MODEL: S1G-100-LEL and S2G-100-LEL with PE1100
UNI-TROL GAS CONTROLLER
™
Single-Channel Field Mount Controller with LEL Sensor
REVISED: MAY, 1998
WARRANTY POLICY
The products of Net Safety Monitoring Inc, are carefully designed and manufactured from high
quality components and can be expected to provide many years of trouble free service. Each
product is thoroughly tested, inspected and burned-in prior to shipment. Failures can occur which
are beyond the control of the manufacturer. Failures can be minimized by adhering to the
operating and maintenance instructions herein. W here the absolute greatest of reliability is
required, redundancy should be designed into the system.
Net Safety Monitoring Inc, warrants its sensors and detectors against defective parts and
workmanship for a period of 24 months from date of purchase and other electronic assemblies for
36 months from date of purchase.
No other warranties or liability, expressed or implied, will be honoured by Net Safety
Monitoring Inc.
Contact Net Safety Monitoring Inc. or the authorized distributor for details.
Table of Contents
Unit I - GENERAL INFORMATION
DESCRIPTION ............................................................... 1
FEATURES .................................................................. 1
SPECIFICATIONS ............................................................ 1
Figure 1 - Controller Dimensions in Inches ................................... 2
Figure 2 - Controller Front Panel ........................................... 2
BASIC OPERATION ........................................................... 2
FACEPLATE DESCRIPTION.............................................. 2
OUTPUTS ............................................................ 3
RELAY OUTPUTS ...................................................... 3
RECOMMENDATION .......................................................... 3
CURRENT OUTPUTS ................................................... 3
Figure 3 - Jumper Selections For Isolated or Non-Isolated Current Output . . . . . . . . . . . 4
Table 1 - Current Outputs................................................. 4
PROGRAMMING OPTIONS .................................................... 4
Table 2 - Selectable Output Options ........................................ 5
EXTERNAL RESET ..................................................... 5
AUTOMATIC DIAGNOSTICS AND FAULT IDENTIFICATION . . . . . . . . . . . . . . . . . . . . 5
OPERATING MODES .......................................................... 5
NORMAL OPERATING MODE ............................................ 6
RESET MODE ......................................................... 6
FORCED RESET MODE ................................................. 6
SENSOR REPLACEMENT MODE(SrP) ..................................... 6
SENSOR CALIBRATION MODE(CAL) ...................................... 6
SET-POINT DISPLAY (Spd) .............................................. 7
ADDRESS SET (Adr Set) ................................................. 7
ERROR MESSAGE DISPLAY (ErrChc) ...................................... 7
UNIT II - GENERAL INFORMATION (SENSOR) ............................. 7
DESCRIPTION ......................................................... 7
FEATURES ........................................................... 8
SPECIFICATIONS ...................................................... 8
Figure 4 - Sensor and Transmitter Dimensions ................................ 9
LOWER EXPLOSIVE LIMIT ..................................................... 9
Table 3 - Flammable Gas Volume for 100% LEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
OPERATIONS OVERVIEW .................................................... 10
Table 4 - K Factor for Various Gases....................................... 11
UNIT III - GENERAL INFORMATION (SENSOR)
INSTALLATION .............................................................. 12
SENSOR LOCATIONS ................................................. 12
GENERAL WIRING .................................................... 12
CONTROLLER WIRING ................................................ 13
Figure 5a - Wiring for S1G with Non-Isolated Current Output . . . . . . . . . . . . . . . . . . . . 14
Figure 5b - Wiring for S1G With Isolated Current Output . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 6a - Wiring for S2G with Non-Isolated Output . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 6b - Wiring for S2G With Isolated Current Output . . . . . . . . . . . . . . . . . . . . . . . . 17
DIP SWITCH SETTINGS ...................................................... 18
Figure 7a - Dip Switch Position ........................................... 18
Figure 7b - Dip Switch .................................................. 18
ACTIVE CHANNELS ................................................... 18
CALIBRATION GAS CONCENTRATION ................................... 18
POW ER-UP TIME DELAY ............................................... 19
