Emerson MRLDS-250 User manual

026-1315 Rev 2 11-APR-2017
MRLDS-250 Infrared Gas Detector
Installation and Operation Manual

Emerson Retail Solutions
1065 Big Shanty Road NW, Suite 100
Kennesaw, GA 30144, USA
Phone [phone]
Fax [phone]

Table of Contents • i
TABLE OF CONTENTS
1 INTRODUCTION.......................................................................................................................................................... 1
1.1. OVERVIEW .................................................................................................................................................................... 1
1.2. DETECTION OPTIONS .................................................................................................................................................... 1
1.2.1. Broadband vs. Gas Specific .................................................................................................................................. 1
1.2.2. Broadband Gas Detection..................................................................................................................................... 1
1.2.3. Detecting Specific Gases....................................................................................................................................... 2
1.3. REMOTE CONTROLLER OPTIONS .................................................................................................................................. 3
1.4. PARTS LIST ................................................................................................................................................................... 3
1.5. SPECIFICATIONS ............................................................................................................................................................ 3
2 MOUNTING THE GAS DETECTOR......................................................................................................................... 4
2.1. WARNINGS AND PREREQUISITES .................................................................................................................................. 4
2.2. MOUNTING LOCATIONS ................................................................................................................................................ 4
2.2.1. General Placement Guidelines ............................................................................................................................. 4
2.2.2. Machinery Rooms ................................................................................................................................................. 4
2.2.3. Refrigerated Spaces .............................................................................................................................................. 5
2.2.4. Chillers.................................................................................................................................................................. 5
2.3. MOUNTING PROCEDURE ............................................................................................................................................... 5
3 WIRING AND CONFIGURATION ............................................................................................................................ 7
3.1. OVERVIEW .................................................................................................................................................................... 7
3.2. WIRING SUPPLY POWER (24VAC OR 24VDC) ............................................................................................................ 7
3.3. WIRING ALARM OUTPUT (ANALOG SIGNAL)............................................................................................................... 8
3.4. WIRING THE DIGITAL ALARM OUTPUT RELAY............................................................................................................ 8
3.5. FINISH INSTALLATION .................................................................................................................................................. 9
4 OPERATION AND STABILIZATION..................................................................................................................... 10
4.1. POWER UP AND WARM UP......................................................................................................................................... 10
4.2. STABILIZATION ........................................................................................................................................................... 10
4.3. PERFORM A MANUAL ZERO ....................................................................................................................................... 10
4.4. ALARMS...................................................................................................................................................................... 10
4.5. GAS DETECTOR FAULTS ............................................................................................................................................. 10
4.5.1. Overview ............................................................................................................................................................. 10
4.5.2. Non-Critical Faults ............................................................................................................................................. 11
4.5.3. Critical Faults ..................................................................................................................................................... 11
5 CONFIGURE THE GAS DETECTOR ..................................................................................................................... 12
5.1. USER INTERFACE OVERVIEW ..................................................................................................................................... 12
5.2. SETTING PARAMETERS ............................................................................................................................................... 12
5.2.1. Overview ............................................................................................................................................................. 12
5.2.2. Configuration Parameters .................................................................................................................................. 12
5.3. COMPLETING SETUP ................................................................................................................................................... 15
6 FUNCTIONAL TESTS AND ADJUSTMENTS....................................................................................................... 16
6.1. INTRODUCTION ........................................................................................................................................................... 16
6.2. BUMP TESTING VS. ADJUSTING DETECTOR RESPONSE .............................................................................................. 16
6.3. BUMP TESTING ........................................................................................................................................................... 17
6.4. ADJUSTMENT USING CALIBRATION GAS.................................................................................................................... 18
7 TROUBLESHOOTING .............................................................................................................................................. 19

ii • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
7.1. FAULT CODES ............................................................................................................................................................. 19
7.2. DIAGNOSTIC ATTRIBUTES (P.-18) .............................................................................................................................. 20
7.3. RESETTING THE MRLDS-250 TO DEFAULT VALUES ................................................................................................. 20
7.4. OTHER SYMPTOMS...................................................................................................................................................... 21
8 REPLACEMENT PARTS AND ACCESSORIES.................................................................................................... 22

