patients without heart disease (increase in cardiac output
and in blood flow in coronary arteries)
10-20 Slight headache, weakness, possible effect on foetus
20-30 Strong headache, nausea, loss of movement in hands
30-40 Strong headache, irritability, confusion, loss of vision, nausea, muscle
weakness, dizziness
40-50 Convulsions and loss of consciousness
60-70 Coma, respiratory arrest, death
Table 1.2
This issue is covered in other similar tables and a wide range of literature. In its document,
"Air quality for CO", the US department of Health, Education and Welfare refers to an
observed weakening in vision observed with 3% of COHb and in other psychomotor tests
with 5% of COHb.
More recently, subjects exposed to a dose of 100 ppm CO for one hour have shown a loss
of motor skills.

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ppm % VOL LEL % (methane gas)
1.000.000
100
impossible combustion
100.000 10
100 Lower Explosive Limit
40
10.000 1
20
10
5
1.000 0,1
100 0,01
10 0,001
1 0,0001
Fig. 1.1
2 DESCRIPTION OF SYSTEM
The system (called EW40) is formed of a control unit UCE40... and field devices that
communicate by means of a shared line (BUS) and a dedicated master protocol (PEW40).
Therefore, this solution is suitable for central applications when a dedicated gas detection
control system is required. Each control unit has its own default identification code. The
following field devices are available:
• UR.40..: gas detectors for application in hazardous and/or non hazardous areas
• MAR40: relay modules for energising and/or local alerts
• MDD40:display modules for distributed monitoring of the system
• MID40: alarm modules for acquiring digital input from the field
NOTE: the words "detector" and "sensor" are used without distinction throughout this document
and have the same meaning, except where this may create ambiguity.
The system structure is shown in Fig. 2.1.
Possible combustion
range
Limit value range of
gas detectors

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Fig. 2.1 – Layout of the EW40 system
During standard operation, the control unit receives information about the measurements taken
by the detectors or by the digital input statuses of the alarm modules; three threshold limit
values and one fail condition can be defined for both of these, respectively called:
• pre-alarm: Pr
• alarm threshold one: 1t
• alarm threshold two: 2t
• device fail: FA
If the concentration of gas exceeds those thresholds (or the status of a digital input assigned to
them switches), the control unit sends a command to the relay modules (MAR40) assigned to
the relay energiser to activate the relay at the alarm threshold. The control unit also transmits
the relative information to the interfaced display modules (MDD40). A maximum of 99 field
devices can be connected to each control unit. By number of field devices we mean the total
number of sensors, relay modules, display modules and alarm modules. In addition, there can
be no more than 16 (DM) and 10 (AM) of the latter two types of field device, respectively.
1. Unità Centrale
2. Sensori gas
3. Moduli Display
4. Moduli Relè
5. Moduli Allarmi
. Pulsanti
7. Batterie
8. UPS
Bus di comunicazione
Alimentazione 12 Vdc
Collegamento seriale
Al sistema di
supervisione
(opzionale)
1. Unità Centrale
2. Sensori gas
3. Moduli Display
4. Moduli Relè
5. Moduli Allarmi
. Pulsanti
7. Batterie
8. UPS
Bus di comunicazione
Alimentazione 12
Collegamento seriale
Bus di comunicazione
Alimentazione 12
Collegamento seriale
Al sistema di
supervisione
(opzionale)
1
2
7
8
1
42
53
4
1
2
7
8
1
2
7
8
1
2
7
8
11
4242
5353
4858585
1. Unità Centrale
2. Sensori gas
3. Moduli Display
4. Moduli Relè
5. Moduli Allarmi
. Pulsanti
7. Batterie
8. UPS
Bus di comunicazione
Alimentazione 12 Vdc
Collegamento seriale
Bus di comunicazione
Alimentazione 12 Vdc
Collegamento seriale
Al sistema di
supervisione
(opzionale)
1. Unità Centrale
2. Sensori gas
3. Moduli Display
4. Moduli Relè
5. Moduli Allarmi
. Pulsanti
7. Batterie
8. UPS
Bus di comunicazione
Alimentazione 12
Collegamento seriale
Bus di comunicazione
Alimentazione 12
Collegamento seriale
Al sistema di
supervisione
(opzionale)
1
2
7
8
1
2
7
8
1
2
7
8
11
4242
5353
44
1
2
7
8
1
2
7
8
1
2
7
8
1
2
7
8
11
4242
5353
485858585
To
Monitoring
System (option)
Serial connection
Communication bus
12Vdc Power supply
1.Control unit
2.Gas detectors
3.Display modules
4.Relay modules
5.Alarm modules
6.Buttons
7.Batteries
8.UPS

