Emerson MRLDS-450 Installation Manual

MRLDS-450 Refrigerant Gas
Detection Installation and Operation
Manual

026-1316 Rev 2

Emerson Commercial & Residential Solutions

1065 Big Shanty Road NW, Suite 100

Kennesaw, GA 30144 USA

770-425-2724 • www.emerson.com

Email: [e-mail]

CONTENTS

1 INTRODUCTION .............................................................................................................................. 1

1.1. ABOUT THIS MANUAL....................................................................................................................... 1

1.2. ICONOGRAPHY .................................................................................................................................. 1

1.3. GENERAL SAFETY REQUIREMENTS................................................................................................... 2

1.4. SAFE CONNECTION OF ELECTRICAL DEVICES .................................................................................. 3

2 PRODUCT DESCRIPTION ............................................................................................................. 4

2.1. INTENDED USES/APPLICATIONS ........................................................................................................ 4

2.2. MRLDS-450..................................................................................................................................... 4

2.2.1. MRLDS-450 Product Overview................................................................................................ 4

2.2.2. MRLDS-450 Design Features .................................................................................................. 5

2.2.3. MRLDS-450 Component Overview .......................................................................................... 6

3 INSTALLATION ............................................................................................................................... 7

3.1. GENERAL INFORMATION ................................................................................................................... 7

3.2. RESTRICTIONS ................................................................................................................................... 8

3.3. MECHANICAL INSTALLATION ........................................................................................................... 8

3.4. ELECTRICAL INSTALLATION ............................................................................................................. 8

3.4.1. Preparations............................................................................................................................. 8

3.4.2. Power and Signal Wiring ......................................................................................................... 9

3.4.3. Relay Wiring........................................................................................................................... 10

3.4.4. Modbus RTU RS-485 Interface .............................................................................................. 10

3.4.5. Conclusion.............................................................................................................................. 13

3.5. SET UP MRLDS-450 APPLICATION IN E2 ...................................................................................... 14

3.5.1. New Installation: Uploading the MRLDS-450 Description File to E2 .................................. 14

4 OPERATION.................................................................................................................................... 23

4.1. OVERVIEW OF NORMAL OPERATION .............................................................................................. 23

4.1.1. Applying Power and the Start-up Sequence ........................................................................... 23

4.1.2. Verifying Analog Signals........................................................................................................ 23

4.1.3. Verifying the Modbus Signal .................................................................................................. 24

4.1.4. Status Indication..................................................................................................................... 24

4.1.5. Switch Functions .................................................................................................................... 25

4.1.6. Reset System to Factory Default Settings............................................................................... 27

4.2. MRLDS-400 SERIES APPLICATION ................................................................................................ 27

4.2.1. Enable Bluetooth® Connection.............................................................................................. 27

4.2.2. Checking Status ...................................................................................................................... 28

4.2.3. Instrument Configuration ....................................................................................................... 29

5 CARE AND MAINTENANCE ....................................................................................................... 36

5.1. MAINTENANCE INTERVALS ............................................................................................................ 36

5.2. ADJUSTMENTS................................................................................................................................. 37

5.2.1. Introduction ............................................................................................................................ 37

5.2.2. General Calibration Procedure ............................................................................................. 37

Table of Contents • v

5.2.3. Zero Adjustment..................................................................................................................... 38

5.2.4. Span Adjustment .................................................................................................................... 39

5.2.5. System Bump Test .................................................................................................................. 40

5.3. TROUBLESHOOTING ........................................................................................................................ 41

5.3.1. Hexadecimal Format ............................................................................................................. 41

5.3.2. Fault Codes ........................................................................................................................... 41

5.4. SENSOR MAINTENANCE.................................................................................................................. 44

5.4.1. Replacing Sensor Module ...................................................................................................... 45

5.5. CLEANING THE INSTRUMENT.......................................................................................................... 46

6 ADDITIONAL INFORMATION................................................................................................... 47

6.1. SENSOR PRINCIPLE ......................................................................................................................... 47

6.1.1. Electrochemical Sensors........................................................................................................ 47

6.1.2. Catalytic Bead Sensors .......................................................................................................... 47

6.1.3. Semiconductor Sensors .......................................................................................................... 48

6.1.4. Infrared Sensors..................................................................................................................... 48

6.2. DISPOSING OF THE INSTRUMENT .................................................................................................... 49

6.2.1. Disposing of the Electrical and Electronic Equipment ......................................................... 49

6.2.2. Disposing of Sensors.............................................................................................................. 49

6.3. TECHNICAL SPECIFICATIONS .......................................................................................................... 50

6.3.1. General Specifications........................................................................................................... 50

7 ORDERING INFORMATION....................................................................................................... 51

vi • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

1 Introduction

1.1. About this Manual

Thank you for investing in an MRLDS-450 Gas Detector. To ensure operator safety
and the proper use of the gas detector, please read the contents of this manual for
important information about the operation and maintenance of the instrument.

IMPORTANT: Before installing this product, carefully read and strictly follow the
instructions in the manual.

1.2. Iconography

Alert Icon Description

Danger Imminently hazardous situation which, if not avoided,

will result in serious injury or death.

Warning Potentially hazardous situation which, if not avoided,

could result in serious injury or death.
Potential electrical shock hazard which, if not avoided,
could result in serious injury or death.

Caution Potentially hazardous situation which, if not avoided,

could result in physical injury or damage to the product
or environment. It may also be used to alert against
unsafe practices.

Important Additional information on how to use the product.

Table 1-1 - Icons

About this Manual Introduction • 1

1.3. General Safety Requirements

IMPORTANT: Before using this product, carefully read and strictly follow the instructions
in the manual. Ensure that all product documentation is retained and available to anyone
operating the instrument.

DANGER! This instrument is neither certified nor approved for operation in
oxygen-enriched atmospheres. Failure to comply may result in personal injury or death.

DANGER! This instrument has not been designed to be intrinsically safe for use in areas
classified as being hazardous locations. For your safety, DO NOT use it in hazardous
(classified) locations.

WARNING! Use this product only for the purposes specified in this document and under
the conditions listed.

CAUTION! In the event of an alarm or over-range condition, the sensor must be
re-calibrated to ensure continued accuracy.

CAUTION! This product must be re-calibrated if installed in a non-room condition
environment (For example, temperature or humidity extremes).

CAUTION! The gas diffusion path can become occluded (moisture, dust, debris, frozen
condensation) over time resulting in reduced or complete lack of gas detection and
alarming function. Routine visual inspection of the gas detector and bump testing are
suggested to ensure proper gas detection and alarm function.

CAUTION! Except for maintenance detailed in this manual, these products should only be
opened and/or serviced by authorized Emerson Technical Support personnel.
Failure to comply may void the warranty.

CAUTION! Operator assumes responsibility for complying with all laws, rules and
regulations governing the use of this product.

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CAUTION! Use only genuine Emerson parts and accessories. Failure to comply may
impair the operation of the product and/or void the warranty.

CAUTION! Only operate the product within the framework of a risk-based alarm signaling
concepts.

WARNING! The gas diffusion path can become occluded (moisture, dust, debris, frozen
condensation) over time, resulting in reduced or complete lack of gas detection and
alarming function. Routine visual inspection of the gas detector and bump testing are
recommended to ensure proper gas detection and alarm function. For information on

calibrating the sensor, refer to the “Care and Maintenance” section of this manual.

1.4. Safe Connection of Electrical Devices

WARNING! Before connecting this instrument to electrical devices not mentioned in this
manual, consult the manufacturer or a qualified professional. Failure to comply may result
in personal injury and/or damage to the product.

Safe Connection of Electrical Devices Introduction • 3

2 Product Description

2.1. Intended Uses/Applications

MRLDS-450 Gas Detection Series instruments continuously monitor ambient air
(indoor or outdoor) for the following gas types:

• Refrigerants

• Oxygen

• Toxic and combustible gases

The MRLDS-450 refrigerant gas detector is designed for use in refrigeration
applications and with the integrated audio-visual alarm indication, can be operated
as a stand-alone unit (with additional local alarm signaling as required), or it may be
connected to a facility's building management system (BMS). It enables compliance
with refrigerant safety codes (ASHRAE 15 and EN378) and alarms to alert
personnel in the event of a refrigerant leak.