Overview Introduction • 1
1 Introduction
1.1. Overview
The MRLDS-250 NDIR (non-dispersive infrared)
is a fixed gas detector that can detect a wide range of
refrigerant gases. The MRLDS-250 can be used on a
stand-alone basis or integrated into controls or a
Building Management System (BMS).
The MRLDS-250 can be used in locations that
require continuous monitoring and to add gas
detection solutions to an existing system.
Figure 1-1 MRLDS-250 Components
1.2. Detection Options
1.2.1. Broadband vs. Gas Specific
The MRLDS-250 NDIR refrigerant gas detectors
are available in two versions: broadband and
gas-specific.
1.2.2. Broadband Gas Detection
The broadband gas detector (P/N 809-0030) is
used as a general purpose gross leak detector and is
factory tested and certified. It is shipped from the
factory with ±35% accuracy. If more accurate
detection is needed, gas-specific versions are
available (see Table 1-2), which are factory certified
and calibrated to the target refrigerant.
The broadband gas detector combines refrigerants
into three groups shown in Table 1-1. Measurement
performance is based on an average response profile
for all of the gases within the group.
1See Section 5, Configure the Gas Detector for information on
Parameter 11 and other configuration instructions.
NOTE: Greater accuracy may be achieved
through the use of calibration gas and the
adjustment procedure detailed in Section 6,
Functional Tests and Adjustments.
Group # Value for
Param 111Refrigerant
1 P.-11 = 1
R123
R134a
R404a
R407a
R407c
R407f
R410a
R427a
R507
HFO1233ZD
R448A
R449A
2P.1-11 = 2
R422a
R422d
HFO1234YF
HFO1234Ze
R452A
R513A
3 P.-11 = 3 R22
4 P.-11 = 4 R32
Table 1-1 Broadband Gas Groups

2 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
Figure 1-2 Broadband Gas Groups 1-3
1.2.3. Detecting Specific Gases
Each gas-specific gas detector is shipped factory
calibrated to its specific target refrigerant. Refer to
Figure 1-3 and Table 1-2.
Figure 1-3 Gas-Specific MRLDS-250 Gas Detectors
1See Section 5, Configure the Gas Detector for Information on
Parameter 11 and other configuration instructions.
Part Number Refrigerant1Accuracy
809-0031 R22 ±3%
809-0034 R404a ±3%
809-0035 R407a ±3%
809-0040 R422d ±3%
Table 1-2 Gas-specific Detector Measurement Performance
NOTE: Gas-specific detectors can be re-
calibrated in the field to new target gases. Use
optional calibration instructions in Section 6,
Functional Tests and Adjustments for
increased accuracy when detecting new target gas that
is different from the “as shipped” target gas. Refer to
the example in Table 1-3.
As Shipped
Part number 809-0031 (R22) is factory
calibrated to R22.
Changed
Gas Type
(Reduced
Accuracy)
The gas detector may be changed to respond to
any of the other listed refrigerants (see
parameter P.-11, in Section 5.2., Setting
Parameters). If changed, the gas detector will
have a lower accuracy for the target refrigerant
(without calibration).
Table 1-3 Changing Gas Types and Accuracy

