SST GT814, Design Manual

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September, 2015 814-9
MODEL GT814 NOVA-Sensor ELITE™ Toxic Gas Detector
High Gas Alarm Mode
If the gas concentration continues to increase above the low alarm setpoint, the following occur:

The present gas concentration is displayed (The SCREEN FLASHES and the LOW
ALARM indicator will remain flashing during this time due to the low gas alarm)

The 4-20 mA signal to external equipment increases to report the present gas con-
centration

When gas concentration reaches the high alarm set point, the red HIGH ALARM
indicator also flashes.

The high alarm relay is activated
!
A typical application might use this high alarm relay contact to shut down
all electrical equipment in the protected area and activate evacuation alarm
signals to alert personnel.

A high gas alarm condition is always locked in or “latched” in the detector, and the
high alarm indicator and the screen will continue to flash even after the gas concen -
tration has returned to zero.

Activate the ▲MagPoint▲ on the top side of the detector to cancel the high alarm
and return the detector to the protection mode. The high alarm may also be canceled
from a remote location if the reset function has been installed in your detector.
Fault Mode
The NOVA-Sensor ELITE is designed to continually monitor it’s own operation and to alert
personnel when it is not functioning properly. This condition is reported as a FAULT. When
a fault condition is active, the following occur:

The SCREEN FLASHES and displays SYSTEM FAULT, and the yellow FAULT indi-
cator flashes (if failure is not due to power source failed)

The 4-20 mA signal to external equipment decreases to 2.0 mA or 0.0 mA

The fault relay contact to external equipment changes state
!
While in fault mode the NOVA-Sensor ELITE might not be able to report an alarm condition.
The source of fault conditions should be corrected as soon as possible for safety reasons.
Possible causes of a Fault
Electrochemical fuel cell in the sensor head is past the rated 2 year operating life
Sensor head failure due to intrusion of moisture, dust, or silicones
Sensor failure due to exposure to extremely high concentrations of gas for an ex-
tended period of time
An open-circuit or short-circuit on the wiring going to a remote sensor
24 volt DC power source out of range or failed
Failure of the electronic circuits inside the NOVA-Sensor ELITE itself
Maintenance Reminder Mode
We recommend a monthly test of the NOVA-Sensor ELITE as explained in the Maintenance
section of this manual. The following reminders may be displayed when additional service
is recommended:

If the sensor display is showing negative gas values of -5 or lower, CHECK
CALIBRATION is displayed on the screen. (The screen illumination will remain dim
during this display)

If the sensor display is showing negative gas values of -10 or lower, SYSTEM FAULT
will display, the screen back light will flash and the yellow FAULT indicator will flash.

90 days after the last full calibration was made, CHECK CALIBRATION is displayed.

After the sensor fuel cell element has been in service for 2 years, the detector will