MRLDS-250 Infrared Gas Detector
Installation and Operation Manual
026-1315 Rev 6

Introduction

1.1. Overview
The MRLDS-250 NDIR (non-dispersive infrared) is a state-of-the-art 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.

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 accuracy as shown in Table 1-1 (gas dependent). If more accurate detection is needed, gas specific
versions are available, which are factory certified and calibrated to the target refrigerant.
The broadband gas detector combines refrigerants into 4 groups shown in Figure 1-2. Measurement performance is based on an average response profile for all of the gases within the group.

Group#

| Value for Param 11 1|

Refrigerant

| As Shipped Accuracy
---|---|---|---
1| P.-11 = 1| R134a| ±25%
R404a| ±35%
R407a| ±25%
R407c| ±20%
R407f| ±20%
R410a| ±20%
R427a| ±15%
R452B| ±40%
R507| ±35%
HFO1233ZD| ±35%
2| P.1-11 = 2| R448A| ±40%
R449A| ±40%
R422a| ±25%
R422d| ±20%
HFO1234YF| ±25%
HFO1234Ze| ±25%
R452A| ±25%
R513A| ±35%
R514A| ±20%²
3| P.-11 = 3| R22| ±25%
4| P.-11 = 4| R32| ±35%

Table 1-1 Broadband Gas Groups
NOTE: Greater accuracy may be achieved through the use of calibration gas and the adjustment procedure detailed in Section 6, Functional Tests and Adjustments.
¹See Section 5, Configure the Gas Detector for Information on Parameter 11 and other configuration instructions.

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.

Table 1-2 Gas-specific Detector Measurement Performance
¹See Section 5 , Configure the Gas Detector for Information on Parameter 11 and other configuration instructions.

NOTE: Emerson recommends not re-calibrating gas-specific detectors in the field to a new target gas; purchase a new gas-specific detector instead. In the event you prefer not to purchase a new gas-specific detector, use optional calibration instructions in Chapter 6 for increased accuracy when detecting a new target that is different from the “as shipped” target gas. Refer to the example in Table 1-3.
¹ See Section 5, Configure the Gas Detector for Information on Parameter 11 and other configuration instructions.

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).
Optional Recalibration (For Improved Accuracy)| By applying calibration gas containing the new target refrigerant, and via the routine described in Section 6.4. , the gas detector may then be adjusted to respond with the calibrated accuracy as shown in Table 1-2 for the new target refrigerant.

Table 1-3 Changing Gas Types and Accuracy
1.3. Remote Controller Options
The MRLDS-250 can connect to any controller through the standard analog output (voltage and current; see Table 1-4 for options), the standard alarm relay, or the digital Modbus RTU communications interface.
1.4. Parts List
Table 1-4 shows a list of components that are available.

Table 1-4 Parts List;
1.5. Specifications
For default values, refer to Section 5.2., Setting Parameters.

VAC, 5 VA min @ 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
Squelch1| Readings below 75 PPM are squelched by default
Communication: MODBUS RTU over RS-485| Baud rate: 9,600 or 19,200 (selectable)
Start bits: 1
Data bits: 8
Parity: None, odd, even (programmable)
Stop bits: 1 or 2, programmable
Retry time: 500 ms (min time between retries)
End of msg; Silent 3.5 characters
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.

Table 1-5 – Specifications

altitude
Standard Dimensions and Weights| 4.0” x 5.5” x 1.5”     6.3oz.
102 x 140 x 37mm  180g
Enclosure| ABS plastic; UL flammability rating of 94V-0
Approvals| CE, MET/IEC/EN 61010-1

Table 1-5 – Specifications
¹ When filtering is disabled (see Configuration Parameters P.-19), the unit will respond to concentrations sub-10 PPM.

Mounting the Gas Detector

2.1. Warnings and Prerequisites
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 and servicing.
NOTE: The gas detector must be connected to a marked, suitably located and easily reached switch or circuit breaker as means of disconnection.
CAUTION: Connect monitor power and signaling terminals using wiring that complies with local electrical 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.
2.2. Mounting Locations
2.2.1. General Placement Guidelines
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 6031100) should be used in conjunction with the MRLDS-250.
Gas detectors must be located within the appropriate wire lengths from the central controller (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.
• Halocarbon and hydrocarbon refrigerants are heavier-than-air gases and as such, the gas detectors should be located  near round level (6 to 18 inches from the floor).

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.

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.
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.