DANGER! This instrument is neither certified nor approved for operation in
oxygen-enriched atmospheres. Failure to comply may result in EXPLOSION.

DANGER! This instrument has not been designed to be intrinsically safe for use in areas
classified as being hazardous locations. For your safety, DO NOT use it in hazardous
(classified) locations.

2.2. MRLDS-450

2.2.1. MRLDS-450 Product Overview

The Emerson MRLDS-450 continuously monitors indoor or outdoor ambient air for
the following gases:

• Refrigerants

• Oxygen

• Toxic and combustible gases

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With the integrated Modbus communication, analog output and relays, the
instrument can be operated as a stand-alone unit or as a third-party device capable
of accepting digital and/or analog outputs from the gas detectors, such as a Building
Management System (BMS) or a Supervisory Controller. The instrument is
designed to be installed in non-classified, non-hazardous, permanent locations.

Figure 2-1 - MRLDS-450

2.2.2. MRLDS-450 Design Features

• Transmitter: IP66 rated ABS enclosure

• Power options:

• 24VAC

• 19.5 to 28.5VDC

• Diagnostic/Status LED (3 color): Green, Orange, and Red

• Configurable output signal options

• 3× Relays (high alarm/low alarm/fault)

• 1× Analog Output (4 to 20mA, 0 to 5V, 0 to 10V, 1 to 5V, 2 to 10V)

• Digital Output (Modbus RTU signal)

Bluetooth communication allows for full instrument configuration, initiation of
calibration, bump test and functional test mode, and viewing of status information
via the corresponding MRLDS-450 iOS/Android app.

Non-intrusive magnetic wand can be used to initiate calibration of the device.

MRLDS-450 Product Description • 5

2.2.3. MRLDS-450 Component Overview

Figure 2-2 - MRLDS-450 Component Locations

# Component Description

1 M16 Cable Glands (x6)

2 Rubber Gasket

3 Internal Alarm Buzzer

4 Power Connections (x2)

5 Digital Connection (Modbus)

6 Analog Connection

7 Tactile Switch #1

8 Ribbon Cable Connection (To Sensor)

9 Tactile Switch #2

10 Relay 3 Connection (FAULT)

11 Relay 2 Connection (HIGH)

12 Relay 1 Connection (LOW)

13 Magnetic (Mag) Switch #1

14 Magnetic (Mag) Switch #2

15 M20 Cable Glands (x2)

Table 2-1 - MRLDS-450 Component Descriptions

6 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

3 Installation

CAUTION! The manufacturer of this product requires that a bump test or calibration be
performed following installation to verify instrument functionality.

3.1. General Information

Every detail of installation site selection is critical to ensure overall system
performance and effectiveness. Strict compliance and considerable thought must be
given to every detail of the installation process, including, but not limited to the
following:

• Regulations as well as local, state, and national codes that govern the installation of
gas monitoring equipment.

• Electrical codes that govern the routing and connection of electrical
cables to gas monitoring equipment.

• The full range of environmental conditions to which the instruments

• The physical characteristics of the gas or vapor to be detected.

• The specifics of the application (For example, possible leaks, air movement/draft,
etc.)

• The degree of accessibility required for maintenance purposes.

• The types of optional equipment and accessories that will be used with the system.

• Any limiting factors or regulations that would affect system performance or
installations.

• Wiring details, including:

• The MRLDS-450 enclosure provides the following cable gland openings:

• 2×, M20, supports 10-14mm cable outer diameter

• 6×, M16, supports 4-8mm cable outer diameter

• Secondary circuit must be supplied from an isolating source.

• The wiring for the relays must be selected and fused according to the rated
voltages, currents, and environmental conditions.

• If stranded conductions are used, ferrule should be used.

• To comply with RFI immunity regulations, it is necessary to ground the shield of
the communications cable at the PLC, GDA controller, front-end controller or
Building Management System (For example, the chassis, the ground bus-bar,
etc.).

power and signal

will be exposed.

General Information Installation • 7

3.2. Restrictions

The installation location must have appropriate supply power available for the
instrument (For example, 19.5 to 28.5VDC or 24VAC). This ultimately determines
the distance the instrument can be mounted from the controller or power supply.

3.3. Mechanical Installation

WARNING! DO NOT allow the lid/sensor to hang from the ribbon cable. Failure to
comply may result in damage to the product.

1. Using the provided hardware, securely mount the MRLDS-450 Gas Detector
according to the product dimensions, maximum wiring lengths and following
considerations:

a. Environment: the full range of environmental conditions when selecting a

location.

b. Application: the specifics of the application (possible leaks,

etc.) when selecting a location.

c. Accessibility: the degree of accessibility required for maintenance purposes

when selecting a location.

d. Target Gas: the specific gravity of the target gas when selecting

instrument.

2. Using a 5/32” (4mm) hex key/allen wrench (not included) remove the lid and
disconnect the ribbon cable from the base.

3. Set the lid and rubber gasket aside to be reinstalled later.

air movement/draft,

the height of the

3.4. Electrical Installation

3.4.1. Preparations

IMPORTANT: If analog output is configured for 4 to 20mA output, ensure that the current
loop is connected to a sinking current loop monitor before powering on the instrument.
Otherwise, a fault may be displayed indicating an open loop condition. If analog output is
unused, ensure it is configured as a voltage output (1-5V) to prevent an open loop fault

condition. The analog output is designed as sourcing.

WARNING! Ensure wiring for relays and connections for sensor(s) are made before
applying power.

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CAUTION! This product uses semiconductors which can be damaged by electrostatic
discharge (ESD). When handling the printed circuit boards (PCBs), observe proper ESD
precautions so that the electronics are not damaged.

3.4.2. Power and Signal Wiring

The product comes with cable glands and plugs pre-installed. The power entry cable
gland is without a gland plug. Use the appropriate cable glands to insert and connect
the wires for power and signal to the appropriate terminals as indicated in the figure
and wiring table that follow. The PCB terminal blocks are a pluggable type and may
be removed to aid termination.

IMPORTANT:

• For 24VAC installations sharing a transformer in a daisy-chain configuration, neutral
polarity must be maintained for all instruments.

• 24VAC power polarity must not be reversed.

• For a more robust system, a dedicated transformer for each MRLDS is recommended to
prevent damage caused by wiring errors.

• Fasten terminal screws.

Power Description Label Wiring Termination

24VDC/VAC IN

Power

Digital Output

Analog
Output

Table 3-1 - Power and Signal Wiring

24VDC/VAC OUT
(power daisy chain
terminal)

MODBUS Network
Communications

Voltage or Current
Output

24V IN: - 24VDC/VAC neutral/ground

24V IN: + 24VAC neutral

24V OUT: - 24VDC/VAC neutral/ground

24V OUT: + 24VAC neutral

MODBUS: B RS-485 “B” (inverted)

MODBUS: A RS-485 “A” (non-inverted)

MODBUS: GND RS-485 GND

MODBUS: SH RS-485 Shield

ANALOG: - Analog output ground

ANALOG: + Analog output signal (+)

3.4.3. Relay Wiring

WARNING! Relays are rated for 0 to 30V AC/DC. DO NOT apply main power onto these
relays.

Electrical Installation Installation • 9

Using appropriate cable glands, connect the wires for relay 1, relay 2, and relay 3 to
the terminals as indicated in Table 3-2.

Relay Function

1 Low Alarm

2 High Alarm

3 Fault Alarm

Table 3-2 - Relay Wiring Configuration

When configured according to the factory default settings, the relays are
de-energized during normal operation (not fail-safe). Fail-safe mode can be
configured. When configured for Failsafe operation, relays are energized during
normal operation. Failsafe operation ensures relays are triggered in cases of power
failure at the instrument. In Failsafe operation, normally open and normally closed
terminals are reversed as indicated in Table 3-3

Terminal Normal Operation Failsafe Operation

NC Normally Closed Normally Open

COM Common Common

NO Normally Open Normally Closed

Table 3-3 - Relay Wiring Terminal Configuration

3.4.4. Modbus RTU RS-485 Interface

For the Modbus RS-485 network use a 16 to 24 AWG (0.5 to 1mm2) 3-core,
2 twisted pair + ground, shielded cable with 120Ω characteristic impedance.

