RKI Instruments 35-3000RK-LEL/O - Manual (Page 8)

4 • 35-3000RK-LEL/O Sample-Draw Detector
Status Lights
Two status lights are above the flowmeter. They are also visible through the window in
the housing door.
Pilot light
The green Pilot light is on when the sample-draw detector is receiving power from the
controller.
Fail light
The red Fail light is on when the sample flow rate is below the low flow level.
NOTE: The factory set low flow level is 0.6 SCFH (±0.2). See “Adjusting the Low Flow
Setting” on page 15 to adjust this setting.
Pressure Switch
The pressure switch is mounted to the opposite side of the main circuit board. The
pressure switch monitors the flow rate of the incoming gas sample.
If the flow rate falls below the preset low flow level, the pressure switch causes the fail
relay to interrupt the signal from the combustible gas detector. The interrupted detector
signal causes a fail condition at the controller on the combustible channel. The low flow
level is factory-set at 0.6 SCFH (±0.2 SCFH).
NOTE: There is no low flow alarm for the oxygen sensor.
Flow Block
The flow block is located in the lower right corner of the sample-draw detector. Both
sensors are installed in the flow block. The flow block routes the sampled air to each
sensor.
EXHAUST Fitting
The EXHAUST fitting on the right side of the housing allows the gas sample to exit the
sample-draw detector. The EXHAUST fitting accepts 1/4 in. rigid tubing. See the
Installation section on page 7 to connect tubing to the EXHAUST fitting.
Detection System
The detection system consists of the combustible gas sensor , the oxygen sensor, and the
main circuit board.
Combustible Gas Sensor
The combustible gas sensor is installed in the flow block. The combustible gas sensor
includes the sensing elements, flame arrestor, connector, and sensor leads.
Sensing elements
Two sensing elements are protected within the sensor assembly. Through a series of
thermal and electronic reactions, these elements produce an electrical output that is
proportional to the detection range of the sample-draw detector.
Flame arrestor
The porous flame arrestor allows the gas sample to enter the sensor assembly and contact
the sensing elements. The flame arrestor also contains any sparks that may occur within
the sensor.