Bacharach HGM300 Guide

HGM300 / RDM800
Refrigerant Gas Monitoring System
Instruction 3015-4148
Installation / Operation / Maintenance
Rev. 5 – April 2006
INSPECTION EQUIPMENT
MEASURING EQUIPMENT
61KN
Product Leadership • Training • Service • Reliability

AInstruction 3015-4148
Notice:
Product improvements and enhancements are continuous; therefore the specifications and information
contained in this document may change without notice.
Bacharach, Inc. shall not be liable for errors contained herein or for incidental or consequential damages in
connection with the furnishing, performance, or use of this material.
No part of this document may be photocopied, reproduced, or translated to another language without the
prior written consent of Bacharach, Inc.
Copyright © 2000–2006, Bacharach, Inc., All Rights Reserved
BACHARACH®is a registered trademark of Bacharach, Inc. All other trademarks, trade names,
service marks and logos referenced herein belong to their respective owners.

Instruction 3015-4148 i
Table of Contents
TABLE OF CONTENTS..................................................................................................................................................... I
INTRODUCTION............................................................................................................................................................. II
SAFETY PRECAUTIONS................................................................................................................................................. III
WARNING STATEMENTS .............................................................................................................................................. IV
CAUTION STATEMENTS ...............................................................................................................................................IV
HAZARD SYMBOLS ON MONITOR ................................................................................................................................IV
FUNCTIONAL OVERVIEW .............................................................................................................................................. V
HGM300 INSTALLATION...........................................................................................................................................1
HGM300 -INSTALLATION CONSIDERATIONS................................................................................................................2
HGM300 -MOUNTING INSTRUCTIONS..........................................................................................................................3
HGM300 -CONNECTING AIR LINES..............................................................................................................................4
HGM300 -INTERIOR SCHEMATIC .................................................................................................................................6
HGM300 -ELECTRICAL WIRING...................................................................................................................................8
HGM300 -CONNECTING COMMUNICATION DEVICES .................................................................................................10
MULTIPLE HGM’S.......................................................................................................................................................12
CONNECTING TO A BUILDING MANAGEMENT SYSTEM ................................................................................................12
HGM300 -PC SOFTWARE...........................................................................................................................................13
HGM300 -CURRENT LOOP INTERFACES.....................................................................................................................16
HGM300 -CONNECTING EXTERNAL ALARMS ............................................................................................................17
RDM800 INSTALLATION.........................................................................................................................................19
RDM800 -INSTALLATION CONSIDERATIONS..............................................................................................................20
RDM800 -MOUNTING INSTRUCTIONS ........................................................................................................................21
RDM800 -INTERIOR SCHEMATIC................................................................................................................................22
RDM800 -ELECTRICAL WIRING.................................................................................................................................24
RDM800 -COMMUNICATION CONNECTIONS ..............................................................................................................26
RDM800 -CONNECTING EXTERNAL ALARMS ............................................................................................................28
RDM800 OPERATION................................................................................................................................................29
RDM800 -OVERVIEW.................................................................................................................................................30
RDM800 -SCREEN DISPLAYS .....................................................................................................................................31
RDM800 -SYSTEM PROGRAMMING............................................................................................................................32
RDM800 -SETUP PROGRAMMING...............................................................................................................................33
HGM300 -SETUP PROGRAMMING ..............................................................................................................................37
RDM800 -ZONE SETUP PROGRAMMING.....................................................................................................................41
GENERAL OPERATION .................................................................................................................................................44
WORKING WITH ALARMS ............................................................................................................................................50
WORKING WITH THE TREND SCREEN...........................................................................................................................53
WORKING WITH SYSTEM FAULTS................................................................................................................................54
WORKING WITH THE CALIBRATION SCREEN................................................................................................................57
WORKING WITH THE DIAGNOSTIC SCREEN..................................................................................................................60
SERVICE MODE............................................................................................................................................................62
APPENDIX....................................................................................................................................................................63
HGM300 /RDM800 MAINTENANCE ..........................................................................................................................64
OPTIONAL ACCESSORIES .............................................................................................................................................65
RDM800 -LOGIC DIAGRAM .......................................................................................................................................66
TABLE OF RECOMMENDED ALARM SETTINGS .............................................................................................................67
RS-485 COMMUNICATION PROTOCOL.........................................................................................................................68
HGM300 MODBUS RTU OPERATION.......................................................................................................................69
WARRANTY AND SERVICE....................................................................................................................................82
HGM300 -SPECIFICATIONS ........................................................................................................................................84
RDM800 -SPECIFICATIONS.........................................................................................................................................85