IMPORTANT: Recommended: Belden 3105A (or equivalent).

The Modbus address, baud rate, stop bit, parity and slave termination is configured
through the setup menu. No jumpers or hardware switch settings are required.
Ensure that the communication parameters within the network, including the BMS,
are configured identically.

To ensure optimal performance of the Modbus network ensure the following
guidelines are implemented:

• Ensure instruments are configured in a single bus topology, connecting multiple buses in
parallel or branching multiple units from the main bus, may introduce impedance mismatches,
reflections and/or signal distortions.

• Avoid long stubs when connecting instruments to the bus, stubs should be less than one (1)
meter in length.

10 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

• Ensure A/B signal polarity is maintained throughout RS-485 network.

• Connect cable shield drain to physical earth or ground at the controller only.

• Ensure cable shield integrity is maintained throughout RS-485 network.

For Modbus end-of-line termination, use 150Ω ohm resistor or termination block

P/N 537-2711. Do not use MRLDS 120Ω ohm on-board termination with Site
Supervisor or E2.

Site Supervisor Setup - Device and COMM

Figure 3-1 - Site Supervisor Network Setup

Electrical Installation Installation • 11

E2 Setup - Device and COMM

Figure 3-2 - E2 Network Setup

3.4.5. Conclusion

After all wiring is completed, power the transmitter and confirm operation, and then
prepare to seal the enclosure.

Align the enclosure gasket (primary transmitter and remote sensor if equipped),
replace the lid, and tighten the six (6) screws. Tightening torque should be limited to
tightening by hand, and should be uniform in pattern.

12 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

3.5. Set Up MRLDS-450 Application in E2

Note: Installing the MRLDS-450 requires version E2E 4.10F01 or later. You must
add a description file for version E2 3.10F01 or less.

3.5.1. New Installation: Uploading the MRLDS-450 Description File to E2

The MRLDS-450 requires adding a description file (P/N 527-0754) and license key
to E2 version 3.0X or later. Contact Customer Service to obtain this information:

Email: [e-mail]
Phone: [phone] Option 4

Note: UltraSite32 software should be installed to perform a
description file upload.

Connect to E2 using UltraSite32

1. Launch UltraSite program and login.

2. View the Directory Level and then Site Level.

3. Right-click Site Level and click Connect.

4. Locate the E2 where the MRLDS_450.dsc will be installed.

5. Right-click the unit and select Upload Description File.

6. Click Browse to select the appropriate description file (5270754.dsc) file for

MRLDS-450 from the computer and click Open.

7. Click Upload. A window will display the description file was successfully

imported. Click OK. The description file should appear inside the window.

8. Once completed, disconnect from the E2 and reboot the E2 controller.

Note: Do not omit the step of rebooting the controller.

Device Setup

E2 Serial Port Setup

1. Log into the E2 controller.

2. Press I, , , and  (General Controller Information), then

press B twice to move to the C3: Serial tab.

Set Up MRLDS-450 Application in E2 Installation • 13

3. Press the down arrow key to the COM Connection where the device is
wired.

4. Press D (LOOK UP) and select MODBUS-1, MODBUS-2 or
MODBUS-3, then press > to set configuration.

5. Press D to select options and set the MODBUS connection as follows:

COM Baud: 19200 Baud

COM Data Size: 8

COM Parity Even

COM Stop Bits: 1

6. Press >to set configuration, then J to save changes.

7. Press H to return to the Home screen.

Adding the MRLDS-450 Application in E2

1. Press Ithen , , and  to enter Connected I/O Boards and

Controllers.

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2. Press B to move to the C3: ECT tab. Highlight the MRLDS-450

application and enter the desired number of devices under Quantity up to a
maximum of 15.

Figure 3-3- ECT Tab

3. Press J to save the changes.

4. Press H to return to the Home screen.

Commissioning the MRLDS-450

1. Press Ithen , , and  to enter the Network

Summary screen.

Set Up MRLDS-450 Application in E2 Installation • 15

2. Highlight the MRLDS-450 to be commissioned and press D

Figure 3-4- Network Summary Screen

3. If a box with Select Network appears on the screen, select the MODBUS
number where you configured the device – either MODBUS-1,

MODBUS-2, or MODBUS-3 and press >

Figure 3-5- Select MODBUS output

16 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

4. Select the address for the device and press >

Figure 3-6- Select Device Address

Note: The MODBUS address must be the same as the address assigned on the
device.

Set Up MRLDS-450 Application in E2 Installation • 17

5. A window will appear. Press > to continue.

Figure 3-7- Set Physical Address for the MRLDS-450

6. Press J to save the assigned address.

7. Press H to return to the Home screen and press I then , ,
and  to enter the Network Summary screen again.

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8. After a few seconds, the MRLDS-450 should appear Online.

Figure 3-8- MRLDS-450 Network Summary Screen Online Status

Set Up MRLDS-450 Application in E2 Installation • 19

Viewing the Status

1. Press I then , ,  and  (this is equivalent to pressing

I, , ) or use the cursor to navigate to MRLDS-450

and press >

Figure 3-9- Configured Applications

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2. View the status of the detector on the MRLDS-450 Summary screen and

press E to go to Setup.

Figure 3-10-MRLDS-450 Status Screen

Set Up MRLDS-450 Application in E2 Installation • 21

4 Operation

4.1. Overview of Normal Operation

CAUTION! Before leaving the instrument for normal operation, check the configuration
for proper settings and check calibration.

4.1.1. Applying Power and the Start-up Sequence

After applying power, the instrument will go through a start-up sequence
(initialization, audible/visual test and self-test sequence). After the start-up sequence
completes, the instrument will enter a warm-up period to allow the sensor element
to stabilize before reporting a valid output.

Step Description

1 Switch power on.

Observe start-up sequence and warm-up phase:

• Green LED will blink at 0.5 Hz for about five (5) minutes

2

3

Table 4-1 - Instrument Start-up Sequence

• Modbus flag for warm-up is set

• Buzzer is off

• Relay state is “no alarm”

• Gas reading invalid

Observe normal operation:

• Green LED is steady on

• Modbus flag for warm-up is cleared

• Buzzer is off

• Relay state is “no alarm”

• Gas reading valid

4.1.2. Verifying Analog Signals

The MRLDS-450 gas detector features a single configurable analog output. During
normal operation, the analog output of the instrument is proportional to the detected
gas concentration and can be selected from the following:

• 1 to 5V (default)

• 0 to 5V

22 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

• 2 to 10V

• 0 to 10V

• 4 to 20mA

The MRLDS-450 Gas Detector uses different voltage/current values to indicate
various modes of operation. In normal operation the relative gas concentration
output is indicated by the analog output level. Output level is proportional to the gas
level as shown in Table 4-2:

Gas Concentration 1-5V 0-5V 2-10V 0-10V 4-20mA

0% 1V 0V 2V 0V 4mA

50% 3V 2.5V 6V 5V 12mA

100% 5V 5V 10V 10V 20mA

Table 4-2 - Gas Concentration Levels

The instrument may also enter several special states, these are indicated by the
specific analog output levels indicated in Table 4-3:

Mode of Operation 1-5V 0-5V 2-10V 0-10V 4-20mA

Instrument Fault ≤ 0.3V N/A ≤ 0.6V N/A ≤ 1.2mA

Offline Mode/Maintenance 0.75V N/A 1.5V N/A 3mA

Drift below zero 0.95V N/A 1.9V N/A 3.8mA

Normal operation 1-5V 0-5V 2-10V 0-10V 4-20mA

Measuring range exceeded 5.12V 5.12V 10.25V 10.25V 20.5mA

Fault on analog interface > 5.25V > 5.25V > 10.5V > 10.5V > 21mA

Table 4-3 - Analog Output Levels

4.1.3. Verifying the Modbus Signal

The MRLDS-450 Gas Detector provides a Modbus RTU digital interface. All status
messages and most parameters that can be accessed and/or configured through the
Bluetooth® interface can also be accessed and/or configured via RS485 for Modbus
RTU.

4.1.4. Status Indication

The MRLDS-450 gas detections provide external indication of its current
operational state via audible and visual feedback. Visual indication of the instrument
status is provided by a single tri-color LED (Green/Red/Orange). MRLDS-450 gas
detection instruments also provide relays outputs. Instrument states and
corresponding outputs are shown in Table 4-4.

