Bulletin AQ-GSTC
3-23/64
®
Series GSTC Carbon Monoxide/Nitrogen Dioxide Gas Transmitter
Specications - Installation and Operating Instructions
Wall mount
with LCD
The Series GSTC Carbon Monoxide/Nitrogen Dioxide Gas Transmitter monitors
the gas concentration in underground parking garages and loading docks. The carbon
monoxide transmitter is used to measure the exhaust of gasoline engines, while the
nitrogen dioxide transmitter is used for diesel engines. The Series GSTC is compatible
with either BACnet or Modbus
to be used with almost any building management controller. The GSTC output is
communicated over an RS-485 wire via BACnet or Modbus
To maximize the accuracy of the Series GSTC, the sensor can be eld-calibrated using
the A-449 remote LCD display. When the sensor reaches the end of its life, the display
will indicate that the sensor needs to be replaced.
®
BACnet and Modbus
nodes in any segment to 32. Therefore, the transceiver may be rated at one unit load.
Fractional loads are also acceptable. The Series GSTC accounts as an eighth of a
load on the MSTP network.
WARNING
accordance with the job wiring diagram and in accordance with national and local
electrical codes. Use copper conductors only.
NOTICE
NOTICE
NOTICE
NOTICE
replacements will not be covered under warranty, but they can be revived by allowing
them to stabilize in an environment above 40% RH for 10 days. Once revived, they
need to be recalibrated before use.
INSTALLATION
NOTICE
• The transmitter should be mounted at normal breathing height, approximately 5 to 6
ft above the oor.
• The unit may be mounted in the horizontal or vertical position. It should be mounted
in an area that is shielded from direct contact with the elements or direct sunlight.
• Mount in an area that will prevent the sensor from having any direct contact with
water.
• The unit should be placed in an area that will give an average of the air quality. Do
not place the unit so it will receive direct engine exhaust. Prolonged exposure to
direct engine exhaust may damage the sensor.
communication protocol recommend limiting the number of
Disconnect power supply before installation to prevent electrical
shock and equipment damage. Make sure all connections are in
Use electrostatic discharge precautions (e.g., use of wrist straps)
during installation and wiring to prevent equipment damage.
Avoid locations where severe shock or vibration, excessive
moisture, or corrosive fumes are present.
Do not exceed ratings of this device, permanent damage not
covered by warranty may result.
The electrochemical sensors should be stored in an environment
with a minimum humidity level of 20% RH. If the sensor dries out,
These are general guidelines. Local laws or ordinances will take
precedence.
Wall mount
without LCD
®
communication protocol, allowing the transmitter
®
communication protocol.
Duct mount
3-45/64
[94.06]
3-1/8
[107.95]
4-17/32
[115.09]
5-7/64
[129.78]
SPECIFICATIONS
Sensor: Field replaceable electrochemical, 4 years typical lifespan.
Range: CO: 0 to 500 PPM, NO2: 10 PPM.
Output Drift: <5% per year in air.
Coverage Area: 5000 to 7500 sq ft typical.
Accuracy: CO: 2% FS, NO2: 3% FS, at the time of calibration.
Resolution: CO: 1 PPM; NO2: 0.1 PPM.
Temperature Limits: -4 to 122°F (-20 to 50°C).
Storage Temperature: For best sensor life, 32 to 68°F (0 to 20°C).
Humidity Limits: 15 to 90% RH constant; 0 to 99% RH intermittent.
Response Time: <45 s to 90% CO, <25 s to 90% NO2.
Span and Zero Adjustment: Via pushbutton, using optional A-449 display. Zero
only via BACnet or Modbus
Housing: UV resistant glass lled polycarbonate.
Output Signals: BACnet MS/TP or Modbus
communication protocol.
Power Requirements: 10 to 36 VDC or isolated 21.6 to 33 VAC.
Electrical Connection: Removable terminal block, knock outs for conduit tting.
Calibration: Via pushbuttons using A-449 auxiliary display. Span gas
concentration is eld selectable.
Enclosure Rating: IP64.
Weight: 1 lb (0.45 kg).
Agency Approvals: CE.
Figure 1 shows the location of the wiring terminal, 8 position DIP Switch SW1, used for
conguring the RS-485 address, the 4 position DIP Switch SW2, used for conguring
hardware and software options, sensor, span and zero adjustments, and status LEDs.
The device provides three LEDs to indicate status and activity. The LEDs are located to
the right of DIP Switch SW1. The yellow LED indicates that the unit is sending a BACnet
or Modbus
BACnet or Modbus
red LED will ash once periodically if the BACnet or Modbus
address is set incorrectly or the red LED will ash twice periodically if the auto serial
conguration is in progress.
®
communication protocol. The green LED indicates the unit is receiving a
Span
Sensor
DIP Switch
SW2
Wiring
Terminal
®
communication protocol.
®
communication protocol addressed to this specic device. The
2-15/64
[56.75]
Duct mountWall mount
®
RTU (switch selectable)
[85]
2-55/64
[73]
2-15/64
[57]
3-59/64
[100]
®
communication protocol
Zero
DIP Switch
SW1
Status
LEDs
DWYER INSTRUMENTS, INC.
