65-2660XL-XX-04 M2A-XL Transmitter
Chapter 2: Description
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9
M2A-XL Junction Box
The M2A-XL’s cast aluminum junction box protects the terminal PCB and wiring connections
made to the terminal PCB. Use the three 3/4 NPT conduit hubs to wire the remotely installed IR
CO
2
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-XL Transmitter” on
page 17 for complete wiring instructions.
Use the junction box’s two mounting holes to mount the M2A-XL 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 detector junction box is intended to be installed remotely from the M2A-XL junction box.
The IR CO
2
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-XL junction box. This wiring should go through the top 3/4 NPT conduit hub. Three
spacers installed on the back of the junction box controls the distance of the junction box from a
mounting surface.
Infrared CO
2
Detector
The infrared carbon dioxide (CO
2
) detector is made up of a miniature infrared CO
2
detector
housed and encapsulated in a pipe nipple. The pipe nipple has 3/4 NPT threads on each end and a
1 1/4” hex that allows removal or installation of the detector with a wrench. A porous flame
arrestor that is coated with a hydrophobic film that repels liquids is on one end of the detector and
allows sample gas to enter the detector. Four color coded leads, red, white, green, and black,
extend from the other end of the detector. The leads allow you to connect the detector to the
terminal strip.
Calibration Adapter/Splash Guard
A calibration adapter/splash guard is installed on the IR CO
2
detector. A fitting at the bottom of
the calibration adapter/splash guard allows a length of tubing to be connected for calibration and
routed to a more easily accessible location (near the M2A-XL junction box is optimal for ease of
calibration). The calibration adapter/splash guard also protects the detector from splashing water
or direct water spray.
