Potter VSR Series VSR-S Series CyclingFlowswitch

Vane type waterflow switches should be tested using the inspectors test valve to indicate water flow equivalent to that of a sprinkler some instances the waterflow switch will on and off during this test This is usually an indication of excessive air in the sprinkler system phenomenon has increased with the use of backflow preventors and inspector test valves in close proximity to the instead of at the hydraulically remote locations a valve at the far end of the sprinkler system being open when the system is being filled the air in the piping vent as the water enters All of this air compresses and can result in sprinkler pipes being partially filled with water addition to excessive amounts of oxygen leading to increased corrosion it can also cause the waterflow switch to cycle and off delayed operation of the flowswitch or false alarms When the inspectors test valve is opened the trapped air expands pushing system water out of the test valve When the system pressure drops enough the or check valve opens allowing fresh supply water to enter the system The supply water flows past the waterflow moves the paddle and starts the retard action The incoming supply water also compresses the air in the system pressure to build up When the system pressure equals the supply pressure the backflow will close and the resets Then the entire cycling process starts all over While there may be as a steady stream of water flowing of the test valve there is not a steady stream of water flowing past the flowswitch delayed flowswitch operation occurs because the cycling keeps going until eventually it takes long enough for the to close that the flowswitch finally goes into alarm or in the event of a real fire another sprinkler opens and now flows enough water that the backflow stays open alarms can occur because when you open the ITV you bleed off any pressure that may have built up in the system when the city turns on their pumps late at night to build up pressure for the morning water demand of the city this flows into the system and trips the flowswitch because the pipes are only partially full and the system pressure is than the supply pressure because the system pressure was vented through the ITV the day before makes an automatic air vent model PAAR B or PAV that can be used to automatically vent air from the system or valves can be installed for venting the system as it is being filled Henke CET Manager Products Division Electric Signal Company LLC St Louis MO Phone 800 325 3936 www pottersignal com PAGE 1 OF 1 Cycling Technical Bulletinfirealarmresources com