RKI Instruments 65-2650RK-04 User manual

RKI Instruments, Inc.
www.rkiinstruments.com
65-2650RK-04
Molecular Property Spectrometer
M2A Transmitter
Operator’s Manual
Part Number: 71-0634
Revision: P1
Released: 3/23/23
TM

2• 65-2650RK-04 Molecular Property Spectrometer M2A Transmitter Operator’s Manual
WARNING
Read and understand this instruction manual before operating instrument.
Improper use of the gas monitor could result in bodily harm or death.
Periodic calibration and maintenance of the gas monitor is essential for proper
operation and correct readings. Please calibrate and maintain this instrument
regularly! Frequency of calibration depends upon the type of use you have and
the sensor types. For most applications, typical calibration frequencies are
between 3 and 6 months but can be more often or less often based on your
usage.

65-2650RK-04 Molecular Property Spectrometer M2A Transmitter Operator’s Manual • 3
Product Warranty
RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in
materials, workmanship, and performance for a period of one year from date of shipment from
RKI Instruments, Inc. Any parts found defective within that period will be repaired or replaced, at
our option, free of charge. This warranty does not apply to those items which by their nature are
subject to deterioration or consumption in normal service, and which must be cleaned, repaired, or
replaced on a routine basis. Examples of such items are:
• Absorbent cartridges
• Pump diaphragms and valves
•Fuses
•Batteries
• Filter elements
Warranty is voided by abuse including mechanical damage, alteration, rough handling, or repair
procedures not in accordance with the operator’s manual. This warranty indicates the full extent
of our liability, and we are not responsible for removal or replacement costs, local repair costs,
transportation costs, or contingent expenses incurred without our prior approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES AND
REPRESENTATIONS, EXPRESSED OR IMPLIED, AND ALL OTHER OBLIGATIONS OR
LIABILITIES ON THE PART OF RKI INSTRUMENTS, INC. INCLUDING BUT NOT LIMITED TO,
THE WARRANTY OF MERCHANTABILITY OR FITNESS FOR APARTICULAR PURPOSE. INNO
EVENT SHALL RKI INSTRUMENTS, INC. BE LIABLE FOR INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL LOSS OR DAMAGE OF ANY KIND CONNECTED WITH THE USE OF ITS
PRODUCTS OR FAILURE OF ITS PRODUCTS TO FUNCTION OR OPERATE PROPERLY.
This warranty covers instruments and parts sold to users by authorized distributors, dealers, and
representatives as appointed by RKI Instruments, Inc.
We do not assume indemnification for any accident or damage caused by the operation of this gas
monitor, and our warranty is limited to the replacement of parts or our complete goods.

4• 65-2650RK-04 Molecular Property Spectrometer M2A Transmitter Operator’s Manual
Table of Contents
Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Mounting the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Wiring the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Information Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Viewing & Changing M2A Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

65-2650RK-04 Molecular Property Spectrometer M2A Transmitter Operator’s Manual • 5
Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Replacing Components of the M2A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Wiring the M2A in a Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Using the M2A in a 4-wire Modbus System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Chapter 9: Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Appendix A: Control Button Quick Reference Guide . . . . . . . . . . . . . . . . . . . . 58
Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Appendix C: Function Code 16 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6• Chapter 1: Introduction 65-2650RK-04 Transmitter Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the 65-2650RK-04 M2A Transmitter. This chapter also describes
the 65-2650RK-04 Transmitter Operator’s Manual (this document). Table 1 at the end of this
chapter lists the specifications for the M2A.
About the M2A Transmitter
The M2A transmitter is a fixed mount, continuous-monitoring detector head. All user adjustable
parameters may be accessed using push button switches. In addition, calibration may be
performed non-intrusively by use of a magnetic wand accessory which activates magnetic
switches through a window at the front face of the detector head.
The M2A displays the current gas reading on an OLED display which is visible through the
window in the cover (front face) and provides a 4 - 20 mA signal which indicates the target gas
reading for use by a gas monitoring controller, recording device, or programmable controller. The
M2A also provides an RS-485 Modbus output. Three sets of relay contacts, two controlled by the
gas alarms and one by the fail alarm, rated at 115 VAC 5 amps are available for controlling
devices such as lights or horns or for controlling higher rated relays.
Four operating modes allow you to display and change setup and calibration settings and change
the gas type. They are Calibration Mode, Configuration Mode, Gas Type Mode, and Modbus
Mode.
About this Manual
The M2A Transmitter Operator’s Manual uses the following conventions for notes, cautions, and
warnings.
NOTE: Describes additional or critical information.
CAUTION: Describes potential damage to equipment.
WARNING: Describes potential danger that can result in injury or death.

