All:
I hope I am not misunderstanding the question. 1. Do wet systems using a pressure switch without integral retard installed at the top of a retard chamber generate unwanted alarms? The answer is definitely yes. The problem in the city I work for seems largely associated with systems with large internal volume. Flow switches and pressure switches as described both seem to have problems. But that may be result that the city I work in is characterized with distribution centers. Many have 0.39 gpm/sf over 5,600 sf. systems. Depending on the decade of installation, large tree, looped, or gridded systems. It also characterized by a large area without residences. Instead of many small water uses turn on and off, a fewer bigger industrial users turn water on and off. Use peaks in summers. Highest use is not 0500 to 0700 or 1700 to 1900 hrs. as most people, or at least me, guessed. Highest use is as 0200-0300 hrs. This non-intuitive use is landscaping irrigation sprinklers coming on. During this time another use that turns water on and off is parking lot washers. The pressures switches at top of retard chambers seem allowed by code; often within a few months of installation it is obvious they are problematic, and an alternative is used. Given the cost that is entailed by everyone concerned I fail to understand why if pressure swiches are to be use on a wet system, an integral retard are not always used. It costs to send a fitter out to correct the problem. (I always assume this is a call back the spk co. eats. Am I wrong - does the owner pay again?) 2. I've yet to see a prv on dry systems. It was my understanding the dry systems leak air, and that seasonally they bleed air excess air in the spring. The compressor just runs less. Is installing prv's a regional adaptation? Puget Sound is not known for blistering cold or blistering heat. My experience is all from here. 3. I've never seen the 300 psi on wet systems, and I've looked at a lot of guages. Those little 175 psi relief valves seem to be the most precise thing installed on a system. The bleed right to 175. 4. Jockey pumps. I want to make sure I am saying the same thing. I think of a jockey pump as a small pump of a few gpm in paralel with a big fire pump. The small pump runs to prevent the big pump from starting. Its start pressure is set above the start pressure for the big pumps controller. They use a real pump controller. Where fire pumps and jockey pumps are installed false alarm associated with pressure fluctuations are rare. They are usally corrected by sending the right person out to adjust controller settings. Most of our fire pumps are associated with ESFR pre-K25 heads. We have had a few customers who had to install excess pressure pumps at their systems. The problem was associated with normal pump runs causing false alarms. It also seems more of a problem with pumps serving a number of buidlings in industrial/distribution center campuses, as opposed to a just serving a single building. 5. Excess pressure pump. An excess pressure pump is again a small pump. It is not required to be listed for fire pump usage. It is normally 120 VAC. It's UL listing is just like my table lamp. The listing is for electrical safety, not functionality. It pumps from supply side of a (alarm usually) check valve to system side. (Please install the system connection above the flow switch.) They do not use a real fire pump controller. They maintain pressure in the system above that expected from pressure surges in the system. I've usually seen ~20 psi above observed system gauge prior to installation of pump. If the question is false alarms in wet sprinkler systems excess pressure pumps are a definitive solution. Once an excess pressure switch is installed our experience is that any further false alarms are associated with human communication difficulties, lightning activity.... Any thing but pressure fluctations. Yours, Bruce Verhei ----- Original Message ----- From: "Ed Vining" <[email protected]> To: [email protected] Sent: Friday, March 20, 2009 11:38:15 AM GMT -08:00 US/Canada Pacific Subject: Re: air pockets and false alarms (aka: Statistics) Yes Jim. Pressure in the retard chamber is relieved through the drain when the alarm port is closed. On Fri, Mar 20, 2009 at 10:26 AM, <[email protected]> wrote: > I had not been following the thread because the subject title hasn't > changed, but am I correct in assuming this problem does not occur with > pressure switches at the top of retard chambers? > > James L.(Jim) Roberts, PE/SET > Fluor Corporation > 100 Fluor Daniel Drive - C104F > Greenville, SC 29607 > 864.281.5149 > 864.281.4916(Fax) > > > > > > Jay Jay Blocker <[email protected]> > Sent by: [email protected] > 03/03/2009 08:09 PM > Please respond to sprinklerforum > > To > [email protected] > cc > > Subject > Re: statistics > > > > > > > > Rodney i do not believe you are a nut im just not sure we are looking at > the same equipment. Maybe no one else is admitting this is a problem > because it may not be. I say that to say this. > Lets look at basic common science here. If you have a flow switch set at > 76 seconds and an air pocket tripped it that would suggest that there was > enough air in one single pocket to not only move the paddle but hold it > in the activated position. THis would mean the velocity of the air would > have to have enough force to over power the spring and hold it for 76 > seconds. None moving air could not perform this action. So if there is a > pocket of air that can do this i do not believe moving the ITC would > help. I would have to work with the water dept. and find a way to prevent > these air pockets from entering the system. Maybe even check with > businesses