ALARM SETTINGS .................................................... 19
LATCHING/NON-LATCHING SELECTION .................................. 20
Table of Contents (Cont)
ENERGIZED/DE-ENERGIZED SELECTION ........................................ 21
RELAY SETTINGS ............................................................ 21
Figure 9a - Relay Positions ............................................... 21
Figure 9b - Relay Settings ................................................ 21
Table 5 - Summary of Dip Switch Settings ................................... 22
UNIT IV - SYSTEM OPERATION ........................................... 22
MENU AND FUNCTION SELECTION ............................................. 22
Table 6a - Menu and Function Selection..................................... 22
Table 6b - Main Menu Selection ........................................... 23
Table 7 - Special Function Menu Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
START-UP PROCEDURE ...................................................... 24
MAIN MENU SELECTIONS ..................................................... 24
ERROR CHECK MODE(ERR CHC) ........................................ 24
SET-POINT DISPLAY MODE (SPd) ........................................ 25
Table 8 - System Status Codes............................................ 26
SENSOR CALIBRATION (CAL) .................................................. 27
GENERAL INFORMATION ............................................... 27
CALIBRATION PROCEDURE ............................................ 27
SENSOR REPLACEMENT MODE (SrP) .................................... 28
SPECIAL FUNCTION MENU SELECTIONS ........................................ 29
FORCED CURRENT OUTPUTS (FoP) ..................................... 29
CURRENT CALIBRATION MODE (CuC) .................................... 29
ADDRESS MODE (Adr Set) .............................................. 29
CHANNEL DISPLAY (Chd) ............................................... 29
BYPASS (bPS) ........................................................ 29
OPERATING MODES ......................................................... 30
RESET MODE ......................................................... 30
FORCED RESET MODE ................................................ 30
NORMAL OPERATING MODE ............................................ 30
FORCED DISPLAY (FdP) ................................................ 31
UNIT V - SYSTEM MAINTENANCE
ROUTINE MAINTENANCE ..................................................... 32
MANUAL CHECK OF OUTPUT DEVICES ................................... 32
SYSTEM CHECK IN NORMAL MODE ...................................... 32
SENSOR REPLACEMENT ..................................................... 32
TROUBLESHOOTING ......................................................... 33
REPLACEMENT PARTS ....................................................... 33
DEVICE REPAIR AND RETURN ................................................. 34
Table 10 - Troubleshooting Guide.......................................... 34
-1-
Unit I
GENERAL INFORMATION (CONTROLLER)
DESCRIPTION
TheS1G and S2G Uni-Trol Controller accepts input directly from PE1100 combustible gas
™
sensors. The controller is designed to accept the millivolt signal from the SC1100 LEL sensor
without the need for a transmitter to change the signal to a 4-20mA current signal. Controller
response includes actuation of relays for direct control of field response devices, 4-20mA DC
current output and, a full array of faceplate indicators.
FEATURES
< Controller accepts millivolt inputs (PE1100 LEL sensor).
< Two digital displays, one bar graph display, and high intensity LEDs indicate important
system status information.
< AutoCal feature provides easy and accurate calibration.
< Microprocessor-based controller is easily field programmable.
< 4-20mA current output send important system information to other devices.
< Relay alarm and fault outputs.
SPECIFICATIONS
< Operating Voltage:
24 Volts DC. Device can operate between 18 and 32 Volts DC
< Power Consumption (Controller Only):
3.0 Watts nominal, 5.2 Watts maximum (125 mA nominal, 215 mA maximum at
24 Volts DC).
Maximum startup current is 1.0 Amperes for 5 seconds. Power supplies with fold
back current limiting are not recommended
< Maximum Ripple:
Ripple should not exceed 5 Volts peak-to-peak. The sum of DC plus ripple must
be $18 Volts DC and #32 Volts DC.
< Temperature Range:
Operating: -40ºC to +85ºC (-40ºF to +185ºF)
Storage: -55ºC to +150ºC (-65ºF to +302ºF)
< Relay Contacts:
Form C normally open/normally closed contacts rated for 5 Amperes at 30 Volts
DC/ 250 Volts AC
< Current Outputs:
One 4-20mA DC current, with a maximum external loop resistance of 600S at 18-
32 Volts DC.
< Dimensions:
Refer to Figure 1
-2-
< Shipping Weight (Approximate):
6 lbs. (2.7 kilograms)
< Certification:
CSA certified for hazardous locations, Class 1, Division 1, Groups B, C, and D.