65-2650RK-04 Transmitter Operator’s Manual Chapter 1: Introduction • 7
Specifications
Table 1 lists specifications for the M2A Transmitter. Table 2 and Table 3 lists detection ranges,
accuracy statements, and specifications for the MPS LEL combustible gas detector.
Table 1: M2A Transmitter Specifications
Alarm Settings
(Alarm 1/Alarm 2)*
• Combustible Gas (%LEL): 10% LEL / 50% LEL
Construction
(housing)
Explosion-proof Junction Box, NEMA 4X
Controls • Three push button switches
• Three magnetic switches for non-intrusive calibration
Input Power 10 - 30 VDC
Weight 4.5 lbs.
Signal Output
• 4 to 20 mA with impedance maximums listed below:
-12 VDC input: 500 ohms impedance max
-24 VDC input: 1000 ohms impedance max
• RS-485 Modbus
* These are RKI factory settings. See “Viewing & Changing M2A Parameters” on page 30 to change the
alarm settings.
** Independent of zero drift
Table 2: MPS LEL Detection Ranges and Accuracy
Target Gas Formula Detection Range Accuracy
at 50% LEL
Butane C4H10 0 - 100% LEL ± 5% LEL
Ethane C2H60 - 100% LEL ± 5% LEL
Hydrogen H20 - 100% LEL ± 5% LEL
Isobutane HC(CH3)30 - 100% LEL ± 5% LEL
Isobutylene C4H80 - 100% LEL ± 5% LEL
Isopropanol C3H8O 0 - 100% LEL ± 10% LEL
Methane CH40 - 100% LEL ± 3% LEL
Methyl Ethyl Ketone C4H8O 0 - 100% LEL ± 5% LEL
Octane C8H18 0 - 100% LEL ± 5% LEL
Pentane C5H12 0 - 100% LEL ± 5% LEL

8• Chapter 1: Introduction 65-2650RK-04 Transmitter Operator’s Manual
WARNING: When using the M2A, you must follow the instructions and warnings in this
manual to assure proper and safe operation of the M2A and to minimize the risk
of personal injury. Be sure to maintain and periodically calibrate the M2A as
described in this manual.
Applications
The MPS combustible detector is most effective in the following applications:
• High concentrations of hydrogen sulfide (H2S) or silicones present where sensor
poisoning is a common problem
• High-humidity environments where catalytic or IR sensors may not hold up
• Environments more likely to have mixtures of hydrocarbons present
Propane C3H80 - 100% LEL ± 6% LEL
Propylene C3H60 - 100% LEL ± 5% LEL
Toluene C7H80 - 100% LEL ± 12% LEL
Xylene C8H10 0 - 100% LEL ± 12% LEL
NOTE: The MPS sensor will respond to other combustible gases, but the accuracy has
only been determined for these 14 gases.
Table 3: MPS LEL Combustible Gas Detector Specifications
Sampling Method Diffusion
Area Classification Explosion-proof for Class I, Groups B, C, and D
Operating Temperature
Range
-20ºC to +50ºC (-4ºF to +122ºF)
Humidity Range 0 - 100% RH (non-condensing)
Pressure Range 80 - 120 kPa
Response Time T90 in 25 seconds
Dead Bands
•Methane(CH
4): 3% LEL
• All other gases: 5% LEL
NOTE: If the M2A’s or a connected controller’s dead band setting is
2% LEL for an MPS channel, a reading will not be displayed until it
has exceeded the MPS sensor's internal dead band.
Table 2: MPS LEL Detection Ranges and Accuracy
Target Gas Formula Detection Range Accuracy
at 50% LEL