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.
Modbus® is a registered trademark of Schneider Automation, Inc.
Phone: 219/879-8000
Fax: 219/872-9057
Figure 1
www.dwyer-inst.com
e-mail: info@dwyermail.com
Wall Mounting
TO
PWRCOM A(-)B(+)
TO
NEXT
PWRCOM A(-) B(+)
1. Remove the cover plugs from the face of the unit and the top cover.
2. Disconnect the display cable from the USB connector on the main circuit board (if
present).
3. Remove the desired conduit tting knock out and install conduit tting (not
provided).
4. Position the transmitter where it is to be mounted and mark the mounting holes in
each corner of the housing.
5. Drill or punch out marked locations.
6. Place the transmitter box over mounting holes on wall and align. Install wall mount
screws (not provided) in mounting holes.
7. Proceed with wiring diagrams according to Figures 3 and 4.
8. Set DIP Switches SW1 and SW2 as desired. Refer to Figure 5, Figure 6, and
Appendix I.
9. Reconnect the LCD cable to the USB port on the main circuit board (if present).
10. Replace cover and cover plugs on the face of the unit.
CO:
Locate GSTC carbon monoxide transmitter about 5 ft (1.5 m) off the oor. Carbon
monoxide weighs about the same as air and distributes evenly throughout the
monitored space. Install GSTC CO alarm at least 15 to 20 ft (4.6 to 6.1 m) away from
boiler or fuel burning heat source. Avoid extremely dusty, dirty, humid or greasy areas.
Do not place in direct sunlight or areas subjected to extreme temperature. Do not place
in turbulent air, near fans, heat vents, air conditioners, air returns or open windows.
Blowing air may prevent CO from reaching the CO sensor.
2:
NO
2 sensors should be mounted in the breathing zone, 4 to 6 ft (1.2 to 1.8 m) from the
NO
oor. This is primarily because NO
2 is a poisonous gas which should be detected in
the area where people would be exposed to it, but also because 4 to 6 ft from the oor
is an appropriate elevation to detect NO
2 gas.
Duct Mounting
Duct mounting kit includes an air ow pitot tube, air lter with barbed connections, two
short pieces of tubing, and one long piece of tubing.
1. Mount the pitot tube into the duct observing the ow direction marked on the pitot
tube.
2. Attach the two short pieces of tubing to the barbed connections on each side of the
air lter. See Figure 2.
3. Attach the remaining side of one of the short pieces of tubing to the barbed
connection on the transmitter.
4. Attach the remaining side of the other short piece of tubing to the high port on the
pitot tube.
5. Attach the long piece of tubing to the open barbed connection on the transmitter.
6. Attach the other end of the long tubing to the low port on the pitot tube.
Figure 3 shows how to connect the GSTC in a network containing a common power
supply. Use a cable containing two twisted pairs. One pair is to be used for the power
and common. The other pair is to be used for A(-) and B(+). Attach the shields together
with a wire nut. This conguration is not suitable for AC supplies. Use a DC supply
only. Care should be taken that there are not too many devices powered from the
same supply as voltage drops will occur in the wiring. If you have many devices, or
have long cable runs, the local supply conguration, shown in Figure 4, may be a
better choice.
1234
PREVIOUS
DEVICE
B(+)
A(-)
PWR
COM
ATTA CH SHIELDS
TOGETHER W/WIRE NUT
TO NEXT
DEVICE
B(+)
A(-)
PWR
COM
Figure 3 - Common Power Supply
Figure 4 shows how to connect the GSTC in a network containing individual local
supplies. Use a cable containing a single conductor and a twisted pair. The single
conductor is to be used for common, and the pair is to be used for A(-) and B(+).
Attach the shields together with a wire nut. Both AC and DC supplies are suitable for
this conguration.
1234
PREVIOUS
DEVICE
B(+)
A(-)
COM
TO
DEVICE
B(+)
A(-)
COM
-+
ATTA CH SHIELDS
TOGETHER W/WIRE NUT
Figure 4 - Local Power Supply
All devices in the network should be daisy-chained. Star connections and T connections
are not permitted.
The A(-) and B(+) lines must be terminated at both ends with a 120 ohm resistor. If
the GSTC is an end device it has an on-board resistor that may be used. See Table
1 to enable it.
The network must be biased properly. If needed, there are bias resistors on-board the
GSTC. No more than two sets of bias resistors should be enabled in the network. See
Table 1 to enable them.
WIRING
NOTICE
Figure 2
Wiring should comply with Electrical Characteristics of Generators
and Receivers for Use in Balanced Digital Multipoint Systems,
TIA-EIA-485-A-1998, Telecommunications Industry Association, 1998.
NOTICE
BACnet installations should comply with ANSI/ASHRAE Standard
135-2010 BACnet A Data Communication Protocol for Building
Automation and Control Networks, American Society of Heating, Refrigerating and
Air-Conditioning Engineers, Inc., 2010.
