[Bldg-sim] chilled water pump power
Itzhak Maor
imaor at pwienergy.com
Fri Jan 9 06:55:11 PST 2009
Hello Bill
You are correct. The 22 W/GPM is combined Primary and Secondary pumping.
The assumption that used to derive this number is total head of 75'.
Thanks
Itzhak
Itzhak Maor Ph.D., P.E., C.E.M
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________________________________
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of William
Bahnfleth
Sent: Thursday, January 08, 2009 7:52 PM
To: James V. Dirkes II P.E.; xiaodongyi at hotmail.com;
bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] chilled water pump power
I sincerely doubt it.
A fairly typical total pump head for plant and distribution for a
primary/secondary systems might be 100 -120 ft. (Note, I am not saying
that is GOOD practice, but it is typical. One can generally do better.)
Let's say that the overall efficiency of pump, motor, and drive is ~85%.
If we use the common engineering approximation HP = (Q*H)/(3960*eta_t),
and given that 1 HP = 745.7 W, the power associated with 1 gpm and 100
ft wg head is
W = 745.7*(1*100)/(3960*0.85) = 22.15
I cannot think of a reasonable scenario under which 44 W/gpm could be
construed to represent minimally acceptable practice.
Bill Bahnfleth
At 07:14 PM 1/8/2009, James V. Dirkes II P.E. wrote:
Good question! My guess is that each pump may be 22W / gpm.
Since they are required to use variable speed drives (for >300T), it
won't affect energy adversely.
There may be an ASHRAE clarification on this topic; have you
checked with them?
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
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"urn:schemas-microsoft-com:office:office" />
________________________________
From: bldg-sim-bounces at lists.onebuilding.org [
mailto:bldg-sim-bounces at lists.onebuilding.org
<mailto:bldg-sim-bounces at lists.onebuilding.org> ] On Behalf Of xiao
dongyi
Sent: Thursday, January 08, 2009 6:18 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] chilled water pump power
Hi,
I have a question regarding the chilled water pump power
calculation in ASHRAE 90.1 Appendix G:
ASHRAE 90.1 Appendix G Paragraph G3.1.3.10 requires that "The
baseline building design pump power shall be 22 W/gpm.". If the chilled
water pumping system is a primary-secondary system, how does this rule
apply? i.e. does the 22 W/gpm apply to the primary pump, secondary pump,
or both? Or, do I need to divide it between the primary and secondary
pump?
Your suggestions will be greatly appreciated.
Thanks,
Dongyi
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William P. Bahnfleth, PhD, PE, FASHRAE
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