Johnson Controls GS3000 Manuale utente
GS3000 Indoor Modbus Carbon Monoxide
Transmitter Installation Guide
Introduction
The GS3000 Modbus Carbon Monoxide (CO) Transmitter
uses an electrochemical sensor to monitor CO levels in a
range of 0 ppm to 500 ppm and communicates through an
RS-485 network configured for Modbus protocol.
Figure 1: GS3000 Modbus CO Transmitter
Important: Read these instructions carefully before
you install and commission the CO transmitter.
Failure to follow these instructions may result
in product damage. Do not use in an explosive
or hazardous environment, with combustible or
flammable gases, as a safety or emergency stop
device, or in any other application where failure
of the product could result in personal injury.
Take electrostatic discharge precautions during
installation and do not exceed the device ratings.
Dimensions
Figure 2: Dimensions of the GS3000 Modbus CO
Transmitter
Mounting
About this task:
• Mount the transmitter on a flat surface three to five feet
from the floor of the controlled area.
• Do not mount the sensor near doors, opening windows,
supply air diffusers, or other known air disturbances.
• Avoid areas with vibrations or rapid temperature
changes.
To install the transmitter, complete the following steps:
1. The transmitter has two integrated mounting tabs
on either side of the enclosure. Use a No. 10 screw
(not supplied) to mount the transmitter. See Figure
3.
2. To remove the cover from the enclosure, loosen the
4 Phillips screws in each corner of the enclosure.
See Figure 4.
3. Complete the wiring instructions outlined in the
Wiring section.
Figure 3: Integrated mounting tabs
Figure 4: Removing the cover
*241148400021-*
Part No. 24-11484-00021 Rev. —
2020-10-01
(barcode for factory use only)
GS3000, GS3001
Figure 5: Reinstalling the cover
4. Reinstall the cover and tighten the screws with a
Phillips screwdriver. See Figure 5.
Wiring
About this task:
This device has a half-wave type power supply so use
caution when you wire multiple devices. Ensure that the
circuit ground point is the same on all devices and on the
controller. This device is reverse voltage-protected and will
not operate if you connect the power supply backwards.
Important: Use 22 AWG shielded wire for all
connections and do not locate the device wires in the
same conduit as wires that supply inductive loads
such as motors. Disconnect the power supply before
you make any connections to prevent electrical shock
or equipment damage. Make all connections in
accordance with national and local codes.
Note: If you install the device at either end of the
network, install an end-of-line (EOL) termination
resistor (121 ohm) in parallel to the A (-) and B (+)
terminals. This device includes a network termination
jumper that connects the resistor correctly on the
Printed Circuit Board (PCB). Simply move the PCB
jumper to the EOL position and you do not require
an external resistor. Connect the ground wire of
the shielded pair to earth ground at the end of the
network, the master wire is not grounded. Do not
run bus wiring in the same conduit as line voltage
wiring.
Note: A network segment is a single-shielded wire
loop run between several devices (nodes) in a daisy
chain configuration. The total segment length should
be less than 4000 ft (1220 m) and the maximum
number of nodes on one segment is 255 for Modbus.
Nodes are any device that you connect to the loop
and include controllers, repeaters, and sensors
such as the CO sensor but does not include the EOL
terminators.
To wire the transmitter, complete the following
steps:
1. Connect the RS-485 network with a twisted shielded
pair to the terminals marked A-, B+, and SHIELD.
The positive wire connects to B (+), the negative
wire connects to A (-), and you must connect the
cable shield to the SHIELD terminal on each device.
See Figure 6.
Figure 6: Wiring connections
Figure 7: Daisy chain configuration
2. To install more devices, or to increase the network
length, requires the use of repeaters for correct
communication. The maximum daisy chain
length (segment) depends on transmission speed
(baud rate), wire size, and number of nodes. If
communication is slow or unreliable, it may be
necessary to wire two daisy chains to the controller
with a repeater for each segment. See Figure 7.
Network communication
Each device must have a unique Modbus address for
start-up and you must set the Modbus address before
connection to the network. Use the local DIP switch to
set the Modbus device address from 1 to 255. The factory
default baud rate is 9600. Other Modbus parameter
settings can be found in Modbus protocol. The CO sensor
operates as a subordinate and will not communicate
unless a master connects to the network. When the
master sends a request for information, the subordinate
answers the request.
If the device does not communicate correctly, first check
that you did not reverse the communication wires.
Then check that the subordinate address, baud rate,
transmission mode, parity bit, stop bit, and RTU mode
CRC polynomial are correct. Set the device address. See
GS3000 Indoor Modbus Carbon Monoxide Transmitter Installation Guide2
Table 1. Each device on the network must have a unique
address.
Table 1: Device address settings
Dip switch position Modbus
address
128 64 32 16 8 4 2 1
OFF OFF OFF OFF OFF OFF OFF ON 1
OFF OFF OFF OFF OFF OFF ON OFF 2
OFF OFF OFF OFF OFF OFF ON ON 3
OFF OFF OFF OFF OFF ON OFF OFF 4
↓↓↓↓↓↓↓↓ ↓
ON ON ON ON ON ON ON OFF 254
ON ON ON ON ON ON ON ON 255
Calibration
About this task:
The CO sensor features a simple snap-mount sensor pre-
calibrated PCB. You can replace the entire sensor PCB
with a new calibrated PCB without the removal of the
enclosure. This sensor swap requires no tools and you
can complete it in seconds. Disconnect the device wiring,
remove the old sensor PCB, snap in the new PCB and
reconnect the device power. There is no need to make any
adjustments or apply gas to the device when you use the
sensor swap method.
If necessary, calibrate the device or verify with CO gas.