®
communication protocol installations should comply with
NOTICE
and Implementation Guide V1.02, Modbus
NOTICE
Modbus
®
communication protocol over Serial Line Specication
Modbus
®
Organization, Inc., 2006.
Communication wiring must be in a daisy-chain fashion. Star
connections are not permitted.
NOTICE
Cable shield must be connected to earth ground at one location
only.
Dip Switch Congurations
NETWORK BIAS
PROTOCOL NETWORK TERMINATION
Use DIP Switch SW1 (see Figure 5) to congure the RS-485 address of the device. A
valid address depends on the protocol selected. Valid BACnet addresses range from
1 to 127. Valid Modbus
default, the device is shipped with Modbus
®
communication protocol addresses range from 1 to 247. By
®
communication protocol selected and the
address set to 127, as shown in Figure 5. A valid and unused address should be set
before connecting to an existing network. See Appendix I to congure the required
address using DIP Switch SW1. The device will not function properly if an invalid
address is set. During the power up sequence, the LCD (if present) will display the
RS-485 address as the primary value and either “BAC” to indicate BACnet or “MOD” to
indicate Modbus
®
communication protocol as the primary text. If the RS-485 address
is invalid, the invalid address is shown as the primary value with “ERR” as the primary
text, and the red LED will periodically blink once.
ON
1 2 3 4 5 6 7 8
Figure 5
To activate auto serial conguration, set a valid RS-485 address using DIP Switch
SW1, connect the serial bus, common and power wires, and apply power. The device
will power up and begin examining the serial bus for communication.
When the device is installed ofine or away from the main network, it is necessary to
generate the appropriate trafc in order to congure the serial communication whether
BACnet or Modbus
®
communication protocol is selected. While the serial conguration
is in progress, the device may not respond. The device may require multiple read
requests to complete the serial conguration process.
The auto serial conguration process is completed once a message addressed to the
device is received and processed successfully. If the serial conguration of the bus
changes, a power cycle of the device is required to restart the auto serial conguration
process.
More detailed information for BACnet protocol can be found in Appendix II, and
information for Modbus
®
communication protocol can be found in Appendix III.
MENU
The menu is only shown if a display is present. Figure 7 below outlines the display
components. To enter the menu, press and hold both the SPAN and ZERO pushbuttons
for at least 3 seconds. The menu descriptions and list of the available values for each
standard menu item is shown on in Table 3. Table 4 lists the available values for each
manual menu item.
Use DIP Switch SW2 (see Figure 6) to congure other hardware and software options.
Table 1 shows available options. Table 2 shows supported congurations for either
BACnet or Modbus
®
communication protocol.
ON
1 2 3 4
Figure 6
DIP SWITCH SW2 FUNCTIONS
Switch On Off
1 - Protocol
2 - B(+) Bias Resister
3 - A(-) Bias Resister
4 - Terminating Resister
®
Modbus
511Ω Pull-up to 5V
511Ω Pull-down to GND
120Ω between A(-) and B(+)
BACnet
Pull-up not connected
Pull-down not connected
Open
Table 1
Auto Serial Conguration
Use the auto serial conguration to enable the device to determine the baud rate,
parity, and stop bits directly from the serial trafc. After a valid RS-485 address is
chosen, the GSTC can be quickly and easily deployed. The auto serial conguration
procedure assumes a serial conguration appropriate to the chosen protocol, shown
in Table 2. Otherwise, the serial communication must be congured manually in the
setup menu.
SUPPORTED CONFIGURATIONS
Protocol Supported Baud Rates Data Size Parity Stop Bits
BACnet 9600
19200
®
Modbus
38400
57600
76800
8
None 1
Even
Odd
None 2
1
115200
Table 2
Text
Secondary
Display
Text
Primary
Display
Numeric
Figure 7
Standard Menu Descriptions
BAC or MOD: Displays the RS-485 address
CAL: Start user CO or NO2 calibration process
AUT: Auto serial conguration enabled
RST: Reset settings to factory default
Manual Menu Descriptions
BAU: Baud rate selection (only available if AUT = OFF)
PAR: Parity selection (only available if AUT = OFF)
STP: Stop bits selection (only available if AUT = OFF)
Menu Navigation
A menu owchart, located in Appendix IV, illustrates the navigation process.
1. Press and hold the SPAN pushbutton while in the menu to move to the previous
menu item.
2. Press and hold the ZERO pushbutton while in the menu to move to the next menu
item.
3. Press and hold both the SPAN and ZERO pushbuttons for 5 seconds to activate
the current menu item. In the lower left corner of the display “SET” is shown to
indicate a setting change.
4. Press and hold either the SPAN or ZERO pushbutton to change the setting.
5. Press and hold both the SPAN and ZERO pushbuttons for 5 seconds to accept the
setting.
6. After 30 seconds of inactivity, the display will return to normal operation.
STANDARD MENU OPTIONS
Menu Name Value Description
BAC or MOD xxx ADR RS-485 address (view only)
CAL xxx PPM Current CO or NO2 concentration
AUT ON Auto-baud will start and return to the main menu
OFF Starts the manual serial conguration menu sequence
RST NO
YES Will reset settings to factory default
Table 3
Loading...