[Bldg-sim] chilled water pump power

[xiao dongyi]

Hi Itzhak,
 
If that is the assumption used to derive the 22 W/gpm, then how should I divide it between the primary and secondary pump?Thanks,
 
Dongyi



Subject: RE: [Bldg-sim] chilled water pump powerDate: Fri, 9 Jan 2009 09:55:11 -0500From: imaor at pwienergy.comTo: wbahnfleth at psu.edu; jvd2pe at tds.net; xiaodongyi at hotmail.com; bldg-sim at lists.onebuilding.org
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 Manager, Energy Efficiency Services 
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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of William BahnflethSent: Thursday, January 08, 2009 7:52 PMTo: James V. Dirkes II P.E.; xiaodongyi at hotmail.com; bldg-sim at lists.onebuilding.orgSubject: 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 isW = 745.7*(1*100)/(3960*0.85) = 22.15I cannot think of a reasonable scenario under which 44 W/gpm could be construed to represent minimally acceptable practice.Bill BahnflethAt 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 TeamJames V. Dirkes II, P.E., LEED AP1631 Acacia Drive NWGrand Rapids, MI 49504616 450 8653<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />  

From: bldg-sim-bounces at lists.onebuilding.org [ mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of xiao dongyiSent: Thursday, January 08, 2009 6:18 PMTo: bldg-sim at lists.onebuilding.orgSubject: [Bldg-sim] chilled water pump powerHi, 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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