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The UR.40.. detectors come in four models (E, S, I, L) and their use depends on the protection
mode required:
Application
Protection mode Part number
Group II
Category 2G
Ex d IIC T6
T
AMB
: -20  +50 
UR.40.E
Classified (hazardous)
areas
(ATEX certification
required)
Group II
Category 3G
Ex nA d IIC T6
T
AMB
: -20  +50 
UR.40.S
Heavy-duty applications
Construction conforming to
Ex d requirements
IP65
UR.40.I
Unclassified (non-
hazardous) areas
(ATEX certification not
required)
Standard applications
Construction conforming to
Ex nA requirements
IP55
UR.40.L
Tab.2.1 – Gas sensors: available models
In turn, each model (E, S, I, L) has two possible executions:
• with Standard sensor (code S: UR.20S.; UR.40S.)
• with Professional sensor (code P: UR.20P.; UR40P.)
Two types of sensors are commonly used for the gases that most frequently require detection
(methane, LPG, gasoline vapours, carbon monoxide etc.): catalytic (Pellistor) and
electrochemical cell. In both cases, the Professional execution is differentiated from the
Standard execution by the use of sensors that are based on the same operating principle as
the others but that over time have more measurement stability and higher poison resistance to
interfering gases.
As you can see in the table below, the part number includes several fields for rapid
identification in order to facilitate the choice of the detector according to the technical features
described above:

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Tab. 2.2 – Gas detector part numbers
3 INSTALLATION
3.1 Installation of the UCE 40…control unit
The control unit is housed in a flame-resistant plastic enclosure for flush panel mounting.
The enclosure has slots on the sides to house screw clamps for mounting on the back of
the front panel of the board (Fig. 3.2). Mount as follows:
UR _ 40 _ _
Certified to
•
E:
ATEX II 2G Ex d IIC T
•
S:
ATEX II 3G Ex nA d IIC T
Complying with requirements below
•
I: Industrial version IP 5
•
L: Industrial version IP55
Configur
ation:
•
S:
Standard sensor
•
P:
Professional sensor
Gas type (examples):
•
G
Methane
•
P
LPG
•
B
Gasoline
vapours
•
M
Ammonia
•
I
Hydrogen
•
C
Propane
•
T
Octane
•
L
Acetylene
•
E
Ethyl Alcohol
•
O
CO
(Other gases: on demand)
Example:
URG40PS:
Methane detector (G), Professional sensor (P),
ATEX II 3G Ex nA d IIC T certified (S)
Product code:
UR _ 40 _ _
odel:
•
E:
ATEX II 2G Ex d IIC T
•
S:
•
•
:
•
S:
•
P:
•
G
•
P
•
B
•
M
•
I
•
C
•
T
•
L
•
E
•
O
CO
Gas detection
unit
URG40PS:

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1. fit the device into the cover frame (Fig. 3.1)
2. position the cover frame (Fig. 3.2)
3. knock out a 136x136 mm opening in the front panel of the electric board (Fig.3.3)
4. insert the control unit into the knock-out and push it from the outside towards the inside
until it fits into position
5. Insert the clamps into the dedicated slots on the sides of the device (Fig.3.4)
6. push the clamps towards the back of the housing until they fit into the dedicated hooks
on the side of the housing (Fig. 3.4)
7. Tighten the screws to secure the external frame of the cover to the front panel of the
electric board (Fig. 3.5)
Fig. 3.1 – Fitting in the cover Fig. 3.2 – Housing with cover
Fig. 3.3 – Preparing the plate Fig. 3.4 – Fitting UCE40... onto the panel
11
22
136
136
3
136
136
136
136
3
44

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Fig. 3.5 – Inserting hooking clamps Fig. 3.6 – UCE 40…: flush panel mounting
3.2 Installation of the detectors
The detectors must be wall-mounted at whatever height is appropriate for the type of gas to
be detected (Fig. 3.7).
Fig. 3.7 – Possible detector positions
56
56
Screw clamp
Screw clamp
7
7
7
7
20 cm from
the ceiling
20 cm from
the floor
1,5-2 m
from
the floor
URG40.. (Methane)
URO40.. (Carbon monoxide - CO)
URP40.. (LPG) URB40.. (Gasoline vapours)