Overview of Normal Operation Operation • 23

State LED Buzzer

Warm-up OFF OFF OFF

Relay 1
(LOW)

Relay 2
(HIGH)

Relay 3
(Fault)

Normal

Low Alarm ON OFF OFF

High Alarm

Offline

Fault

Negative Gas Fault

Zero Cal. Fault OFF OFF OFF

Span Cal. Fault OFF OFF OFF

Table 4-4 - Status Indicators

OFF OFF OFF

ON ON OFF

OFF OFF OFF

OFF OFF ON

OFF OFF ON

4.1.5. Switch Functions

User interaction with the MRLDS-450 gas detector is accomplished through the use
of two magnetic switches located on the bottom of each unit. To actuate a magnetic
switch, apply the supplied magnetic wand to the relevant switch location as shown
in Figure 4-1.

24 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

Figure 4-1 - Magnetic Switches

Switch locations above are referred to in this document as MAG#1 and MAG#2.
Depending on the duration the switch is held, a short “tap” or long “hold” will be
detected.

• To carry out a tap function, tap the relevant switch location for one (1) second, until a

single “chirp” is heard and remove the wand to confirm a “tap.”

• To carry out a hold function, do not remove the magnetic wand after

but continue to hold for more than five (5) seconds, until a double “chirp” is heard,
and remove wand to confirm a “hold.” If either switch is held for more than 30
seconds, a stuck switch fault will be indicated.

• To interact with the instrument without use of the magnetic wand, two internal push

button tactile switches may be used. Remove the lid without removing the ribbon
cable to access. Internal switches T

MAG#1 and MAG#2.

ACT#1 and TACT#2 mirror the functions of

the first “chirp”

The function of each switch depends on the current state of the instrument. Refer to
Table 4-5 for switch functions in each instrument state.

Overview of Normal Operation Operation • 25

State Switch 1 Tap Switch 1 Hold Switch 2 Tap Switch 2 Hold

Warm-up Enable

Normal

Low Alarm Mute Buzzer Ack. Latched Alarm

High Alarm Mute Buzzer Ack. Latched Alarm

Offline

Fault Mute Buzzer Ack. Latched Fault

Negative Gas
Fault

Zero Cal. Fault

Span Cal. Fault Acknowledge Fault

Table 4-5 - Switch Functions

Bluetooth®
Connectivity

Start Zero
Calibration

Mute Buzzer Start Zero Calibration

Acknowledge
Fault

Disable
Bluetooth®
Connectivity

Start Span Calibration

4.1.6. Reset System to Factory Default Settings

To reset system to factory defaults, remove lid and hold TACT#1 and TACT#2
simultaneously for 30 seconds. Instrument will restart to confirm factory reset.

Alternatively, see Section 4.2.3.4., Reset to Factory Defaults, for instructions on
resetting instrument configuration via the MRLDS-400 Series App.

4.2. MRLDS-400 Series Application

Download the MRLDS-400 Series App.
The companion smartphone application allows users to perform a variety of

functions to configure and interact with the MRLDS-450 gas detector, including:

• View real-time measurements

• Configure instrument

• Test outputs

• Calibrate/Bump test instrument

• Generate customizable calibration certificates

4.2.1. Enable Bluetooth® Connection

1. Enable Bluetooth® discovery by tapping MAG#1 for 1-second. (After 10 seconds, the
device will indicate that it is discoverable with audible heartbeat until it has been
paired, discovery has timed-out, or has been canceled.)

26 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

2. Launch the MRLDS-400 Series App and select the Bluetooth® icon at the bottom of
the screen to initiate a scan.

3. Select MRLDS-450 default alias is “18TMAE” from the list of available

gas detectors.

4. When prompted, enter the passkey (default is “123456”).

IMPORTANT: Default alias, passkey, and unlock code can be changed via the
MRLDS-400 Series App’s configuration menu. Default values should be changed after
instrument installation for security purposes.

4.2.2. Checking Status

Current Instrument status can be viewed from the Home tab. The Home tab displays
the following status information:

Figure 4-2 - MRLDS-400 Series App Home Tab

No. Description

1 Alias, user-configured instrument name.

2 Serial, instrument 8-digit serial number.

3 Gas, gas type currently detected by instrument.

4 Status ring, provides visual indication of various instrument states (expanded on Table 4-7)

5 Live measurement, current measurement in given measurement units.

6 Measurement unit, displayed measurement unit (PPM/PPB/%LEL/%VOL)

Table 4-6 - MRLDS-400 Series App Home Tab Features

MRLDS-400 Series Application Operation • 27

State Status Ring Description

Warm-up Green Gas detector stabilizing after power on or restart.

Normal Green Normal Operation.

Low Alarm Yellow Gas measurement has exceeded low alarm setpoint.

High Alarm Red Gas measurement has exceeded high alarm setpoint.

Offline Orange Gas Detector in maintenance mode and is not actively monitoring gas.

Fault Orange A fault has been detected.

Negative Gas
Fault

Zero Cal.
Fault

Span Cal.
Fault

Table 4-7 - Status Ring of Various Instrument States

Orange

Orange

Orange

Gas Detector calibration has drifted below zero, requires zero
calibration.

Error occurred during zero calibration. Zero calibration has not be
updated. Zero calibration required.

Error occurred during span calibration. Span calibration has not be
updated. Span calibration required.

4.2.3. Instrument Configuration

For security, access to configuration and calibration options are restricted to
authorized users only. Access to these functions require use of an unlock code.

To unlock instrument configuration, go to the Configure tab to set up the device.
When prompted, enter unlock code to access device configuration. (The
instrument’s default code is “1234”). Instrument will remain unlocked until
Bluetooth® connection has ended.

IMPORTANT: Default alias, passkey, and unlock code can be changed via the
MRLDS-400 Series App’s configuration menu. Default values should be changed after
instrument installation for security purposes.

4.2.3.1. Change Alias

To allow easy identification of a given instrument, an alias can be assigned to each
instrument. This alias is displayed when searching for an instrument via Bluetooth®,
on Calibration Cert and in the Home tab. To set the alias:

• On the Configure tab select Alias. Enter the required alias for instrument and select
OK.

• The instrument must be restarted for change to take effect. Selecting the Home tab
then Restart will reboot device.

• Reconnect to instrument to confirm the alias has been updated.

28 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

4.2.3.2. Change Unlock Code

To prevent unauthorized access to instrument configuration and calibration, the
default instrument unlock code should be changed during commissioning. To
change unlock code:

• On the Configure tab select Modbus Unlock Code. Enter the new 4-digit unlock

code for instrument and select OK.

• The instrument must be restarted for changes to take effect. Selecting the Home tab,

then Restart will reboot the device.

• Reconnect to instrument to confirm the unlock code has been updated.

IMPORTANT: If the custom unlock code is forgotten, the unlock code may be reset to
default value (1234) by resetting system to factory defaults. Refer to Section 4.1.6., Reset
System to Factory Default Settings for the system reset procedure. Note that a system reset
will return all custom system configurations to defaults.

4.2.3.3. Change Bluetooth® Passcode

To prevent unauthorized access to instrument status, the default instrument
Bluetooth® passcode code should be changed during commissioning. To change
Bluetooth® passcode:

• On the Configure tab select Bluetooth Passcode. Enter new 6-digit passcode for the

instrument and select OK.

• The instrument must be restarted for changes to take effect. Selecting the Home tab,

then Restart will reboot the device.

• Reconnect to instrument to confirm the Bluetooth

IMPORTANT: If the custom passcode is forgotten, the unlock code may be reset to default
value (123456) by resetting system to factory defaults. Refer to Section 4.1.6., Reset System
to Factory Default Settings for system reset procedure. Note that a system reset will return
all custom system configurations to defaults.

® Passcode has been updated.

MRLDS-400 Series Application Operation • 29

4.2.3.4. Reset to Factory Defaults

Instrument configuration may be reset to factory defaults via the smartphone
application:

• On the Configure tab select Reset to Factory Default and select OK to confirm.

• The instrument will automatically restart and disconnect from the smartphone
application.

