[Equest-users] W/gpm for pumps

Nick Caton ncaton at smithboucher.com
Tue Feb 25 08:26:29 PST 2014


To the 1st question:  Verify the W/GPM referencing the lower half of the PV-A report.  For baseline pumps,  I like to start with head/motor/impeller efficiancies in accordance with Chapter 11, Table 11.3.2.A, footnote c.  This usually gets me close.  If you need to tweak up or down to get to 22 W/GPM, adjust mechanical efficiency up/down incrementally.  This approach allows for auto-sized flows.

To your 2nd question:  this has multiple right answers, depending on the context.  If you are asking for a LEED project, consult the language in the most current EAp2 documentation spreadsheet, as applicable for your project, for GBCI's current stance on the matter.  Last I checked, they were explicitly requiring 22W/GPM for both loops.

Otherwise, if you are modeling purely per Appendix G (outside a LEED framework), ASHRAE has put out a conflicting interpretation which states 22 W/GPM is to be the net total between primary and secondary loops:  ASHRAE interpretation<https://www.ashrae.org/File%20Library/docLib/StdsInterpretations/IC-90-1-2007-14.pdf>.  The choice of how to distribute that quantity is up to the modeler, I believe.  I have in the past simply dumped it all on the secondary loop (making the primary operate "free") just for simplicity of inputs, but be mindful of CV vs. variable loops and whether that has an impact for your model.  Another logical approach is to proportion between the loops using a ratio to match the proposed design, if applicable.

~Nick


[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Wahid Mohamed
Sent: Tuesday, February 25, 2014 8:33 AM
To: Omar Osama; equest
Subject: [Equest-users] W/gpm for pumps

Hi Omar,

In the design case (proposed) model, the design is supposed to give you how much GPM and head the pump will deliver in the chilled water system, based on each pump of the system GPM you can assign the power input.

In baseline case model, you have to run the model and get the system GPM from the output report, then return back to the model input to put the calculated pump power corresponding to GPM will be delivered for each pump.

Hope it helps and best regards,


Wahid H. Mohamed, BSc, LEED AP BD+C
Mechanical Project Engineer
T: +966 2 6999 888    Ext. 9798




From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Omar Osama
Sent: Tuesday, February 25, 2014 4:34 PM
To: equest
Subject: [Equest-users] W/gpm for pumps

Dear All,
            I've found this subject before on eQuest directory but didn't find an answer yet, I just need to know if there is a field where I can input the (22 W/gpm) value directly to a pump in eQuest? or I need to make some conversion to other units to define to eQuest that my pump is 22W/gpm?

Another question is: How to distribute the 22W/gpm on 2 primary and 2 secondary pumps?
Omar ElRawy
Project Engineer,
EA Sustainable Building Consultants
www.ea-buildingconsultants.com<http://www.ea-buildingconsultants.com/>
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