Remote Controller Options Introduction • 3
1.3. Remote Controller
Options
The MRLDS can connect to any controller
through the standard analog output (voltage and
current; see Table 1-5 for options) such as the
standard alarm relay.
1.4. Parts List
Table 1-4 shows a list of components that are
available.
1.5. Specifications
For default values, refer to Section 5.2., Setting
Parameters.
1When filtering is disabled (see parameter P.-19 in Section
5.2.2., Configuration Parameters), the unit will respond to con-
centrations sub-10 PPM.
Optional
Recalibra-
tion
(For
Improved
Accuracy)
By applying calibration gas containing the
new target refrigerant, and via the routine
described in Section 6.4., Adjustment Using
Calibration Gas, the gas detector may then be
adjusted to respond with the calibrated
accuracy as shown in Table 1-2 for the new
target refrigerant.
Part Number Description
809-0030 MRLDS, Broadband
809-0031 MRLDS, Calibrated to R22
809-0034 MRLDS, Calibrated to R404A
809-0035 MRLDS, Calibrated to R407A
809-0040 MRLDS, Calibrated to R422D
809-0041 MRLDS, Calibrated to R448A
809-0042 MRLDS, Calibrated to R449A
809-0043 MRLDS, Calibrated to R513A
603-1100 Splash Guard
026-1315 Installation and Operation Manual
Table 1-4 Parts List
Table 1-3 Changing Gas Types and Accuracy
Specification Description
Power Supply 24 VDC, 24 VAC 50/60 Hz,
2.5 W max
Power Monitoring Green LED
Visual Alarm Red 4-digit LED display
Audible Alarm Buzzer (audible alarm), enable/disable
(Default enabled)
Fault Monitoring Fault codes presented to user
Analog Outputs 4-20 mA; 0-5V; 0-10V; 1-5V; 2-10V
(Default 1-5V)
Relay 1 relay rated 1 A @ 24 VAC//VDC
(0.5A, 125V AC UL rating)
Range 0-3500 PPM
Squelch1Readings below 75 PPM are squelched
by default
Alarm Delay Selectable: 0 to 15 minutes
(Default, 0)
IP Rating Not IP rated. An accessory splash
guard is available for areas requiring
additional protection from wash down.
Response Time,
T90
Five (5) minutes
Temperature
Rating
-22°F to 10°F (-30°C to 40°C)
Humidity and
Elevation
5-90% relative humidity, non-
condensing, 0-10,000ft. altitude
Standard
Dimensions and
Weights
4.0” x 5.5” x 1.5” 6.3oz.
102 x 140 x 37mm 180g
Approvals CE, MET/IEC/EN 61010-1
Table 1-5 Specifications

4 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
2 Mounting the
Gas Detector
2.1. Warnings and
Prerequisites
2.2. Mounting Locations
2.2.1. General Placement Guidelines
Gas detectors must be located within the
appropriate wire lengths from the central control unit
(if used).
2.2.2. Machinery Rooms
There is no absolute rule in determining the
number of gas detectors and their locations. However,
a number of simple guidelines can help in making a
decision. Gas detectors monitor a point as opposed to
an area. If the gas leak does not reach the detector, no
alarm will be triggered. Therefore, it is extremely
important to select the gas detector location carefully.
Also consider ease of access for maintenance.
The size and nature of the site can help in deciding
which method is the most appropriate to use.
Locations requiring the most protection in a
machinery or plant room would be in close proximity
to compressors, pressurized storage vessels,
refrigerant cylinders, storage rooms, or pipelines. The
most common leak sources are valves, gauges,
flanges, joints (brazed or mechanical), and filling or
draining connections.
• In machinery rooms where there is little or no
airflow, placement options are:
• Point Detection: where gas detectors are located as
near as possible to the most likely sources of
leakage, such as the compressor, expansion valves,
mechanical joints, or cable duct trenches.
• Perimeter Detection: where gas detectors
completely surround the area or equipment.
WARNING: Explosion hazard! Do not mount
the MRLDS-250 in an area that may contain
flammable liquids, vapors, or aerosols.
Operation of any electrical equipment in such
an environment constitutes a safety hazard.
CAUTION: The MRLDS-250 contains
sensitive electronic components that can be
easily damaged. Do not touch or disturb any of
these components.
NOTE: The mounting location of the monitor
should allow it to be easily accessible for visual
monitoring.
NOTE: The monitor must be connected to a
marked, suitably located and easily reached
switch or circuit breaker as a means of
disconnection.
CAUTION: Connect monitor power and sig-
naling terminals using wiring that complies
with local ethical codes or regulations for the
intended application.
CAUTION: Do NOT mount the MRLDS-250
directly to vibrating machinery as the
vibrations may degrade the gas detector’s
performance.
NOTE: The MRLDS-250 should be installed
plumb and level and securely fastened to a
rigid mounting surface.
NOTE: When installed in areas that may be
subjected to water spray, the optional splash
guard (P/N 603-1100) should be used in
conjunction with the MRLDS-250.

