Page 11 - NG-1 100, NG-1 250, NG-1 500 - Wall-Mounted Nitrogen Generator System Installation Manual

OPERATIONAL INFORMATION
System Operating Pressures
When multiple dry-pipe and/or preaction fire sprinkler systems are connected to one nitrogen generator, the fire sprinkler systems must operate at the same supervisory gas pressure.
In applications where multiple dry pipe or preaction fire sprinkler systems are connected to one nitrogen generator and there is more than one supervisory gas pressure a TYCO Nitrogen Interface Controller (TNIC) must be included in the project.
System Operating Pressure Adjustments
The nitrogen generator operating pressure settings in conjunction with the pressure setting of the fire sprinkler system’s air maintenance device(s) are established and set during the installation process.
• The operating pressure settings of the fire sprinkler air maintenance device(s) or the nitrogen generator must not be readjusted after the system has been commissioned.
• Any adjustments to the operating pressure settings of the fire sprinkler air maintenance device(s) or the nitrogen generator will have an adverse effect on the nitrogen inerting process and could damage the nitrogen generation equipment.
• Any changes to the fire sprinkler air maintenance device(s) or nitrogen generator operating pressure settings must be authorized by Johnson Controls.
Sprinkler System Gauge Accuracy
The accuracy of the gauges used in fire sprinkler systems can affect the operating pressure of the fire sprinkler system as well as determining the required 3-5 psig (.2-.3 bar) pressure range needed to properly remove the oxygen from a fire sprinkler system. NFPA 25 indicates that gauges in excess of ±3% must be replaced or recalibrated. FM Global allows the gauges used in fire sprinkler systems to be accurate within ±2% over the center third of its scale and ±3% over the remaining two-thirds of its scale. This can become paramount when operating a low-pressure valve sprinkler system with an operating pressure of 15-20 psig (1-1.4 bar).
Example: NFPA 25 – A 200 psi (14 bar) gauge with ±3% accuracy equates to ±6 psi (.4 bar) variance in the actual pressure reading of the gauge. Therefore, a sprinkler system indicating a 40 psig (2.8 bar) operating pressure can actually be operating between 34 psig (2.3 bar) and 46 psig (3.2 bar).
FM Global - A 200 psi (14 bar) gauge with ±2% accuracy in the center third of the gauge equates to ±4 psi (.3 bar) variance in the actual pressure reading of the gauge; and ±3% accuracy in the upper and lower third of the gauge equates to ±6 psi (.4 bar) variance in the actual pressure reading of the gauge.
TFP1273
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A 200 psi (14 bar) gauge on a sprinkler system indicating a 100 psig (6.9 bar) (center third of the gauge) operating pressure can actually be operating between 96 psig (6.6 bar) and 104 psig (7.2 bar).
A 200 psi (14 bar) gauge on a sprinkler system indicating a 20 psig (1.4 bar) (lower third of the gauge) operating pressure can actually be operating between 14 psig (.9 bar) and 26 psig (1.8 bar).