SAFETY SYSTEMS TECHNOLOGY GIR911 Guide

Model GIR911
Infrared Carbon Dioxide
NOVA-Sensor
DESIGN MANUAL
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disclosed by this document may be
used and disseminated only for the
purposes and to the extent
specifically authorized by SAFETY
SYSTEMS TECHNOLOGY in writing. Such
information and technical data are
proprietary to SAFETY SYSTEMS
TECHNOLOGY and may not be used or
disseminated except as provided in the
foregoing sentence.
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SAFETY SYSTEMS TECHNOLOGY
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Tel[phone] Fax [phone]
www.safetysys.com
The information in this document is applicable to
sensors built on or after October, 2001

Quick Finder - Model GIR911 CO2 NOVA-Sensor
QUICK START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-1
Apply Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-1
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-1
Alarm Setpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-1
DIP Switch: Latch/No Latch Setting for LOW Alarm Output . . . . . . . . . . . . . . . . .911-1
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-2
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-2
TECHNICAL SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-3
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-3
The GIR911 Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-3
Installation Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-3
Mounting the enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-4
Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-5
Remote Sensor Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-6
DIP Switch settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-7
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-8
Power-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-8
Changing the Setpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911-8
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-9
Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-11
Recalibration Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-11
NOVA-SENSOR OUTPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-11
0 to 20 mA Current Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-11
Relay Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-11
FINAL OPERATIONAL CHECK-OUT (CompTest™) . . . . . . . . . . . . . . . . . . . . . . 911-12
How to Start the CompTest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-13
Entering the Safety-Code™ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-13
CompTest™Operational Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-14
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-14
Replacing the sensor lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-15
Electronics Module Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-15
Spare Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-15
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-15
Drifting/Shifting display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-15
Wiring of the CHASSIS Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911-16
i December, 2003 i

MODEL GIR911 INFRARED CARBON DIOXIDE GAS
NOVA-SENSOR
QUICK START
Apply Power
Apply +24 volts DC to the labeled terminals (+24V, 24V RET).
A 30 second countdown is displayed, followed by a brief display of the firmware revision
(e.g. “1.17”). Then the decimal points will flash while the unit displays “000” to confirm
to the user that the NOVA-Sensor readout unit is properly functioning. The readout will
next display approximately “-12" and the yellow fault LED will light. This condition
remains during the remainder of the warm-up period for the IR sensor head. If “000” is
not displayed within 5 minutes, and there isno background gas, the sensor requires initial
calibration.
Calibration
Calibration requires test gas. The concentration must be one half of the full scale rating
of the sensor (for instance, 1% test gas is required to calibrate a 2% by volume CO2
sensor). Insure that no background gas is present before initiating calibration. Press the
large MODE button on the outside of the sensor housing for at least 10 seconds. The
sensor flashes “000” while sampling the zero gas condition (10 seconds). Apply test gas
when the 000 stops flashing. “CAL” will be flashed as the gas is sampled. When finished
(approx. 40 seconds), the display will stop flashing - remove the gas now. The sensor
begins normal operation once the gas level is safely below the LOW alarm setpoint.
Alarm Setpoints
Setting
Remove housing cover to access buttons labeled “UP” and “DOWN”. Press the large
externally mounted MODE button for 1 second, orpress the UP/DOWN button. The LOW
alarm LED will light as the setpoint is displayed. Use the UP/DOWN button to alter the
value. After 5 seconds, the HIGH alarm LED and setpoint are displayed. Finally, after 5
seconds of button inactivity, the sensor will return to normal operation.
Confirming
To confirm or inspect the alarm setpoints without declassifying the area, simply press the
large external MODE button for 1 second. Each alarm setting will be displayed for 5
seconds, along with its corresponding alarm LED (LOW or HIGH).
DIP Switch: Latch/No Latch Setting for LOW Alarm Output
DIP switch position 4 (of the 4-position DIP) in the UP (Open) position selects LATCHING
mode for the LOW alarm. Placing the switch DOWN (Closed) configures the LOW alarm
as NON-LATCHING. Power must be cycled to “read” the new DIP setting.
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-1 December, 2003 911-1

!The HIGH alarm is always latched due to code requirements. DIP switch
positions 1, 2 and 3 are set at the factory - DO NOT change setting! If you
suspectthatsettingshavebeenchanged,resetperinstructions onpage 911-7.
