Ralphy,
From the material that Brian sent over to me, he did indeed show the
pump flowing 150% of it's rated capacity back to the municipal supply.
At that point on the supply curve the municipal supply could deliver the
flow, but it would only be at a pressure of approximately 18.8 psi
The supply curve was 86 psi static, 68 psi residual, at a flow of 920
gpm. The pump was rated at 1250 gpm at 75 psi.
And I think you're right, based on the info I read in the '10 edition of
NFPA-20, as well as the notes in NFPA-25 on annual testing, this
calculation should be done.
The FM who Brian was dealing with wasn't concerned about the sizing of
the underground, or for that matter, the demand of the fire sprinkler
system. His only concern was - apparently - what pressure is available
from the supply when the flow is pushed to 150% of the rated capacity?
Sounds to me like a legitimate question.
PARSLEY CONSULTING
Ken Wagoner, SET
760.745.6181 voice
760.745.0537 fax
[email protected] <mailto:[email protected]>e-mail
www.ParsleyConsulting.com <http://www.ParsleyConsulting.com>website
On 11/17/2010 1:12 PM, Ralphy Henderson wrote:
I've done separate calcs in the past just showing the friction losses occurring
during 150% of rated flow. Shouldn't this be done anyways to verify that the
municipal water pressure isn't getting dangerously low?
I'd just show the fire pump flowing the 150% with nothing else going on just to
verify A) The UG is sized appropriately and B) You're not sucking the municipal
water dry.
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