Page 63 - NG-1 1150, NG-1 1500, NG-1 2000, NG-1 3000 - Stand-Alone Nitrogen Generator System Installation Manual

Nitrogen Generator Short Cycling Prevention Procedure (NG-1 2000/3000 Only)
In situations where the nitrogen generator experiences short cycling, the short cycling is typically the result of an erratically operating air maintenance device (AMD). Installations where the AMD doesn’t close properly or partially closes, the nitrogen supply line pressure increases to the cut-out pressure of the nitrogen generator before the sprinkler systems being supplied are at operating pressure. Because one or more of the supplied systems did not reach operating pressure once the nitrogen generator shuts off the nitrogen supply line depressurizes through the AMD and into the sprinkler system(s). This depressurization allows the nitrogen generator to turn on and repeat the process of filling the nitrogen supply line.
NOTES:
• Exacerbated by a small or short nitrogen supply line between the nitrogen generator.
• Nitrogen Generator Short Cycling Prevention Device regulator should be fully closed unless used.
• Typically not needed in most applications. Adjust as necessary, when needed.
Procedure:
1. Increase set point of AMD to prevent premature shut-off of AMD regulator
2. If set point modifications do not prevent short-cycling, repair (clean out) or replace the erratically
operating AMD
3. If AMD repair/replacement unsuccessful, the nitrogen generator includes a short cycling
prevention assembly.
a. The short cycling prevention assembly allows a controlled leak after the sprinkler system’s
AMD closes, and during the pressurizing of the supply line to the cut-out pressure of the
nitrogen generator.
b. If needed, the short cycle prevention regulator is to be adjusted to open at 10 psig (.7 bar)
above the sprinkler system operating /AMD set pressure.
i. Normal Operation - Regulator should be closed completely
ii. Short Cycle Prevention - Adjust regulator to open 10 psig (.7 bar) above the sprinkler system operating /AMD set pressure.
1. Turn regulator clockwise to increase pressure
2. Turn regulator counter-clockwise to decrease pressure
NOTE: The short cycle prevention assembly is not a substitute for repairing an erratically operating AMD, the short cycle prevention assembly reduces short cycling of the nitrogen generator by increasing the time to pressurize the nitrogen supply line.
Air Maintenance Device (AMD) Pressure Adjustment Procedure
The sprinkler system air maintenance device (AMD) operating pressures are determined by the sprinkler system valve, system water pressure and water delivery time requirements as defined by NFPA 13. The AMD operating pressures should not need to be readjusted unless one of the above fire sprinkler system parameters change.
The following procedure has been developed to account for:
1. Tolerances of the gauges used on fire sprinkler systems
TFP1275
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