65-2643-05SS-4S M2A Transmitter Operator’s Manual
9
M2A Junction Box
The M2A’s stainless steel junction box is dust and weather resistant. The junction box also protects the M2A and
all connections made to it. Use the three 3/4 NPT conduit hubs to wire the remotely installed combustible gas
detector and connect wiring from an external device, typically an RKI controller. The top hub is shipped with a
factory installed and sealed conduit plug to avoid leaks into the junction box. If necessary, the conduit plug can
be removed and the top hub can be used for wiring.
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. See “Wiring the M2A Transmitter” on page 17 for complete wiring
instructions.
Use the junction box’s two mounting holes to mount the M2A to a vertical surface at the monitoring site. The
window in the cover on the front of the junction box allows you to view the OLED display and use the magnetic
wand to actuate the magnetic control switches so you can perform non-intrusive calibration. Removing the cover
allows you to access the interior of the junction box.
Detector Junction Box
The stainless steel, corrosion resistant junction box is intended to be installed remotely from the M2A junction
box. The oxygen detector is factory installed in the bottom 3/4 NPT conduit hub. A terminal strip is provided for
wiring connections and the detector is factory wired to one side of this terminal strip. The other side of the
terminal strip is for user-supplied wiring to the detector terminal strip located in the M2A junction box. This
wiring should go through the top 3/4 NPT conduit hub. An O-ring seals the interface between the junction box
cover and the junction box base. A locking set screw on the junction box cover allows you to secure the junction
box cover and prevent it from being removed.
Oxygen Detector
The oxygen detector consists of the detector housing body, detector housing cap, cap gasket, and the plug-in
sensor.
Figure 2: Oxygen Detector Component Location
Flame Arrestor
Guard
Detector Housing Cap
Oxygen Sensor
Detector Housing Body
Cap Gasket