ii Instruction 3015-4148
Introduction
How to Use This Manual
Thank you for investing in a BACHARACH HGM300 Refrigerant Gas Monitor.
This manual provides important information on how to install, operate, and service the HGM300 Refrigerant
Monitor and RDM800 Display Module.
Please read this manual carefully before use.
If you have a working knowledge of refrigerant monitors, you will find this manual useful as a reference tool. If
you are new to the use of refrigerant monitors, you can educate yourself about the principles of refrigerant gas
detection and the proper operation of this device by reading this manual thoroughly.

Instruction 3015-4148 iii
Safety Precautions
AC Power Supply
Ensure the source voltage matches the voltage of the product before energizing the equipment. It is highly
suggested that the HGM300 be placed on a separate circuit with UPS or surge protection.
•A switch or circuit-breaker shall be included in the building installation
•It shall be in close proximity to the equipment and within easy reach of the operator
•It shall be marked as the disconnecting device for the equipment
Protective Grounding
Under no circumstances should this equipment be operated without connection to a protective ground. Doing
so poses a potential shock hazard and is also a violation of electrical safety standards applicable to this type
of equipment.
Explosive Atmosphere
Do not operate this equipment in the presence of flammable liquids, vapors or aerosols. Operation of any
electrical instrument in such an environment constitutes a safety hazard.
Proper Exhaust Venting
It is imperative that the exhaust port on this instrument be properly vented as described in this manual. Failure
to do so constitutes a safety hazard.
Working Inside Instrument
Extreme care should be exercised when accessing the interior of this instrument. Only qualified electrical
maintenance personnel should perform connections and adjustments. Always de-energize the power supply
before working inside the instrument.
Modifications to the Instrument
Under no circumstances should this instrument be modified without written consent from Bacharach, Inc.
Changes or modifications to this instrument, not expressly approved, will void the warranty.
In Case of Malfunction
Do not continue to use this equipment if there are any symptoms of malfunction or failure. In the case of such
occurrence, de-energize the power supply and contact a qualified repair technician or the nearest Bacharach
Service Center. ONLY provided knockout are to be used for electrical and communication wiring. Drilling into
the box will void the warranty.
Fusing
HGM300, 120 VAC Input, Power Supply P/N 3015-3167
F1: 0.5 A, 250V Fast Acting, 5mm x 20mm, P/N 604-2538
F2: 250 mA, 250V Fast Acting, 5mm x 20mm, P/N 604-2537
F3: 5 A, 250V Fast Acting, 5mm x 20mm, P/N 604-2539
F4: 63 mA, 250V Fast Acting, 5mm x 20mm, P/N 604-2535
HGM300, 240 VAC Input, Power Supply P/N 3015-3161
F1: 250 mA, 250V Fast Acting, 5mm x 20mm, P/N 604-2537
F2: 125 mA, 250V Fast Acting, 5mm x 20mm, P/N 604-2536
F3: 5 A, 250V Fast Acting, 5mm x 20mm, P/N 604-2539
F4: 32 mA, 250V Fast Acting, 5mm x 20mm, P/N 604-2534
RDM800
F1 & F2: 1 A, 250VAC, Fast Acting, 5mm x 20mm, P/N 3015-4011

iv Instruction 3015-4148
Safety Precautions (Cont.)
Installation Category
Installation Category II, Pollution Degree II, as defined by UL.
Altitude Limit
2,000 meters
Cleaning
USE a dry cloth to clean the outside of the case. DO NOT use soap and water.
Warning Statements
The use of the word WARNING in this manual denotes a potential hazard associated with the use of this
equipment. It calls attention to a procedure, practice, or condition, or the like, which if not correctly performed
or adhered to, could result in personal injury or death.
Caution Statements
The use of the word CAUTION in this manual denotes a potential hazard associated with the use of this
equipment. It calls attention to a procedure, practice, condition, or the like, which if not correctly performed or
adhered to, could result in damage to the equipment.
Hazard Symbols on Monitor
This symbol indicates the need to consult this operating
instruction manual when opening the enclosure.
WARNING: A potential risk exists if the operating instructions
are not followed.
This symbol indicates the presence of electric shock hazards
when the enclosure is opened.
WARNING: To avoid risk of injury from electric shock, do not
open the enclosure when power is applied.