WARNING! Resetting system to factory defaults will remove all custom system
configuration including unlock code and Bluetooth passcode. After system reset custom
unlock and Bluetooth passcodes should be configured to prevent unauthorized access and
reconfiguration of instrument.

4.2.3.5. Alarm Configuration

Low Alarm Setpoint

The value above which a low alarm condition occurs. The low alarm setpoint must
be less than the high alarm setpoint and greater than the low alarm limit. The low
alarm limit is the fixed minimum limit that is sensor–specific and not editable.

Range of acceptable setpoints is displayed when updating the parameter. To update
the setpoint:

• On the Configure tab select Alarm then Low Alarm Setpoint. Enter the new
setpoint and select OK to confirm.

IMPORTANT: In instruments with an oxygen sensor installed, low alarm behavior
operates in a depletion mode where gas measurements BELOW the low alarm setpoint
initiate a low alarm. This allows monitoring of oxygen displacement and enrichment
scenarios.

IMPORTANT: To prevent intermittent alarm operation at the setpoint due to measurement
noise this instrument implements hysteresis at the setpoint. Once the alarm level is
exceeded, the gas measurement must return a fixed percentage below the alarm threshold
before the alarm is disabled. Typical hysteresis value is set at 5% of full scale; however,

this is sensor-specific and non-editable.

High Alarm Setpoint

The value above which a high alarm condition occurs. The high alarm setpoint must
be less than the sensor full scale range and greater than the low alarm setpoint.

Range of acceptable setpoints is displayed when updating the parameter. To update
setpoint:

• On the Configure tab select Alarm then High Alarm Setpoint. Enter the new
setpoint and select OK to confirm.

30 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

IMPORTANT: To prevent intermittent alarm operation at the setpoint due to measurement
noise, this instrument implements hysteresis at the setpoint. Once the alarm level is
exceeded, the gas measurement must return a fixed percentage below the alarm threshold
before the alarm is disabled. Typical hysteresis value is set at 5% of full scale; however,

this is sensor-specific and non-editable.

Alarm Latching

Enabling alarm latching will maintain alarm or fault condition even after the alarm
or fault condition is no longer active. When latched, the alarm or fault condition
must be manually acknowledged before the condition will be cleared. This allows
transient alarm or fault conditions to be identified.

If an alarm is latched, for example, the condition has occurred but is no longer active,
an acknowledgment button will appear on the Home screen. Select this button to
acknowledge the latched condition and clear the alarm or fault.

When disabled, the alarm or fault status clears automatically as soon as the condition
is no longer active. To configure:

• On the Configure tab select Alarm then Alarm Latching. Select Enable/Disable

and OK to confirm.

4.2.3.6. Modbus Configuration

Address

Sets instrument address for connection to RS-485 Modbus interface. (Default: 1).
To set address:

• On the Configure tab select Modus, then Address. Select 1-247 and OK to confirm.

IMPORTANT: Ensure all instruments on RS-485 bus have been configured with unique
node addresses. If two instruments have been configured with same address, bus contention
will occur preventing communications with these instruments via the RS-485 interface.

Baud Rate

Sets instrument baud rate for connection to RS-485 Modbus interface baud).
To set baud rate:

• On the Configure tab select Modus then Baud Rate. Select 9600/19200 (default)

and OK to confirm.

MRLDS-400 Series Application Operation • 31

Stop Bits

Sets instrument stop bits for connection to RS-485 Modbus interface (Default: 1 stop
bits). To set number of stop bits:

• On the Configure tab select Modus then select Stop Bits. Select 1 or 2 and OK to
confirm.

Parity

Sets instrument parity for connection to RS-485 Modbus interface (None, Odd, or
Even (default).

To set parity:

• On the Configure tab select Modus then select Parity. Select None/Odd/Even and
OK to confirm.

IMPORTANT: Stop bits must be set to 1 where parity is Odd or Even.

Enable 120Ω Termination

For optimal communication reliability, in RS-485 Modbus networks the last
instrument physically connected to the RS-485 bus must include a 120Ω termination
resistor. This is to reduce the potential for electrical signal reflection on long buses
due to impedance mismatches. Typically, this requires a physical resistor with the
same characteristic impedance of the bus cable to be installed on the bus.

MRLDS-450 instruments include this termination resistor on all instruments and
allow this termination to be enabled via this configuration setting without the need
for an external physical resistor. To enable this termination resistor:

• On the Configure tab select Modbus then select Enable 120Ω Termination.
Select Enable/Disable and select OK to confirm.

IMPORTANT: Termination resistor should only be enabled on last instrument physically
connected to RS-485 bus. An external resistor should not be connected where this is enabled
on the instrument.

4.2.3.7. Output Configuration

Analog Output Range

Sets instrument analog output range. Available ranges: 1-5V (default), 0-5V,
0-10V, 2-10V, 4-20mA. To set range:

• On the Configure tab select Outputs, then select Analog Output Range. Select
desired range and select OK to confirm.

32 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

Buzzer

Enable or disable buzzer. Buzzer provides local audible alarm/fault indication.
Buzzer is enabled by default. To enable/disable buzzer:

• On the Configure tab select Outputs, then Buzzer. Select Enable/Disable and select

OK to confirm.

Relay Failsafe

Enable or disable Relay Failsafe operation. When configured for fail-safe operation,
relays are energized during normal operation. Failsafe operation ensures relays are
triggered in cases of power failure at the instrument. In Failsafe operation, normally
open and normally closed terminals are reversed as indicated in Section 3.4.3., Relay
Wiring. Relays are configured as non-Failsafe by default. To enable/disable relay
Failsafe:

• On the Configure tab select Outputs then Relay Failsafe. Select Enable/Disable

and OK to confirm.

Alarm Delay

Sets delay in minutes before instrument will indicate an alarm condition after low or
high alarm threshold has been exceeded. May be used to prevent short transient
alarm conditions from activating alarms. Alarm delays may be set for 0-15 minutes.
Alarm delay is configured as 0 minutes by default. To set alarm delay:

• On the Configure tab select Outputs then Alarm Delay. Enter the desired delay in

minutes (0-15) and OK to confirm.

Analog Zero Adjust

Analog zero adjust applies a fixed offset to the analog output. This allows removal
of small errors in the output between the gas detection instrument and the
measurement at the controller due to cable resistance when using voltage outputs.

To apply adjustment ensure instrument is outputting fixed voltage (default 1V at
zero ppm or use output test function to set specific voltage value), monitor remote
measurement and adjust zero offset until remote measurement matches expected
voltage output. Adjustment is limited to ±10% full scale. To set analog zero
adjustment:

• On the Configure tab select Outputs then Analog Zero Adjust. Use the slider to set

desired offset adjustment.

• Alternatively, select “Analog Zero Adjust (X.X%)” text and enter specific offset

required (-10 to 10).

MRLDS-400 Series Application Operation • 33

Analog Span Range

Analog span range scales the FSD (full-scale deflection) of the analog output. The
selected range determines the equivalent gas measurement at the analog output
maximum range.

Example: R134A 1000ppm, 0-5V analog output. If Analog Span Range is set to
20%, the full analog output range only covers the first 20% of the gas measurement
range, for example, 0-200ppm will output 0-5V, above 200ppm the output will be
truncated to 5V. Note that sensor resolution stays at the value for the max range.

To set analog span range:

• On the Configure tab select Outputs then Analog Span Range. Use the slider to set
desired range.

• Alternatively, select “Analog Span Range (X.X%)” text and enter specific offset
required.

34 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

5 Care and Maintenance

5.1. Maintenance Intervals

Interval Function

Check calibration

During Commissioning

Every 6-12 Months**

As Required Replace sensor module(s)

Table 5-1 - Maintenance Intervals and Functions

* These can be activated via Modbus commands or via MRLDS-400 Series App.

** Typical maintenance frequency can vary by sensor type.

Sensor Type Recommended Maintenance Interval Typical Sensor Lifetime

Electrochemical* 12 months 2-3 years

Catalytic Bead

Semiconductor*

Infrared 12 months 5-7 years

Table 5-2 - Maintenance Intervals and Functions

* Sensors should be checked after exposure to significant concentrations of gas, which can
shorten the sensor lifetime and/or reduce its sensitivity.