near bye the affected buildings and see if there domestic water > has had any problems. I dont see how air pockets would discriminate > between systems (honestly seems like the domestic would be more > susseptible to this problem). Im not saying your wrong i am just really > lost as to how this > could happen. Have you tied changing out the flow switch? > > Jay > > > > > ________________________________ > From: Rodney Hamm <[email protected]> > To: [email protected] > Sent: Tuesday, March 3, 2009 3:26:47 PM > Subject: Re: statistics > > Jay, > > It is really not a "theory" at this point. I have found this problem at so > many locations and resolved the issue that I am absolutely convinced the > large trapped air pockets are causing the false alarms. > > I have placed my digital LPT Data Logger on the downstream side of wet > systems and recorded the system pressure on 30 second intervals for 7 day > periods. The graph shows the gradual pressure increases/decreases caused > by > temperature changes and the exact time of the false fire alarms are always > indicated by a distinct pressure increase which lasts for more than 60 > seconds. This happens when the water supply increases at the same time as > a > cold front (or significant drop in temperature). Public water supply > systems > typically fill gravity tanks at night and temperature changes usually drop > at night during Spring and Fall (this is typically the time of year these > false alarms are most common). I use the weather channel to determine the > greatest temperature drop on the night when the false fire alarm occurred. > > After I bleed as much air from the system as possible, the LPT Data Logger > verifies that the pressure fluctuations are much less severe and the false > fire alarms are a thing of the past. > > I have one customer where this problem occurred when there was a > temperature > drop and the jockey pump filled the system EVEN WITH THE DELAY ON THE FLOW > SWITCH SET AT 76 SECONDS! After we bled the air from the system, the > problem > was resolved. LPT Data Logger was also used on this system. Yes that is > correct same problem even with a fire pump......the jockey pump at this > facility typically requires 20-25 seconds to start/stop, but when the > underground main pressure is just right and the air pocket/temperature > issue > combines.......we had false fire alarms. I checked the electronic water > flow > switch 7-8 times and the delay was always between 70-80 seconds! > > In summary, air will expand and contract with temperature changes while > water will not. All system have some air, but systems with a significant > percentage/volume of air will allow water to flow into the system to > equalize the system pressure when the pressure downstream of the alarm > check > valve drops below the upstream pressure. When the time required to > replenish > the system exceeds the flow switch delay.....the fire alarm will activate. > It is even more common for systems which have pressure switches on the > retard chambers. > > The flow switch cycling issue is also a huge problem in some instances! > Refer to my previous post regarding the typical test method used by alarm > technicians. > > I sincerely hope this helps. I imagine some of the people on this forum > think I am a freak'n nut. I'm really not crazy! I will admit that I seem a > little obsessed with this issue, but I am getting tired of finding the > problem and none of my buddies in the Fire Sprinkler Industry want to > admit > this is an issue. It has become a bit of a pet-peeve of mine I suppose. > > Take care, > > Rodney K. Hamm, P.E. > President/Owner > Falcon Fire Protection > Office (478) 953-1677 > Cell (478) 396-6988 > > -----Original Message----- > Date: Mon, 2 Mar 2009 17:07:39 -0800 (PST) > From: Jay Jay Blocker <[email protected]> > Subject: Re: statistics > To: [email protected] > Message-ID: <[email protected]> > Content-Type: text/plain; charset=iso-8859-1 > > Rodney could you please elaborate on your theory of the air pocket > tripping > the flow switch. Several of us in my office are baffled. > > Jay > > > _______________________________________________ > Sprinklerforum mailing list > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email > to:[email protected]<to%[email protected]> > > (Put the word unsubscribe in the subject field) > > > > > _______________________________________________ > Sprinklerforum mailing list > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email > to:[email protected]<to%[email protected]> > > (Put the word unsubscribe in the subject field) > > ------------------------------------------------------------ > The information transmitted is intended only for the person > or entity to which it is addressed and may contain > proprietary, business-confidential and/or privileged material. > If you are not the intended recipient of this message you are > hereby notified that any use, review, retransmission, dissemination, > distribution, reproduction or any action taken in reliance upon > this message is prohibited. If you received this in error, please > contact the sender and delete the material from any computer. > > Any views expressed in this message are those of the individual > sender and may not necessarily reflect the views of the company. > ------------------------------------------------------------ > _______________________________________________ > Sprinklerforum mailing list > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email > to:[email protected]<to%[email protected]> > > (Put the word unsubscribe in the subject field) > -- Ed Vining 4819 John Muir Rd Martinez CA 94553 925-228-8792 _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