65-2650RK-04 Transmitter Operator’s Manual Chapter 2: Description • 9
Chapter 2: Description
Overview
This chapter describes external and internal components of the M2A Transmitter. The transmitter
is a 4 - 20 mA type detector head. It consists of the MPS LEL detector, calibration adapter/splash
guard, terminal PCB, the M2A junction box, and the detector junction box. The two junction box
configuration is intended for situations where the detector needs to be installed at an inaccessible
location. The detector junction box can be installed at the inaccessible location and the M2A
junction box can be installed in a more readily accessible area.
External Description
This section describes the junction boxes and all external components of the M2A transmitter.
Figure 1: M2A External Components
Magnetic
Wand
Terminal
Strip
3/4 NPT Conduit Hub3/4 NPT Conduit
Hub, Plugged
Calibration Adapter/
Splash Guard
3/4 NPT
Conduit Hub
M2A
Junction
Box MPS LEL Detector
Detector
Junction Box
Mounting Slot (2x)
3/4 NPT
Conduit Hub
Window

10 • Chapter 2: Description 65-2650RK-04 Transmitter Operator’s Manual
Gas Detector
The MPS™ LEL detector is made up of the MPS combustible gas LEL detector housed and
encapsulated in a pipe nipple. The MPS sensor is immune to poisons, can be used in high
humidity, and does not require calibration as often as catalytic combustible sensors. It also
responds accurately to 14 different combustible gases.
A porous flame arrestor coated with a hydrophobic film that repels liquids is on one end of the
detector and allows sample gas to enter the detector. Four color coded leads, red, white, green, and
black, extend from the other end of the detector. Use the leads when connecting the detector to the
terminal block in the junction box.
M2A Junction Box
The M2A’s cast aluminum junction box protects the terminal PCB and wiring connections made
to the terminal PCB. Use the three 3/4 NPT conduit hubs to wire the remotely installed IR LEL
detector and connect wiring from an external device, typically an RKI controller. The top hub is
shipped with a factory installed and sealed conduit plug to avoid leaks into the junction box. If
necessary, the conduit plug can be removed and the top hub can be used for wiring.
WARNING: If the top conduit port is used for wiring, be sure to seal the threads to ensure
water does not enter the junction box. See “Wiring the M2A Transmitter” on
page 17 for complete wiring instructions.
Use the junction box’s two mounting holes to mount the M2A to a vertical surface at the
monitoring site. The window in the cover on the front of the junction box allows you to view the
OLED display and use the magnetic wand to actuate the magnetic control switches so you can
perform non-intrusive calibration. Removing the cover allows you to access the interior of the
junction box.
Detector Junction Box
The detector junction box is intended to be installed remotely from the M2A junction box. The
MPS LEL combustible gas detector is factory-installed in the bottom 3/4 NPT conduit hub. A
terminal strip is provided for wiring connections and the detector is factor- wired to one side of
this terminal strip. The other side of the terminal strip is for user-supplied wiring to the detector
terminal strip located in the M2A junction box. This wiring should go through the top 3/4 NPT
conduit hub. Three spacers installed on the back of the junction box controls the distance of the
junction box from a mounting surface.
Calibration Adapter/Splash Guard
A calibration adapter/splash guard is installed on the MPS LEL detector. A fitting at the bottom of
the calibration adapter/splash guard allows a length of tubing to be connected for calibration and
routed to a more easily accessible location (near the M2A junction box is optimal for ease of
calibration). The calibration adapter/splash guard also protects the detector from splashing water
or direct water spray.

65-2650RK-04 Transmitter Operator’s Manual Chapter 2: Description • 11
Magnetic Wand
The magnetic wand is a short plastic rod with a magnet in one end. It is used to actuate the
magnetic control switches on the control PCB while the junction box cover is still installed so that
non-intrusive calibration can be performed.
Internal Description
This section describes the internal components of the M2A. The internal components of the M2A
include the terminal PCB which provides for all the wiring connections to the M2A and the
control PCB which displays the gas reading and has the control buttons.
Figure 2: M2A Internal Components
Terminal PCB
The terminal PCB is encapsulated in epoxy for protection against moisture and physical damage.
It is mounted into the rear of the junction box with three standoffs and rests on a thin layer of
foam. A banana jack is screwed into each of the standoffs and is used for mounting the control
PCB. The terminal PCB converts the electrical output from the detector to a signal which can be
displayed by the OLED display, a 4 - 20 mA signal (that is proportional to the detection range),
and an RS-485 Modbus output signal. The 4 - 20 mA signal may be used by a recording device,
gas monitor controller, or programmable controller. The Modbus output may be used to connect
the M2A to a Modbus network. The terminal PCB also controls three relays: one fail and two gas
alarm.
NO
Control PCB
Junction Box
Terminal PCB
3/4 NPT Conduit
Opening for Wire Entry
M2A TRANSMITTER
RKI INSTRUMENTS
3/4 NPT Conduit Opening, Plugged

