I believe intent here is that with a dbl interlock system you essentially have, as Chris stated, a glorified dry system. Water does not start to move until the head is fused and the air sufficiently evacuated. With single interlock an early warning detector (low temp heat, low temp pilot head or smoke detector) goes off well before any sprinkler head activates so you have a wet system when the opens. Of course you have end pipes with air in them but if your supervisory air was set up properly it was twelve ounces above atmosphere and so it has very little impact. With dbl interlock your supervisory air was 30-509 pounds so, yeah, big deal. As Ed tells the story there was a contractor who following his first deluge system did his first pre-action system. As a final act he had the fitter bust out all the links. This guy had no business messing with pre-action. I've seen single interlocks with high pressure supervisory air and double interlocks in computer rooms. Poor applications spec'd by engineers that don't understand the various iterations of these systems or sold by contractors with the bigger and more complicated is better mindset. My two pieces of silver.
On Dec 18, 2007 10:20 AM, Ed Vining <[EMAIL PROTECTED]> wrote: > I see a bit of logic here. With a single interlocked system, the detection > feature will trip the valve. System pressure will go from the supervisory > pressure to water supply pressure. Perhaps two thirds or so of the piping > will be wet. When a sprinkler operates air will leave the dry portion as a > function of supply pressure, rather than fading supervisory pressure. > > > [EMAIL PROTECTED] > Ed Vining > 4819 John Muir Rd > Martinez CA 94553 > 925-228-8792 > > > > > ----- Original Message ---- > From: Chris Cahill <[EMAIL PROTECTED]> > To: [email protected] > Sent: Tuesday, December 18, 2007 9:57:37 AM > Subject: Gridded pre-action and dry > > So we can't grid dry systems '02 - 7.2.3.5. > > > > We can't grid double interlock pre-action '02-7.3.3.2. > > > > Because there is no prohibition by default we can grid single and > non-interlock pre-action systems? Aren't these glorified dry systems? > Just because the valve might start filling the system before the head fuses > doesn't change the reason dry system grids are prohibited. We still have to > get most of the air out before a consistent flow is achieved. With the risk > of applying logic to the code (which is very risky territory) does any one > have an explanation for the apparent inconsistency? Or have I just left for > vacation already? > > > > Chris Cahill, P.E. > > Fire Protection Engineer > > Sentry Fire Protection, Inc. > > > > 763-658-4483 > > 763-658-4921 fax > > > > Email: [EMAIL PROTECTED] > > > > Mail: P.O. Box 69 > > Waverly, MN 55390 > > > > Location: 4439 Hwy 12 SW > > Waverly, MN 55390 > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > -- Ron Greenman at home.... _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