Instruction 3015-4148 v
Functional Overview
General Description
Refrigerant monitors are specified to support compliance to federal, state and local safety codes governing
refrigerant emissions. Avoiding significant refrigerant loss reduces equipment replacement costs, maintains
equipment efficiency, promotes safety, and protects the environment.
The HGM300 provides for the continuous monitoring of refrigerant gas levels in up to 16 separate test zones.
The instrument is easily programmed to monitor a variety of gasses and independent leak (small), spill
(medium), and evacuation (large) levels may be designated for each zone. The instrument also retains a log
of previous readings that can be easily accessed for analysis.
An audible alarm and large LED indicators are provided to signal alarm conditions, and relay contacts are
provided for connection of external alarm devices. The system also includes two (2) 4-20mA current loop
interfaces (optional) for connection to external devices.
The HGM300 requires only minor periodic maintenance such as the occasional replacement of filters. The
instrument incorporates active diagnostics that continuously monitor the system for proper operation. An LED
indicator is provided to indicate system malfunctions and fault codes are generated that enable the user to
identify the source of the fault.
Communication Options
The HGM300 features full two-way communications via an RS-485 interface. MODBUS RTU is the
communication protocol standard. The instrument can be connected directly to a Building Management
System or it may be operated as a stand-alone system using the Bacharach Display Module
(P/N 3015-2875).
An RS-232C port is also provided for connection to a PC. This enables the HGM300 to be setup from a
personal computer.
Please refer to the Appendix for a more complete discussion of communication protocols.
Understanding Monitoring Levels
Effective use of this instrument requires an understanding of what constitutes reasonable alarm set points for
the type of gasses being monitored. All AC&R systems leak some refrigerant. In a good “tight” installation
these background levels will be acceptably low and often do not require corrective action. You can reduce
nuisance alarms and needless service calls if the alarm levels are set at practical limits.
Refrigerant manufacturers define allowable exposure levels and threshold limit values in units of parts per
million (PPM). Bacharach has developed recommended monitoring levels based on compliance to ANSI/BSR
ASHRE 15-1994 and ASHRAE Safety Code 34-1992. These reference levels are listed in the Appendix.
Setting the unit at these recommended alarm levels will satisfy the needs of most users. However, the PPM
levels generated by system leaks into the environment are greatly influenced by the volume of air in the
sampling area, air circulation, size of the leak, distance to the monitoring point, and a host of other variables.
In some cases the set points may need to be adjusted either up or down to achieve effective monitoring.
Suggested Location of Sampling Points
At the point of a refrigerant leak the gas is nearly pure. As the refrigerant is dispersed into the air, the gas
molecules diffuse causing a dilution of the original concentration. The HGM300 measures the refrigerant
concentration at the precise point the sample is collected. Therefore, if the termination of the collection line is
not at the exact point of the refrigerant leak, then the unit will read a diluted mixture of the refrigerant gas
and air.
It should also be noted that refrigerant gas is heavier than air and tends to collect below the point of a leak.
Therefore samples taken near the floor will have a greater concentration of gas than those collected above
the source of a leak will. Consequently, sampling points should ideally be located as close as possible to the
source of potential leaks. Line-end filters should be mounted 12" to18" above the floor. If this is impractical,
then the alarm set points should be adjusted for that zone to compensate for the dilution of the refrigerant gas.
DO NOT plug any of the zones. Plugging a zone will give the monitor a false indication during start up.