Figure 1 - Controller Dimensions in Inches
Figure 2 - Controller Front Panel
BASIC OPERATION
FACEPLATE DESCRIPTION
The controller faceplate provides LEDs for identifying status conditions, two digital displays and a
bar graph display for indicating the sensor input, and magnetically activated MENU/SET and
SELECT/RESET reed switches (see the appendix for activation instructions) for programming,
calibrating and resetting the system. Refer to Figure 2 for the location of indicators and switches.
< Digital Displays - Two digital displays are used to display the sensor input in both the
Normal and Calibrate Modes; one display indicates the channel and one display indicates
the corresponding sensor input. In the event of a fault, it identifies the nature of the fault
using an alphanumeric code. In the Normal Operating Mode the gas concentration at the
sensor is shown. In other operating modes, the digital displays show the alarm set-points,
programmed calibration gas concentration, output current, or the communication
addresses for the CAN interface. A negative zero drift condition is indicated by a minus
sign in the left-hand digit. Since at least one display is always lit, they also function as a
power indicator.
< Bar Graph Display - The common 10-segment bar graph display provides readings of
the sensor input in 5% LEL increments, from 0% to 50% LEL; all 10 segments are
illuminated when 50% LEL is exceeded.
< High Alarm LED (HI) - Flashes in response to a sensor signal that exceeds the high
alarm set-point.
< Low Alarm LED (LOW) - Flashes in response to a sensor signal that exceeds the low
alarm set-point.
< Calibrate LED (CAL) - is illuminated while the controller is in the Calibration Mode.
-3-
< Fault LED (Fault) - is illuminated upon detection of an overall system fault or a channel
related fault.
< Channel LEDs - are illuminated when status on the corresponding channel is displayed
on the common indicators (digital displays and bar graph). During power-up, a channel
LED is on if the channel is selected for operation.
< MENU/SET Reed Switch - is used for changing the menu display resetting the controller
calibration and other system programming and calibration functions.
< SELECT/RESET Reed Switch - is used for menu selection, and other system
programming, for resetting the controller.
OUTPUTS
Relay Outputs:
The relay outputs have SPDT contacts rated for 5 Amperes at 30 Volts DC or 250 Volts AC. The
four relays include an Area 1 low alarm (channel 1), an Area 2 low alarm (channel 2) one common
high alarm, and fault alarm.
RECOMMENDATION
The fault relay output should not be used to activate an automatic shutdown procedure.
The fault output indicates a potential problem with the controller, not an alarm condition.
Current Outputs:
Two 4-20mA DC current output for transmitting system information to other devices are also
included. The current outputs can be wired for isolated or non-isolated operation by changing the
jumpers as shown in Figure 3. Refer to Table 1 for a description of the current output signal
levels.
-4-
Figure 3 - Jumper Selections For Isolated or
Non-isolated Current Output
Current Output Situation
0mA Open or shorted signal output, or loss of power
1mA Fault or Power-Up
2mA Power Fault
3mA Calibration
4mA to 20mA 0 to 100% LEL gas concentration
Table 1 - Current Outputs
-5-
PROGRAMMING OPTIONS
A set of dip-switches, located on the circuit board, can be used to “program” various options and
set-points, including:
< channels selected for operation,
< low and high alarm settings,
< calibration gas concentration,
< power-up delay time (either 45 or 90 seconds),
< latching / non-latching relay action
< energized / de-energized relay action
The alarm relays are programmable for either normally energized or normally de-energized
operation (programmable as a group only, not individually). The fault relay is normally energized.
The low alarm relays are programmable for either latching or non-latching operation. The high
alarm relay is always latching and the fault relay is non-latching. Refer to Table 2.
Jumper selections are provided for normally open or normally closed relay outputs and for isolated
or non-isolated current outputs.
OUTPUT
Selectable Normally
Open/Closed
Selectable Normally
Energized/De-Energized
Selectable
Latching/Non-latching
LOW Y Y Y
12
HIGH Y Y N
23
FAULT Y N N
45
Table 2 - Selectable Output Options
1 Low alarms are programed together, not individually
Programmable together, not individually
2
High alarm relay is always latching
3
Fault relay is normally energized
4
Fault relay is non-latching
5
EXTERNAL RESET
A normally open, momentary closure switch can be connected between the external reset terminal
and the negative power terminal to provide remote reset capabilities.