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Use the information below to correctly position the detectors:
• 20-30 cm from the floor to detect gases heavier than air (LPG or Gasoline Vapours)
• 20-30 cm from the ceiling to detect gases lighter than air (Methane)
• midway between floor and ceiling (1.2 - 1.8m) to detect gases as heavy as air (Carbon
monoxide - CO)
The detectors must be wall-mounted only, using anchors and screws. The direction of the
detector must always have the sensor facing downwards.
Fig. 3.8 – Wall-mounting of the sensors
The cable entries on the ATEX certified detectors must be through a cable gland with the
same protection specifications. The installation grade will be declassified if other types of
cable glands are used.
To guarantee correct operation of the system, in addition to the instructions above, the
positions of the detectors must take into consideration the following specific installation
guidelines:
The detector must be mounted:
• where accidental gas leakages are possible
• at least 1.5 metres from heat sources
• not in spaces where ventilation is poor and where gas pockets may form
• at least 1.5 metres from vent holes
• away from hindrances to natural gas flow
• in environments with a temperature range of -20°C to 50°C and relative humidity below
90% (non-condensing).
Wall-mounting
slots
Cable connection
with cable gland
Cable connection
with cable gland
Wall-mounting
slots

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The number of detectors to be installed for correct coverage of an environment are
proportionate to the height and area of the room itself. This parameter (see installation
guidelines) depends on a wide range of variables; the graph below should be seen as an aid
and NOT AS INSTALLATION GUIDELINES.
Fig. 3.9 – Coverage of sensors [m
2
]
3.3 Installation of the Relay modules, the Display modules and the Alarm modules
The MAR40 (RM) relay modules, the MDD40 (DM) Display modules and the MID40 (AM)
Alarm modules must be mounted on DIN rails, whether they are fitted to a mounting plate or
panel mounted. In the latter case, the detector must be wired before fixing, since it is no
longer possible to access the terminal boards after the panel is fixed.
3.3.1 Wall mounting
Prepare and horizontally attach a DIN rail no shorter than 100 mm to the wall. Then place
the module at the top of the rail and slowly but firmly push downwards until it clicks into
place (Fig. 3.10).
Height from floor in [m]
x
9 x
x
8 x
x
7 x
x
6 x
x
5 x
x
4 x
x
3 x
x
2 x
x
1 x
20 30 40 50 80 100 200
Coverage of one detector [m
2
]
CAUTION
The sizes and information
provided by the graph on
the side are for guidance
only.
The curve shows the
volume (floor surface and
ceiling he
ight) covered by
a Methane sensor or,
generally speaking, a light
gas detectors.

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Fig. 3.10 – Fixing the modules to DIN rail
To unhook the devices from the
support rail, insert a small
screwdriver into the slot of the spring
situated at the bottom of the
enclosure (Fig. 3.11).
Fig. 3.11 – Unhooking slot

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3.3.2 Flush panel mounting
Mount as follows:
1. prepare a piece of DIN rail no shorter than 160 mm with holes on the side to pass
through dedicated tie rods (Fig. 3.12)
2. knock out a 46x106 mm opening on the front panel of the electric board and drill two
holes on the sides for the tie-rods to pass through (line them up with the DIN rail
holes (Fig. 3.13)
3. fit the module on to the DIN rail as shown in Par. 3.3.1
4. Use the dedicated tie rods to fix the whole thing to the panel (Fig. 3.14).
Fig. 3.12 – Preparing the DIN rail Fig. 3.13 – Preparing the panel
Fig. 3.14 – Fixing the module to the panel
106
46
106
46

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3.4 Numbering the field devices
After installation, all the field devices must be numbered as follows:
1. Attach a clearly visible label to each detector and write a progressive identification
name on each one, from 1 to N, where N is the number of detectors installed. The
numbering criteria is at operator's discretion (for example, the detectors can be grouped
by type, by zone or any other way)
2. Apply the same number identification procedure to the relay modules (MAR40), the
display modules (MDD40) and the alarm modules (MID40). In each case, numbers
begin from 1 (one), like for the detectors.
Fig. 3.15 – Identifying the field devices
Below is an example table that can be used to input all the data indicated above. It may
need to be extended for large systems, if it is too small.
The alarm modules can be seen as detectors since each of the four inputs must be
configured (using DIP switches) as a pre-alarm, a threshold one alarm or a threshold two
alarm.
At the AM level, again by DIP switches, it is possible to configure the nature of the input
signal between steady and pulsed, the latter necessary for acquisition of push buttons.
SENSIGAS
MDD40
DM01
P
SENSIGAS
MAR40
!P I II
RM01
P
SENSIGAS
MID40
IVI II III
AM01
S01
SENSIGAS
MDD40
DM01
SENSIGAS
MDD40
SENSIGAS
MDD40
DM01
P
SENSIGAS
MAR40
!P I II
RM01
P
SENSIGAS
MAR40
!P I II
P
SENSIGAS
MAR40
!P I II
P
SENSIGAS
MAR40
!P I II
RM01
P
SENSIGAS
MID40
IVI II III
P
SENSIGAS
MID40
IVI II III
AM01
S01S01