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.
3| For 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. Refer 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.
4| Unless you are ready to wire the device (see Section 3, Wiring an Configuration ), carefully snap the cover onto the base unit.
|
---|---

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.

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.
3.2. Wiring Supply Power (24VAC or 24VDC)
CAUTION: Incorrect wiring may permanently damage the gas detector and void the warranty.
Double check all terminations before applying power.
Either 24VAC or 24VDC may be used to power the MRLDS-250. Connect wiring to the appropriate terminal locations (see Table 3-1. Use two wires, between 14 and 22 AWG. Refer to Figure 3-2 for (AC wiring left) or DC wiring (right).

Table 3-1 – Power Options and Terminal Block Connections
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.

3.3. Wiring Alarm Output (Analog Signal)
The MRLDS-250 provides an analog output signal that is proportional to the level of gas detected.
NOTE: No jumpers or hardware switch settings are required to configure the analog output. This is done electronically from the front panel display. Connect two 18 to 20 AWG wires to terminal block positions 5 and 6 (see Figure 3-4), noting ground and signal polarity per Table 3-2.

Figure 3-4 – Analog Output Wiring

Table 3-2 – Alarm Output Terminal Block Connections
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 MRLDS250 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.

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.
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 per Table 3-3.

Table 3-3 – Relay Output Terminal Block Connections
3.5. MODBUS Network Configuration
If your application includes a MODBUS network, make network connections (RS-485 A and RS-485 B) using 18 to 24 AWG shielded twisted pair wires (with 120 ohm characteristic impedance) to terminal block positions 7 and 8 Figure 3-6 noting inverted B (-) and
non-inverted A (+) signal connectors per Table 3-4.

MODBUS
Network Communications| 7| RS-485 “B” (inverted)
8| RS-485 “A” (non-inverted)
9| RS-485 shield

Table 3-4 – MODBUS Network Communications Connections
CAUTION: For MODBUS network communications wiring, use only 18-24 AWG shielded twisted pair wire with 120 ohm characteristic impedance.
CAUTION: Connect the RS-485 cable shield to pin 9 (board ground).
NOTE: Selection of the MODBUS Address and Baud Rate is completed through the gas detector setup menu, described later. No jumpers or hardware switch settings are required to configure the MODBUS communications network. This is done electronically from the front panel display.
NOTE: For MODBUS communications with the MRLDS250, the default communications parameters are as follows.
Baud rate = 9600
Parity = no parity
Stop bits = 1
Confirm that all devices on the MODBUS communications network (including a Building Management System) are configured similarly.
If the MRLDS-250 is at the end of the RS-485 network, be sure to set the RS-485 terminator on the printed circuit board (PCB) to IN. This applies a terminating resistor to the end of the wires per the requirements of the RS-485 protocol. The terminator should be set to OUT for all other installation conditions.
NOTE: Be sure to enable the termination resistor on the device at each end of the network (See Figure 3-7). This includes the Building Management System (if used).
CAUTION: Care should be exercised when changing the terminator switch. Before powering the gas detector, use a fine pointed device or paper clip to slide the switch position. Do not apply force to the switch or push on the switch with any device. The switch changes position up and down along the access slot direction.

3.6. 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: 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.
NOTE: 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.

Operation and Stabilization

4.1. Power Up and Warmup On powering up, the MRLDS-250 will sense for the presence of gas after an initial warm-up period of toot five minutes. The green LED will flash at a one-second interval during the warm up.
4.2. Stabilization
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 offers portable gas detectors for this purpose. Contact Technical Support for more information.
4.3. Perform a Manual Zero
After the gas detector stabilizes, the power LED stops flashing and is lit continuously. Emerson recommends manually zeroing the MRLDS-250 after a 1-hour stabilization period. Increase this stabilization period to 3 hours for freezer applications.
To manually zero the gas detector, press and hold the UP and DOWN buttons simultaneously for 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. Additionally, certain system faults (F.-08, F.-10 through 14, and/or
F.-16) will prevent a manual zero from being performed.
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 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.
4.4. Alarms
The following occurs during an alarm condition:

etc.

Table 4-1 – MRLDS-250 Behavior During Alarm Conditions
NOTE: The alarm feature includes a 20% deadland 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.
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

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.

Table 4-2 – MRLDS-250 Behavior During a Non-Critical Fault

Configure the Gas Detector

5.1. User Interface Overview
The gas detector is configured through the built-in menu system. Once mounting is complete, attach thetas 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.

writing to memory when the parameter list is active. Used to mute the audible alarm for the time period configured in parameter P.-12.
| Used to increment the value or parameter displayed.
| Used to decrement the value or parameter displayed.
Button| Description
---|---

__

| When pressed together and held for five seconds, this key combination manually zeros the gas detector.

