Connection - Macurco MRS-485 User Instructions

Macurco MRS-485 Modbus RS-485 Adapter
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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