DESCRIPTION
The SST Model GIR911 Infrared Carbon Dioxide Gas NOVA-Sensor is a completely
self-contained device that measures and displays the concentration of gas accumulated
in a protected area, performs local control functions, and transmits this information to a
central control point.
Principle of Operation
The GIR911 uses the absorption of carbon dioxide at 4.25 µm for the detection of CO2.
The GIR911 contains an incandescent lamp pulsed at 4 Hz in conjunction with two
piezoelectric light sensors all contained in a plug-in housing ("optical bench"). In a
patented configuration, the sensors are close to each other and are exposed to the direct
light from the lamp, with no mirrors or other optical structures involved. In addition, almost
no light is reflected by the walls of the bench thus eliminating all possible influences from
wall contamination. The active sensor has an optical filter tuned to 4.25 µm; the reference
sensor sees the wide-band infrared signal from the lamp.
The presence of carbon dioxide will decrease the signal to the active sensorsignificantly,
while the signal to the reference sensor is almost unchanged. The electronics module
contained in the GIR911 constantly measures the signals from both sensors, averages
them to filter out noise and then calculates the ratio of the averaged active and reference
signals. With a constant length of the optical axis, the relation between the A/R ratio and
the actual gas concentration is logarithmic. The length of the optical path yields an output
for hydrocarbons that allows measurements with a resolution of 1%-2% of reading. The
ratiometric principle makes it possible to eliminate almost all effects of temperature,
aging, or fogging that would otherwise spoil the measurement. The optical operation
principle has the following advantages:
• Readings independent of Oxygen, wind, etc.
• Readings NOT influenced by cross-sensitivity and poisoning
• No burn-out, saturation, shift or drift when the detector is exposed to high gas
concentrations
Each SST NOVA-Sensor includes a high reliability microcontroller based transmitter/con-
troller in the associated explosion proof junction box. A digital read-out is provided to
continuously display operating status and the actual concentration of gas present in
percentage by volume. The transmitter converts this reading to a standard 4-20 mA
signal. This signal may be connected to a suitable SST NOVA-5000 Gas Detection
Module, or to any other device with a standard 4-20 mA input. Connections between the
transmitter and control device are normally made with 3 conductor cable [+24 VDC, 24
V return, 4-20 mA signal]. Dry contact relay outputs are provided for the LOW alarm,
HIGH alarm, and fault. The LOW and HIGH relays operate at user adjustable alarm
setpoints; the fault relay operates upon loss of power or internal failure of the unit. Relays
are suitable for controlling local HVAC or equipment shutdown.
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-2 December, 2003 911-2

TECHNICAL SPECIFICATIONS
Power Supply . . . . . . . . . . . .24 volts DC nominal, 180 mAstandby,
240 mA when in alarm. Will operate within
specifications at any supply voltage between 16
and 32 volts.
Range . . . . . . . . . . . . . . . .0 to 2% or 5% by volume Carbon Dioxide
Start-up time . . . . . . . . . . . . .15 seconds operational
20 minutes to specification
Response time . . . . . . . . . . . .5 seconds typical. Time required for measured
concentration to reach one half of the final
concentration. Measured at half scale.
Operating Temperature . . . . . . .-4 to +167oF. -20 to +75oC
Humidity . . . . . . . . . . . . . . .0-100% Relative Humidity
Resolution . . . . . . . . . . . . . .0.2% CO2
Relay Contact Ratings . . . . . . . .6 amps @ 28 VDC resistive
6 amps @ 300 VAC resistive
1/8 HP @ 120/240 VAC
Analog Output . . . . . . . . . . . .Sensor will source 0 to 20 mA DC into a load
of 600 ohms or less.
INSTALLATION
The GIR911 Unit
A complete GIR911 unit consists of an explosion-proof housing with MODE button,
Infrared gas sensor head, terminal blocks for field wiring and transparent lid used to
observe the operational status of the numerical readout and LED’s. The field wiring is
connected to the terminal blocks inside the enclosure. The terminal blocks are accessible
after removing the enclosure lid and the plug-in electronics module. The face plate on the
electronics module carries various displays and controls. These are:
• Three-digit LED readout to display of gas concentration and status.
• Four round LED’s, labeled “FAULT” (yellow), “HIGH” (red), “LOW” (red) and “CAL”
(green). These LED’s are used to signal alarms and operating modes.