AUTOMATIC DIAGNOSTICS AND FAULT IDENTIFICATION
The microprocessor-based controller features self-testing circuitry that continuously checks for
problems that could prevent proper system response. W hen power is applied, the microprocessor
automatically tests memory. In the Normal Operating Mode, it continuously monitors the input
signals from the sensor to ensure proper functioning. In addition, a "watchdog" timer is maintained
to ensure that the program is running correctly. The timer resets the micro-controller if it enters
erroneous processor states within a reasonable period of time.
-6-
If a fault is detected, the Fault LED illuminates, the digital display identifies that a fault has
occurred, the fault relay output becomes de-energized, and the current output drops to less than 1
mA.
The nature of the fault can be identified by a numeric code, which can be viewed in the Fault
Message Display mode.
OPERATING MODES
The controller can operate in any of the modes discussed in this section. Operating modes other
than Normal are selected by activating the appropriate MENU/SET and SELECT/RESET switches
located on the controller front panel. Refer to Figure 2 for a diagram of the controller front panel.
NOTE
This section is intended to acquaint the user with the basic operation of the controller.
Refer to “Unit III” for detailed instructions and description.
Normal Operating Mode:
If no alarms or faults are present, the Module will be in a Level 1 Display Mode; the bar graph and
digital display indicate the sensor inputs. Relay outputs are in their normal state, and the current
output corresponds to the sensor input.
If a low alarm condition occurs, the controller will be in a Level 2 Display Mode; the bar graph and
digital display will display the gas concentration at the sensor. The low alarm LED will flash, the
low alarm relay changes state, and the current output changes to indicate the alarm. If the signal
decreases below the low set-point again, the low alarm relay returns to its normal state if
programmed for non-latching operation and remains unchanged if programmed for latching
operation. The current output returns to normal. The low alarm LED will remain illuminated, but
will no longer flash.
If a high alarm condition occurs, the module will be in a Level 3 Display Mode; the bar graph and
digital display will display the gas concentration at the sensor and the high alarm LED will flash.
Reset Mode:
The system is reset by activating the SELECT/RESET switch located on the front panel of the
controller. (Refer to Figure 2) W hen the SELECT/RESET switch is activated momentarily, all
outputs return to their normal condition if no alarms or faults are present. (basic reset).
Forced Reset Mode:
If the controller receives a signal beyond 100% LEL from the sensor, a reset will not clear the
alarms, even if the channel has returned to levels below the low alarm set point. The error
resulting from this occurrence must be cleared and a forced reset applied. To apply a forced
reset, activate the SELECT/RESET switch for 1 second, the LEDs turn off and the outputs return
to their normal condition. The remote reset performs a forced reset.
NOTE
The remote reset performs a reset function only. It cannot be used for other controller
functions.
Sensor Replacement Mode (SrP):
This mode inhibits all controller outputs to allow replacement of the sensor without removing
power from the controller. Alarm set-points and calibration gas concentration are not affected.
The left display will show ‘SrP’ while in the sensor replace mode. The right display will show the
status of the sensor being replaced (‘NoS’ means no sensor is connected). The fault LED is on
and the fault relay is de-energized. The channel LED will be on for the sensor being replaced.
-7-
All other display features will be inhibited. In order to exit this mode the SELECT/RESET switch
must be activated.
Sensor Calibration Mode (CAL):
The Uni-Trol Controller uses a fully automatic calibration procedure that requires no adjustments
™
by the operator. The controller displays ‘Air’ on the left display and channel status on the right
display while automatically performing the zero adjustments. Next the controller will signal the
user to apply calibration gas by alternating ‘gAS’ and ‘in’ on the left display. When the controller
detects that the gas has been applied to the sensor, the left display will read ‘gAS’. Once the
controller has finished the gain adjustm ents it will alternate ‘Cut’ and ‘gAS’ on the left display,
telling the user that it is time to remove the calibration gas. Upon completion of calibration the
controller will automatically return to normal operating mode, after the gas level has dropped
below 50% of the low alarm setting.
