Bacharach MGS-250 Operating Manual

Infrared Gas Detector

Installation and Operation Manual

Instruction 6490-9000

November 2017

Revision 5

Product Leadership  Training  Service  Reliability

MGS-250 Manual

2 6490-9000 Revision 5

WARRANTY POLICY

BACHARACH, INC. WARRANTS THIS GAS DETECTOR TO BE FREE FROM DEFECTS
IN MATERIALS AND WORKMANSHIP FOR A PERIOD OF ONE YEAR FROM THE DATE
OF PURCHASE BY THE ORIGINAL OWNER. IF THE PRODUCT SHOULD BECOME
DEFECTIVE WITHIN THIS WARRANTY PERIOD, WE WILL REPAIR OR REPLACE IT AT
OUR DISCRETION.

THE WARRANTY STATUS MAY BE AFFECTED IF THE GAS DETECTOR HAS NOT
BEEN USED AND MAINTAINED PER THE INSTRUCTIONS IN THIS MANUAL OR HAS
BEEN ABUSED, DAMAGED, OR MODIFIED IN ANY WAY. THIS GAS DETECTOR IS
ONLY TO BE USED FOR PURPOSES STATED HEREIN. THE MANUFACTURER IS NOT
LIABLE FOR AUXILIARY INTERFACED EQUIPMENT OR CONSEQUENTIAL DAMAGE.

DUE TO ONGOING RESEARCH, DEVELOPMENT, AND PRODUCT TESTING, THE
MANUFACTURER RESERVES THE RIGHT TO CHANGE SPECIFICATIONS WITHOUT
NOTICE. THE INFORMATION CONTAINED HEREIN IS BASED ON DATA CONSIDERED
ACCURATE. HOWEVER, NO WARRANTY IS EXPRESSED OR IMPLIED REGARDING
THE ACCURACY OF THIS DATA.

ALL GOODS MUST BE SHIPPED TO THE MANUFACTURER BY PREPAID FREIGHT.
ALL RETURNED GOODS MUST BE PRE-AUTHORIZED BY OBTAINING A RETURN
MERCHANDISE AUTHORIZATION (RMA) NUMBER. CONTACT THE MANUFACTURER
FOR A NUMBER AND PROCEDURES REQUIRED FOR PRODUCT TRANSPORT.

SERVICE POLICY

BACHARACH, INC. MAINTAINS SERVICE FACILITIES AT LOCATIONS
WORLDWIDE. SOME DISTRIBUTORS / AGENTS MAY ALSO HAVE REPAIR
FACILITIES, HOWEVER, BACHARACH ASSUMES NO LIABILITY FOR SERVICE
PERFORMED BY ANYONE OTHER THAN BACHARACH PERSONNEL. REPAIRS
ARE WARRANTED FOR 90 DAYS AFTER DATE OF SHIPMENT (SENSORS,
PUMPS, FILTERS AND BATTERIES HAVE INDIVIDUAL WARRANTIES). SHOULD
YOUR GAS DETECTOR REQUIRE NON-WARRANTY REPAIR, YOU MAY
CONTACT THE DISTRIBUTOR FROM WHOM IT WAS PURCHASED OR YOU MAY
CONTACT BACHARACH DIRECTLY.

IF BACHARACH IS TO DO THE REPAIR WORK, SEND THE GAS DETECTOR,
PREPAID, TO THE APPROPRIATE ADDRESS BELOW.

Location

Contact Information

Shipping Address

United States

Phone: [phone]
Toll Free: 1-800-736-4666
Fax: [phone]
Email: [e-mail]

Bacharach, Inc.

621 Hunt Valley Circle

New Kensington, PA 15068, USA

ATTN: Service Department

Europe

Phone: [phone]
Fax: [phone]
Email: [e-mail]

Bacharach, Inc.

114A Georges Street Lower

Dun Laoghaire, Dublin, Ireland

ATTN: Service Department

Canada

Phone: [phone]
Fax: [phone]
Email: [e-mail]

Bacharach, Inc.