• Two square pushbutton switches, labeled “UP” and “DOWN”. These switches are
accessible with a small screw driver or ball point pen and are used to adjust the
alarm trip points of the unit.
Installation Sequence
The electronics module contains parts that are delicate and potentially sensitive to
electrostatic discharge (ESD). Remove the electronics module and store in the shipping
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-3 December, 2003 911-3

box during installation. Reinstall the module just before system start-up, after all drilling
and wiring is completed. The recommended installation procedure is as follows:
• Mount the enclosure
• Wire the power and signal cables
• Double check the field wiring for errors
• Set the DIP switches and suitcase jumpers on the electronics module
• Plug the electronics module into the housing
• Apply 24VDC power
• Set the alarm setpoints, if required
• Calibration and functional check out with CompTest, if required
Mounting the enclosure
The dimensions of the GIR911 are shown in the figure below. It is preferable to attach the
sensor to a wall or bracket, using bolts through the two mounting holes. However, these
mountings may be omitted if the electrical conduit is sufficiently rigid to support the weight
of the detector.
The location of the sensor is important. For heavier than air gasses, such as carbon
dioxide, locate the sensor below the expected leak. However, always locate the sensors
at least one foot (30.5 cm) above the floor to prevent damage from water, dust, etc.
Preferred orientation of the sensor is with the sensor head pointing down, as shown in
figure 911-1. If necessary, it may be installed at an angle or horizontally.
Figure 911-1 Mounting Dimensions
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-4 December, 2003 911-4

Wiring
Power input and Analog Signal Output
A typical installation is shown in figure 911-2. This setup uses three wires between the
NOVA-Sensor and the associated control modules. These wires carry the 24 VDC
operating power for the sensor, and transmit the 20 mA signal to the controls. The wires
should be shielded or installed in metal conduit to prevent undesirable noise pickup. To
wire the NOVA-Sensor, carefully remove the electronics module from the housing by
pulling upward. Connect the three wires to the screw terminals in the housing as shown.
Note that the “24VRET” wire is the common return for DC power and the 4-20 mAsignal.
MODE Pushbutton and Remote RESET
The external MODE pushbutton on the NOVA-Sensor housing can be used to clear any
relays or alarms in the NOVA-Sensor which have been latched when activated. Pressing
the button for less than 3 seconds (0.5 second minimum) will cause the latched relays to
clear and the alarm setpoints to be momentarily displayed.
An optional external, remotely located, pushbutton can be wired to the terminal marked
RESET. This should be a normally open contact, and should connect the reset terminal
to 24VRET (common) to reset the sensor. The remote RESET button, when active for
between 0.5 and 3 seconds will clear any latched relays.
Figure 911-2 Typical Output Wiring
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-5 December, 2003 911-5

Relay Contacts
If the internal alarm and fault relay contacts are being used, additional wiring is required.
The terminals for the three relays are marked as shown in figure 911-3. Connect wires to
the respective terminals for an relays to be used. These are voltage-free “dry” contacts
for connection to external equipment. Each of the three contacts may be independently
set to be normally open or normally closed. As shipped, the low and high alarm relay
contacts are normally open, and will close when an alarm condition is detected. As
shipped, the fault contact will be closed under normal operating conditions, and will open
upon loss of power or a fault in the NOVA-Sensor. The sense of the relay contacts can
be changed by moving the programming jumper plugs on the bottom circuit board of the
electronics module.
• To change the HIGH
ALARM contact from nor-
mally open to normally
closed, move the jumper
on the pins marked
HI ALM from the NO to
the NC pins.
• To change the LOW
ALARM contact from nor-
mally open to normally
closed, move the jumper
on the pins marked
LO ALM from the NO to
the NC pins.
• To change the FAULT
contact from normally
closed to normally open,
move the jumper on the
pins marked FAULT from
the OF (Open on Fault)
pins to the CF (Closed on
Fault) pins.
!Relay contacts may require
external protection to sup-
press transients. See figure 911-5 and the section Relay Protection Circuitry
below.
Remote Sensor Version
The remote sensor version is the same as a standard version, except that the sensor
head is located away from the electronics enclosure. A SST Model GIR910 Infrared
carbon dioxide Gas Sensor is required for use with the remote GIR911 electronics
package. A second 3/4 inch conduit connection is provided to connect the sensor
electronics to the remotely located sensor head.
