Macurco MRS-485 User manual

IMPORTANT: Keep these user instructions for reference.
Macurco™ MRS-485
Modbus® RS-485 Adapter
User Instructions

Macurco MRS-485 Modbus RS-485 Adapter
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Table of Contents
1General Safety Information .................................................................................................................... 4
1.1 List of warnings ............................................................................................................................... 4
2Use Instructions and Limitations ............................................................................................................ 4
2.1 Use For ........................................................................................................................................... 5
2.2 Do NOT use for ............................................................................................................................... 5
2.3 Features.......................................................................................................................................... 5
2.4 Specifications .................................................................................................................................. 6
3Installation Instructions.......................................................................................................................... 6
3.1 Location .......................................................................................................................................... 7
3.2 Installation...................................................................................................................................... 7
3.3 Connection ..................................................................................................................................... 8
3.4 Wiring ............................................................................................................................................. 9
3.4.1 Signal Wire........................................................................................................................ 9
3.4.2 Topology......................................................................................................................... 10
3.4.3 Length............................................................................................................................. 11
3.4.4 Grounding....................................................................................................................... 11
3.4.5 Power Wire ..................................................................................................................... 11
4Configuration ....................................................................................................................................... 12
4.1 Dip Switches and Addressing......................................................................................................... 12
4.2 Changing MRS-485 Settings .......................................................................................................... 13
4.3 Programming Mode ...................................................................................................................... 13
5Operations ........................................................................................................................................... 16
5.1 Power up ...................................................................................................................................... 16
5.2 4-20mA Loop ................................................................................................................................ 17
5.3 Normal Operation ......................................................................................................................... 17
6Troubleshooting................................................................................................................................... 17
6.1 On-Board Diagnostics.................................................................................................................... 17
6.1.1 Unknown Sensor Code .................................................................................................... 17
6.1.2 Error Codes ..................................................................................................................... 18
6.2 DIP Switch Settings Codes ............................................................................................................. 18

Macurco MRS-485 Modbus RS-485 Adapter
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7Maintenance........................................................................................................................................ 19
7.1 Cleaning ........................................................................................................................................ 19
8Testing ................................................................................................................................................. 19
8.1 Operation Test .............................................................................................................................. 20
8.2 Manual Operation Test ................................................................................................................. 21
9Appendix A – Table of Figures .............................................................................................................. 22
10 Macurco Gas Detection Product Limited Warranty .............................................................................. 23
Technical Support Contact Information ......................................................................................................... 24
General Contact Information......................................................................................................................... 24

Macurco MRS-485 Modbus RS-485 Adapter
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1General Safety Information
The Macurco MRS-485 Adapter is an accessory used to convert the 4-20mA analog signal from Macurco 6-Series
type detectors to a digital signal for use with multipoint addressable systems. The Macurco MRS-485 simply
connects to the back of the detector and a single screw fastens it in place. The MRS-485 accepts the 4-20mA
output and is powered from the same connection as the detector. The MRS-485 has the ability to interface with
Building Automation Systems, Control Panels or other Control Devices that accept Modbus communications.
1.1 List of warnings
WARNING
Each person using this equipment must read and understand the information in this user manual before
use. Use of this equipment by untrained or unqualified persons or use that is not in accordance with this
user manual, may adversely affect product performance.
This equipment may not function effectively below 0°F or above 125°F (-18°C or above 52°C). Using the
detector outside of this temperature range may adversely affect product performance.
Do not disassemble unit or attempt to repair or modify any component of this instrument. This instrument
contains no user serviceable parts, and substitution of components may impair product performance and
void product warranty.
2Use Instructions and Limitations
WARNING
Each person using this equipment must read and understand the information in this user manual before
use. Use of this equipment by untrained or unqualified persons or use that is not in accordance with this
user manual, may adversely affect product performance.

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2.1 Use For
The Macurco MRS-485 Adapter converts the Macurco 6-Series 4-20mA analog output to a digital output for use
with addressable network systems. The Macurco 6-Series is a family of fully programmable, low voltage, dual
relay gas detectors, controllers and transducers for BAS, HVAC and Fire & Security applications. The 6-Series
detectors are used to measure the concentration of various gases and provide feedback and automatic control
to help ensure a safe environment: Carbon Monoxide, Methane, Propane, Hydrogen, Nitrogen Dioxide and
other gases.
2.2 Do NOT use for
The MRS-485 is not intended for use in hazardous locations or industrial applications such as refineries, chemical
plants, etc. Do not mount the MRS-485 where the normal ambient temperature is below 0°F or exceeds 125°F (-
18°C or above 52°C). The MRS-485 mounts to a Macurco 6-Series detector installed on a 4” x 4” electrical box
electrical box supplied by the contractor.
2.3 Features
•The Macurco MRS-485 interfaces the detector power and 4-20mA output lines with a mounted
connector
•The MRS-485 monitors sensor type, gas level and trouble status communications from any of the
Macurco 6-Series detectors
•Communication is on a Modbus serial line with a “Two-Wire” electrical interface in accordance with
EIA/TIA-485 standard using RTU Transmission Mode
•Commercial type enclosure to protect and support the electronics
•Tricolor LED indicates power, test and communication status
•Mounts behind the detector inside of a standard 4” x 4” electrical box
•Held in place on the back of the 6-Series detector with a single screw
•8-bit DIP switch address selector
•RS-485 termination uses 4 pin connectors with jumper to select termination: The user selects no
termination or one of the two Modbus line termination options
•Communications connections include signal (A and B), Common and shield terminals