10 West Pearce Street, Unit 4

Richmond Hill, Ontario LB4 1B6, Canada

ATTN: Service Department

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ALWAYS INCLUDE YOUR RMA # (WHICH CAN BE DOWLOADED FROM
WWW.MYBACHARACH.COM/RMAFORM/), ADDRESS, TELEPHONE NUMBER,
CONTACT NAME, SHIPPING/BILLING INFORMATION AND A DESCRIPTION OF
THE DEFECT AS YOU PERCEIVE IT. YOU WILL BE CONTACTED WITH A COST
ESTIMATE FOR EXPECTED REPAIRS PRIOR TO THE PERFORMANCE OF ANY
SERVICE WORK. FOR LIABILITY REASONS, BACHARACH HAS A POLICY OF
PERFORMING ALL NEEDED REPAIRS TO RESTORE THE GAS DETECTOR TO
FULL OPERATING CONDITION.

PRIOR TO SHIPPING EQUIPMENT TO BACHARACH, CONTACT THE
APPROPRIATE OFFICE FOR AN RMA # (RETURN MERCHANDISE
AUTHORIZATION). ALL RETURNED GOODS MUST BE ACCOMPANIED BY AN
RMA NUMBER.

PACK THE EQUIPMENT WELL (IN ITS ORIGINAL PACKING IF POSSIBLE), AS
BACHARACH CANNOT BE HELD RESPONSIBLE FOR ANY DAMAGE INCURRED
DURING SHIPPING TO OUR FACILITY.

NOTICES

COPYRIGHTS: THIS MANUAL IS SUBJECT TO COPYRIGHT PROTECTION; ALL
RIGHTS ARE RESERVED UNDER INTERNATIONAL AND DOMESTIC
COPYRIGHT LAWS. THIS MANUAL MAY NOT BE COPIED OR TRANSLATED, IN
WHOLE OR IN PART, IN ANY MANNER OR FORMAT, WITHOUT THE WRITTEN
PERMISSION OF BACHARACH, INC.

ALL SOFTWARE WHICH BACHARACH UTILIZES AND/OR DISTRIBUTES, HOLDS
A PROPRIETARY INTEREST AND IS ALSO SUBJECT TO COPYRIGHT
PROTECTION AND ALL RIGHTS ARE RESERVED. NO PARTY MAY USE OR
COPY SUCH SOFTWARE IN ANY MANNER OR FORMAT, EXCEPT TO THE
EXTENT THAT BACHARACH GRANTS THEM A LICENSE TO DO SO. IF THIS
SOFTWARE IS BEING LOADED ONTO MORE THAN ONE COMPUTER, EXTRA
SOFTWARE LICENSES MUST BE PURCHASED.

TECHNICIAN USE ONLY

THIS UNIT MUST BE INSTALLED BY A QUALIFIED TECHNICIAN WHO WILL
INSTALL THIS UNIT IN ACCORDANCE WITH THESE INSTRUCTIONS AND THE
STANDARDS IN THEIR PARTICULAR INDUSTRY/COUNTRY. OPERATORS OF
THE UNIT SHOULD BE AWARE OF THE REGULATIONS AND STANDARDS IN
THEIR INDUSTRY/COUNTRY FOR THE OPERATION OF THIS UNIT. THESE
NOTES ARE ONLY INTENDED AS A GUIDE, AND THE MANUFACTURER BEARS
NO RESPONSIBILITY FOR THE INSTALLATION OR OPERATION OF THIS UNIT.

FAILURE TO INSTALL AND OPERATE THE UNIT IN ACCORDANCE WITH THESE
INSTRUCTIONS AND WITH INDUSTRY GUIDELINES MAY CAUSE SERIOUS
INJURY INCLUDING DEATH, AND THE MANUFACTURER WILL NOT BE HELD
RESPONSIBLE IN THIS REGARD.