Check LEDs for proper operation*

Check for proper buzzer and relay operation*

Check signal transmission to the BMS.BAS (central controller) if connected*

Inspection by trained service personnel.

Check LEDs for proper operation*

Check for proper buzzer and relay operation*

Check signal transmission to the BMS/BAS (central controller) if connected*

Calibrate the sensor or contact Emerson Technical Support for sensor exchange
with factory - calibrated sensor

Zero calibration -1-3 months
Span calibration - 6 months

6 months after commissioning
12 months thereafter

5-7 years

4-6 years

Maintenance Intervals Care and Maintenance • 35

5.2. Adjustments

5.2.1. Introduction

Adjustment of the detector must be performed at regular intervals as required by
national standards or regulations (For example, EN 378, ASHRAE 15, BREEAM,

etc.).

Breathing Hazard: Calibration gas MUST NOT be inhaled! See appropriate
Safety Data Sheets. Calibration gas should be vented into a fume hood or to
the outside of the building.

Zero First, Then Span: For proper operation, never adjust the span before
completing a zero adjustment. Performing these operations out of order will
cause faulty calibration.

IMPORTANT: Emerson recommends calibrating detectors within the application-specific
condition and with target gas. This method of zeroing the detector in the application
environment and performing a target gas calibration is more accurate. A surrogate gas
calibration may only be performed as an alternative if a target gas calibration is

not possible.

IMPORTANT: The sensor should be fully stabilized (at least 2 hours, preferably 24 hours).

IMPORTANT: When entering the functions for zero or span adjustment, the detector will
automatically enter OFFLINE mode, and will remain OFFLINE until either the
OFFLINE mode is canceled by tapping the respective magnetic switch, or the OFFLINE
mode times out within 6 minutes (typical) after the adjustment has ended.

5.2.2. General Calibration Procedure

IMPORTANT: The MRLDS-450 Gas Detector MAY NOT be in an alarm or fault condition
during calibration. Acknowledge any alarms or faults BEFORE attempting to begin the
calibration process.

IMPORTANT: Except for CO2 or O2 sensors, calibration gas must be in a balance of air,
not nitrogen (N

36 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

).

2

IMPORTANT: Calibration and/or bump testing requires the MRLDS-450 Calibration
Adapter Kit (P/N 809-1190).

IMPORTANT: At elevations higher than 6,560’ (ft) (3,000 m), calibration will result in a
lower reading. Above 6,560’ (ft), the instrument should be calibrated in the environment of
operation.

1. Fit calibration adapter to the gas detector lid.

Figure 5-1 - Calibration Adapter Fitting

2. If using a variable flow regulator, adjust the gas flow to approximately 0.3 L/min.

5.2.3. Zero Adjustment

Ambient air can be used to zero the sensor instead of synthetic air only if the area is
known to be free of the target gas or any gas to which the sensor may be
cross-sensitive. In this case, no cylinder or calibration adapter is needed for the zero
adjustment.

IMPORTANT: The MRLDS-450 MAY NOT be in an alarm or fault condition during
calibration. Acknowledge any alarms or faults BEFORE attempting to begin the
calibration process.

IMPORTANT: Except for CO2 or O2 sensors, ambient air may be used instead of zero gas
if the area is known to be free of the target gas or any gases to which the sensor may be
cross-sensitive.

Adjustments Care and Maintenance • 37

1. Begin zero adjustment:

a. MRLDS-400 App: On the Home tab select Calibrate then scan the barcode on gas cylinder

or manually enter values for zero gas.

b. Manual: Hold MAG#1 for more than five (5) seconds. The LED will blink GREEN-GREEN-

RED when the instrument is ready.

2. Apply zero gas (or ambient air per warning above).

3. Confirm the start of calibration:

a. MRLDS-400 App: Press the Start Zero button.

b. Manual: Tap MAG#1 within 30 seconds or the instrument will time-out and return to normal

operation.

4. Complete zero adjustment:

a. MRLDS-400 App: App will countdown to completion. If calibration is successful, proceed to

Step 5. If calibration is unsuccessful, return to the Home screen and press the Acknowledge
button to clear the zero calibration fault.

b. Manual: The LED will blink GREEN-RED, GREEN-RED-RED, GREEN-RED-RED-RED,

etc. until calibration is complete. To abort, hold MAG#1 for >5-seconds, turn off gas flow and
remove the calibration adapter. If calibration is successful (green LED), proceed to Step 5. If
calibration is unsuccessful (LED blinks orange @ 2 Hz), tap MAG#1 to discard the calibration
attempt.

5. Turn off gas flow from zero gas.

6. Replace zero gas with calibration gas in preparation for span adjustment.

5.2.4. Span Adjustment

IMPORTANT: Except for CO2 or O2 sensors, calibration gas must be in a balance of air,
not nitrogen (N2).

IMPORTANT: At elevations higher than 6,560’ (ft) (2,000 m), calibration will result in a
lower reading. Above 6,560’ (ft) the instrument should be calibrated in the environment of
operation.

1. Begin span adjustment:

a. MRLDS-400 App: Scan barcode on gas cylinder or manually enter values for zero gas.

b. Manual: Hold MAG#2 for more than five (5) seconds. The LED will blink GREEN-GREEN-

ORANGE when the instrument is ready.

2. Apply calibration gas at the concentration listed on the calibration gas concentration
label (located on top of the instrument).

• Part Number

• Serial Number

• Sensor Type

• Maximum Range

3. Confirm the start of calibration:

38 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

a. MRLDS-400 App: Press the Start Span button.

b. Manual: Tap MAG#2 within 30 seconds or the instrument will time-out and return to normal

operation.

4. Complete zero adjustment:

a. MRLDS-400 App: App will countdown to completion. If calibration is successful, proceed to

Step 5. If calibration is unsuccessful, return to the Home screen and press the Acknowledge
button to clear the zero calibration fault.

b. Manual: The LED will blink GREEN-ORANGE, GREEN-ORANGE-ORANGE, GREEN-

ORANGE-ORANGE-ORANGE, etc. until calibration is complete. To abort, hold MAG#2 for
>5-seconds, turn off gas flow and remove the calibration adapter. If calibration is successful
(LED blinks green-orange-red), proceed to Step 5. If calibration is unsuccessful (LED blinks
orange @ 2 Hz), tap MAG#2 to discard the calibration attempt.

5. Turn off gas flow from calibration gas and remove the calibration adapter.

6. Allow sensor to recover/stabilize before the instrument returns to normal operation
(green LED).

5.2.5. System Bump Test

A bump test is a live test of the system to verify that the detector responds to gas and
all connected alarm devices, BMS, etc. are operating accordingly. It is
recommended that all involved persons are informed about the test and certain
alarms might have to be inhibited (For example, shutdown valves, notification of
authorities, etc.).

IMPORTANT: The manufacturer of this product requires that a bump test or calibration
be performed following installation to verify instrument functionality.

1. Connect adapter and gas cylinder according to the instructions in the General
Calibration Procedure.

2. If desired, disable/silence external annunciators (For example, shutdown valves,
notification of authorities, etc.):

a. MRLDS-400 App: On the Home tab select Calibrate then Bump. Toggle TAKE OFFLINE

to disable communications to external devices.

b. Manual: Inform building personnel of test so that external devices can be disabled/silenced.

3. Apply a sufficiently high concentration of the target gas to trigger alarms, but NOT
pure refrigerant or hydrocarbons (For example, do not use a butane lighter).

4. Once thresholds have been exceeded, relays should activate, digital outputs should
transmit the gas concentration and:

a. MRLDS-400 App: Gas concentration should be displayed, the instrument status should be

LOW ALARM or HIGH ALARM and alarms states should be ON.

b. Manual: LED status should display LOW ALARM or HIGH ALARM.

5. Turn off gas flow and remove the calibration adapter.

Adjustments Care and Maintenance • 39

6. Allow sensor to recover/stabilize before the instrument returns to normal operation
(green LED).

5.3. Troubleshooting

5.3.1. Hexadecimal Format

All fault codes can be retrieved through the Modbus interface and are shown in
hexadecimal (hex) format. A hex digit can represent multiple codes as shown below:

Hex
Code

0 0 6 1+2+3 D 1+4+8

1 1 7 1+2+4 E 2+4+8

2 2 8 8 F 1+2+4+8

3 1+2 9 1+8

4 4 A 2+8

5 1+4 B 1+2+8

Table 5-3 - Hexadecimal Code Format

Equivalent
Error
Code(s)

Hex
Code

Equivalent
Error
Code(s)

Hex
Code

Equivalent
Error
Code(s)

5.3.2. Fault Codes

IMPORTANT: If a sensor fault occurs during a gas alarm condition, then the fault
overrides the alarm condition.