vi Instruction 3015-4148
The HGM300 should be centrally located in the mechanical room and be readily accessible for easy visual
monitoring and servicing. Air sample tubing may be run in lengths up to 500 feet. The fresh air purge line
should draw from an area that does not contain any refrigerant gas and cannot exceed 300 feet in length. The
exhaust line should run to an out side location if possible. The length of the exhaust line cannot exceed
300 feet.
Ideally, two to three pick up points spaced around each chiller will provide sufficient coverage. It may be
necessary to perform a “smoke” test of the mechanical room to determine the best locations. The smoke test
would provide the pattern of air currents present in the mechanical room.
HGM300 / RDM800 Refrigerant Gas leak monitor mechanical room placement
The RDM800 should be mounted outside of the mechanical room or at least just inside of a door to the room.
This is the “split architecture design” for safety of the operator. The RDM800 can be located up to 4500 feet
from the HGM300. The RDM800 is the man machine interface by which you program the HGM300,
acknowledge alarms and observe conditions inside of the mechanical room. Note that there are two additional
alarm relay contacts in the RDM800 that can be programmed to alarm with “leak, spill, evacuate, fault or
monitor on”.
Response to the Presence of Multiple Refrigerants
Technically speaking, the HGM300 is a refrigerant level monitor, not a gas analyzer. You must program the
instrument to test for a specific refrigerant in each zone, and it will only return accurate concentration readings
for that particular refrigerant. If a leak occurs of another refrigerant gas type, the instrument may return
deceptive readings.
Most applications only require detection of a single refrigerant and the problems that are associated with
monitoring multiple gasses are rarely an issue. If there is a possibility of multiple refrigerants leaking in the
same sampling zone, you should consider carefully which refrigerant compound you program the instrument
to monitor.
RDM800
Remote Display
Module outside of
mechanical room
HGM300
Halogen
Gas
Monitor
Outside Hallway
Machine Room
Sample Inlet Pickup Points
Chiller
Exhaust Fan
Sample Inlet
Pickup Point
Aux. Horn/Strobe
Remote Alarm Fresh air purge
from area away
from refrigerant
gas

Instruction 3015-4148 1
HGM300 Installation
HGM300 Oblique Photo
Upper & Lower Mounting Brackets
LED Indicators
Water Trap
Upper Mounting
Bracket
LED
Indicators
STANDARD ACCESSORIES FOR A 4-POINT SYSTEM
5 Line-End Filters (P/N 3015-3420)
Charcoal Filter & T-Bolt Bracket (P/N 3015-3125)
HGM300/RDM800 Instruction Manual
Water Trap
Lower Mounting
Br
ac
k
et

2Instruction 3015-4148
HGM300 - Installation Considerations
Locating the Monitor
The HGM300 should be centrally located in the facility and should be easily accessible for visual monitoring
and servicing. Intake sample lines can be up to 500 feet in length, but it is important to remember that
sampling cycle time is proportional to the total number and length of individual sample lines.
Dirt, grease, and oils can adversely affect the operation of the HGM300. The monitor should be installed out
of direct sunlight in a clean, dry area that is not subject to temperature or humidity extremes. Installation of the
monitor in a mechanical room is acceptable provided reasonable environmental conditions exist. If there is a
question, consider installing the unit outside of the mechanical room in a cleaner area of the facility.
WARNING – Drilling holes in the HGM300 and
RDM800 enclosure will void the warranty.
Please use knockouts provided for electrical
connections.
WARNING - Do not operate this equipment in the
presence of flammable liquids, vapors or aerosols.
Operation of any electrical instrument in such an
environment constitutes a safety hazard.
WARNING - Always de-energize the power supply
before working inside the instrument.
CAUTION - The HGM300 contains sensitive
electronic components that can be easily damaged.
Be careful not to touch or disturb any of these
components.
Inspection
The HGM300 has been thoroughly inspected and tested prior to shipment from the factory. Nevertheless, it is
recommended that the monitor be re-checked prior to installation. Inspect the outside of the enclosure to
make sure there are no obvious signs of shipping damage. Open the door latches and inspect the interior of
the instrument for loose components that may have become dislodged during shipment. If damage is
discovered, please contact the nearest Bacharach Service Center for assistance.

Instruction 3015-4148 3
HGM300 - Mounting Instructions
Screw Locations
The HGM300 should be installed plumb and level and securely fastened to a rigid mounting surface. The
enclosure utilizes keyhole mounting brackets designed for #12 pan head fasteners. Locate the four screws as
shown in the diagram and leave the screw heads protruding approximately 3/16".
HGM300 Mounting Specs
Installation
Hold the monitor flat against the mounting surface and allow it to slide down engaging the screw heads in the
keyhole slots of the mounting brackets. Adjust the screws as necessary to hold the monitor securely against
the mounting surface.