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Table of Contents

SECTION 1. INTRODUCTION ........................................................................ 9

1.1. Overview ...................................................................................................... 9

1.2. Detection Options ........................................................................................ 9

1.2.1. Broadband vs. Gas Specific ................................................................ 9

1.2.2. Broadband Gas Detection ................................................................ 10

1.2.3. Detecting Specific Gases .................................................................. 11

1.3. Remote Controller Options ........................................................................ 15

1.4. Parts List ..................................................................................................... 15

1.5. Specifications ............................................................................................. 16

SECTION 2. MOUNTING THE GAS DETECTOR ............................................. 17

2.1. Warnings and Prerequisites ....................................................................... 17

2.2. Mounting Locations ................................................................................... 17

2.2.1. General Placement Guidelines ......................................................... 17

2.2.2. Machinery Rooms ............................................................................ 18

2.2.3. Refrigerated Spaces ......................................................................... 18

2.2.4. Chillers ............................................................................................. 19

2.3. Mounting Procedure .................................................................................. 19

SECTION 3. WIRING AND CONFIGURATION ............................................... 22

3.1. Overview .................................................................................................... 22

3.2. Wiring Supply Power (24VAC or 24VDC) .................................................... 23

3.3. Wiring Alarm Output (Analog Signal) ......................................................... 25

3.4. Wiring the Digital Alarm Output Relay ....................................................... 26

3.5. Modbus Network Configuration ................................................................ 27

3.6. Conclusion .................................................................................................. 29

SECTION 4. OPERATION AND STABILIZATION ............................................ 30

4.1. Power Up and Warmup.............................................................................. 30

4.2. Stabilization ................................................................................................ 30

4.3. Perform a Manual Zero .............................................................................. 30

4.4. Alarms ........................................................................................................ 31

4.5. Gas Detector Faults .................................................................................... 31

4.5.1. Overview .......................................................................................... 31

4.5.2. Non-Critical Faults ............................................................................ 31

4.5.3. Critical Faults .................................................................................... 32

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SECTION 5. CONFIGURE THE GAS DETECTOR ............................................. 33

5.1. User Interface Overview ............................................................................ 33

5.2. Setting Parameters ..................................................................................... 34

5.2.1. Overview .......................................................................................... 34

5.2.2. Configuration Parameters ................................................................ 34

5.3. Completing Setup ....................................................................................... 42

SECTION 6. FUNCTIONAL TESTS AND ADJUSTMENTS ................................ 43

6.1. Introduction ............................................................................................... 43

6.2. Bump Testing vs. Adjusting Detector Response ......................................... 44

6.3. Bump Testing ............................................................................................. 45

6.4. Adjustment Using Calibration Gas ............................................................. 46

SECTION 7. MODBUS COMMUNICATIONS ................................................ 49

7.1. Introduction ............................................................................................... 49

7.2. Communications Settings .......................................................................... 49

7.3. Analog Input Registers ............................................................................... 50

7.4. Analog Output Registers ............................................................................ 51

7.5. Input Status Flags ....................................................................................... 52

7.6. Output Status Flags .................................................................................... 52

SECTION 8. TROUBLESHOOTING ............................................................... 53

8.1. Fault Codes ................................................................................................. 53

8.2. Diagnostics Attributes (P.-18) .................................................................... 55

8.3. Resetting MGS-250 to Default Values ........................................................ 56

8.4. Other Symptoms ........................................................................................ 57

SECTION 9. REPLACEMENT PARTS AND ACCESSORIES ................................... 58

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List of Figures

SECTION 1. INTRODUCTION ........................................................................ 9

Figure 1. MGS-250 Components ......................................................................... 9

Figure 2. Broadband Gas Groups 1-3 ................................................................ 11

Figure 3. Gas Specific MGS-250 Gas Detectors ................................................. 12

Figure 4. Changing Gas Types and Accuracy ..................................................... 14

SECTION 2. MOUNTING THE GAS DETECTOR ............................................. 17

Figure 5. Initial Housing Separation .................................................................. 20

Figure 6. Front and Back Views of MGS-250 Base ............................................ 21

SECTION 3. WIRING AND CONFIGURATION ............................................... 22

Figure 7. Terminal Blocks and Cable Glands ..................................................... 22

Figure 8. Supply Power Wiring Options ............................................................ 23

Figure 9. Maintaining Neutral Polarity .............................................................. 24

Figure 10. Analog Output Wiring ...................................................................... 25

Figure 11. Sample Relay Output Wiring ............................................................ 26

Figure 12. Modbus Network Wiring .................................................................. 27

Figure 13. Setting Network Termination Resistors ........................................... 29

SECTION 5. CONFIGURE THE GAS DETECTOR ............................................. 33

Figure 14. The User Interface of the MGS-250 ................................................. 33

Figure 15. Analog Output Scaling Options ........................................................ 39

SECTION 6. FUNCTIONAL TESTS AND ADJUSTMENTS ................................ 43

Figure 16. Using Calibration Gas ....................................................................... 46