Sensor faults may be decoded using the following table. Note that several faults may
be reported at the same time. For example, fault code “00000003” is a combination
of fault codes 00000001 (No sensor signal) and 00000002 (Voltage out of
specification 1V).

IMPORTANT: If a “last fault” attribute indicates that a fault has occurred at some point
in time, but the corresponding “current fault” attribute shows no fault, then the problem
has self-healed and no service action is required.

40 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

Fault Bit System Fault Possible Cause Required Action(s)

0x00000001 Software fault

0x00000002

0x00000004

0x00000008

0x00000010

0x00000020

0x00000040

0x00000080

0x00000100

0x00000200

0x00000400

Voltage out of
specification 1V

Voltage out of
specification 3.3V

Voltage out of
specification 5V

Voltage out of
specification 5.4V

Voltage out of
specification 12V

Voltage out of
specification VIN

System Flash Memory
Read Fault

System Flash Memory
Write Fault

System Flash Memory
CRC fault

System Invalid
Configuration

0x00000800 GPIO fault

0x00001000 Modbus Fault

0x00002000

Analog Output Fault
(MRLDS-450 Only)

0x00004000 Bluetooth Fault

0x00008000 Stuck switch

0x00010000 Sensor Element Out

0x00020000 Sensor Element Fault

Firmware error (e.g.
unexpected state)

Voltage rail out of range

Voltage rail out of range

Voltage rail out of range

Voltage rail out of range

Voltage rail out of range

Voltage rail out of range

Error reading from
internal Flash

Error writing to internal
Flash

Error in internal Flash
CRC

Error in system
configuration

Error detected on GPIO
pin

Error detected in Modbus
Communications

Error updating DAC value

Error detected in
Bluetooth module

Magnetic and/or Tactile
switch activated for > 1
minute

Cannot detect sensor
element

Fault detected in sensor
element

Power-cycle. If it re-occurs,
call product support

Call product support

Power-cycle. If it re-occurs,
call product support

Call product support

Power-cycle. If it re-occurs,
call product support

Call product support

Check sensor connection

Replace sensor nodule

Table 5-4 - Sensor Fault Codes

Troubleshooting Care and Maintenance • 41

Fault Bit System Fault Possible Cause Required Action(s)

0x00040000

0x00080000

0x00100000

0x00200000

0x00400000

0x00800000

0x01000000

0x02000000

0x04000000

Sensor ADC Sensor Read
Fault

Sensor ADC Current Read
Fault

Sensor AFE Read Fault
(EC only)

Sensor AFE Write Fault
(EC only)

Sensor AFE Status Fault
(EC only)

Sensor EEPROM Read
Fault

Sensor EEPROM Write
Fault

Sensor EEPROM CRC
Fault

Sensor EEPROM
Configuration Fault

0x08000000 Sensor UART Read Fault

0x10000000 Sensor Temperature Fault

0x20000000

Negative Gas
Concentration Fault

0x40000000 Zero Calibration failure Zero calibration failed

0x80000000 Span Calibration failure Span calibration failed

Cannot read from sensor
ADC

Cannot read from current
ADC

Cannot read from EC
sensor AFE

Cannot write to EC sensor
AFE

Error in EC sensor AFE

Error in reading from
sensor EEPROM

Error in writing to sensor
EEPROM

Error in CRC from sensor
EEPROM

Error in sensor EEPROM
data

Cannot read from sensor
UART

Temperature cannot be
read or is out of
specification

Sensor output has drifted
too negative

Check sensor connection/
Replace Sensor Module

Power-cycle / check sensor
connection / replace sensor
module

Call product support

Power-cycle / replace sensor
module

Replace sensor module

Check sensor connection /
replace sensor module

Ensure sensor is operating
within specified temperature
range / check sensor
connections

Initiate zero calibration (Via

App / Hold MAG#2)

Acknowledge failed

calibration (Via App / Hold
MAG#1)

Acknowledge failed

calibration (Via App / Hold
MAG#2)

Table 5-4 - Sensor Fault Codes

42 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

5.4. Sensor Maintenance

CAUTION! This product uses semiconductors that can be damaged by electrostatic
discharge (ESD). When handling the PCB, care must be taken so that the electronics are
not damaged.

Figure 5-2 - MRLDS-450 Components

Figure 5-3 - IP66 Sensor Configuration

Sensor Maintenance Care and Maintenance • 43

IP66 Product arrangement shown for reference; Remote Daughterboard PCB shown
(used for Remote IP66 Sensor Configurations). Note: Cable Glands and labeling are

factory installed.

5.4.1. Replacing Sensor Module

CAUTION! This product uses semiconductors that can be damaged by electrostatic
discharge (ESD). When handling the PCB, care must be taken so that electronics are not
damaged.

To replace the gas detector’s sensor module:

1. Power-down the gas detector.

2. Using a 5/32” (4mm) hex key/allen wrench (not included), remove the lid and
disconnect the ribbon cable from the sensor module.

3. Remove installed sensor module from the lid by holding onto the housing and turning
counter

-clockwise 90°. Take care not to apply excessive force to the sensor module’s
circuit board. When the square tab of the sensor housing is aligned with the lock icon,
firmly pull the module to remove it from the housing.

4. Install the new sensor module by aligning the square tab with the lock icon before
firmly pressing it into the enclosure.
sensor module’s circuit board, rotate the sensor module clockwise 90° (or until the
triangle icon aligns with the lock icon on the lid).

5. Connect the ribbon cable (to the sensor module and transmitter) and close the lid.

6. Ensure gasket is aligned correctly and tighten the lid using
“X” pattern. Tightening torque should be limited to hand tight and should be uniform.

Taking care not to apply excessive force to the

the supplied hardware in an

44 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

Figure 5-4 - Tightening Pattern

7. Power-up the gas detector.

8. After the start-up sequence has finished, check sensor response (bump test).

5.5. Cleaning the Instrument

Clean the detector with a soft cloth using water and a mild detergent. Rinse with
water. Do not use any alcohols, cleaning agents, sprays, polishes, detergents, etc.

6 Additional Information

6.1. Sensor Principle

6.1.1. Electrochemical Sensors

Electrochemical sensors measure the partial pressure of gases under atmospheric
conditions. The monitored ambient air diffuses through a membrane into the liquid
electrolyte in the sensor. The electrolyte contains a measuring electrode, a
counter-electrode, and a reference electrode. An electronic “potentiostat” circuit
ensures a constant electrical voltage between measuring electrode and reference
electrode. Voltage, electrolyte, and electrode material are selected to suit the gas
being monitored so that it is transformed electrochemically on the measuring
electrode and a current flows through the sensor. This current is proportional
to the gas concentration. At the same time, oxygen from the ambient air reacts at
the counter electrode electrochemically. The current flowing through the sensor is
amplified electronically, digitized and corrected for several parameters (For
example, the ambient temperature).

6.1.2. Catalytic Bead Sensors

A catalytic bead sensor measures the partial pressure of combustible gases and
vapors in ambient air. It uses the heat-of-combustion principle.

The monitored air diffuses through the sintered metal disc into the sensor. The
mixture of combustible gases, vapors, and air are catalytically combusted at a heated
detector element (called a pellistor). The oxygen content in the air must be greater
than 12 Vol%. Due to the resulting heat-of-combustion, the temperature of the
detector element rises. This increase in temperature causes a change of resistance in
the detector element, which is proportional to the concentration of the mixture of
combustible gases and vapors in the monitored air. In addition to the catalytically
active detector element, there is a compensator element. Both elements are parts of
a Wheatstone bridge. Thus environmental effects like changes in ambient
temperature or humidity are almost entirely compensated.