Cableconsiderations
Four conductors are required between the Model GIR910 Sensor and the GIR911
electronics. These wires will be carrying a maximum of 20 mA at 24 volts DC to provide
Figure 911-3 Relay Contact Connections
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-6 December, 2003 911-6

the required operating current to the Infrared Sensor transmitter. In general, the length of
cable is not critical, as long as thetotal resistance of thecable does notexceed 650ohms.
It is important to use shielded cable, or to install the wires in metallic conduit. Excessive
noise picked up in the cables can make the display on the NOVA-Sensor jump between
various values and can
make calibration impos-
sible. This is because the
noise makes the NOVA-
Sensor believe that the
gas values are constantly
changing. A constant gas
value is the criteria for the
end of a calibration.
• If shielded cable is
used, it must be
grounded only at
the GND terminal in
the GIR911
electronics
enclosure. The
GIR911 enclosure
must also be
properly grounded.
Insulate the shield
at the sensor end so
that it will not be
grounded.
• Avoid running the
cable close to high-
powered cables or
equipment or close
to radio transmitters
or antennas.
Cable Color Codes
The GIR910 infrared gas sensor head is supplied with five color coded wires which
connect to the terminals in the GIR911 electronics package. See figure 911-4 for hookup.
Be extremely careful to connect each lead to the proper terminal. Interchanging two wires
will almost always result in a burned out sensor.
DIP Switch settings
One or two piano-type DIP switches are visible from the side of the electronics module.
These switches set the electronics for the type of sensor head installed, and set the
operating mode.
Four-Position DIP Switch
Switch position 4 selects the LOW alarm relay as latching or non-latching. The UP
position selects LATCHING mode: once activated, the low alarm relay will remain in the
Figure 911-4 Sensor head color codes
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-7 December, 2003 911-7

alarm state until the NOVA-Sensor is manually reset with the MODE button ortheremote
reset signal. The DOWN position selects NON-LATCHING mode: after activation, the low
alarm relay will return to the normal state as soon as the gas concentration sensed is less
than the low alarm set point.
NOTE: The HIGH alarm is always latched to conform to code requirements.
The remaining DIP switch positions are set at the factory - DO NOT adjust these
switches! The factory default settings for these DIP switch positions are:
Product 123
911-84-5 DOWN DOWN UP
911-84-2 DOWN UP DOWN
!The switch setting must exactly match the sensitivity rating of the sensor head.
You cannot change the sensitivity of a NOVA-Sensor by just changing the
switch setting.
Five-Position DIP Switch
This switch is not provided on all models. If provided, all five positions on this DIP switch
are normally set in the DOWN position. However, if your NOVA-Sensor is a “low-power”
version, all five positions on this switch must be in the UP position to select the low-power
mode. Any other setting will cause the NOVA-Sensor to operate in standard power mode.
OPERATION
Power-Up
When power isfirst applied, the microcontroller executes abuilt-in test (BIT),during which
various internal components and parameters are checked. During the BIT, the indicator
lights will be flashing. Upon successful completion of the BIT, the NOVA-Sensor begins
a 30 second countdown period to allow time for proper temperature stabilization. The
countdown is displayed on the digital read-out. At the end of the countdown, the
NOVA-Sensor displays its firmware revision code (e.g. “1.17”). Next, the readout will
display approximately “-12" and the yellow fault LED will illuminate. The unit is now
waiting for the IR sensor head to warm up sufficiently to provide stable readings.
Following warm up, the digital read-out displays “000”. As a further verification that the
unit is operating properly, the decimal points on the digital read-out slowly rotate from one
digit to the next while displaying “000”). Three to five minutes after the power was first
applied, the NOVA-Sensor is operating at the factory default calibration and alarm
setpoints. Calibration data and alarm setpoints are maintained in non-volatile memory to
insure proper operation should the +24 VDC supply be temporarily interrupted. No
special care is required to maintain this memory.
Changing the Setpoints
Setpoints for HIGH alarm and LOW alarm are available for user modification. Factory
defaults for the HIGH and LOW alarms 0.5% and 1.5% carbon dioxide by volume.