If the operator fails to complete the calibration procedure, if an error in the calibration procedure
occurs, or if a successful calibration cannot be com pleted, the microprocessor will automatically
return to the Normal Operating Mode and continue to use the previous calibration data. A fault
indication will be displayed until a reset occurs. If the microprocessor determines that the sensor
is approaching the end of its useful life, a fault code will indicate this.
W hile in the calibration mode, all controller outputs are inhibited and the ‘Cal’ LED is illuminated.
Set-Point Display (Spd):
In this mode, the digital display sequentially shows the
programmed low and high alarm set-points, calibration gas concentration, and communication
addresses. Each value is displayed for approximately 2 seconds.
Address Set (Adr Set): DO NOT USE THIS FUNCTION
The communication addresses for the CAN bus are set in this mode, which is found in the special
function menu. The MENU/SET and SELECT/RESET switches are used to raise and lower the
address. This mode can only be exited by allowing ten seconds to go by without activating either
switch.
Error Message Display (ErrChc):
The microprocessor-based controller features self-testing circuitry that continuously checks for
problems that could prevent proper system response. As a diagnostic and troubleshooting tool,
identifiable faults are displayed on the digital display, using error codes, during the Error Message
Display Mode. The controller will also display an error message after the last channel in the
cycling routine.
NOTE
If no errors exist, this function is hidden and can not be accessed.
-8-
Unit II
GENERAL INFORMATION (SENSOR)
DESCRIPTION
The Net Safety Monitoring Inc. SC1100 combustible gas sensor head consists of an explosion-
proof enclosure, which contains sensor electronic circuitry. The sensors used are catalytic
oxidation sensors, or pellistors, designed to provide continuous monitoring of combustible gasses
such as methane and butane, etc. in the percent lower explosive limits (LEL). Each sensor is a
matched pair of detector and reference elements which are operated in a Wheatstone Bridge
circuit.
FEATURES
High degree of poison resistance means sensors will maintain their sensitivity over extended
periods of operation.
< Designed and manufactured for low drift over temperature extremes.
SPECIFICATIONS
< Range:
0 to 100% LEL
< Operating Humidity Range:
0 to 100% relative humidity
< Response Time:
Less than 30 seconds to reach 90% of full scale reading with methane (in still air).
< Zero Drift:
Typically less than 2% LEL per month
< Sensor Life:
Operation: 2 to 5 years expected.
Storage: Indefinite
< Calibration Cycle:
60 to 90 Days Groups
< Certification:
CSA certified for hazardous locations,
Class 1, Division 1, Groups B, C, and D.
-9-
Figure 4 - Sensor and Transmitter Dimensions
LOWER EXPLOSIVE LIMIT
A combustible gas is one that will burn when mixed with air (or oxygen) and ignited. The lower
explosive limit (LEL), or lower flammable limit (LFL), of a combustible gas is defined as the
smallest amount of the gas that will support a self-propagating flame when mixed with air and
ignited. In gas detection systems, the amount of gas present is specified in terms of % LEL; 0%
LEL being a combustible gas-free atmosphere and 100% LEL being an atmosphere in which the
gas mix is at its lower explosive limit. The relationship between % LEL and % by volume differs
from gas to gas. Refer to Table 3.
GAS, 100% LEL CONCENTRATION
2
Hydrogen (H ) 4.0%
4
Methane (CH ) 5.0%
26
Ethane (C H ) 3.0%
24
Ethylene (C H ) 2.7%
512
Pentane (C H ) 1.5%
38
Propane (C H ) 2.2%
Table 3 -Flammable Gas Volume for 100% LEL
For data on other gases, refer to NFPA 5th Edition 325M.
-10-
The LEL of gas is affected by temperature and pressure. As the temperature increases, the LEL
decreases and hence the explosion hazard increases.
The relationship between LEL and pressure is fairly complex, but at approximately one
atmosphere, a pressure increase usually lowers the LEL. The LEL of a gas is not significantly
affected by the humidity fluctuations normally encountered in the operation of a gas detection
system.
