Original Design
Circa 1993 - OHII .19/2000 (still a viable point on the OHII curve)
Extended coverage heads 20'x20' ELO 20 k14.5. Minimum flow 76 gpm. I have
a cut sheet that shows a .19 was OK with the 1989 ed. of 13. It is
certainly possible the legal requirement in '93 was the '89.
Safety factor about 4-5 psi. (hard to read the exact off the graph and I'm
lazy to plug it into the formula. OK it's exactly (within the limits of the
generally accepted formula) 4.69 psi)
So original seems OK.
Today
New potential owner is doing due diligence. We note recalled heads. Looked
at EC14 as the closest replacement available. I do some cross checking and
find two compounding problems - smaller k raises start pressure and minimum
flow is now 80 gpm and further raises start pressure. A swap of the head
gives a new starting pressure 5.18 psi higher. I don't really need to calc
it to know I'm over the original design curve. I call Central and they have
never heard of this problem. And really don't have a suggestion. Confirm
can't use EC14 with a .19 density.
I can run a new flow test - the area has seen a lot of growth - could mean
better infrastructure or same infrastructure and more demand. Better
results today might clear it, worse and we're even in more trouble.
Could re-pipe portions to make OK?
I checked Reliable and Viking and don't see a k17 EC or better out to 20' x
20'.
If I re-calc for whatever reason the age old question of c-factor.
Any thoughts? Anyone run into this before (we've done exactly 0 recall
replacements)? Anyone who did/does replacements actually check to see if
the replacement heads work?
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
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