12 • Chapter 2: Description 65-2650RK-04 Transmitter Operator’s Manual
Two columns of plug-in style terminal strips are used to make all wiring connections to the M2A.
The column on the left consists of the power/signal, detector, and Modbus terminal strips. The
column on the right consists of the relay terminal strips. A 20 position connector at the bottom of
the terminal PCB is used to connect the terminal PCB to the control PCB with a ribbon cable. A 5
position connector on the left side of the terminal PCB is used by factory or field service
personnel to program the M2A. A factory adjust pot just above the programming connector is
used to set the detector current.
Figure 3: Terminal PCB Component Location
Power/Signal Terminal Strip
The power/signal terminal strip is a three position plug-in style terminal strip located at the top of
the left terminal column. It is used to connect 24 VDC power to the M2A and to connect the 4 - 20
mA output signal to a device.
The signal output, the S terminal, does not have to be connected for the M2A to function. The S
terminal is used if you want to connect the 4 - 20 mA output signal to another device such as a gas
monitoring controller, chart recorder, or programmable controller (PLC).
Detector Terminal Strip
The detector terminal strip is a four position plug-in style terminal strip and is the middle terminal
strip in the left terminal column.
NOTE: The detector is factory-wired to the M2A. See “Wiring the M2A Transmitter” on
page 17 for all wiring procedures related to M2A.
Modbus Terminal Strip
The Modbus terminal strip is a three position plug-in style terminal strip and is the bottom
terminal strip in the left terminal column. It allows connection of the M2A into a Modbus
network.
Relay
Terminal
Strips
Termination Jumper
Ribbon Cable Connector
Detector Current Adjust Pot
Detector Terminal Strip
Power/Signal Terminal Strip
Programming Connector
(Factory Use)
Ground Jumper
Modbus Terminal Strip
C NC NO
ALARM 1 C NC NO
ALARM 2
C NC NO FAIL
- S +
A B C
RS 485 PWR/SIG
R W G B
LEL

65-2650RK-04 Transmitter Operator’s Manual Chapter 2: Description • 13
Relay Terminal Strips
The right column of terminal strips consists of, from top to bottom, the fail, alarm 1, and alarm 2
relay terminal strips. They are three-position plug-in style terminal strips. The relay terminal
strips are used to connect devices such as lights and horns that are controlled by the relay contacts.
The relay contacts are rated at 115 VAC, 5 amps. The relay contacts may also be used to control
higher rated relays.
Termination Jumper
A two pin header with a termination jumper installed is located below the Modbus terminal strip.
Leave this jumper installed unless directed to remove it for a Modbus installation. See “Chapter 8:
RS-485 Modbus Output” on page 46 for a description of using the M2A in a Modbus system.
Ground Jumper
A two pin header with a jumper installed is located along the left side of the terminal PCB. Leave
this jumper installed unless directed to remove it for a Modbus installation. See “Chapter 8: RS-
485 Modbus Output” on page 46 for a description of using the M2A in a Modbus system.
Control PCB
The OLED display and control switches are located on the control PCB. It is installed on top of
the terminal PCB by lining up its three spacing standoffs with the banana jacks in the terminal
PCB mounting standoffs and pushing it onto the banana jacks. The jacks retain the control PCB.
Figure 4: Control PCB Component Location
ENTER
UP/YES
DOWN/NO
ENTER
DOWN/NO
UP/YES
Push Button
Control Switches
Fail LED
Magnetic Switches
Alarm 1 LED
OLED Display
RX LED
TX LED
Alarm 2 LED
RKI INSTRUMENTS
M2A TRANSMITTER