Mounting Procedure Mounting the Gas Detector • 5
• Halocarbon and hydrocarbon refrigerants are
heavier-than-air gases and as such, the gas
detectors should be located near ground level
(6 to 18 inches from the floor).
2.2.3. Refrigerated Spaces
In refrigerated spaces, gas detectors should be
located away from doors, in the return airflow to the
evaporators on a sidewall (below head-high is
preferred), or on the ceiling, not directly in front of an
evaporator, nor in any direct airflow. In large rooms
with multiple evaporators, gas detectors should be
mounted on the central line between two adjacent
evaporators, as turbulence will result in airflows
mixing.
2.2.4. Chillers
In the case of small water- or air-cooled enclosed
chiller units, mount the gas detector to monitor
airflow to the extract fans. With larger models also
place a gas detector inside the enclosure under or
adjacent to the compressors.
For enclosed air-cooled chillers or the outdoor unit
for variable refrigerant volume and variable
refrigerant flow (VRV/VRF) systems, mount the gas
detector to monitor airflow to the extract fan. With
large units also place a gas detector inside the
enclosure under or adjacent to the compressors.
2.3. Mounting Procedure
To open the housing as received, use a flat blade
screwdriver and depress the top latch. While pushing
the latch, grasp the back edge of the housing near the
latch and pull the back away.
When mounted, the housing is simply opened by
pressing the top latch with a suitable screwdriver or
other flat blade. With the top latch depressed, pull the
housing apart by grasping the sides and pulling
straight out. With the housing separated, the
mounting base with terminal blocks will be visible.
See Figure 2-1.
NOTE: Gas detectors should be positioned just
far enough back from any high-pressure parts
to allow gas clouds to form and be detected.
Otherwise, a gas leak might pass by in a high-
speed airflow area and go undetected by the gas
detector.
• Make sure that pits, stairwells, and trenches are
monitored since they may fill with stagnant pockets
of gas.
• For racks or chillers pre-fitted with refrigerant gas
detectors, these should be mounted so as to monitor
the compressors.
• Do not mount the gas detector directly to pipes or
structures that are subject to strong vibration.
CAUTION: Do not apply caulking or other
material around the gas detector base. The gas
detector relies on air exchange through the
spaces between the base and the gas detector
housing. Do not obstruct the small gap around the
housing and the base with any material.
Step Mounting Procedure
1 Open the housing (see Figure 2-1).
2 Position the base to the pre-determined
(acceptable) mounting location. Use the gas
detector base to mark the mounting locations
as needed. The hole pattern on the backplate is
sized to mount the gas detector onto various
electrical junction boxes. The other holes may
be used as needed to mount the gas detector to
other structures, or onto a wall.
3For Wall Mount, attach the MRLDS-250 base
to the mounting surface using two #6 screws
(provided) through two of the 7 mounting holes,
and be careful not to over-tighten the screws. Re-
fer to Figure 2-2 for the locations of mounting
holes on the base.
For Junction Box Mount, attach the MRLDS-
250 base to the junction box (using mounting
hardware provided with your junction box)
through the two junction box holes. Refer to
Figure 2-2 for the locations of the two junction
box mounting holes on the base.
4Unless you are ready to wire the device (see
Section 3, Wiring and Configuration),
carefully snap the cover onto the base unit.
Table 2-1 Mounting Procedures