4Instruction 3015-4148
HGM300 - Connecting Air Lines
Overview
Individual sample lines are run from the HGM300 to each area of the facility to be monitored. Additionally, a
purge line is installed to provide clean air for resetting the infrared zero baseline. An exhaust line is installed
to vent residual gas away from the monitor. All air line connections are made on the left side of the enclosure
as indicated in the photograph below.
HGM300 Side View
Intake Ports
Exhaust Port
Purge Port
RS-232 Connector
Inlet / Purge Ports
RS-232
Inlet/Purge Ports
(see below) Exhaust Port

Instruction 3015-4148 5
Tubing Considerations
Use ¼" outside diameter (0.040" wall) flex tubing for all air lines (P/N 3015-3235) or equivalent. The tubing
should be clean and free of residual moisture or other contaminants. The tubing should be cut cleanly with a
sharp knife and care should be taken not to distort the tubing end.
To connect the air lines to the monitor simply push the tubing firmly onto the connector. All tubing bends
should have a radius of no less than 5" to assure proper airflow. If kinks or obstructions occur in any of the air
lines the instrument may not function properly.
Connecting Purge Line
A purge line is required to draw fresh air into the instrument and should not exceed 300 feet in length. A
charcoal filter assembly (P/N 3015-3125) has been provided to assure clean air is being drawn in through the
purge line. This filter should be mounted close to the HGM300.
It is advisable to terminate the line outdoors, provided the input is not exposed to rain, snow, ice, exhaust
fumes, or other airborne contaminates. If an outdoor installation is impractical, the line should be run to an
area inside the facility that you are certain is not contaminated with ambient refrigerant gas. A line-end filter
(P/N 3015-3420) should be attached to the end of the purge line.
Connecting Exhaust Line
An exhaust line is required to vent gas samples away from the instrument and should not exceed 300 feet in
length. The exhaust line should terminate in a location that is completely isolated from the purge line
termination point and other areas of the facility that will be monitored. Ideally this line should terminate
outdoors in a location that is not exposed to the elements. This line does not require a line-end filter. If the
exhaust line terminates outside the building, position the tubing so that no water or moisture can enter it.
Connecting Sample Intake Lines
The HGM300 is designed to accommodate up to 16 separate sample intake lines. The standard configuration
of the unit includes one manifold of 4 intake connectors and 1 purge connector. Additional manifolds can be
easily installed to increase monitoring capacity (field installation kit P/N 3015-3419, and 4 zone line end filter
kit P/N 3015-3411).
Sample intake lines can be up to 500 feet. All line terminations should be positioned to reduce the possibility
of mists, aerosols, oil, water, dust, or other contaminates being drawn into the instrument. A line-end filter
(P/N 3015-3420) should be attached to the end of each sample intake line. Line-end filters should be placed
12" to 18" above the floor.
IMPORTANT: DO NOT plug any of the zones. Plugging a zone will give the monitor a false indication during
start up.
Please refer to the earlier Section Suggested Location of Sampling Points to learn more about where to place
the ends of the sample intake lines.
Water Trap
A water trap has been installed as a standard feature. The water trap prevents condensation or moisture
from entering the infrared device and causing serious damage. To empty the water trap, loosen the wing nut
and allow water to drain – be sure to retighten the wing nut.
CAUTION - The introduction of contaminants through
the air intake lines can result in serious and permanent
damage to the monitor.

6Instruction 3015-4148
HGM300 - Interior Schematic
Primary Filter
Intake Manifold Solenoids
Intake Solenoid Connectors
Power Supply Board
Main Board
Microcontroller Board
Infrared Optical Bench
Gas Sample Pump
Primar
y
Filter
(
P/N 3015-3071
)
Intake
Manifold
Solenoids
Gas Sample
Pump
Infrared
Optical Bench
Microcontroller
Board
Main Board
Power Supply
Board
120 or 240 VAC
Determined by
Sales Order
Intake
Manifold
Solenoid
Connectors