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•Intended for use in non-hazardous areas such as parking garages, warehouses or other commercial
facilities
2.4 Specifications
•Power & Current (with detector): 3.25W (max) from 12 to 24 VAC or VDC, 85mA in alarm, 60mA fan relay
on and 33mA stand by @ 24 VDC
•Shipping Weight: 0.25 lb (0.11 kg)
•Size: 3 1/2 x 2 x 1 3/4 in. (8.9 X 5.1 X 4.4 cm)
•Operating Environment: 0°F to 125° F (-18°C to +52°C), 10 to 90% RH non-condensing
•Connections: plugs/terminals
•Color: Black
•Mounting screw and screwdriver included
•MRS-485 operates in the RTU Modbus Transmission Mode
•Baud Rate: 4800, 9600, 19200 (default), 38400, 57600, 115200 bps
•Parity: Odd, Even (default) and None
3Installation Instructions
The following instructions are intended to serve as a guideline for the use of the Macurco Modbus RS-485
Adapter MRS-485. It is not to be considered all-inclusive, nor is it intended to replace the policy and procedures
for each facility. If you have any doubts about the applicability of the equipment to your situation, call Technical
Service at 1-877-367-7891.
WARNING
This equipment may not function effectively below 0°F or above 125°F (-18°C or above 52°C). Using the
detector outside of this temperature range may adversely affect product performance.

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3.1 Location
Refer to the user instructions of the specific Macurco 6-Series gas detector to which the MRS-485 will be
connected.
3.2 Installation
The Macurco MRS-485 Adapter converts the Macurco 6-Series 4-20mA analog output to a digital output for use
with addressable network systems. The Macurco 6-Series is a family of fully programmable, low voltage, dual
relay gas detectors, controllers and transducers for BAS, HVAC and Fire & Security applications. The 6-Series
detectors are used to measure the concentration of various gas and provide feedback and automatic control to
help ensure a safe environment: Carbon Monoxide, Methane, Propane, Hydrogen, Nitrogen Dioxide and other
gases.
1. Remove the 4-20mA/Power connector from the Macurco 6-Series gas detector.
2. Plug the MRS-485 adapter into the empty socket.
3. Install the provided MRS-485 screw.
4. See the wiring diagram for wire connection.
Figure 3-1 MRS-485 Installation Expanded

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5. The 6-Series detector mounts on a 4”x 4” electrical box supplied by the contractor.
6. Connect the detector to the control cables with terminal plugs. When making connections, make
sure the power is off.
7. There are two terminals for the dry alarm relay contacts, again with no polarity preference. The
alarm relay can switch up to 0.5 A 120 V, or 60 VA. The alarm relay is activated if gas reaches or
exceeds the alarm settings. See Operation of the detector User Instructions for details on relay
settings.
8. The alarm relay can be configured to normally open (default) (N.O.) or normally closed (N.C.) and
will activate if the gas concentration exceeds alarm set point. It will deactivate once the gas
concentration drops below the alarm set point. Note that the “disable” setting will cause the
alarm relay not to engage at all.
9. The dry contact, SPDT fan relay has three terminals: The Common (COM), normally open (N.O.)
and the normally closed (N.C.) contact. The fan relay can switch up to 5.0 A up to 240 VAC. See
Operation section of the detector User Instructions for details on relay settings.
3.3 Connection
The Macurco MRS-485 output is connected via a four-terminal screw type connector. The MRS-485 adapter is
wired in the standard 2W-Modbus circuits definition with selectable built-in terminating resistors at the ends of
the RS-485 bus. The power for the MRS-485 adapter is connected via a two-terminal screw type connector, 12
to 24 VAC or 12 to 24 VDC and no polarity.
Note: Running the Modbus cable adjacent to or in the same conduit with high voltage wires is not
recommended as there may be interference from the high voltages. Line polarization should not be required for
the MRS-485 but may be required for other devices on the RS-485 line - see manufacturer’s directions.

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Figure 3-2 Connection Expanded
3.4 Wiring
3.4.1 Signal Wire
A Modbus over Serial Line Cable should be shielded for best performance. The shield should be connected on
each detector at SHD terminal and connected to a ground terminal or chassis only at one end of the bus. An RS-
485-Modbus must use a balanced pair (for A & B) and a third wire (for the Common). For RS-485-Modbus, Wire
Gauge must be chosen sufficiently wide to permit the maximum length (1,000m or 3,281ft). AWG 24 is always
sufficient for the Modbus Data. Category 5 cables may operate for RS-485-Modbus, to a maximum length of 600
m 1968.5 ft. For the balanced pairs used in an RS-485-system, wire with a characteristic impedance of higher
than 100 Ohms may be preferred, especially for 19200 and higher baud rates.

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Note: It is recommended to always use twisted wires to reduce noise and allow for reliable data communication
over greater distances. Use at least 3-conductor wire with one twisted pair providing a pair for signal (A & B) and
Common (COM) connections.
For best performance use shielded 3-conductor wire with one twisted pair providing a pair for signal (A & B),
Common (COM) and shield ground (SHD) connections.
3.4.2 Topology
An RS-485-Modbus configuration without repeater has one trunk cable, along which devices are connected,
directly (daisy chaining) or by short derivation cables. The trunk cable, also named “Bus”, can be long. Its two
ends must be connected on Line Terminations. (see Line Termination - End of Line Resistor section). The use of
repeaters between several RS-485-Modbus is also possible.
Figure 3-3 Modbus Wiring