6 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
Figure 2-1 Initial Housing Separation
Figure 2-2 Front and Back Views of MRLDS-250 Base

Overview Wiring and Configuration • 7
3 Wiring and
Configuration
3.1. Overview
Prior to wiring and configuring the MRLDS-250,
ensure the following conditions have been met:
• MRLDS-250 backplate is mounted in an appropriate
location.
• The cover panel is removed.
If the cover panel was reattached after mounting,
open the gas detector enclosure by pressing the top
latch with a suitable screwdriver or other flat blade.
With the top latch depressed pull the housing apart by
grasping the sides and pulling straight out. Align and
press together to close.
Figure 3-1 Terminal Blocks and Cable Glands
3.2. Wiring Supply Power
(24VAC or 24VDC)
Either 24VAC or 24VDC may be used to power
the MRLDS-250. Connect wiring to the appropriate
terminal locations (see ). Use two wires, between 14
and 22 AWG. Refer to Figure 3-2 for (AC wiring left)
or DC wiring (right).
Figure 3-2 Supply Power Wiring Options
NOTE: The pre-installed cable gland (left) and
the optional cable on the gland (right) have a
1/4 cable capacity (each).
NOTE: Install the optional cable gland in the
right side of the base unit if needed. Otherwise,
install the blanking plug that is included in the
mounting kit.
CAUTION: Incorrect wiring may permanently
damage the gas detector and void the warranty.
Double check all terminations before applying
power.
Power
Option
Pin Label Wiring Termination
24 VAC 1L
24V AC line
2N
24V AC neutral
24 VDC 3+
24V DC positive
4 GND 24V DC ground
Table 3-1 Power Options and Terminal Block Connections

8 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
Figure 3-3 Maintaining Neutral Polarity
3.3. Wiring Alarm Output
(Analog Signal)
The MRLDS-250 provides an analog output signal
that is proportional to the level of gas detected.
Connect two 18 to 20 AWG wires to terminal
block positions 5 and 6 (see Figure 3-4), noting
ground and signal polarity.
Figure 3-4 Analog Output Wiring
The type of output signal on pins 5 and 6 is
programmable using the analog output type parameter
P.-03. Refer to Section 5, Configure the Gas
Detector for details.
3.4. Wiring the Digital
Alarm Output Relay
An alarm setpoint may be programmed from the
front panel of the MRLDS-250. When the level of the
detected gas exceeds the alarm setpoint, the
MRLDS-250 enters the alarm state. An on-board
relay is tied to the alarm state, so you may activate (or
deactivate) external equipment based on the
MRLDS-250’s current alarm status.
WARNING: The MRLDS-250 must be
powered by either:
• A suitable UL 60950/CSA certified power supply
that is isolated from line voltage by double insulation,
or
• An appropriately rated UL listed/CSA Class 2
transformer.
Failure to comply can result in personal injury or
death.
WARNING: Neutral polarity must be
maintained across units. Refer to Figure 3-3.
NOTE: No jumpers or hardware switch
settings are required to configure the analog
output. This is done electronically from the
front panel display.
Function Pin Wiring Termination
Analog 5Analog output ground
Output 6Analog output signal (+)
Table 3-2 Alarm Output Terminal Block Connections

