16
NORMAL OPERATION AND ALARMS
Normal Operation
During normal operation each control module will display the current gas
concentration on the display. If the sensor reading is below alarm level then
all the alarm relays and the visual alarm LED indicators on the front panel
should be off.
Alarms
Each PT902M control monitor is equipped with four (4) alarm relay contacts.
The alarms are labeled as Low, High & High-High. The fourth alarm contacts
is for sensor malfunction. The monitor activates the alarm relays when the
sensor reading exceeds the programmed alarm set point. Also LEDs on the
front panel will also light up for visual alarm indication.
Standard alarm set points are programmed at the factory before shipment. The
user must verify the alarm set points and make changes if desired. Refer to
section on Programming Alarm Set points. See table 1 for range and default
alarm levels for few of the PT902M Control monitor modules.
Alarm Reset
Once the gas concentration has dropped below the alarm level the relay will
deactivate itself. However, this is true only of the relay is configured as non-
latching (NL). If the relay is configured latching then it must be deactivated
manually. To deactivate the latching alarm press and hold the push button on
the front panel until relays and LED indicators turn off. A master alarm reset
switch on the control module rack assembly can also be used to reset the
alarms. This will reset alarms on all control modules.
Note: If the gas concentration continues to be higher than the programmed alarm set
point the alarm will be activated again.
