Detcon 840 - Manual (Page 30)

840 Operators Manual
Model 840 Operator Manual Rev. 1.9 Page 26 of 29
8.
Options
8.1 Option for Battery Back-up Operation
This option provides a nominal 1-hour of battery back-up power to the Gas Detection Alarm System. The
battery back-up system consists of two 12VDC / 0.8 Amp-hour batteries in series, along with the requisite
low voltage cut-off circuitry. The batteries may be isolated during exchange or while in long-term storage
by using the battery disconnect switch shown in Figure 4. The low voltage cut-off circuit is designed to
disconnect the battery supply if the voltage is drained below 20VDC. This is for battery protection
purposes. There is a battery restore switch on the Motherboard PCB, which must be pressed after the low
voltage cut-off is triggered. This is only necessary if the unit is going to be restored under battery power.
It is not necessary if restored under VAC power.
8.2 Optional Interface PCB for Remote Display
The optional 4-20mA Output PCB is used as the required interface for the Remote Display option (Figure
19). The RS-485 terminal block labeled ‘A B S - TO REMOTE’ is used to connect to the Remote Display.
The actual Remote Display hardware is ordered separately as a Model 840-RD Read-Only-Remote display.
Figure 19 Remote Output Display
8.3 Optional Remote Alarm Reset/Acknowledge Switch
Model X40 controllers are designed for an optional Remote Alarm Reset/Acknowledge Switch. This
enables the user to reset or acknowledge alarms without having to open the NEMA 4X enclosure. The
Reset Switch is a momentary type switch and will typically be mounted on the bottom or side of the NEMA
4X enclosure. Toggle the momentary switch to execute the reset/acknowledge function.
The Remote Alarm Reset/Acknowledge Switch is wired to the terminal block labeled SW3 on the backside
of the Main Controller PCB. Refer to Figure 5.