Finish Installation Wiring and Configuration • 9
Figure 3-5 Sample Relay Output Wiring
Make relay connections (NO, NC, or both) using
18 to 20 AWG wires to terminal block positions 10,
11, and 12 (see Figure 3-5), noting normally open,
normally closed, and common connectors.
3.5. Finish Installation
Once the base is mounted and all wiring is
complete, align the gas detector housing and press it
onto the base. The gas detector will snap into position,
completing all electrical connections. Ensure the top
and bottom snap locks are engaged.
NOTE: The relay can be programmed to be
failsafe (normally energized). By default, the
relay is set to be normally de-energized. This
can be set using parameter P-06.
Function Pin Mounting Procedure
Relay (Alarm) 10 Relay NC contact
Output 11 Relay common contact
12 Relay NO contact
Table 3-3 Relay Output Terminal Block Connections
CAUTION: If the right cable gland was not
needed during installation and wiring, be sure
to install the blanking plug.
CAUTION: Do not apply caulking or other
material around the gas detector base. The gas
detector relies on air exchange through the
spaces between the base and the gas detector
housing. Do not obstruct the small gap around the
housing and the base with any material.

10 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
4 Operation and
Stabilization
4.1. Power Up and Warm
Up
On powering up, the MRLDS-250 will sense for
the presence of gas after an initial warm-up period of
two (2) to five (5) minutes. The green LED will flash
at a one-second interval during the warm up.
4.2. Stabilization
4.3. Perform a Manual Zero
After the gas detector stabilizes, the power LED
stops flashing and is illuminated continuously.
Emerson Retail Solutions recommends manually
zeroing the MRLDS-250 after a 1-hour stabilization
period.
To manually zero the gas detector, press and hold
the UP and DOWN buttons simultaneously for five
(5) seconds. The gas detector will beep and the
display will show “zEro” when zeroing is complete.
The display will show “fAiL” if the temperature is
changing too quickly or there is an active alarm
condition.
4.4. Alarms
The following occurs during an alarm condition:
4.5. Gas Detector Faults
4.5.1. Overview
There are two levels of fault monitoring built into
the gas detector:
1. Non-critical
2. Critical
CAUTION: It is vital when first installing the
gas detector that it warms up in an atmosphere
that is known not to contain any background
concentrations of refrigerant. Emerson Retail
Solutions offers portable gas detectors for this purpose.
Contact Technical Support for more information.
NOTE: A manual zero should be performed in
the environment of operation and at the typical
operating temperature.
NOTE: Subsequent manual zeros may be
performed, provided the atmosphere around
the gas detector is free of all background
concentrations of refrigerant. Clean air or
nitrogen applied to the calibration port for five (5)
minutes may be used to ensure the gas detector is clear
of all background gas. Re-zeroing with background
refrigerant present will cause the gas detector to report
incorrect readings.
Item Behavior During Alarm State
Green
LED
On (solid)
Display On (blinks); reports detected PPM
concentration
Audible
Alarm
On (if enabled and after programmed delay
expires)
Relay
Output
Activates (after any programmed delay
expires)
Analog
Output
Changes proportionally with gas
concentration (as configured)
Table 4-1 MRLDS-250 Behavior During Alarm Conditions
NOTE: The alarm feature includes a 20% dead
band to prevent alarm “chatter” if the
concentration hovers near the alarm setpoint.
Once the alarm has been triggered, it will
remain latched until the concentration drops below
80% of the alarm setpoint.

Gas Detector Faults Operation and Stabilization • 11
4.5.2. Non-Critical Faults
Non-critical faults typically recover by allowing
the gas detector surroundings to stabilize, for
example, after a defrost cycle. The gas detector
continues to monitor its surroundings during
non-critical faults, but may report inaccurate
readings.
The following occurs when a non-critical fault
condition exists.
4.5.3. Critical Faults
Critical faults may indicate an unrecoverable
condition. Please refer to Section 7, Troubleshooting
for more information. The following occurs when a
critical fault condition exists:
Item Behavior During Non-Critical
Faults
Green LED On (solid)
Display Shows the appropriate fault code
Analog Output Operates Normally
Table 4-2 MRLDS-250 Behavior During a Non-Critical Fault
Item Behavior During Critical Faults
Green LED Off (solid)
Display Shows the appropriate fault code
4-20 mA output Changes to 2 mA
Analog Output 1- 5V output Changes to 0.5V
2-10V output Changes to 1.0V
Table 4-3 MRLDS-250 Behavior During a Critical Fault

