RKI Instruments 65-2641RK-04 - Manual (Page 9)

65-2641RK-04 M2A Transmitter Operator’s Manual 4
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 in. conduit hubs to wire the remotely installed
hydrogen 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 11 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 hydrogen detector is factory installed in the bottom 3/4” NPT conduit hub using a 3/
4 in. x 1/2 in. NPT reducer. 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” conduit hub. Three spacers installed on
the back of the junction box controls the distance of the junction box from a mounting
surface.
Hydrogen Detector
The hydrogen detector is a catalytic type detector that produces an electrical output that
corresponds to the detection range. It is packaged in a 1/2 inch NPT nipple with a
sintered metal flame arrestor on one end allowing ambient air to diffuse into the detector.
The flame arrestor also contains any sparks which may occur within the detector. The
detector has a built in molecular sieve that only allows hydrogen to diffuse into the
detector. The 1/2 inch NPT mounting threads at the top of the detector allow you to
mount it into the bottom conduit hub of the junction box. The junction box conduit hub is
3/4” NPT, so a 3/4 in. x 1/2 in. NPT reducer is used to install the hydrogen detector. A
rainshield screws onto the bottom of the detector (flame arrestor end). The rainshield
helps protect the detector from rain and debris in the monitoring environment. Four color-
coded leads extend from the top 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 hydrogen 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.