Water Flow Retard Setting

Today I ran into something strange.  We recently installed two new Bosch FPD-7024 addressable fire alarm systems for two small office buildings.  Each building had their own automatic sprinkler system which we had connected to through the C-16 provided Potter water flow switches.  Now we all know that water flow switches have a built in retard diaphragm to reduce or eliminate false alarms due to the back flow of city water pressure.  I was called out to the site today to investigate the cause of 3 false water flow alarms.  When I arrived, the first items I noticed were no water around the inspector test valve and that the automatic sprinkler system pressure gauges appeared normal.

My first thought was to check the setting on the water flow retard diaphragm.  I typically like to use setting "B" (20 - 40 seconds) since the NFPA 72 code states a water flow alarm signal must be received within 90 seconds.  This particular water flow switch was set to "B" but seemed to activate instantly upon the flow of water.  I changed the retard to setting "E" (60 - 90 seconds) and still the water flow activates instantly. 

It was then that I informed the general contract to replace the two Potter water flow switches.  I have taken the stance that the retard diaphragms are malfunctioning and had to bypass the two addressable points to avoid constant nuisance alarms throughout the night.  The two buildings are currently on fire watch until the devices are replaced and re-connected to our Bosch FPD-7024 addressable fire alarm panels.