IMPORTANT: Certain substances in the atmosphere to be monitored may

impair the sensitivity of the sensors. Such substances include, but are not limited to:

1. Polymerizing substances such as acrylonitrile, butadiene, and styrene.

2. Corrosive compounds such as halogenated hydrocarbons (releasing halogens such as
bromine, chlorine or fluorine when oxidized) and halogen hydride acids as well as acidic gaseous
compounds such as sulfur dioxide and nitrogen oxides, Catalyst poisons such as sulfurous and
phosphorous compounds, silicon compounds (especially silicones), and metal-organic vapors.

46 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

It may be necessary to check the calibration if the sensor has been exposed for a long
time to a high concentration of flammable gases, vapors, or the above-mentioned
contaminating substances.

The nature of catalytic bead sensor technology means that sensor drift may typically
be up to ±5% LEL per month. Instruments using these sensors should be zeroed
regularly following the instructions in Section 5, Care and Maintenance.

6.1.3. Semiconductor Sensors

Semiconductor or metallic oxide sensors (MOSs) are among the most versatile of all
broad-range sensors. They can be used to detect a variety of gases and vapors in low
ppm or even combustible ranges. The sensor is made up of a mixture of metallic
oxides. They are heated to a temperature between 302ºF and 572ºF (150ºC and
300ºC) depending on the gas(es) to be detected. The temperature of operation as well
as the “recipe” of mixed oxides determines the sensor selectivity to various toxic
gases, vapors, and refrigerants. Electrical conductivity greatly increases as soon as a
diffusion process allows the gas or vapor molecules to come in contact with the
sensor surface. Water vapor, high ambient humidity, temperature fluctuations, and
low oxygen levels can result in higher readings.

IMPORTANT: Certain substances in the environment to be monitored may impair the
sensitivity of the sensors:

1. Materials containing silicone or silicone rubber/putty.

2. Corrosive gases such as hydrogen sulfide, sulfur oxide, chlorine, hydrogen chloride, etc.

3. Alkaline metals, saltwater spray.

6.1.4. Infrared Sensors

The infrared (IR) gas sensor is designed to measure the concentration of combustible
gases and vapors in the ambient air. The sensor principle is based on the
concentration-dependent absorption of infrared radiation in measured gases.

The monitored ambient air diffuses through a sintered metal material into the
enclosure of an optical “bench.” The broadband light emitted by an IR source passes
through the gas in the optical bench and is reflected by the walls from where it is
directed towards a dual-element detector. One channel of the detector measures the
gas-dependent light transmission, while the other channel is used as a reference.
The ratio between measurement and reference signal is used to determine the gas
concentration. Internal electronics and software calculate the concentration and
produce an output signal.

Sensor Principle Additional Information • 47

6.2. Disposing of the Instrument

6.2.1. Disposing of the Electrical and Electronic Equipment

EU-wide regulations governing the disposal of electrical and electronic appliances
which have been defined in the EU Directive 2012/19/EU and in national laws have
been effective since August 2012 and apply to this device.

Common household appliances can be disposed of using special collecting and
recycling facilities. However, this device has not been registered for household
usage. Therefore it must not be disposed of through these channels. The device can
be returned to Emerson for disposal. Please do not hesitate to contact Emerson
Technical Support if you have any further questions on this issue.

6.2.2. Disposing of Sensors

Dispose of sensors in accordance with local laws.

DANGER! Do not dispose of sensors in fire due to the risk of explosion and resulting
chemical burns.

WARNING! Do not force open electrochemical sensors.

IMPORTANT: Observe the applicable local waste disposal regulations. For information,
consult your local environmental agency, local government offices or appropriate waste
disposal companies.

48 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

6.3. Technical Specifications

6.3.1. General Specifications

Category Specifications

Analog Current

Signals to Central
Controller

Power Supply and
Relays

Wiring

Table 6-1 - General Specifications

Analog Voltage

Modbus RTU over RS-485

Operating voltage 19.5 to 28.5VDC; 24VAC ± 20%, 50/60 Hz

Inrush current 1.5 A

Operating power (max) MRLDS-450: 4W, 170mA @ 24VDC

Relay rating

Audible alarm Internal Buzzer ≥72 dB at 4” (10cm)

Alarm delay 0 to 15 minutes (selectable)

Power and analog signal

Modbus network

Cable gland

Normal operation: 4 to 20mA

Drift below zero: 3.8mA

Measuring range exceeded: 20.5mA

Instrument fault: ≤ 1.2mA

Fault on analog interface: > 21mA

Offline mode/Maintenance signal: 3mA steady signal

0 to 5V; 1 to 5V (default); 0 to 10V; 2 to 10V
(selectable)
During fault condition, 1 to 5V and 2 to 10V outputs
are 0V.

Baud rate: 9,600 or 19,200 (default) (selectable)

Start bits: 1

Data bits: 8

Parity: None, Odd, Even (default) (selectable)

Stop bits: 1 or 2 (selectable)

Retry time: 500 ms, min time between retries

End of message: Silent 3.5 characters

3 SPDT
1 A at 24VAC/VDC, resistive load

2-core shielded cable, 16 to 20 AWG (0.5 to 1.5mm2)

3-core, 2 twisted pair + ground, shielded cable with 120
Ω characteristic impedance, 16 to 24 AWG (0.5 to 1.5

2

)

mm

M20, 10-14mm cable outer diameter
M16, 4-8mm cable outer diameter

Technical Specifications Additional Information • 49

Category Specifications

Enclosure protection IP66

Physical
Specifications

Environmental

Agency
Approvals

Table 6-1 - General Specifications

Enclosure Size (W×H×D)
(Approx.)

Weight (Approx.) MRLDS-450: 1lb, 1oz (480g)

Temperature - 40 to 120ºF (-40 to 50ºC)

Storage temperature - 5 to 100ºF (-20 to 40ºC)

Humidity

Pressure 23.6 to 32.5 inch Hg/800 to 1,100 mbar

Elevation 0 to 10,000 ft. (3,000 m) altitude

Influences

CE, EN 50270:2015, UL/CSA/IEC/EN 61010-1

MRLDS-450 IP66: 6.5×6.5×3.4” (165×165×87mm)

5 to 90% RH, non-condensing
(15 to 90% RH, non-condensing, EC sensors excl. O2)

For influences on the measurement performance and
restrictions

7 Ordering Information

of a particular sensor, see sensor data sheet.

Emerson

P/N

809-1040 CO2 0-5,000ppm 809-1140 CO2 0-5,000ppm IR

809-1041 CO2 0-10,000ppm 809-1141 CO2 0-10,000ppm IR

809-1047 R404A 0-1,000ppm 809-1147 R404A 0-1,000ppm SC

809-1048 R407A 0-1,000ppm 809-1148 R407A 0-1,000ppm SC

809-1049 R410A 0-1,000ppm 809-1149 R410A 0-1,000ppm SC

809-1050 R22 0-1,000ppm 809-1150 R22 0-1,000ppm SC

809-1056 R448A 0-1,000ppm 809-1156 R448A 0-1,000ppm SC

809-1058 R513A 0-1,000ppm 809-1158 R513A 0-1,000ppm SC

809-1066 R422D 0-1,000ppm 809-1166 R422D 0-1,000ppm SC

809-1068 R449A 0-1,000ppm 809-1168 R449A 0-1,000ppm SC

Table 7-1 - Part Numbers and Ordering Information

50 • MRLDS-450 Refrigerant Gas Detection I&O Manual 026-1316 Rev 2

IP66, 3 x Relays, Analog
Output, Modbus Output,
Audible & Visual Alarms

Gas Type and Detection
Range

Emerson

P/N

Replacement Sensor

Pre-calibrated Sensor
Modules

Sensor
Type

Emerson P/N MRLDS-450 Accessories

809-1190 Calibration Adapter Kit

809-1191 Horn + strobe 24VDC; blue lens

809-1192 Horn + strobe 24VDC; amber lens

809-1193 Horn + strobe 24VDC; red lens

809-1194 Horn + strobe; blue lens; MP120K 120VAC adapter

809-1195 Horn + strobe; amber lens; MP120K 120VAC adapter

809-1196 Horn + strobe; red lens; MP120K 120VAC adapter

Table 7-2 - Accessory Part Numbers and Ordering Information

Technical Specifications Ordering Information • 51

For Technical Support call 770-425-2724 or email [e-mail]

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