Owner manual

840 Operators Manual

Model 840 Operator Manual Rev. 1.9 Page 1 of 29

1. Description

Housed in a NEMA 4X weatherproof enclosure, the Detcon

Model 840-N4X Gas Detection Alarm System has the

capability to handle eight 4-20mA sensor inputs or eight RS-

485 serial sensor inputs. The remotely mounted gas sensor,

(purchased separately), can include any Detcon 4-20mA or

RS-485 serial input device such as combustible gas, toxic gas,

or oxygen deficiency sensors.

The system displays real time channel information on a

backlit LCD. Configuration inputs are completely field-

programmable and include channel number, gas type, and gas

concentration. It also shows the current Alarm/Fault status

via front panel LED indicators. Standard features include

recorded history of Time Weighted Average (TWA), Peak

readings, and Alarm/Fault/Maintenance Events. Additional

features include one-touch Alarm Reset and Alarm Silence

(Acknowledge) functions.

The Model 840-N4X has a built-in power supply, giving the user a multitude of power options. It can be

event of temporary power loss.

Each control channel has three field programmable alarm relays and one fault relay. The relays have two

discrete form “C” contacts and are rated for 5 Amps at 30VDC and 250VAC. The low, high, and high-high

alarms have individually field adjustable set points for each gas channel and include the provision to

configure the alarm relays in a normally energized (failsafe) or normally de-energized mode of operation.

The low, high, high-high and fault alarm relays may also be configured for latching / non-latching and

silenceable / non-silenceable operation.