14 • Chapter 2: Description 65-2650RK-04 Transmitter Operator’s Manual
OLED Display
The OLED display is located at the top of the control PCB. It indicates the current gas reading and
displays messages and parameters in the M2A’s programs.
Control Buttons
The M2A includes three push button switches that allow you to enter the M2A’s operating modes,
navigate through the modes, update settings, and save changes to the settings. The push button
switches are located along the bottom edge of the control PCB (see Figure 4). The UP/YES button
is on the left, the DOWN/NO button is in the middle, and the ENTER button is on the right.
Just above each push button switch is a magnetic switch with the same function as the push button
switch below it. The magnetic switches are for use in non-intrusive calibration. They are actuated
by bringing the magnetic wand close enough to them to actuate them. Although the magnetic
switches have the same functions as the push button switches, it is not practical to use them for
operations other than calibration because it is not possible to actuate two magnetic switches at
once with only one magnetic wand. Since displaying the Information Screen only requires the use
of one switch, the wand may be used to show the Information Screen (see “Information Screen”
on page 25).
Table 4: M2A Control Button Functions
Switch Function
UP (YES) • Saves settings
• Changes the displayed setting
• Enters the Calibration Program
• Enters Gas Type Mode (press with DOWN/NO
button)
• Enters Configuration Mode (press with ENTER
button)
DOWN
(NO)
• Cancels setting changes
• Changes the displayed setting
• Enters Gas Type Mode (press with UP/YES
button)
• Enters Modbus Mode (press with ENTER
button)
• Displays the Information Screen
ENTER • Initiates operations
• Enters Configuration Mode (press with UP/YES
button)
• Enters Modbus Mode (press with DOWN/NO
button)
• Functions as an alarm reset switch

65-2650RK-04 Transmitter Operator’s Manual Chapter 2: Description • 15
Status LEDs
The M2A includes five status LEDs that are located above the display (see Figure 4).
• Fail LED
The fail LED turns on when the M2A is experiencing a fail condition. A fail condition can
be caused by a detector failure or low detector signal.
• Alarm 1 LED
The alarm 1 LED is on when the M2A is experiencing an alarm 1 condition.
• Alarm 2 LED
The alarm 2 LED is on when the M2A is experiencing an alarm 2 condition.
• RX & TX LED’s
These LED’s indicate data being received (RX) and transmitted (TX) when the M2A’s
Modbus output is operating.

16 • Chapter 3: Installation & Startup 65-2650RK-04 Transmitter Operator’s Manual
Chapter 3: Installation & Startup
Overview
This chapter describes procedures to mount the M2A Transmitter in the monitoring environment
and wire it to input power and devices.
Mounting the M2A Transmitter
1. Select a mounting site that is representative of the monitoring environment. Consider the
following when you select the mounting site.
• Select a site where the M2A is not likely to be bumped or disturbed. Make sure there is
sufficient room to perform start-up, maintenance, and calibration procedures.
• Select a site where the target gas is likely to be found first. For lighter gases, mount the
detector near the ceiling; for heavier gases, mount the detector near the floor.
• The junction boxes should be mounted no further than 200 feet from each other.
2. At the monitoring site, use #10 screws through the junction box’s two mounting holes to
secure the junction box to a vertical surface. Figure 5 and Figure 6 show the outline and
mounting dimensions for the M2A transmitter and the MPS LEL detector. Mount the M2A
with the detector facing down as shown in the following figures.
Figure 5: Outline & Mounting Dimensions, M2A Transmitter
.30 (2X)
3/4 NPT
Conduit Hub
5.23
.47 (2X)
2.41
5.00
1.02
5.86
4.59

65-2650RK-04 Transmitter Operator’s Manual Chapter 3: Installation & Startup • 17
Figure 6: Outline & Mounting Dimensions, MPS LEL Remote Detector
Wiring the M2A Transmitter
WARNING: Always verify that the power source is OFF before making any wiring
connections.
1. Remove the junction box cover.
2. Grasp the control PCB by its edges.
Rubber
Spacer,
3X
J-Box
.382.70
.75
MPSLEL
Detector
3/4 NPT
Female
3.65
9.00 MAX
Calibration
Adapter/
Splash Guard
5.25

18 • Chapter 3: Installation & Startup 65-2650RK-04 Transmitter Operator’s Manual
3. Gently pull until the control PCB is pulled away from the banana jacks. Take care not to pull
too hard and damage the cable which connects the control and terminal PCBs.
4. Let the control PCB hang by the cable. The terminal strips are now visible on the terminal
PCB. The control PCB may be left hanging while wiring is done. If desired, the control PCB
may be disconnected from the cable and set aside while wiring.
5. The detector leads are factory wired. Verify that the detector leads are wired to the detector
terminal strip as shown in the applicable figure below:
Figure 7: MPS LEL Detector Wiring
6. To gain access to a plug-in terminal strip for wiring, pull it out of its socket by grasping the
wall between two terminal positions with needle nose pliers and pulling. Be careful not to
exert too much force on the wall to avoid damage to the terminal strip. The detector terminal
strip and the alarm 1 relay terminal strip may be removed by grasping them with your fingers
if the adjacent terminal strips have been removed.
Green
Black
Cable
Shield
Install conduit seal
within 18 inches
Red
White
Detector
Terminal
Strip
C NC NO
ALARM1 C NC NO
ALARM2
C NC NO FAIL
Green
White
Calibration Adapter/SplashGuard
Install conduit seal within
2 inches(for Group B
environments) or 18
inches (for Groups C and
D environments)
Black
Red
Detector J-Box
M2A
J-Box
- S +
A B C
RS 485 PWR/SIG
R W G B
LEL
MPS LEL
Detector