12 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
5ConfiguretheGas
Detector
5.1. User Interface
Overview
The gas detector is configured through the built-in
menu system. Once mounting is complete, attach the
gas detector to the base and apply power.
Figure 5-1 The User Interface of the MRLDS-250
The user interface consists of four pushbuttons, a
4-digit LED numeric display, and a power LED. The
four buttons allow the gas detector to be adjusted
based on a parameter list shown below. Button
functions are listed in Table 5-1.
5.2. Setting Parameters
5.2.1. Overview
Press and hold the information button for
five (5) seconds to activate the parameter list:
Each parameter is shown in turn by using the UP
or DOWN buttons. The parameter is shown as P.-XX,
with XX being the parameter value. Pressing Enter
while a parameter is displayed allows the attributes of
the parameter to be set. Each Parameter has its own
attributes, as shown in the following table. Set the
attributes as desired, and then press Enter to save the
setting.
5.2.2. Configuration Parameters
Button Description
Used to access the parameter list as well
as wake the display (when parameter
P.-09 is set to default). Used to back up
one level without writing to memory
when the parameter list is active.
Used to increment the value or parameter
displayed.
Used to decrement the value or parameter
displayed.
When pressed together and held for
five (5) seconds, this key combination
manually zeros the gas detector.
Table 5-1 Button Functionality
Saves the currently displayed parameter
to memory.
Parameter Description
Maintenance Mode
Sets gas detector to offline mode for 30
minutes.
00 Gas detector is online, with normal
response to its surroundings (default).
01 Gas detector is offline, and
suppresses all outputs. Display reads
“oFFL” (offline) during 30-minute
timeout.
Alarm Setpoint
Sets desired PPM value above which
alarm occurs. Use UP or DOWN buttons.
For faster “coarse” adjustment, hold both
buttons to sweep through the adjustment
range quickly. Default setpoint is 100
PPM.
Table 5-2 Configuration Parameters
Button Description
Table 5-1 Button Functionality

Setting Parameters Configure the Gas Detector • 13
Analog Output Type
Selects output type:
00 Selects 0-5V
01 Selects 1-5V (default)
02 Selects 0-10V
03 Selects 2-10V
04 Selects 4-20 mA
Alarm ON Delays
Sets the ON delay time (0-15 minutes) for
the alarm output signals (relay). The
default delay is 0 minutes.
Alarm OFF Delays
Sets the OFF delay time for the alarm
output signals (relay) in minutes (0-15).
The default delay is 0 minutes.
Relay Contact Behavior (Failsafe
Mode)
Sets the default relay power state so that
power loss can be detected.
The behavior of the relay changes from
energizing when an alarm condition
occurs (default) to energizing at power up
(Failsafe). In both cases the relay changes
state when an alarm occurs, failsafe is
simply inverted. This allows power
failures to be detected as alarms.
00 NO (default mode)
01 Failsafe mode
Relay Latching
Controls the relay latching behavior.
00 OFF (default). Relay does not latch,
and resets once the alarm condition is
removed.
01 ON. Relay remains latched; reset by
BMS command by pressing and holding
the Enter button for five (5) seconds.
Audible Alarm
The units have an internal audible alarm.
You can disable this, but the default setting
is “enabled” in compliance with EN378.
00 OFF
01 ON (default)
Display Mode
The display can be turned on by using this
parameter. When set to ON, the display
never shuts off (all operating modes).
When ON, the display shows the current
gas concentration (or 0 if below the
squelch). Note that P.-09 is disabled if
P.-19=0.
00 OFF during normal operation
(default)
01 ON
Parameter Description
Table 5-2 Configuration Parameters
RS485 Node Address
Sets the RS485 node address (0001 to
0255)
Gas Groups / Specific Gas Selection
Selects either gas group number for
broadband operation or specific gas name
for gas-specific mode.
Broadband:
1 R134a, R404a, R407a, R123, R407c,
R407f, R427a, R507, R410A: Select from
three groups of gases:
2 R422a, R422d HFO1234YF, and
HFO1234Ze
3 R22 (by itself).
Specific Gas: The actual refrigerant name
is displayed. Select the appropriate
refrigerant.
NOTE: Gas-specific detectors are factory
calibrated to a single refrigerant using
specialized manufacturing equipment. If
another refrigerant is selected that differs
from the factory calibrated setting, the
built in calibration no longer applies.
Further improvement in detector accuracy
may be gained by applying calibration gas
containing the newly selected refrigerant
and adjusting the gas detector reading to
match (see Parameter P.-17).
Buzzer Mute Time
Sets a time (0 to 59 minutes) during which
the active buzzer remains muted:
• After the “I” button is pressed, or
• After Modbus register 4000 is set to
0.
Baud Rate
Sets the baud rate for Modbus (RS485)
communications.
00 9,600 baud (default)
01 19,200 baud
Stop Bits
Sets the number of stop bits required to
match the controlling communications
equipment (for example, Building
Management System - BMS).
01 1 stop bit (default)
02 2 stop bits
Parity
Sets Modbus parity option.
00 None (default)
01 Odd parity
02 Even parity
Parameter Description
Table 5-2 Configuration Parameters