__

| Saves the currently displayed parameter to memory.

Table 5-1 – Button Functionality
5.2. Setting Parameters
5.2.1. Overview
Press and hold the information button for five 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

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 offal** (offline) during 30-inute timeout.

Table 5-2 – Parameter Numbers, Names, and Descriptions

Sets desired PPM value (range 75 to 3500 ppm) above which alarm occurs. Use UP or DOWN buttons. For faster “coarse” adjustment, hold either button to sweep through the adjustment range quickly. Default setpoint is 200 ppm.

| 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, Modbus). The default delay is 0 minutes.
| Alarm OFF Delays
Sets the OFF delay time for the alarm output signals (relay, Modbus) 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
Parameter| Description
---|---
| 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 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 when the ppm value is below the alarm setpoint (default)
01 ON
In either case, the display will blink the measured PPM value during an alarm state.
| RS485 Node Address
Sets the RS485 node address (0001 to 0255)
Parameter| Description
---|---
| Gas Groups / Specific Gas Selection
Selects either gas group number for broadband operation or specific gas name for gas-specific mode. Broadband: Select from 4 groups of gases:
1.   R134a, R404a, R407a, R407c, R407f, R427a, R507, R514A, HFO1233ZD
2. R448a, R449a, R422a, R422d HFO1234YF, and HFO1234Ze, R513a, R452a, R452B
3.  R22 (by itself)
4. R32 (by itself). Specific Gas: The actual refrigerant name is shown. Select the appropriate refrigerant.
NOTE : Gas-specific detectors are factory calibrated to a single refrigerant using specialized manufacturing equipment. If another refrigerant is selected which 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 (0-59 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 (RS-485) communications.
00 9,600 baud (default).
Parameter| Description
---|---
| Stop Bits
Sets the number of stop bits required to match the controlling communications equipment (for example, building management system, etc.).
01 1 stop bit (default)
02 2 stop bits
| Parity
Sets Modbus parity option.
00  None (default)
01 Odd parity
02 Even parity
| 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.

Places the gas detector in gas test mode.
00 Disabled (default)
01 Enabled
When enabled, the display continuously cycles through the following:
• CAL is displayed briefly.
• Next, the gas group number or gas type (based on product code) is displayed.
• Then four dashes (  -) are displayed.
After gas is applied and the 75 PPM squelch level is exceeded, the live concentration replaces the four dashes.
See Sectio n 6.4., Adjustment Using Calibration Gas if using Gas Test Mode to initiate 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.
Once the gas test mode is enabled to perform a gas test or calibration, the unit will automatically go offline for a 10- minute period after the parameter list is exited. (This allows time for the test gas to clear before the unit becomes active) If no activity occurs for ten minutes, the unit exits the Gas Test Mode
Parameter| Description
---|---
| 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 To aid in troubleshooting, the operator may choose to reset the gas detector to its default state by holding both the UP and DOWN buttons for 5 seconds while in the Diagnostics Menu. All settings, including the alarm setpoint, gas adjustments, the selected gas curve, calibration data, the Modbus address, etc. revert to specific default values after a reset.
IMPORTANT : Calibrations on either gas-specific or broadband models are lost after a reset. This returns the gas detector to an uncalibrated condition. See parameter P.-17 for information on how to recalibrate the gas detector.
See Sect i on 9, Replacement Parts and Accessories for a complete list of codes and details on the reset option.
Parameter| Description
---|---
| Response Filtering
This parameter is used to turn filtered output ON (01) or OFF (00).
The default setting is ON (01). The Modbus and analog output are filtered so that responses below 75 ppm are squelched. If the display mode ( P.-09 ) is set to ON (01) the display shows 0 for any signal level below 75 ppm. Some installations may wish to monitor the small analog output changes that may be created by the detector environment.
Turning filtering OFF (00) allows these small variations around the minimum analog output (for example, 4 mA, 1V, etc.) to be transmitted via Modbus and the analog output terminals.
NOTE : The detector display is OFF when filtering is OFF
( P.-09 is disabled).
NOTE : Whenever filtering is OFF the detector display will turn ON for 10 minutes if the detector is re-zeroed (see Section 4.3., Perform a Manual Zero ). This is intended to aid maintenance testing. The analog outputs continue to transmit the full, unfiltered range, and the alarm setpoint remains active.
NOTE : If filtering is turned off (00), Analog Output Scaling
( P.-16** ) should be adjusted to 500 ppm.

