The master alarm system shall activate when the pressure in the main supply lines changes by what percent?

The master alarm system shall activate when the pressure in the main supply lines changes by what percent?

• A. 10
• B. 20
• C. 40
• D. 50

Answer: (B)

The master alarm is set to respond to meaningful shifts in the main supply pressure, using a percentage change so the system can differentiate between normal fluctuations and real problems. Twenty percent provides a practical balance: it’s large enough to ignore routine variations from demand changes or regulator cycling, yet sensitive enough to alert staff if the supply is truly deteriorating or being disrupted. If the main line runs around a typical nominal pressure (for example, about 50 psi), a 20% change would mean the pressure moving to roughly 40 psi or 60 psi, which would trigger the alarm and prompt investigation into potential leaks, regulator failure, or supply interruption. A smaller threshold could cause nuisance alarms, while a larger threshold might delay notification of a serious issue.

The master alarm is set to respond to meaningful shifts in the main supply pressure, using a percentage change so the system can differentiate between normal fluctuations and real problems. Twenty percent provides a practical balance: it’s large enough to ignore routine variations from demand changes or regulator cycling, yet sensitive enough to alert staff if the supply is truly deteriorating or being disrupted.

If the main line runs around a typical nominal pressure (for example, about 50 psi), a 20% change would mean the pressure moving to roughly 40 psi or 60 psi, which would trigger the alarm and prompt investigation into potential leaks, regulator failure, or supply interruption. A smaller threshold could cause nuisance alarms, while a larger threshold might delay notification of a serious issue.