14 • MRLDS-250 Gas Detector Manual 026-1315 Rev 2 11-APR-2017
Figure 5-2 Analog Output Scaling Options
Analog Output Scaling
Allows the user to select the full-scale
PPM value that represents maximum
analog output (for example, 20 mA) for
scaling the analog output. Adjustment
range is from 100 PPM to 3500 PPM.
Default = 3500 PPM. (The setting cannot
be adjusted above 3500.)
Use the UP and DOWN buttons to set the
desired full scale value. All outputs will
be scaled to the indicated full scale value.
NOTE: Alarm values are not scaled, but
are absolute values. Setting a smaller full
scale does not correspondingly scale the
alarm setting.
NOTE: When the PPM level is greater
than the programmed analog output Full
Scale PPM (P.-16), the analog output will
go to a 10% over range state (indicating
that the concentration is too high for the
analog output to achieve). For example,
for a 1-5V setting the analog output would
go to 5.5V, for 4-20 mA it would go to
22 mA and so on.
NOTE: The analog output signal range is from
100 PPM to the default value of 3500 PPM,
which is scaled across the actual output range
selected by the analog output type parameter
P.-03. The upper PPM limit is programmable using
analog output scaling parameter P.-16. This parameter
sets the full scale PPM value creating a PPM range
across which the analog output is scaled. See
Figure 5-2 for more details.
Parameter Description
Table 5-2 Configuration Parameters
Parameter Description
Gas Test Mode
Places the gas detector in gas test mode.
00 Disabled (default)
01 Enabled
The display changes to four dashes
(----) until gas is applied. When gas is
applied, the live concentration is
displayed. See Section 6.4., Adjustment
Using Calibration Gas for the calibration
procedure.
NOTE: To prevent false alarms, all
outputs are suspended while Test Mode is
active. The only live indication is the
4-digit display.
Diagnostics Menu
Parameter 18 provides access to the
self-diagnostic information. The LED
display shows “DIAG” until the Enter
button is pressed. Use the UP and DOWN
buttons to scroll through the list of
diagnostic attributes.
A.-01 Current fault condition
A.-02 Last fault
A.-03 Days in service
A.-04 Days since last adjust/test
A.-05-A.-07 Factory Use Only
A.-08 Detector temperature in °C
A.-09 Temperature rate of change
A.-10-A.-17 Factory Use Only
See Section 7, Troubleshooting for a
complete list of codes and options.
Table 5-2 Configuration Parameters