Table 5-2 – Parameter Numbers, Names, and Descriptions
5.3. Completing Setup
To complete the setup after all parameters are set as needed, simply press and hold the information button for 5 seconds to exit the Parameter list: The gas detector is now actively monitoring its surroundings.
NOTE: If no buttons are pressed for two minutes, the MRLDS-250 exits setup mode automatically.

Functional Tests and Adjustments

6.1. Introduction
To comply with the requirements of EN378 and the European F-GAS regulation, gas detectors must be tested annually. However, local regulations may specify the nature and frequency of this test.
CAUTION: Check local regulations on calibration or testing requirements.
CAUTION: The MRLDS-250 contains sensitive electronic components that can be easily damaged. Do not touch or disturb any of these components.
WARNING: Annual checks and adjustment using calibration gas is recommended. Calibration gas adjustment frequency may be extended based on application, but should never exceed a time period of two years.
WARNING: In applications where life safety is critical, calibration gas adjustment should be completed quarterly (every three months) or on a more frequent basis. Emerson is not responsible for setting safety practices and policies. Safe work  procedures including calibration policies are best determined by company policy, industry standards, and local codes.
WARNING: Failure to test or adjust the unit in accordance with applicable instructions and with industry guidelines may result in serious injury or death. The manufacturer is not liable for any loss, injury, or damage arising from improper testing, incorrect adjustment, or inappropriate use of the unit.
WARNING: Before testing the gas detectors on-site, the MRLDS-250 must be powered up and allowed to stabilize.
WARNING: After initial installation, the MRLDS-250 should be gas tested to ensure proper operation.
WARNING: The testing and/or adjustment of the unit must be carried out by a suitably qualified technician, and must be completed:

1. In accordance with this manual.
2. In compliance with locally applicable guidelines and regulations. Suitably qualified operators of the unit should be aware of the regulations and standards set down by the industry/country for the testing or calibration of this unit. This manual is only intended as a guide and, insofar as permitted by law, Emerson accepts no responsibility for the calibration, testing, or operation of this unit.

The frequency and nature of testing or calibration may be determined by local regulation or standards.
EN378 and the F-GAS Regulation require an annual check in accordance with the manufacturer’s recommendation.
6.2. Bump Testing vs. Adjusting Detector Response
There are two concepts that need to be differentiated:

• bump test
• gas detector response adjustment

A bump test exposes the gas detector to a gas. The operator then observes the gas detector’s response to the gas. The objectives are two-fold:

• establishes if the gas detector is reacting to the gas
• determines if all of the detector outputs are working correctly

There are two types of bump test:

• quantified: A known concentration of gas is used.
• non-quantified: A gas of unknown concentration is used.

Adjusting gas detector response exposes the gas detector to a calibration gas as well (like a quantified bump test), but additionally sets the actual gas detector response level (via parameter P.-17) to ensure that the gas detector activates at the specified gas concentration.
Refer to the following sections for addition information on bump testing and gas detector response adjustment.
CAUTION: Before you carry out the test or adjustment:

• Advise occupants, plant operators, and supervisors.
• Check if the gas detector is connected to external systems such as sprinkler systems, plant shut down, external sirens and beacons, ventilation, etc., and disconnect as instructed by the customer.
• For bump test or calibration, the MRLDS-250 should be powered up and fully stabilized (see Section 4, Operation and Stabilization).

6.3. Bump Testing
WARNING: Notify others that testing is underway. During bump testing, the alarm outputs are active and will trigger the intended response. It is the operator’s responsibility to ensure that such actions are acceptable and can be performed safely.
After installation and parameter setup (see Section 5, Configure the Gas Detector, the units should be bump tested. Expose the gas detector to test gas. The gas selected should be a high enough concentration to put the system into alarm and light the LED display.
With a bump test you can see the functions of the gas detector:

• the LED display will light and show the detected PPM concentration once the alarm setpoint is reached.
• the relay and audible alarm will function as configured including any delays set (ON or OFF).
• the output (0-10V, for example) will show the gas level.

Ideally bump tests are conducted on-site in a clean air atmosphere.

diameter tubing (see below).
3| Expose the gas detector to gas from the cylinder. Monitor the LED display reading. Refer to the Section 1.5., Specifications for acceptance criteria.