OPERATION OVERVIEW
The sensors used are catalytic oxidation sensors, or pellistors, designed to measure
concentrations of combustible gases in air up to their lower explosive limit. Each sensor is a
matched pair of detector and reference elements which are operated in a Wheatstone Bridge
circuit. The active element, which com prises a coil of platinum wire embedded within a catalytic
bead is capable of oxidizing combustible gases while the inert reference element compensates for
changes in ambient temperature and humidity. The heat generated during oxidation increases the
temperature and resistance of the detector element, producing an out-of-balance signal in the
Wheatstone Bridge circuit proportional to the concentration of combustible gas.
Table 4 lists the theoretical factors by which the signal with a calibration gas should be multiplied
to give the signal for other gases. The following formula may be used:
NOTE
These figures are theoretical, and may differ from sensor to sensor. For best results, the
sensors should be calibrated with the gas they are intended to detect.
Example: For an instrument calibrated with Methane and used to detect Propane.
METHANE
K = 112.0
PROPANE
K = 61.8
Signal shown for 50%LEL Propane is calculated as follows:
Signal = 50% x 61.8 / 112 = 27.6%
-11-
GAS K GAS K GAS K
Acetaldehyde 67.3 n-Decane 36.7 Dimethyl Ether 70
Acetic Acid 60.8 Diethylamine 54.6 Methylethylether 49.3
Acetic Anhydride 51.5 Dimethylamine 64.7 Methylethylketone 46.2
Acetone 57.8 2,3-Dimethylpentane 44.6 Methyl Formate 75
Acetylene 63.6 2,2-Dimethylpropane 44.4 Methylmercaptan 67.9
Alkyl Alcohol 57.1 Dimethylsulphide 48.6 Methylpropionate 57.2
Ammonia 142 1,4-Dioxane 50 Methyl n-propylketone 45.4
n-Amyl Alcohol 36.6 Ethane 75.8 Naphthalene 38.1
Aniline 44.1 Ethyl Acetate 57.4 Nitromethane 64.8
Benzene 45.6 Ethyl Alcohol 81.5 n-Nonane 35.2
Biphenyl 28 Ethylamine 58.9 n-Octane 41.9
1,3-Butadiene 62.5 Ethyl Benzene 39.9 n-Pentane 51.3
n-Butane 65.5 Ethylcyclopentane 44.4 iso-Pentane 51.9
iso-Butane 57.8 Ethylene 79.1 Propane 61.8
Butene-1 50.8 Ethyleneoxide 57.9 n-Propyl Alcohol 52.7
cis-Butene-2 54.2 Diethyl Ether 51.8 n-Propylamine 54.1
trans-Butene-2 56.7 Ethyl Formate 49.5 Propylene 57.7
n-Butyl Alcohol 38.4 Ethylmercaptan 62.8 Propyleneoxide 51.2
iso-Butyl Alcohol 59.2 n-Heptane 43.2 iso-Propylether 48.8
tert-Butyl Alcohol 83.1 n-Hexane 41.2 Propyne 46.5
n-Butyl Benzene 35.2 Hydrazine 50.4 Toluene 45.2
iso-Butyl Benzene 35.8 Hydrogencyanide 53.4 Triethylamine 44.6
n-Butyric Acid 42.5 Hydrogen 85.8 Trimethylamine 54.3
Carbon Disulphide 19.8 Hydrogen Sulphide 45.6 Vinylethylether 46.9
Carbon Monoxide 84.4 Methane 112 o-Xylene 40.1
Carbon Oxysulphide 105 Methyl Acetate 55.6 m-Xylene 43.8
Cyanogen 99.9 Methyl Alcohol 96.2 p-Xylene 43.8
Cyclohexane 46 Methylamine 86.5
Cyclopropane 69.7 Methylcyclohexane 49.4
Table 4 - K Factor for Various Gases
-12-
Unit III
SYSTEM INSTALLATION
INSTALLATION
SENSOR LOCATIONS
Proper location of the sensors is essential for providing maximum protection. The method for
deciding the most effective number and placement of sensors varies depending on the conditions
at the job site. The individual performing the installation must rely on experience, common sense,
and knowledge of plant operations to determine the number of sensors needed and the best
controller locations to protect the area adequately.
The following factors are important and should be considered for every installation:
< Sensors should be located where they are safe from potential sources of contamination.
< Refer to sensor application manuals and follow guidelines for sensor installation.
