Detcon 12B - Manual (Page 9)

Model 12B
12B Control Module Instruction Manual Rev. 1.4 Page 5 of 12
4.4 Energized or De-energized
All alarm relays — alarm 1, 2, 3, and fault — can be jumper programmed as normally energized or normally
de-energized. The standard is de-energized. However, a relay can be programmed as energized to provide
application specific features. A normally energized relay will de-energize when in alarm. A typical application
of the energized configuration is to have the fault relay normally energized so that in the event of a power
failure to the control module card, the fault relay will de-energize causing its relay contacts to change state,
thereby creating a fault output.
It must be noted that when an alarm relay is jumper programmed as normally energized, the contact outputs,
normally open and normally closed, become reversed (see section 2.3.3). The normally open contact becomes
the normally closed and vice versa. Reconfiguration of the contact output jumpers may be required. To
program an alarm relay as normally de-energized, place a jumper tab on pins 1 and 2 (left and center) of its
corresponding jumper location. For normally energized operation, place the tab on pins 2 and 3 (center and
right) of the jumper location. The jumper locations are as follows: fault - JP19, alarm 1 - JP17, alarm 2 - JP15,
and alarm 3 - JP13.
4.5 Ascending or Descending Alarms
Three alarms — alarm 1, 2, and 3 — can be jumper programmed to operate during ascending or descending
gas conditions. This feature is useful mainly for the monitoring of oxygen deficiency whereas a decrease in
oxygen concentration poses a danger to personnel. However, there may be other applications where the
monitoring of a specific gas concentration is desired and alarms can be programmed to operate when that
concentration exceeds or drops below a predetermined range. Typically, most applications of monitoring for
toxic or combustible gases will warrant that the alarm be programmed as ascending.
To program an alarm for ascending gas conditions: place a jumper tab on pins 1 and 2 (left and center) of its
corresponding jumper location. For descending gas conditions, place the tab on pins 2 and 3 (center and right)
of the jumper location. The jumper locations are as follows: alarm 1 - JP10, alarm 2 - JP6, and alarm 3 - JP2.
4.6 Alarm Reset
An alarm reset switch (SW1), located on the control module face plate is used to reset alarms that have been
programmed as latching. Once alarm conditions have cleared, alarms may be reset by simply pushing the
momentary switch and releasing it.
Remote reset outputs are also a feature of the 12B control module. This feature is available when used in
conjunction with Model 12B compatible control enclosures and mainframe motherboards.
4.7 Alarm Disable
An alarm disable switch (S1), located on the control module face plate is used to disable alarm 1, 2, and 3
alarm relays. The corresponding LEDs are not affected. This feature is useful for calibration or
troubleshooting. The alarm disable switch toggle is located slightly behind the face plate in order to help avoid
accidental use. When the switch is in the disable position, it will cause a fault condition that will activate the
fault relay and LED, and output a fault code on the RS-485 serial loop.
To disable alarms, simply toggle the switch to the down position. To re-enable the alarms, toggle the switch
back to the up position.