Table 6-1 – Bump Testing Using Calibration Gas Cylinders

6.4. Adjustment Using Calibration Gas
Adjustment Using Calibration Gas requires a gas cylinder with the appropriate gas and concentration.
Note that a calibration kit if offered that consists of a calibration gas cylinder and a flow regulation valve with flexible non-absorbent tubing.
NOTE: For improved accuracy and response, the gas detector should be protected from excess drafts while performing the adjustment. Excess air circulation may dilute the applied calibration gas and lead to a lower than expected response.

diameter tubing.
Step| Adjustment Using Calibration Gas Cylinders
---|---
2| Enable parameter P.-17 Gas Test Mode (see Section 5, Configure the Gas Detector ). When enabled, the display continuously cycles through the following:
•  CAL is displayed briefly.
• Next, the gas group number or gas type (based on product code) is displayed.
•  Then four dashes (—- ) are displayed.
After gas is applied and the 75 PPM squelch level is exceeded, the live concentration replaces the four dashes.
NOTE : The analog outputs, relay activity, and RS-485 ppm reporting are suspended in Gas Test Mode to prevent false alarms.
3| Expose the gas detector to gas from the cylinder. Monitor the 4-digit LED display reading.
4| Wait for the PPM reading to stabilize. This should take approximately 4-6 minutes. Minor changes (less than 5 PPM in 10 seconds) are considered stable readings. Compare the response value with the calibration gas concentration.
5| Adjust the gas detector displayed value by using the UP or DOWN buttons to increase or decrease the value shown. Adjust until the reading is within ± 2% of the calibration gas. For example, if the calibration gas is 1000 PPM, the gas detector is adjusted properly when the displayed reading is between 980 and 1020 PPM.
6| Press the Enter button to store the new adjustment. Turn off the calibration gas and remove the tubing from the calibration port. If no further changes to the other Parameters are required, press and hold the information button for 5 seconds to exit the Parameter list.
Step| Adjustment Using Calibration Gas Cylinders
---|---
7| If no further changes to the other parameters are required, press and hold the  button for 5 seconds to exit the Parameter list. Upon exiting the parameters list, the gas detector will enter offline mode for a period of 10 minutes. This allows time for the calibration gas to dissipate after testing. During offline mode, the gas detector suppresses all outputs. The display reads oFFL (offline) during 10 minute timeout.

Table 6-2 – Bump Testing
NOTE: All calibration gas mixtures have a blend tolerance. The tolerance will limit the actual adjustment accuracy that is achievable.

MODBUS Communications

7.1. Introduction
The MRLDS-250 gas detector can be configured to communicate on an RS-485 network using MODBUS-RTU protocol. Before configuring the gas detector for MODBUS communications, be sure your network connection is complete and your network termination switches are set appropriately. Refer to Section 3, Wiring and Configuration for details.
7.2. Communications Settings
There are 255 selections available to be set electronically, from addresses 1 to 255 inclusive.
MODBUS data with a zero in the address field is received by all detectors (regardless of the address selected) to enable the master device to broadcast simultaneously to all the detectors.
Refer to the specifications section for information on RS-485 network communications parameters such as data bits, stop bits, and more.
7.3. Analog Input Registers
Analog input registers are read only and use function code 04.

Table 7-1 – Analog Input Registers
7.4. Analog Output Registers
Analog output registers are readable (using function code 03) and writable (using function code 06).

1=1-4 V
2=0-10 V
3=2-10 V
4=4-20 ma| none| P.-03
2009| Baud rate| 0=9600

1=19200

| none| P.-13
2010| Stop bits| 1 or 2| none| P.-14
2011| Gas curve number| 1 to 4 (broadband unit) or gas type (gas specific)| none| P.-11
2012| Analog output full scale PPM (R/O)| 100-3500| PPM| P.-16
2013| Parity| 0=None
1=Odd
2=Even| none| P.-15

Table 7-2 – Analog Output Registers
7.5. Input Status Flags
Input Status Flags are readable (using function code 02).

Table 7-3 – Input Status Flags
7.6. Output Status Flags
Output Status Flags are readable (using function code 01) and writable (using function code 05).