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List of Tables

SECTION 1. INTRODUCTION ........................................................................ 9

Table 1: Broadband Gas Groups and Performance (P/N 6401-0500) ................ 10

Table 2: Gas Specific Detector Measurement Performance .............................. 13

Table 3: Parts List ............................................................................................... 15

Table 4: Technical Specifications ....................................................................... 16

SECTION 3. WIRING AND CONFIGURATION ............................................... 22

Table 5: Power Options and Terminal Block Connections ................................. 23

Table 6: Alarm Output Terminal Block Connections .......................................... 25

Table 7: Relay Output Terminal Block Connections ........................................... 26

Table 8: Modbus Network Communications Connections ................................ 27

SECTION 4. OPERATION AND STABILIZATION ............................................ 30

Table 9: MGS-250 Behavior during Alarm Conditions ....................................... 31

Table 10: MGS-250 Behavior during a Non-Critical Fault .................................. 32

Table 11: MGS-250 Behavior during a Critical Fault .......................................... 32

SECTION 5. CONFIGURE THE GAS DETECTOR ............................................. 33

Table 12: Button Functions ................................................................................ 33

Table 13: Parameter Numbers, Names and Descriptions .................................. 34

SECTION 7. MODBUS COMMUNICATIONS ................................................ 49

Table 14: Analog Input Registers ....................................................................... 50

Table 15: Analog Output Registers .................................................................... 51

Table 16: Input Status Flags ............................................................................... 52

Table 17: Output Status Flags ............................................................................ 52

SECTION 8. TROUBLESHOOTING ............................................................... 53

Table 18: Fault Codes ......................................................................................... 54

Table 19: Diagnostic Attributes .......................................................................... 55

Table 20: Other Symptoms and Possible Causes ............................................... 57

SECTION 9. REPLACEMENT PARTS AND ACCESSORIES ................................... 58

Table 21: Replacement Parts and Accessories ................................................... 58

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Section 1. Introduction

1.1. Overview

The MGS-250 NDIR (non-dispersive infrared) is a state-of-the-art fixed
gas detector which can detect a wide range of refrigerant gases. The
MGS-250 can be used on a stand-alone basis or integrated into controls
or a Building Management System (BMS).

The MGS-250 can be used in locations that require continuous
monitoring and to add gas detection solutions to an existing system.

Figure 1. MGS-250 Components

1.2. Detection Options

1.2.1. Broadband vs. Gas Specific

The MGS-250 NDIR refrigerant gas detectors are available in two
versions: broadband and gas specific.

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1.2.2. Broadband Gas Detection

The broadband gas detector (P/N 6401-0500) 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 (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 three groups
shown in Figure 2. Measurement performance is based on an average
response profile for all of the gases within the group.

NOTE: Greater accuracy may be achieved through the use of
calibration gas and the adjustment procedure detailed in
Section 6.

Table 1: Broadband Gas Groups and Performance (P/N 6401-0500)

Group #

Value for Param 111

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.-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%

1 See Section 5 for information on Parameter 11 and other configuration instructions.
2 Accuracy applies to range from 0 – 1,000ppm.

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Figure 2. Broadband Gas Groups 1-3

1.2.3. Detecting Specific Gases

Each gas-specific gas detector (PNs 6401-0501 to 6401-0520) is
shipped factory calibrated to its specific target refrigerant. Refer to
Figure 3 and Table 2.

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Figure 3. Gas Specific MGS-250 Gas Detectors

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Table 2: Gas Specific Detector Measurement Performance

Part Number

Refrigerant1

Accuracy

6401-0501

R22

±5%

6401-0503

R134a

±5%

6401-0504

R404a

±5%

6401-0505

R407a

±3%

6401-0506

R407c

±3%

6401-0507

R407f

±3%

6401-0508

R410a

±3%

6401-0509

R422a

±5%

6401-0510

R422d

±5%

6401-0511

R427a

±3%

6401-0512

R507

±5%

6401-0513

HFO1234YF

±5%

6401-0514

HFO1234Ze

±5%

6401-0515

HFO1233ZD

±5%

6401-0516

R32

±5%

6401-0517

R448A

±5%

6401-0518

R449A

±5%

6401-0519

R513A

±5%

6401-0520

R452A

±5%

6401-0521

R452B

±5%

6401-0522

R514A

±5%2

1 See Section 5 for information on Parameter 11 and other configuration instructions.
2 Accuracy applies to range from 0 – 1,000ppm.

