The Flow Switch from Hell....

[Fulthrotl]

i have an interesting problem, sort of.

i have a flow switch in a fire alarm system, in a 4" riser,
that is amazingly sensitive. any pulsation in the fire
water pressure flutters it, and gives a false alarm.

the grading contractor was compacting lifts of road base,
using an 1 1/2" hose off the fire hydrant, and when a truck
would run across the hose, the pressure wave will flutter
the flow paddle enough to give a closed switch for about
three seconds.

not a big deal, before the system was commissioned and
put on line. today, i was using a 1 1/2" hose to fill a sewage
lift station to test floats and put it online.... every time i
turned off the hydrant, the alarm was set off... and i was
closing the valve a third of a mile from the flow switch....

this was brought to my attention after the fourth alarm. :dunce:
(you can't hear a fire bell a third of a mile away when there
is a tugboat idling next to you.)

any suggestions to calm this thing down? i'm considering tensioning
up the springs, if possible... i haven't ripped it apart yet to see if
i can hurt it... that is tomorrows adventure.

almost all suggestions appreciated....

 

[George Stolz]

Make the sprinkler guy adjust the timing for a 45 second delay like it should have. There is a diaphragm in the flows I deal with that delay the relay until the flapper has been moved for a period of time.

 

[iwire]

any suggestions to calm this thing down? i'm considering tensioning
up the springs, if possible... i haven't ripped it apart yet to see if
i can hurt it...

It is listed life safety equipment don't even think about DIY tinkering.

Did you supply the flow switch? We don't, we just wire them and if acts up it us not our problem. Also what George said is usally true with adjustments up to a couple of minutes.

 

[Fulthrotl]

It is listed life safety equipment don't even think about DIY tinkering.

Did you supply the flow switch? We don't, we just wire them and if acts up it us not our problem. Also what George said is usally true with adjustments up to a couple of minutes.

sprinkie supplied the switch.... i'll check and see if any adjustment is
possible with this one.... i've never had one that needed adjustment
up until now... as you say, we just hook them up.

 

[hardworkingstiff]

It is listed life safety equipment don't even think about DIY tinkering.

Did you supply the flow switch? We don't, we just wire them and if acts up it us not our problem. Also what George said is usally true with adjustments up to a couple of minutes.

I want to 2nd what Bob said about DIY tinkering.
If it's not your equipment, report the issue, don't adjust it.

 

[gadfly56]

What George said. Have the sprinkler guy adjust the delay. Max allowed is 90 seconds IIRC. In NJ you can do fire alarm work as a licensed electrical contractor, but you need your fire equipment contractor's license ("P" number) to adjust the flow switch.

 

[Fulthrotl]

What George said. Have the sprinkler guy adjust the delay. Max allowed is 90 seconds IIRC. In NJ you can do fire alarm work as a licensed electrical contractor, but you need your fire equipment contractor's license ("P" number) to adjust the flow switch.

fair 'nuff.

90 seconds should do nicely.
i'll pass this back up to the general,
and HE can get this resolved.....

 

[goldstar]

Not trying to be repetitive here but all the warnings that have been suggested so far are legit and should be heeded. If you are not authorized to make any adjustments to the Agastat timing relay in that flow switch you may find that the liability in this action is greater than what the job is worth. In any event, just to make a point, any flow switch of that type should have a retard of about at least 15-30 seconds to avoid the unwanted alarms that you're now getting. Most fire depts. won't allow you to delay the alarm notification 90 seconds. In addition, if the domestic water is tied into the same supply as the sprinkler system there should be a check valve in the sprinkler system so that flushing toilets don't cause that water surge and trip the alarm system. Sometimes that check valve fails and has to be replaced.
Let us know what happens.

 

[GoldDigger]

In any event, just to make a point, any flow switch of that type should have a retard of about at least 15-30 seconds to avoid the unwanted alarms that you're now getting.
Let us know what happens.

If your observation is that the flow switch false triggers for a few seconds immediately after the minor pressure fluctuation (and it sounds like it from your original description), then either it is defective or the delay is set shorter than the time that you see it falsely activating. Either way, it is out of your hands for now.

It may be possible that some alarm panels will also allow a configurable delay and are set to expect an instantaneous signal from the switch. Can anyone confirm or reject that? If that is a possibility, then the problem is at the panel and it may still be out of your hands.

 

[George Stolz]

That would not be an acceptable fix.

 

[Fulthrotl]

If your observation is that the flow switch false triggers for a few seconds immediately after the minor pressure fluctuation (and it sounds like it from your original description), then either it is defective or the delay is set shorter than the time that you see it falsely activating. Either way, it is out of your hands for now.

It may be possible that some alarm panels will also allow a configurable delay and are set to expect an instantaneous signal from the switch. Can anyone confirm or reject that? If that is a possibility, then the problem is at the panel and it may still be out of your hands.

the problem is, that both domestic water and fire sprinklers, each of which has
its own separate feed with separate dual backflow preventers, are being temporarily
fed off a single 2" line, that does not run thru those backflow preventers, so
opening a hydrant elsewhere on the system, (which gets done several times a day)
causes a pressure drop, and resulting water movement in the pipe, triggering the
flow alarm.

the agastat just needed a little extra time, and the problem went away.
after the permanent water service is installed, the issue will be gone.

 

[Little Bill]

the problem is, that both domestic water and fire sprinklers, each of which has
its own separate feed with separate dual backflow preventers, are being temporarily
fed off a single 2" line, that does not run thru those backflow preventers, so
opening a hydrant elsewhere on the system, (which gets done several times a day)
causes a pressure drop, and resulting water movement in the pipe, triggering the
flow alarm.

the agastat just needed a little extra time, and the problem went away.
after the permanent water service is installed, the issue will be gone.

And just who "gave the agastat a little extra time"?:angel:

 

[Fulthrotl]

And just who "gave the agastat a little extra time"?:angel:

why, the sprinkie, of course. who'd ya think?