Table 7-4 – Output Status Flags

Troubleshooting

8.1. Fault Codes
To comply with the requirements of EN378 and the European F-GAS regulation, gas detectors must be tested annually. However, local regulations may specify the nature and frequency of this test.
The MRLDS-250 features sophisticated internal status monitoring and will indicate whether a fault condition exists on the front display (F.-XX, with XX being the fault number).
There are two classes of fault conditions: critical and non-critical. In general, non-critical faults occur when environmental conditions exist that are outside the product’s specified operating range, or if an installation error has occurred (for example, incorrect wiring).
The gas detector will typically continue to monitor its surroundings (except for fault F.-08), and may report inaccurate readings and false alarms.
Correcting non-critical faults is a matter of waiting for the environmental conditions to return to a more typical condition, correcting wiring mistakes, or in some cases, relocating the gas detector. For example, placing the gas detector near a forced air heater may
cause temperature faults. The non-critical fault range is F.-01 to F.-08.
Critical faults indicate a functional problem that results in the gas detector no longer monitoring its surroundings for refrigerant.
The fault number is displayed and the power LED is turned off, indicating that the gas detector is offline.
The critical fault range is F.-09 to F.-16. If any of these faults occur, first try to clear the faults by cycling power to the sensor. The easiest way to do this is by removing the sensor from the base and reattaching. If the fault returns after cycling power, the gas detector should be removed from service and replaced. Additionally, the faults are stored as a hex number and can be accessed in the Diagnostics menu P.-18. The associated hex codes are listed next to the Fault Code in (Table 8-1). Refer to Diagnostics Menu P.-18 in Section 8.2., Diagnostic Attributes (P.-18) for additional information.

Description| Fault Code| Hex Code| Possible Causes
---|---|---|---
Gas Detector Temperature Fault| | 0x00
01| Gas Detector temperature reports > 55°C or < – 35°C.
Gas Detector Temperature Rate of Change Fault| | 0x00
02| Temperature rate of change exceeds ~1°C/min for more than 15 minutes.
RS485 RX Fault| | 0x00
04| Message too long for receive buffer.
RS485 CRC Fault| | 0X00
08| Transmission is corrupted (computed CRC doesn’t match transmitted CRC).
Open Loop Fault| | 0x00
10| Possible wiring, connection, and/or termination issue exists. When analog output type is 4-20ma and loop is open, use
18-24AWG
shielded twisted pair with 120 ohm characteristic impedance for Modbus connections.
Description| Fault Code| Hex Code| Possible Causes
---|---|---|---
MODBUS Fault| | 0x00
20| MODBUS message was truncated or timed out early.
PPM
Overage Fault| __

__

| 0x00
40| PPM exceeds 9999. This may indicate a gross (very large) leak. If no leak is present, it indicates a gas detector error.
Input Voltage Fault| | 0x00
80| Input supply power to the MRLDS-250 is out of range (i.e., 24V ±20%). IMPORTA
NT : If this fault is active, the gas detector is offline and not monitoring. Correct the input supply voltage to restore normal operation.
Critical Faults|

__

| | Critical fault. Cycle power to the sensor and see of the fault clears. If not, contact Emerson technical support for additional guidance.

:

|

:

__

|

IMPORTANT: Fault F.-15 may be caused by rapid changes in temperature and other environmental effects. If the F.-15 fault remains after the ambient temperature has stabilized, perform a manual re-zero to clear the fault. See Section 4.3., Perform a Manual Zero.
8.2. Diagnostic Attributes (P.-18)
Use this option to review the built-in diagnostic attributes. Access the parameter list (see Section 5, Configure the Gas Detector) and select P.-18. Press the Enter button to access the diagnostics, and then use the UP or DOWN button to select each attribute.
The following information is available.

0000 = no faults are active XXXX = HEX number
See Table 8-1 for the HEX format cross reference.
| Displays a hex format code that corresponds to any faults that occurred since the internal fault record was last erased. See Table 8-1 for the HEX format cross reference. The records may be erased by pressing the ENTER button.
| Displays the number of days that the MRLDS-250 has been in service. The value of this attribute rolls over after 9999.
Attribute| Description
---|---
|
| Reserved
:
| Displays the sensor temperature in °C.
| Displays the sensor’s approximate rate of temperature change per half minute interval (°C change over 30 seconds).
| Reserved
:

Table 8-2 – Diagnostics Attributes
8.3. Resetting the MRLDS- 250 to Default Values
The gas detector may be reset to its default state, if needed, to aid in troubleshooting. All settings, including alarm setpoint, gas adjustments, selected gas curve, calibration data, Modbus address, etc. revert to specific default values after a reset. The  broadband sensor option (P/N 809-0030) resets to gas group 1. Gas specific products (P/Ns 809-0031 to 809-0044) are reset to the R134a gas curve.
NOTE: Calibrations on either gas-specific or broadband models are lost after a reset. This returns the gas detector to an uncalibrated condition. See parameter P.-17 for information on how to recalibrate the gas detector.
NOTE: Before performing this operation, it is advisable to write down all the parameter settings so they can be re-programmed.

the following to occur:
•  All the LED segments will then light for 3 seconds.
•  The gas detector resets to the default settings.
•  The gas detector beeper sounds for 3 seconds.
3| After 3 seconds, the user is returned to the parameter list at parameter P.-18.
4| The gas detector may now be re-programmed for further troubleshooting if needed.