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-8 December, 2003 911-8

To adjust either the HIGH or LOW setpoints, momentarily press either the UP or DOWN
pushbutton on the face of the electronics module, using a small screwdriver or ballpoint
pen. At this point, the LOW alarm LED will turn on, and the LOW alarm setpoint will be
displayed. The user has 5 seconds to begin to adjust the LOW alarm setpoint by pressing
the UP or DOWN button. Once the microcontroller has detected 5 seconds of inactivity
(no button press), the unit will light the HIGH alarm LED and display the previously stored
setpoint value. The operator will again have 5 seconds to begin adjusting the HIGH alarm
setpoint. After an additional 5 seconds of inactivity, the NOVA-Sensor will store the new
values in non-volatile memory and return to normal operation.
!Setpoints will “roll over” to zero at full scale
Calibration
The GIR911 NOVA-Sensor is pre-calibrated at the factory for the range by volume of CO2
as marked on the sensor head. It should be recalibrated in the field at regular intervals.
Calibration will take care of changes in detector performance and drift. During the
calibration procedure, clean air as well as gas with a defined percentage of CO2gas are
applied to the detector in order to providethe NOVA-Sensor with referencepoints needed
to measure gas levels.
The presence of “clean” air, i.e. air without any CO2components, is absolutely necessary
to provide the electronics module with a reference point for 0% CO2gas concentration.
In locations where clean air cannot be assured, you may need to “purge” the sensor with
clean air from a gas bottle before starting the calibration procedure. DO NOT USE
nitrogen to purge the sensor, false readings may result!
The calibration can be performed by one person, and with the NOVA-Sensor operating
in a classified area. No manual adjustments are required for calibration.
!NOTE: The sensor must be calibrated using carbon dioxide at a concentration
of exactly one-half of the full range rating of the NOVA-Sensor.
!The GIR911 must “warm up” for at least 3 minutes after power is first
applied before calibrating. Calibration will be more accurate if you can
wait 30 minutes before starting.
The calibration procedure is initiated by depressing the large MODE pushbutton located
onthesideof theenclosureandholdingitin foraminimumof tenseconds.Thecalibration
sequence is as follows:
1) The NOVA-Sensor acknowledges that the MODE button is pressed by lighting the
three dots on the numerical readout.
2) Once the MODE button is released, the numerical readout will flash “000” and “...”
for about ten seconds. During this time, the NOVA-Sensor is storing the zero reference
point, based on clean air applied to the sensor.
3) The NOVA-Sensor then begins a 15-second count-down, during which it displays the
numbers “030” through “000” on the read-out. During this time, the NOVA-Sensor is
simply waiting for the calibration gas to be applied and conveyed to the sensor.
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-9 December, 2003 911-9

!In order to save gas it is recommended to apply calibration gas as soon as the
15-second count-down begins. Up to 3 minutes delay is tolerable for cases
where the sensor head is at a remote location and the calibration gas must be
applied through a long pipe.
4) At this point, only the gas sensor head is being calibrated. During head calibration, the
output of the head is held at the “zero” level, so the digital read-out continues to alternate
between “CAL” and a small number that represents the zero gas concentration, relative
to the previous calibration. Additionally the CAL LED blinks. This condition can last for up
to 90 seconds.
5) When the gas sensor head is successfully calibrated, the head output will be held
constant at the new calibration level, and the readout will start to count up from the
previous zero setting to the new calibration.
!IMPORTANT: The calibration gas should be removed from the sensor headas
soon as the display begins to count up. Leaving the gas on at this point will
result in incorrect calibrations.
6) When the read-out displays exactly half-scale (“1.0” on a 2% sensor), the new
calibration reference for the test gas is stored. At the same time the CAL LED changes
from blinking to steady.
7) The 1% reading will be held for approximately 3 minutes, after which the read-out will
decrease. Once the read-out is below the LOW alarm setpoint or at zero, the NOVA-Sen-
sor returns to normal operation and the CAL LED is switched off. The microcontroller in
the NOVA-Sensor automatically stores the calibration in its internal non-volatile memory
for use in subsequent measurements.
During the calibration process, the 4-20 mA output is set to 2 mA and the relay outputs
are suppressed. The NOVA-Sensor automatically returns to normal operation when the
calibration is complete.