65-2650RK-04 Transmitter Operator’s Manual Chapter 3: Installation & Startup • 19
WARNING: If the M2A is installed in a hazardous location, use appropriately rated
conduit, conduit fittings, and appropriate construction technique that
complies with the local electrical code.
In addition, use appropriately rated conduit, conduit fittings, and appropriate
construction technique to maintain the NEMA 4X environmental rating of
the junction box and avoid water entering the junction box at the conduit
ports.
WARNING: To maintain the explosion proof classification of the M2A, a conduit seal
must be used within 18 inches of the junction box conduit hub used for
wiring to the controller.
7. Guide multi conductor shielded cable or cables or wires in conduit through the conduit port on
the left side of the junction box. The number of cables or wires needed will depend on whether
the M2A is wired to a gas monitoring controller or just to power, whether any relays are used,
and whether the Modbus output is used.
WARNING: If the top conduit port is used for wiring, be sure to seal the threads to ensure
water does not enter the junction box. A conduit seal, which is normally
required to maintain the junction box’s hazardous location rating, will also
help to prevent water from entering through the top port.
NOTE: If the M2A is being wired to a PLC or DCS device, see “Appendix B: PLC
and DCS Device Wiring” on page 59, then continue with step 8.
8. Use the following recommendations to determine how to wire the M2A:
• If Modbus connections will not be used and only the PWR/SIG connections will be used,
use a two or three conductor shielded cable or two or three wires in conduit for
connections to the power/signal terminal strip depending on whether or not the signal (S)
terminal is used. The S terminal has a 4 - 20 mA output, but if you do not need to monitor
this signal and do not connect to the S terminal to access this signal, the M2A will still
function completely.
Table 5: Wire Size for PWR/SIG Connections
Max Distance to
Controller
w/18 Gauge Wire
Max Distance to
Controller w/16 Gauge
Wire
Max Distance to
Controller w/14 Gauge
Wire
2,500 ft. 5,000 ft. 8,000 ft.

20 • Chapter 3: Installation & Startup 65-2650RK-04 Transmitter Operator’s Manual
• If the PWR/SIG connections and one or more relays are used, route the connections to the
M2A in conduit. Use shielded cable in the conduit for the PWR/SIG connections and
unshielded cable or individual wires for the relay connections. Make sure any wire or
cable used for relay wiring is appropriately rated for the power that it will carry.
NOTE: If shielded cable is used for the PWR/SIG connections, leave the cable
shield’s drain wire insulated and disconnected at the M2A. You will connect
the opposite end of the cable’s drain wire at the controller or device.
• If the M2A will be wired into a Modbus network, see “Chapter 8: RS-485 Modbus
Output” on page 46.
See Figure 8 for field wiring connections to the M2A.
Figure 8: Wiring the M2A to a Controller and Alarm Devices
9. Re-install the control PCB (and ribbon cable if necessary). Be sure the ribbon cable is routed
down below the control PCB so it will not be damaged by the cover when it is screwed back
on.
10. Secure the junction box cover to the junction box.
11. Make controller, device, and relay connections as appropriate. If shielded cable is used for the
PWR/SIG connections, connect the cable shield’s drain wire to an available chassis ground at
the gas monitoring controller, recording device, or programmable controller.
Alarm 1
Alarm Device
Fail Alarm
Device
Alarm Device
Power
PWR/SIG
- S +
Typical Alarm
Wiring Shown
4 - 20 mA In (S)
(24 VDC) +
RKI Controller
Terminals
RS 485
A B C
(24 VDC) -
Alarm 2
Alarm Device
See
Modbus
Wiring
See
Detector
Wiring
C NC NOC NC NO
ALARM 2 C NC NO
ALARM 1 FAIL
LEL
R W G B