< Sensors must be accessible for testing and calibration.
< Exposure to excessive heat or vibration can cause premature failure of electronic devices,
and should be avoided if possible.
GENERAL WIRING REQUIREMENTS
NOTE
The wiring procedures in this manual are intended to ensure proper functioning of the
device under normal conditions. However, because of the many variations in wiring codes
and regulations, total compliance to these ordinances cannot be guaranteed. Be certain
that all wiring complies with applicable regulations that relate to the installation of
electrical equipment in a hazardous area. If in doubt, consult a qualified official before
wiring the system.
The use of shielded cable is highly recommended for any signal wires to protect against
interference caused by extraneous electrical 'noise'. This includes power and current outputs;
relay outputs do not require shielded cable. In applications where the wiring cable is installed in
conduit, the conduit must not be used for wiring to other electrical equipment.
NOTE
The S1G and S2G controllers have been certified, as ‘No Seal Required’ since it will not
ignite an explosive atmosphere, under normal operating conditions. Net Safety
Monitoring Inc. does, however, recommend conduit seals to prevent moisture damage.
Since moisture can be detrimental to electronic devices, it is important that moisture not be
allowed to contact the electrical connections of the system. Moisture in the air can become
trapped within sections of conduit. Therefore, the use of conduit seals is recommended to
prevent damage to electrical connections caused by condensation within the conduit.
These seals must be watertight and explosion-proof and should be installed even if they are not
required by local wiring codes. A seal should be located as close to the device as possible. Never
should this seal be located more than 18 inches (46 cm) from the device. When an explosion-
proof installation is required, an additional seal may be needed at any point where the conduit
enters a non-hazardous area. Always observe the requirements of local codes.
-13-
W hen pouring a seal, the use of a fibre dam is required to assure proper formation of the seal.
The seals should never be poured in temperatures that are below freezing, since the water in the
sealing compound will freeze and the compound will not dry properly. Contamination problems
can then result when temperatures rise above the freezing point and the compound thaws.
The shielding of the cable should be stripped back to permit the seal to form around the individual
leads, rather than around the outside of the shield. This will prevent any siphoning action that can
occur through the inside of the shield.
It is recommended that conduit breathers also be used. In some applications, alternate changes in
temperature and barometric pressure can cause 'breathing', which allows the entry and circulation
of moist air throughout the conduit. Joints in the conduit system and its components are seldom
tight enough to prevent this 'breathing'. Moisture in the air can condense at the base of vertical
conduit runs and equipment enclosures, and can build up over a time. This can be detrimental to
electronic devices. To eliminate this condition, explosion-proof drains and breathers should be
installed to bleed off accumulated water automatically.
The maximum distance between the sensor and controller is limited by the resistance of the
connecting wiring, which is a function of the gauge of the wire being used. Three wire, 18 AWG,
shielded cable is recommended. If the recommended wire is used, the sensors may be located
up to 500 feet from the controller.
CAUTION
All terminations between the controller and sensors must be good tight electrical
connections. If proper connections are not made, the voltage monitoring circuit in the
controller will not function properly and the sensors may be damaged or operate
incorrectly.
CONTROLLER WIRING
NOTE
The controller contains semiconductor devices that are susceptible to damage by
electrostatic discharge. An electrostatic charge can build up on the skin and discharge
when an object is touched. Therefore, use caution when handling, taking care not to touch
the terminals or electronic components. For more information on proper handling, refer to
the Appendix.
The sensor direct, Unitrol controllers (S1G and S2G) can be configured for an isolated or non-
isolated current output by changing a jumper on one of the controllers circuit boards (see 6a
Figure 3). Figure 5 and 6 show the terminal configuration for the controllers. Figures 5a and 6a
show the proper wiring of the controller for a non-isolated current output. Figure 5b and 6b show
the proper wiring of the controller for an isolated current output.
NOTE
If local wiring codes permit, and if a ground fault monitoring system is not being used, the
minus side of the DC power source can be connected to chassis (earth) ground.
Alternatively, a 0.47 microfarad, 100 Volt capacitor can be installed between the minus
side of the DC power supply and chassis ground for best immunity against
electromagnetic interference.
-14-
-15-
-16-
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
Page is loading ...
/