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CONFIGURATION OF THE LAYOUT AND NUMBER OF DEVICES
DETECTORS
No. Gas detected Position of detector No. Gas detected Position of detector
1 6
2 7
3 8
4 9
5 10
ALARM MODULES
No. AM position Alarm I-1 Signal I-1 Alarm I-2 Signal I-2 Alarm I-3 Signal I-3 Alarm I-4 Signal I-4
1
2
RELAY MODULES
No. RM position Detectors / AM
assigned
Relay outputs No. RM position Detectors / AM
assigned
Relay outputs
Pr Pr
1t 1t
2t 2t
1
FA
3
FA
No. RM position Detectors / AM
assigned
Relay outputs No. RM position Detectors / AM
assigned
Relay outputs
Pr Pr
1t 1t
2t 2t
2
FA
4
FA
DISPLAY MODULES
No. DM position Detectors / AM assigned No. DM position Detectors / AM assigned
1 3
2 4
Table 3.1
With reference to the system shown in Fig. 4.10 below is an example of table 3.1 filled in
CONFIGURATION OF THE LAYOUT AND NUMBER OF DEVICES
DETECTORS
No. Gas detected Position of detector
1 METHANE ROOM 1 boiler 1
2 METHANE ROOM 1 boiler 2
3 METHANE ROOM 1 boiler 3
4 CARBON MONOXIDE ROOM 1 IN CENTRE
RELAY MODULES
No. RM position Detectors / AM
assigned
Relay outputs
Pr LAMP 1
1t VALVE 1
2t VALVE GEN
1 ROOM 1 S1, S4
FA
No. RM position Detectors / AM
assigned
Relay outputs
Pr LAMP 2
1t VALVE 2
2t VALVE GEN
2 ROOM 1 S2, S4
FA
No. RM position Detectors / AM
assigned
Relay outputs
Pr LAMP 3
1t VALVE 3
2t VALVE GEN
3 ROOM 1 S3, S4
FA
DISPLAY MODULES
No. DM position Detectors / AM assigned
1 ENTRY ROOM 1 S1,S2,S3,S4
Table 3.2
NOTE:
If there are alarm modules, it is
necessary to specify both the alarm
module number and the number of
the relative input and its nature.
Below is an example relative to
alarm module 1, input 3
Example:
In the field Alarm I-3
the type of
alarm which that input represents
must be defined (Pr, 1t, 2t, FA).
In the field Signal I-3
the type of
input (pulsed like the one from a
button or steady) must be defined.
In the field
Detectors / AM
assigned the code AM1-
3 must
appear, signifying that input number
3 of alarm module number 1 has
been assigned to that particular
relay module or display module.

Type / N. Rev. Data Page Total pages
EW095.605 5 November 2010 20
96
EsiWelma s.r.l.
4 ELECTRICAL CONNECTIONS
After the control unit and the field devices have been installed and table 3.1 has been filled in,
the electrical connections must be made.
This operation must be performed by qualified and trained personnel who work in compliance
with laws in force.
The minimum guidelines below must also be adopted for the system to operate
properly:
• the power supply leads can be placed with other cables from a pre-existing system since
these are not high frequency lines
• the communication BUS must preferably be "laid" in a dedicated raceway, or in a double-
groove metal channel, and at a correct distance from power leads and high frequency
lines
• the BUS shield wire must be connected to earth by one part only and close to the
generator; the connection of the subsequent sections is shown in Fig. 4.3
• the maximum length of the communication BUS with the field devices is 1000 m
• the maximum length of the communication BUS with the Monitoring System is
 10 m with RS232 connection
 300 m with RS422 connection.
4.1 Types of cable
• Power supply cable: use flame-resistant cable with a diameter to suit the devices
connected to the control unit (See Tables 4.2 and 4.3). Do not exceed current density of
3A/mm².
• Communication BUS with field devices: the BUS connections must be carried out
using a shielded twisted pair with the same specifications as the BELDEN type 9841 or
3105A cables shown in Table 4.1
• Communication BUS with the Monitoring System:
 Connection RS232: standard cable with plug DB9/F
 Connection RS422: the BUS connections must be carried out using a double
shielded twisted pair with the same specifications as the BELDEN type 9842 cable
shown in Table 4.1
RESISTANCE IN DC RATED CAPACITY
TYPE
PAIRS
No.
WIRES
Ω/km
SHIELD
Ω/km
RATED
IMPEDANCE
ΩBETWEEN
WIRES
pF/m
BETWEEN
WIRES AND
SHIELD
pF/m
AWG
Belden
9841
1 78,7 11,0 120 42,0 75,5 24
Belden
3105A
1 48,2 9,5 120 36,1 65,5 22
Belden
9842
2 78,7 7,2 120 42,0 75,5 24
Table 4.1 – Electrical specifications of the communication BUS