Potter PE-STW Fire Alarm 170007

The Potter PE-STW (P/N 170007) is a single stage waterflow switch for fire alarm systems connected to wet pipe sprinkler systems. Unlike dual-stage waterflow switches that provide pre-alarm and alarm outputs, the PE-STW provides a single alarm output — delivering a clean, straightforward signal to the fire alarm control panel the moment sprinkler flow is detected. This makes it ideal for systems where a single-zone alarm output is all that is required by the system design or AHJ.

The PE-STW is designed for installation on sprinkler system piping where a compact, reliable fire alarm notification appliance interface is needed. It uses a paddle-type flow sensing mechanism that deflects when water flows through the pipe and activates the alarm contacts. A built-in retard mechanism prevents nuisance alarms from pressure surges and water hammer — one of the most common causes of false fire alarm signalling in wet pipe sprinkler systems.

For fire alarm parts suppliers and contractors, the Potter PE-STW 170007 is a reliable, UL Listed solution for commercial and light industrial wet pipe sprinkler monitoring applications. It integrates seamlessly with Potter fire alarm control panels and is compatible with conventional IDC zone wiring, making it a versatile addition to any fire alarm equipment supplies inventory.

Retard Adjustment

The PE-STW includes an adjustable retard mechanism that delays the alarm output for a set period after flow is detected. This prevents nuisance trips from brief pressure fluctuations and water hammer common in wet pipe sprinkler systems. Set the retard to the minimum value that eliminates nuisance alarms while still ensuring alarm transmission within the NFPA 72 maximum allowable time. Document the retard setting on the fire alarm inspection and test records.

Annual Flow Test

Per NFPA 25, the PE-STW must be tested annually using the inspector's test valve to simulate a sprinkler head activation. Verify that the fire alarm control panel receives and annunciates the alarm signal within the specified time delay. Fire alarm inspection and test records must be retained for the minimum period required by the AHJ.

Wiring

Wire the PE-STW to the fire alarm control panel's IDC zone per the Potter wiring diagram. Use the correct wire gauge specified in the panel's installation manual to ensure the circuit supervision and alarm current requirements are met. Verify end-of-line resistor values match the panel's zone configuration before system commissioning.

How does the PE-STW differ from the PE-HSW and PE-HSWC?

The PE-STW (170007) is a single stage waterflow switch with a vertical paddle mechanism. The PE-HSW (170002) and PE-HSWC (170003) are horizontal waterflow switches — the PE-HSWC adds a cover tamper switch. Select the correct model based on your pipe orientation and whether cover tamper supervision is required by the system design or AHJ.

Can the PE-STW be used on dry pipe systems?

The PE-STW is designed for wet pipe sprinkler systems where water is always present in the piping. Dry pipe systems require specialized flow switches rated for the delayed water delivery characteristics of those systems. Using a wet pipe waterflow switch on a dry pipe system can result in delayed or missed alarm signals.

What causes nuisance alarms from waterflow switches?

The most common causes of nuisance trips are water hammer from rapid valve closure, thermal expansion in the piping, and insufficient retard delay settings. If nuisance fire alarm signalling persists after adjusting the retard, inspect the piping for pressure surge sources and consult the Potter technical support documentation for advanced troubleshooting.