Failed or Incomplete Calibrations
If the calibration procedure is aborted (e.g. by not applying calibration gas), the NOVA-
Sensor will return to normal operation after a time-out period of 3 1/2 minutes. In this case
the NOVA-Sensor will use its original, pre-calibration data. Turning the power off will also
abort the calibration procedure. Common causes for incomplete calibration are:
1) Calibration gas runs out during calibration. In this case, wait for the NOVA-Sensor to
return to normal operation and repeat procedure with a fresh calibration gas bottle.
2) Calibration gas concentration too LOW. The NOVA-Sensor will not accept calibration
gas with concentration below 0.5% by volume. Using gas cylinders with low pressure will
often be interpreted by the NOVA-Sensor as low gas concentrations. In this case, wait
for the NOVA-Sensor to return to normal operation and repeat procedure with fresh
calibration gas bottle.
3) Gas applied at wrong time. Gas applied during step 2 above (too early, during clean
air sampling) will result in negative displays and inaccurate readings. If the gas is applied
too late (which may occur due to the pipe length when remote sensors are used) it may
MODEL GIR911 INFRARED CARBON DIOXIDE GAS NOVA-SENSOR
911-10 December, 2003 911-10

not reach significant levels before the 3 1/2 minute time-out and thus abort the calibration
procedure.
Balancing
“Balancing” the GIR911 Infrared Gas Sensor is performed by depressing the MODE
button per the instructions above, but do not apply the calibration gas. This serves
primarily to re-establish the zero reference of the detector.
Recalibration Schedule
Due to the extreme stability of the infrared gas sensor, recalibration is rarely required.
Under normal operating conditions, SST recommends that the gas detectors should be
balanced every 90 days per the instructions above. However, test gas should be applied
to the sensors on a scheduled basis to verify proper sensor operation. Before testing, do
a visual inspection to check for contamination of the sintered metal sensor cover, loose
parts, etc. Be sure to deactivate any connected equipment before applying test gas to the
detector to prevent false alarms!
NOVA-SENSOR OUTPUTS
The characteristics of the various NOVA-Sensor outputs are explained in more detail in
the following sections.
0 to 20 mA Current Loop
The current loop output is normally between 4 and 20 mA, and is a direct linear read-out
of gas concentration. Output is 4 mAwhen no gas being detected. Output is 20 mAwhen
the full scale gas concentration of gas (2.0% or 5.0%CO2) is being detected. The 0 to 20
mAcircuitrywillreliablyandaccurately(.002%typicalnonlinearity)drivealoadresistance
of between 100 and 800 ohms. The 0 to 20 mA circuitry is self calibrating and does not
require adjustment. The Safety Systems “Trim-Not” technology, eliminates the require-
ment for field adjustable trim-pots.
Should a malfunction occur in the sensor or the current loop wiring, the output will, of
course, be 0 mA. Before any calibration has been performed, the output will be 2 mA.
During the start-up time delay and during routine calibrations, the output remains at 4mA.
Relay Outputs
The NOVA-Sensor includes three (3) relays for connection to external devices. The LOW
alarm and HIGH alarmrelays operated whenthe concentration of gasmeasured exceeds
the respective setpoints. The fault relay transfers on detectionof a fault in theNOVA-Sen-
sor.
Each relay can provide either a normally open or normally closed dry contact output. The
LOW alarmrelay can beset as either latchingor non-latching - seesection“DIPSwitch
Settings”. The fault relay is always non-latching (self clearing).
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Relay Protection Circuitry
Heavy duty relay contacts are provided in the NOVA-Sensor. These contacts are rated
for resistive loads. If used for switching inductive loads, such as relay coils, lamps,
beacons, etc., you must provide suitable suppression at the load. This will prevent
burning the relay contacts, and also suppress harmful transients which can affect the
operation of electronic equipment. See figure 911-5 for the recommended protection for
DC and AC loads.
FINAL OPERATIONAL CHECK-OUT (CompTest™)
Once the NOVA-Sensor hasentered normal operation, afinal comprehensive output test
(CompTest)of all detector inputs and outputs is available. TheCompTest isa wayto verify
that the NOVA-Sensor relay outputs and 0 to 20 mA current loop are correctly operating.
It can also be used to determine if the peripheral equipment is properly connected to the
NOVA-Sensor.
