65-2660RK-XX-04 M2A Transmitter Operator’s Manual
9
M2A Junction Box
The M2A’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 Transmitter” on page 16 for complete wiring
instructions.
Use the junction box’s two mounting slots 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 detector junction box is intended to be installed remotely from the M2A 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 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 junction box is optimal for ease of calibration). The calibration adapter/splash
guard also protects the detector from splashing water or direct water spray.
Magnetic Wand
The magnetic wand is a short plastic rod with a magnet in one end. It is used to actuate the magnetic control
switches on the control PCB while the junction box cover is still installed so that non-intrusive calibration can be
performed.