NOTE: Gas specific detectors can be re-calibrated in the field
to new target gases. Use optional calibration instructions in
Chapter 6 for increased accuracy when detecting a new target
gas that is different from the “as shipped” target gas. Refer to
the example in Figure 4.

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As Shipped

Part number 6401-0501 (R22) is factory calibrated to R22 and
has an as-shipped R22 response accuracy of 5% of reading.

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). If
changed, the gas detector will have a lower accuracy for the
target refrigerant (without calibration). In this example, that
accuracy is 16% of reading.

Optional Recalibr

ation

(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 of 5% of reading as shown in Table 2 for the new

target refrigerant.

Figure 4. Changing Gas Types and Accuracy

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1.3. Remote Controller Options

The MGS can connect to any controller through the standard analog
output (voltage and current; see Table 4 for options), the standard alarm
relay, or the digital Modbus RTU communications interface.

1.4. Parts List

Table 3 shows a list of components that are shipped with your order.

Table 3: Parts List

Part Number

Description

Various (Depends on Model Ordere

d)

6401-0500

MGS-250, Broadband

6401-0501

MGS-250, R22

6401-0503

MGS-250, R134a

6401-0504

MGS-250, R404a

6401-0505

MGS-250, R407a

6401-0506

MGS-250, R407c

6401-0507

MGS-250, R407f

6401-0508

MGS-250, R410a

6401-0509

MGS-250, R422a

6401-0510

MGS-250, R422d

6401-0511

MGS-250, R427a

6401-0512

MGS-250, R507

6401-0513

MGS-250, HFO1234YF

6401-0514

MGS-250, HFO1234ZE

6401-0515

MGS-250, HFO1233ZD

6401-0516

MGS-250, R32

6401-0517

MGS-250, R448A

6401-0518

MGS-250, R449A

6401-0519

MGS-250, R513A

6401-0520

MGS-250, R452A

6401-0521

MGS-250, R452B

6401-0522

MGS-250, R514A

6490-9000

Installation and Operation Manual

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1.5. Specifications

Table 4: Technical Specifications

Specification

Description

Power Supply

24 VDC @ 0.15 A min;
24 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

Fault Monitoring

Fault codes presented to user

Analog Outputs

4-20 mA; 0-5 V; 0-10 V; 1-5 V; 2-10 V

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

IP Rating

Not IP rated. An accessory splash shield is available
for areas requiring additional protection from wash
down.

Response Time

T90 < 5 minutes

Temperature Rating

-22 to 104 F (-30 to 40 C)

Humidity and
Elevation

5-90% relative humidity, non-condensing,
0-10,000 ft. altitude

Weights/Dimensions

6.3 oz, 4.0” x 5.5” x 1.5” (180 g, 102 x 140 x 37 mm)

Enclosure

ABS plastic; UL flammability rating of 94V-0

Approvals

CE, UL/CSA/IEC/EN 61010-1

1 When filtering is disabled (see parameter P.-19 on page 42), the unit will respond to

concentrations sub-10 ppm.

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Section 2. Mounting the Gas Detector

2.1. Warnings and Prerequisites

WARNING: Explosion hazard! Do not mount the MGS-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 MGS-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 monitor must be connected to a marked, suitably
located and easily reached switch or circuit-breaker as means
of disconnection.

NOTE: 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 MGS-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 MGS-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: 6900-0001)
should be used in conjunction with the MGS-250.

Gas detectors must be located within the appropriate wire lengths from
the central control unit (if used).

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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 will help to make
a decision. Gas detectors monitor a point as opposed to an area. If the
gas leak does not reach the detector then no alarm will be triggered.
Therefore, it is extremely important to carefully select the gas detector
location. Also consider ease of access for maintenance.

The size and nature of the site will help to decide which method is the
most appropriate to use. Locations requiring the most protection in a
machinery or plant room would be around compressors, pressurized
storage vessels, refrigerant cylinders or storage rooms or pipelines. The
most common leak sources are valves, gauges, flanges, joints (brazed or
mechanical), filling or draining connections, etc.

 In machinery rooms where there is little or no airflow, placement

options are:
o 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.

o 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 ground

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
jet and not be detected 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