This requires a field calibration kit that consists of a
bottle of gas, for example, 250 ppm CO in air, a tank
pressure regulator with flow restrictor, and the necessary
tubing with a calibration cap to cover the sensor. You can
calibrate at 68°F to 81°F (20°C to 27°C).
Verify with gas without removing the device cover. Use the
calibration cap attached directly to the port on the cover
to apply gas and monitor the output value. See Figure 8.
Remove the device cover to perform an actual calibration.
In this case, the gas calibration cap attaches to the sensor
fixture inside the enclosure. See Figure 9.
Figure 8: Calibration cap attached to external cover
port
Figure 9: Calibration cap attached to internal sensor
fixture
Continuously power the sensor for at least 30 min prior
to calibration. Calibrate the sensor first in clean air with
no CO gas present. To calibrate the sensor, complete the
following steps:
1. Adjust the ZERO pot on the sensor board until you
obtain a 0 ppm output.
2. Attach the gas supply.
3. Turn the regulator on/off knob fully off and attach
it to the 250 ppm gas bottle and firmly tighten it by
hand.
4. Moisten the sponge and squeeze out any excess
water.
5. Place the sponge in the cap so that it will not touch
the sensor but does not plug the hole in the side of
the cap.
6. Attach the cap to the fixture over the sensor.
7. Slowly turn the valve knob on the regulator to let
the gas flow. The regulator will restrict the flow rate
to the specified 200 ml/min and the sponge will
ensure the gas is in the right humidity range.
8. Wait for 5 min and adjust the SPAN pot on the
sensor board until the output value reads 250 ppm.
9. Close the valve on the tank and take the cap off
from the sensor. This completes calibration.
10. If the gas cap is too loose on the fixtures, wrap
electrical tape around the cap to tighten it.
Modbus protocol
Use the Modbus protocol in the CO sensor to assist
control system programmers who may need to add
support to their systems to communicate with this device.
The CO sensor communicates on a standard Modbus
network using RTU mode transmission. It operates as a
subordinate device, address from 1 to 255, and expects a
Modbus master device to transmit queries, which it will
answer. The network parameters, except for the device
address, are fixed at the factory to the most common
application. See Table 2 through Table 4 for network
parameters.
GS3000 Indoor Modbus Carbon Monoxide Transmitter Installation Guide 3
Table 2: RTU message format
Modbus framing 8-bit binary
Data bits Start bits: 1
Data bits: 8
Parity bits: none
Stop bits 1
Baud rate 9600
Duplex Half duplex
Error checking Cyclical redundancy check (CRC)
CRC-16 reverse 0xA001
Latency More than 3.5 characters, minimum
Table 3: Framing support and bit sequences
Framing support and bit sequences
RTU mode Start 1 2 3 4 5 6 7 8 Stop
Table 4: Modbus register addressing
Modbus
address
Offset Units Data type Access Notes
40001 +0 Word Read
Unsigned 16-bit integer
0x0000 = CO in normal status,
0x0001 = in abnormal status
40002 +1 PPM Word Read Unsigned 16-bit integer, CO
value
The function codes for RTU mode are shown in Figure 10 and the RTU function codes that the CO sensor supports are
shown in Figure 11.
Figure 10: Function codes, RTU mode
GS3000 Indoor Modbus Carbon Monoxide Transmitter Installation Guide4
Figure 11: Function codes, CO sensor
GS3000 Indoor Modbus Carbon Monoxide Transmitter Installation Guide 5
Technical specifications
Table 5: GS3000 Modbus Carbon Monoxide Transmitter technical specifications
Specification Description
Measurement Electrochemical
Sample method Diffusion
Measurement range 0 ppm to 500 ppm
Accuracy ±5 ppm or ±5% of reading, whichever is greater
32° to 122°F (0°C to 50°C), 15% RH to 90% RH
Operating conditions -4°C to 122°F (-20°C to 50°C), 15% RH to 90% RH, 0.9 atm to 1.1 atm
Stability <5% signal loss per year
Response time <35 s for 90% step change
Area coverage 7500 ft2 (700 m2) or 50 ft (15 m) radius
Power supply 24 VDC ±20%
Consumption 35 mA maximum
Wiring connections Screw terminal block, 14 AWG to 22 AWG
Enclosure (H x W x D) 4.1 in. x 2.8 in. x 1.9 in. (104 mm x 71 mm x 48 mm)
Modbus
Note: Modbus parameters may be factory customized
Hardware: 2 wire RS-485
Software: native Modbus MS/TP protocol (RTU)
Baud rate: 9600
Subordinate address range: 1 to 255
Parity: none
Stop bits: 1
CRC: A001 (CRC-16 reverse)
Country of origin Canada
Compliance Manufactured in an ISO 9001 Registered Quality System
CE Mark - Johnson Controls declares that this product is in
Compliance with the essential requirements and other relevant
provisions of the EMC Directive.
The performance specifications are nominal and conform
- acceptable industry standards. For application at
conditions beyond these specifications, consult the local
Johnson Controls office. Johnson Controls, Inc. shall not
be liable for damages resulting from misapplication or
misuse of its products.
Product warranty
This product is covered by a limited warranty, details of which can be found at www.johnsoncontrols.com/
buildingswarranty.
Software terms
Use of the software that is in (or constitutes) this product, or access to the cloud, or hosted services applicable to
this product, if any, is subject to applicable end-user license, open-source software information, and other terms
set forth at www.johnsoncontrols.com/techterms. Your use of this product constitutes an agreement to such terms.
Patents
Patents: https://jcipat.com
Single point of contact
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JOHNSON CONTROLS
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USA
GS3000 Indoor Modbus Carbon Monoxide Transmitter Installation Guide6
© 2020 Johnson Controls. All rights reserved. All specifications and other information shown were current as of document revision and
are subject to change without notice.
www.johnsoncontrols.com
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