Instruction 3015-4148 7
AC Power / RS-485 / Relay Connector / 4-20 mAdc Current Loop
Switches / Fuses
Auxiliary AC Out Connector T2
(Used to Supply AC power to Alarm Devices)
(Overload Protected by Fuse F3)
AC IN
Connector
T1
Location of
AC Input
Line Filter
(240 VAC
Units Only)
Factory
Default Terminator IN / OUT
Dual 4-20 mAdc
Outputs
(Signal Out Only)
DO NOT APPLY
POWER!
RS-485
Connector
Relay Connector
Alarm 1, 2, 3, Fault
4–20 mAdc
Interface Board
(Optional)
AC Power
ON/OFF
Switch
Ground Stud
CPU
Reset Node Address
Switches
AC Power
ON/OFF
Switch
F1
F2
HGM300
Fuses
(Refer to
Maintenance
Section for
values Page 64)
F3
Connects to Aux. AC Out
Connector T2
5 Amp 250VAC
(P/N 604-2539)
F4

8Instruction 3015-4148
HGM300 - Electrical Wiring
It is highly recommended that the HGM300 be connected directly to the AC power source, preferably on its
own circuit. The connection should be completed with a UL rated multi-conductor wire (14-18 AWG).
Locate service knockouts on exterior of enclosure and install electrical conduit in the typical manner.
The HGM300 is available in either a 120 or 240 VAC configuration. The unit’s AC voltage rating is marked on
the outside of the enclosure. Do one of the following to connect the AC power leads and ground:
• 120 VAC Installation
Locate the AC IN connector T1 and the Ground Stud on the inside of the enclosure (Page 7).
Remove the AC IN connector from the Power Supply board, and then secure the incoming AC power line
(black) and neutral (white) wires to this connector as shown in the following illustration. Carefully plug the
connector back onto the circuit board.
Using the supplied crimp-on ring terminal, washers, and nuts, connect the AC input ground wire (green) along
with the ground wire connected to the enclosure’s lid to the monitor’s Ground Stud.
• 240 VAC Installation
Locate the AC Input Line Filter’s black and white wires, and the Ground Stud on the inside of the enclosure
(Page 7).
Using wire nuts, secure the incoming AC power Line 1 (black) and Line 2 (white) wires to the AC Input Line
Filter as shown in the following illustration.
Using the supplied crimp-on ring terminal, washers, and nuts, connect the AC input ground wire (green) along
with the ground wire connected to the enclosure’s lid to the monitor’s Ground Stud.
WARNING – Drilling holes in the HGM300 enclosure
will void the warranty. Please use knockouts provided
for electrical connections.
WARNING - Electrical installation should be
performed by a certified electrician and should comply
with all applicable local, state, and federal electrical
safety codes.
WARNING - Under no circumstances should this
instrument be operated without connection to a
protective ground. Doing so poses a potential shock
hazard and is also a violation of electrical safety
standards applicable to this type of equipment.
•A switch or circuit-breaker shall be included in the building installation
•It shall be in close proximity to the equipment and within easy reach of the operator
•It shall be marked as the disconnecting device for the equipment

Instruction 3015-4148 9
HGM300 AC Input Power and Ground Connections

10 Instruction 3015-4148
HGM300 - Connecting Communication Devices
Remote Display Module (RDM800) Connection
The HGM300 is connected to the RDM800 using a shielded twisted pair instrument cable. The maximum
distance between the farthest away HGM300 and RDM800 is 4500 feet.
Use any of the remaining service knockouts to gain access to the interior of the monitor. The RS-485
communication wiring between the HGM300 and RDM800 must be connected in the following manner:
Locate the RS-485 connector in the HGM300 (Page 7). Connect one lead of a twisted shielded pair to the
“B” connection point (the far left point), note the wire color. Connect the second wire to the “A” connection
point (the middle), note the wire color. Connect the ground to the “GND” connection point
Locate the RS-485 connector marked “TO MONITORS” in the RDM800 (Page 23). This connector is
located on the far-left bottom of the RDM800 PC board. Make the wire run to the RDM800 and connect
the twisted shielded pair to the RS-485 TO MONITORS connector using the same color code as used on
the HGM300.
Integrating with Building Management Systems
The HGM300 may be connected directly to a Building Management System using a shielded twisted pair
cable. The cable from the Building Management System is connected to the RS-485 connector inside the
HGM300. MODBUS RTU is the standard communication protocol.
Use any of the remaining service knockouts to gain access to the interior of the monitor. Locate the RS-485
connector and remove it from the circuit board. Secure the wire leads to the connector orienting them as
shown in the diagram below. Check to make sure that the polarity matches the wiring to the Building
Management System. When you are through securing the connections, carefully plug the connector back
onto the circuit board.
Larger Integrated Systems
You may also connect the HGM300 to a Building Management System through an RDM800. In this case, first
connect the HGM300 to the RDM800 as described above. Then, follow the instructions under the heading
RDM800 – Communications Connections on Page 26 for information on how to connect the RDM800 to a
Building Management System.
RS-485 Connector

