NFS2-3030 Operations Manual — P/N 52546:N1 06/20//2014 87
Factory Mutual Applications
EXAMPLE:
The following is an example of the FMM-4-20 programmed for use with a gas detection device:
• When monitoring gases, the most significant threshold must be latching. Less significant
thresholds may be non-latching.
• When monitoring combustible gases, the most significant threshold must not be set higher than
60% of the flammable limit of the gas.
• If the gas sensor that the FMM-4-20 Module is monitoring supports a Device Inhibit condition,
one of the FMM-4-20 thresholds should be programmed to detect the Device Inhibit condition.
Programming Field: Setting: Explanation:
• 4 mA Scale Value • 0
• 20 mA Scale Value • 200
• Units • PPM
•Hysteresis •2%
• Threshold Settings •
Threshold 1:
• Threshold value = 52
• Event = Non-Fire
• Tracking/Latching = Tracking
• Event trigger = Upper Level
When the gas sensor has a reading that reaches 52ppm, a Non-Fire
event will be reported at the FACP.
•
Threshold 2:
• Threshold Value = 148
• Event = Supervisory
• Tracking/Latching = Latching
• Event Trigger = Upper Level
When the gas sensor has a reading that reaches 148ppm, a Supervisory
event will be reported at the FACP.
•
Threshold 3:
• Threshold Value = -25
• Event = Trouble
• Trouble Type = Device Inhibit
• Tracking/Latching = Tracking
• Event Trigger = Same Level
For the gas sensor in this example, a Device Inhibit condition will occur
at 2 mA. This is below the 4 mA Scale Value.
To calculate the threshold value for the Device Inhibit condition, use the
following equation:
(20 mA Scale Value - 4 mA Scale Value) / 16 mA
This will give the ppm value for each mA.
For this example:
(200ppm - 0ppm) / 16mA = 12.5ppm/mA
Each mA is the equal to a gas sensor reading of 12.5ppm.
The Device Inhibit setting is 2 mA below the 4 mA Scale Value. If each
mA has a value of 12.5ppm, the threshold value is 2 mA x 12.5ppm,
which equals 25. Since the Device Inhibit condition occurs at a value that
is below the 4 mA Scale Value, the Threshold Value will be subtracted
from it. In this example, the 4 mA Scale Value is zero, so the Threshold
Value will be programmed as a negative number.
NOTE: For further information on programing the FMM-4-20, refer to the Programming Manual
provided with the FACP.
NOTE: If the intensity of the LCD display on the fire panel needs to be increased or decreased to
improve legibility, please refer to LCD Display Programming in the NFS2-3030 Programming
Manual.
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