Table 8-3 – Resetting MRLDS-250 to Default Values
8.4. Other Symptoms
Other common wiring problems can also cause the gas detector to malfunction. Check below for additional conditions that will cause gas detector issues.

leak, try setting an alarm delay. Perform a bump test to ensure proper operation.

Table 8-4 – Other Symptoms and Possible Causes

Replacement Parts and Accessories

The following items are available as replacement parts:
NOTE: All modules come ready to mount to the original mounting base provided.

wash down or impact. Includes mounting hardware for attaching to walls.
NOTE : The gas detector response time will lengthen when the Splash Guard is used. The installer is responsible for determining whether the response time is suitable for the application.
026-1315| Installation and Operation Manual

Table 9-1 – Replacement Parts and Accessories
Appendix: E2 Setup

The Modular Refrigeration Leak Detection Sensor is Emerson’s state-of-the-art infrared refrigerant gas detector that can detect a wide range of gases. The MRLDS-250 can be used on a stand-alone basis or integrated into supervisory controls. The MRLDS-250 can be used in locations that require continuous monitoring and to add gas detection solutions to an existing system.
The MRLDS-250 is available in two versions:

• The broadband gas detector is used as a general purpose gross leak detector and is factory tested and certified to +/- 35% accuracy.
• The gas specific versions come factory certified and calibrated with +/- 3% accuracy to the target refrigerant when there is a need for more accurate detection.

For complete part number and installation information, see the full MRLDS-250 manual (P/N 026-1315).
MRLDS-250 Installation Mounting the MRLDS-250

1. 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.
2. Position the base to the pre-determined mounting location.
3. For Wall Mount, attach the MRLDS-250 base to the mounting surface using two #6 screws (provided) through two of the seven mounting holes (see Figure A-2). For Junction Box Mount, attach the MRLDS-250 base to the junction box through the two  junction box holes.

Figure A-2 – Front and Back of the MRLDS-250 Base
Wiring and Configuration
Either 24VAC or 24VDC may be used to power the MRLDS-250. Connect wiring to the appropriate terminal locations. Use two wires, between 14 and 22 AWG. Refer to Figure A-3 for AC wiring (left) or DC wiring (right):

Figure A-3 – Supply and Power Wiring Options
WARNING: The MRLDS-250 must be powered by:

• A suitable UL 60950/CSA certified power supply that is isolated from line voltage by double insulation.
• An appropriately rated UL listed/CA Class 2 Transformer; a 10VA Transformer is recommended.
• For multiple devices cascaded, a 50VA Class 2 Transformer is recommended and neutral polarity MUST be maintained across units.

Figure A-4- Power Wiring of a Device Network 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 A-5a), noting ground and signal polarity.
Make relay connections (NO, NC, or both) using 18 to 20 AWG wires to terminal block positions 10, 11, and 12 (see Figure A-5b), noting normally open, normally closed, and common connectors.

MODBUS Network Configuration
NOTE: For MODBUS network communications wiring, use only 18-24 AWG shielded twisted pair wire with 120 ohm characteristic impedance.
When connecting MRLDS-250 to an E2 or Site Supervisor via MODBUS, make network connections (RS-485 A and RS-485 B) using 18 to 24 AWG shielded twisted pair wires to terminal block positions 7 and 8 as shown in Figure A-6.

For MODBUS communications with the MRLDS250, the default communications parameters are as follows:

• Baud rate = 9600
• Parity = none
• Stop bits = 1

If the MRLDS-250 is at the end of an RS-485 network, be sure to set the RS-485 Terminator on the inside of the cover panel PCB, to IN. When set to IN, a terminating resistor is applied to the end of the line.
The terminator should be set to OUT for all other installation conditions as shown in Figure A-7.