The CompTest ramps the 0 to 20 mA current loop through each of its assigned values
while changing the relay outputs as well. Each output state for the 0 to 20 mA loop and
each of the three relays is held for about 2 seconds and repeated 3 times. The test lasts
for approximately 1 minute. At the completion of the test, the built-in test (BIT) is executed
and the unit is returned to normal PROTECTIVE MODE operation.
What keeps the CompTest from occurring during operation or by mistake?
BecausetheCompTestexercisesalloutputs,including LOWALARM andHIGHALARM
states, there are several built-in safe guards against its inadvertent use. The button
located on the side of the NOVA-Sensor (the Mode button) will not initiate a CompTest.
The remote reset input on the NOVA-Sensor is used to initiate the test, based on a coded
sequence of ON’s and OFF’s. Upon receiving the proper coded input (the CompTest
Safety Code), the NOVA-Sensor begins the test. The NOVA-Sensor will only start the
output tests if the proper Safety Code is entered. For additional security against inadver-
tent use, the Safety Code can only be entered during the first 6 minutes after the
NOVA-Sensor has been returned to normal operation. Requiring a special Safety Code
Figure 911-5 Relay Contact Protection Scheme
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to be entered within 6 minutes of applying power limits the CompTest to authorized
personnel during system commissioning and periodic inspections.
How to Start the CompTest
!WARNING: Do not execute the CompTest until verifying that all systems
connected to the NOVA-Sensor are properly configured to execute a test.
Failure to do so may result in an unnecessary dispatching of emergency
personnel.
The CompTest must be started within 6 minutes of entering Protection Mode. The
Safety-Code™ is entered into the NOVA-Sensor by using the remote Reset button, not
the MODE switch which is on the NOVA-Sensor housing.
You begin the test in either of the two ways described below.
To begin the Test if Power has just been applied
To begin the test wait at least 3 minutes after power up (but not more that 6 minutes).
Then enter the Safety-Code™as described below.
To begin the test in an already operational system
It is not necessary to remove and reapply system power to initiate entry to Protection
Mode. If the NOVA-Sensor is already powered up and in Protection Mode, press the
Sensor Reset Button and hold it in (active) for 20 to 30 seconds, then release it. This
causes the sensor to begin the normal power up sequence (as if power had beencycled).
Wait for 5 seconds after releasing Reset, then enter the Safety-Code asdescribed in the
following section.
Entering the Safety-Code™
After followingthepreviousinstructions toinsurethat theNOVA-Sensoris readytoaccept
the Safety Code, press the Reset Button for three (3) ON cycles (5 to 10 seconds each,
separated by 5 to 10 second pauses). This will cause the sensor to execute the
CompTest™. The sequence is summarized as follows:
Action Position: Hold For Duration of:
1ON 5 Seconds
2 OFF 5 Seconds
3ON 5 Seconds
4 OFF 5 Seconds
5ON 5 Seconds
6OFF
Upon accepting the Safety Code, the NOVA-Sensor will pause for 10 seconds and begin
the CompTest.
If an incorrect code is entered, the NOVA-Sensor will pause 15 seconds and initiate a
normal reset sequence prior to returning to normal operation.
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CompTest™Operational Sequence
Upon receipt of the Safety Code within the first 6 minutes of entering Protection Mode,
the following sequence is executed:
Fault Test
The following outputs are simultaneously toggled three (3) times, and are held in each
state for approximately 2 seconds.
0 to 20 mALoop Alternates between 0 and 4 mA
Fault Relay Toggles between Fault and no fault
LOW alarm relay Inactive
HIGH alarm relay Inactive
LOW Alarm Test
The following outputs are simultaneously toggled three (3) times, and are held in each
state for approximately 2 seconds.
0 to 20 mALoop Alternates between 4 and 12 mA
Fault Relay In Fault
LOW alarm Relay Toggles between active and inactive
HIGH alarm Inactive
HIGH Alarm Test
The following outputs are simultaneously toggled three (3) times, and are held in each
state for approximately 2 seconds.
0 to 20 mALoop Alternates between 4 and 20 mA
Fault Relay In Fault
LOW alarm Relay Inactive
HIGH alarm Relay Toggles between active and inactive
Upon completion of the CompTest, the built-in test (BIT) is executed and the system then
returns to normal operation. If desired, the output test can be repeated by again entering
the CompTest security code.
MAINTENANCE
The GIR911 is easy to service. Most service activities will require the lid of the detector
base or the enclosure of the GIR910 IR sensor head to be opened.