Instruction 3015-4148 11
Changing Terminator Switch Settings
The terminator switch is shipped from the factory in the terminated or “IN” position. This is the correct setting if
the HGM300 is connected as a single device, or it is the last device on the network chain. If the HGM300 is
being installed in the middle of a network, the terminator must be moved to the “OUT” position.
Locate the switch and determine its position. If it needs to be moved, slide the switch to the appropriate
position.
HGM Node Address Dip Switch Settings
(Refer to Multiple HGM's and Connecting to a Building Management System)
Each HGM300 on the network must have a distinct node address. The node address may be set from 1 to 15.
Four dip switches numbered 1, 2, 4, 8 on the main circuit board are used to define this value by setting the
correct combination of dip switches to their ON positions. The node address is the sum of the switch numbers
that are ON.
Example: - For node address “5” switches 1 and 4 are ON.
- For node address “13” switches 1, 4, & 8 are ON.
Power must be cycled to elect this change.
Personal Computer
(Refer to HGM300 PC Software Section)
The HGM300 may be connected to a personal computer using the RS-232 interface on the left side of
the enclosure.
Software will be provided upon request or as a download from:
http://www.bacharach-inc.com/downloads.htm.
Network Node
Address
Switch
Terminator
Switch
IN OUT

12 Instruction 3015-4148
Multiple HGM’s
MULTIPLE HGM300’S WITH RDM800
NOTE 1: The last HGM300 or RDM800 on either end of the network must have its
terminator in the “IN” position, and all other units must have their terminators in the
“OUT” position.
NOTE 2: The total length of the RS-485 cable cannot exceed 4500 feet. (Use instrument
cable 20 gage multi-strand shielded and twisted pair – similar or equal to Belden
cable #8762.)
RS-485 CONNECTIONS BETWEEN HGM300’s
NOTE: The terminators in the RDM800 and HGM300 Unit 4 must be in the “IN” position.
The terminators in HGM300 Units 1, 2 & 3 must be in the “OUT” position.
TERMINATOR TERMINATOR TERMINATOR TERMINATOR
“OUT” “OUT” “OUT” “IN”
Connecting to a Building Management System
The HGM300 may be connected to a Building Management System via the RS-485 connector. The node
address switch on each HGM300 may be set from “1” to “15” in order to identify itself to the Building
Management System. Note that Building Management Systems set to a “0” or “1” address both respond to
messages from the RDM800 as address “1” therefore you should not have a unit set to “0” and another set to
“1” on the same network.
If the HGM300 network is connected directly to a Building Management System it may not be connected to
the RDM800. However, the RDM800 has two communication ports, an “upstream” port (labeled TO HOST)
and a “downstream port (labeled TO MONITORS). A BMS node may be connected to the up stream RDM800
port while the downstream RDM800 port talks to the HGM300’s. In this case, the BMS is talking “through” the
RDM800 to the HGM300’s, but not physically on the HGM300/RDM800 network.
NOTE: If the HGM300 is not at the end of the line in a series connection, then the terminator on the HGM
must be set to “OUT.” Also, each end of the series must have the terminator set to “IN”.
MULTIPLE HGM300'S CONNECTED TO A BUILDING MANAGEMENT SYSTEM
TERMINATOR
“OUT”
TERMINATOR TERMINATOR TERMINATOR TERMINATOR
“IN” “OUT” “OUT” “IN”
RMD800
HGM300
UNIT 2
NODE 2
HGM300
UNIT 3
NODE 3
HGM300
UNIT 4
NODE 4
HGM300
NODE 1 HGM300 NODE 2 HGM300 NODE 3 HGM300 NODE 4
BMS
TERMINATOR
“IN”
HGM300
UNIT 1
NODE 1
RS-485