Set Up Analog Output Type and Scaling

1. For Analog Output, look for P.-03 on the parameter list then press the Enter button.

2. Set the desired output by pressing Up or Down to select the type designated as follows:
   • 00 Selects 0-5V
   • 01 Selects 1-5V (Default)
   • 02 Selects 0-10V
   • 03 Selects 2-10V
   • 04 Selects 4-20mA

3. Press the Enter button to save.

4. For Scaling, look for P.-16 on the parameter list then press the Enter button.

5. This will allow you to select the full scale PPM value that represents the maximum analog output (for example: 1000PPM = 5V when 1-5V output range was selected for P.-03). Use Up or Down o adjust the value and set it to 1000PPM.

6. Press the Enter button to save the setting.

MRLDS-250 Modbus Setup
Setting Up Modbus Address and Baud Rate

1. Press and hold the information button for five seconds to activate the parameter list.
2. For the Address, look for P.-10 on the parameter list then press the Enter button.
3. Set the desired address by pressing Up or Down and press the Enter button to save.
4. For the Baud Rate, look for the P.-13 parameter then press the Enter button.
5. Select 00 for 9600 Baud or 01 for 19200 Baud. Press the Enter button to save.

How to Add an MRLDS-250 to the E2 Controller

1. MRLDS-250 is only native and licensed for up to 15 devices on E2 Controllers with firmware version 4.09 and above; otherwise you must add a description file and License Key.

2.  Contact Customer Service to obtain the License Key: P/N 527-0476.
   a. Phone Number: 770-425-2724 Option 4
   b. Email: Solutions.CustomerService@Emerson.com

3. Add the description file using Ultraist.

4. Reboot the controller after the upload.

5. Load the License Key on the E2 by logging in and then press .

6. Press F1 for ADD FEATURE and enter the License Key.

7. Add the MRLDS-250 by pressing , to access Connected I/O Boards and Controllers.

8. Press F2 to select C4: Third Party tab.

9. Scroll down to MRLDS-250 and enter the quantity of MRLDS-250 devices up to the maximum indicated.

10. Press the button to save.

11. Press for Network Summary or .

12. Scroll down to the MRLDS-250 and press F4 to COMMISSION. Repeat for each MRLDS250 added.

13. Select the address the MRLDS-250 is set to and press to confirm.

14. The MRLDS-250 should be Online on the E2 Network Summary (press ).

How to Configure Alarm Setup on the E2 Controller

1.  Press and then select MRLDS250.
2.  Press F5 for SETUP and F2 to select C2: Set Points.
3. Set the parameters depending on the System Requirement and press the button to save.

MRLDS to MultiFlex I/O
How to Set a MultiFlex Input Point
An input point on a Multiplex board consists of two terminals. One of these terminals labeled as SIG reads the signal from the sensor, while the other, labeled 0v is where the sensor ground wire is connected:

The Analog Output Signal(+) should go to (SIG) terminal of the Multiplex board and the Ground (GND) should go to (0v) terminal of the board. The DIP switch setting of the Multiplex board terminal for the MRLDS-250 should be in the OFF position (see Figure A-9) because it supplies its own voltage signal to the point:

How to Set the Input Type on the E2 Controller

1. Press to go to the Input Status Screen.
2. Select the input point where the MRLDS-250 is connected, and press F1 for SETUP. Press for Analog.
3. Highlight Sensor Type and press F4 for LOOK UP. Select Linear and press to confirm.
4. Navigate down to Eng Units and press F4 for LOOK UP. Select PPM 33 and press e to confirm.
5. Set the Low End Point and High-end Point equivalent to the range set on P-.03 for Analog Output.
6. Set the Low End EU and the High End EU equivalent to PPM Scaling set on P.-16.
7. For the Low End Limit, set it to -10% of Low End EU and for the High-end Limit, set it to +10% of High End EU.
8. Press the button to save.

The contents of this publication are presented for informational purposes only and they are not to be construed as warranties or guarantees, express or implied, regarding the products or services described herein or their use or applicability. Emerson Climate Technologies Retail Solutions, Inc. and/or its affiliates (collectively “Emerson”), reserves the right to modify the designs or specifications of such products at any time without notice. Emerson does not assume responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use and maintenance of any product remains solely with the purchaser and end-user.
Emerson is a trademark of Emerson Electric Co. ©2020 Emerson Climate Technologies Retail Solutions, Inc. All rights reserved.

EMERSON.CONSIDER IT SOLVED
Digital Solutions
1065 Big Shanty Road NW, Suite 100
Kennesaw, GA 30144 USA
770-425-2724
1-800-829-2724
www.climate.emerson.com
Email: ColdChain.TechnicalServices@Emerson.com

References

• Copeland | Copeland US
• Emerson Global | Emerson

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