Description • 11
Pump Reset Switch
The pump reset switch is located to the left of the status LEDs. When a low flow condition
occurs, the pump will be shut off. To reset the low flow condition and start the pump again,
press and hold the pump reset switch for about 2 seconds, then release.
Hydrophobic Filter
The hydrophobic filter is located toward the bottom left of the main circuit board. The filter
prevents particulates and water in the incoming gas sample from damaging the flow and
detection systems. Replace the filter when it appears dirty, discolored, or clogged.
Pump
The pump is mounted to the right side of the main circuit board. The pump pulls the gas
sample into the sample-draw detector. The pump operates on 24 VAC, which is generated
from the 24 VDC supplied by the controller.
Flow Baffle
A flow baffle is located at the bottom of the main circuit board, behind the hydrophobic filter.
Its function is to isolate the carbon monoxide sensor from vibrations in the flow line that are
caused by the pump.
Combustible Gas Sensor
The catalytic combustible gas sensor detects combustible gas in the % LEL range. It uses a
catalytic element for detection. The reaction of gas with oxygen on the catalyst causes a
change in the resistance of the element which changes the current flowing through it. The
current is proportional to the detection range of the sample-draw detector.
The combustible gas sensor is installed in the flow block and the flow block is mounted to the
middle of the main circuit board. The sensor housing includes a sintered metal flame arrestor
on one end that allows gas to diffuse into the sensor. On the other end, five pins extend from
the sensor and plug into the socket connector. The connector allows you to replace the sensor
without disconnecting the wiring. Four leads extending from the connector allow you to
connect the combustible gas sensor to the main circuit board.
