65-2661RK-XX-04 M2A Transmitter Operator’s Manual
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14. If shielded cable is used between the detector junction box and the M2A junction box, connect the cable’s
drain wire to an available chassis (earth) ground at the M2A junction box. Do not connect the shield drain
wire at the detector junction box.
Wiring the M2A to a Controller and Alarm Devices
1. Guide multi conductor shielded cable or cables or wires in conduit through the left conduit hub of the M2A
junction box. The number of cables or wires needed will depend on whether the M2A is wired to a gas
monitoring controller or just to power, whether any relays are used, and whether the Modbus output is used.
WARNING:
If the top conduit hub is used for wiring, be sure to seal the threads to ensure water does not
enter the junction box. A conduit seal, which is normally required to maintain the junction
box’s hazardous location rating, will also help to prevent water from entering through the top
port.
NOTE:
If the M2A is being wired to a PLC or DCS device, see “Appendix B: PLC and DCS Device Wiring”
on page 54, then continue with step 8.
Use the following recommendations to determine how to wire the M2A:
•
If Modbus connections will not be used and only the PWR/SIG connections will be used, use a two or
three conductor shielded cable or two or three wires in conduit for connections to the power/signal ter
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minal strip depending on whether or not the signal (S) terminal is used. The S terminal has a 4 - 20 mA
output, but if you do not need to monitor this signal and do not connect to the S terminal to access this
signal, the M2A will still function completely.
•
If the PWR/SIG connections and one or more relays are used, route the connections to the M2A in con
-
duit. Use shielded cable in the conduit for the PWR/SIG connections and unshielded cable or individual
wires for the relay connections. Make sure any wire or cable used for relay wiring is appropriately rated
for the power that it will carry.
CAUTION:
If shielded cable is used for the PWR/SIG connections, leave the cable shield’s drain wire
insulated and disconnected at the M2A junction box. You will connect the opposite end of the
cable’s drain wire at the controller or device.
•
If the M2A will be wired into a Modbus network, see “Chapter 8: RS-485 Modbus Output” on page 41.
See Figure 9 below for field wiring connections to the M2A.
Table 3: Wire Size for PWR/SIG Connections
Max Distance to Controller
w/18 Gauge Wire
Max Distance to Controller
w/16 Gauge Wire
Max Distance to Controller
w/14 Gauge Wire
2,500 ft.
5,000 ft.
8,000 ft.