!CAUTION: Before opening lids or enclosures, the area must be free of
any combustible gasses!
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Replacing the sensor lamp
After extended use, the incandescent lamp in the sensor may fail. To replace, remove the
sintered metal cover from the GIR910 by loosening the set screw and then turning the
part of the enclosure with the sintered metal cap counter-clockwise. The incandescent
lamp is contained inside the plug-in gas detection element on the PC board assembly.
Lift the PC boardassembly fromthe housing, unplug anddiscard the gassensor element.
Replace with a new element available from SST.
Electronics Module Replacement
If the electronics module with digital readout ever has to be replaced, the new module
must be calibrated to the sensor head installed on the enclosure.
Spare Parts
Installations which require on-site spare parts inventory should order the following part
numbers:
40911-02 . . . . . . . Carbon Dioxide Electronics Module with digital readout
20286-5 . . . . . . . . . Plug-in Carbon Dioxide Infrared Detection element
TROUBLESHOOTING
Drifting/Shifting display
Drifting or shifting or otherwise unexplainable display (i.e. display of negative or positive
gas values with no apparent cause) on GIR911 Infrared NOVA-Sensors can have the
following causes:
1) Bad contact between electronics module and terminal blocks in enclosure. This effect
is noticeable when pressing on the installed electronics module from the top or when
twisting it.
2) Loosened or contaminated suitcase jumper on relay board of electronics module.
3) If anelectronics module thatis not calibrated orthat hadbeen calibrated with adifferent
sensor (in a different enclosure) is plugged into an enclosure, positive or negative gas
values may be displayed. In this case, make sure that alarming devices are disconnected
before plugging in, and that the unit is calibrated before re-connecting the alarming
devices.
Bad contacts may be fixed with the following procedure:
1) Unplug the electronics module and clean the two green connectors on the back of the
electronics module with a brush and alcohol. Clean the corresponding contacts on the
green terminal blocks in the enclosure in the same way.
2) Unplug the two suitcase jumpers located on the headers labeled “TOX” on the
lowermost printed circuit board of the electronics module stack (note jumper position for
later re-insertion). Clean contacts inside of jumper and on pin header. If possible, insert
a new clean suitcase jumper with gold plated contacts. Alternatively, the two header
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contacts at “TOX” may be connected by wire-wrap or soldering. When soldering, be
careful to apply little heat in order not to loosen the pin strip header from the printed circuit
board.
Wiring of the CHASSIS Terminal
The original wiring scheme of the field wiring in the terminal block on the bottom of the
GIR911 detector enclosure must be changed, if one or several of the following conditions
apply:
• the voltage at the local conduit or EARTH/GND is currently differing more than 2
volts from the voltage at the 0V/RETURN wire of the power supply, or is expected
to do so in the future
• the power supply used for the GIR911 must be floating with respect to
EARTH/GND
The reason for the change is that transient voltage suppressor diodes used in the GIR911
are internally connected to the CHASSIS terminal. This could cause problems in instal-
lations where the 0V/RETURN cable is supposed to be floating with respect to
EARTH/GND and/or where abnormal voltages on the conduit or local EARTH/GND are
expected. The problems in those cases could result from the diodes providing a conduct-
ing current path between the CHASSIS and the 0V/RETURN terminals.
The rewiring procedure will insulate the enclosure from the CHASSIS terminal and
connect the CHASSIS terminal to the 0V/RET cable. The rewiring consists of the
following steps:
1) Disconnect or shut off power to the GIR911 detector(s).
2) Open the enclosure lid.
3) Carefully remove the electronics module from the enclosure.
4) Identify the revision of the electronics module. Look for the marking “REV” followed by
a number on the topmost printed circuit board, in the clear space below the three digit
numerical readout.
5) If the revision is 1.3 or later, no change is necessary. If it is 1.0, 1.1 or 1.2, proceed.
6) Remove the wire connecting the CHASSIS terminal and the internal grounding
terminal on the metal enclosure.
7) Create a connection between the 24RETand the CHASSIS terminals with a wire about
1" long. If the 24RET terminal cannot be used due to too many wires, the connection can
also go from CHASSIS to BUTTON B.
8) Recheck the wiring, carefully insert the electronics module and attach the lid of the
enclosure.
9) Re-apply power and check for function. The modules do not have to be recalibrated.
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