[Bldg-sim] Appendix G Secondary Pump Control

[James Hansen]

To clarify an email I sent to the last thread on the 22 W / gpm:  I
recently received the updated documentation spreadsheet for a v4 pilot
project, and they have updated the notes.  Not sure if this image will
come thru to everybody, so here's what it says:

 

"The sum of primary and secondary must be 22 W / gpm (349 KW/1000 L/s)
per G3.1.3.10.  Recommended that the pump power be split as one third
(primary) and two-thirds (secondary)."

 

 

 

GHT Limited

James Hansen, PE, LEED AP, BEMP

Senior Associate

1110 N. Glebe Road, Suite 300

Arlington, VA 22201

703.243.1200 (main)

703.338.5754 (direct/cell)

www.ghtltd.com <http://www.ghtltd.com> 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Christian
Kaltreider
Sent: Friday, December 20, 2013 11:58 AM
To: 'Bishop, Bill'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Appendix G Secondary Pump Control

 

Bill,

 

Thanks.  Yes, the 22W/gpm total requirement is still fresh in my mind
from the recent discussion on this forum!

 

I understand your approach to pump control.  But...would you be able to
defend that approach if someone (like your client) pushed you about why
you aren't getting them better savings by running your secondary CHW
pump 8760?  Certainly the 90.1 folks had some specific intent, whether
they made it clear or not...

 

Thanks,

Christian 

 

From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com] 
Sent: Friday, December 20, 2013 10:08 AM
To: Christian Kaltreider; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] Appendix G Secondary Pump Control

 

Christian,

I always model one secondary pump for the baseline. I see no reason to
do otherwise.

My approach to loop activation has been to model it the same as the
proposed design. Using DOE-2 for example, it could be SCHEDULED to run
24/7 during cooling months, or DEMAND-ONLY to stay off until a coil or
process load exists. If the proposed design has no CHW plant, but has a
boiler/HHW plant, you could model the baseline CHW loop activation
similarly to the proposed HHW loop. If the proposed design has no
analogous loop operation, you just have to make a judgement call, but I
am not aware of any guidance in 90.1 or LEED. Also keep in mind that
22W/gpm is the total pump power allowance for all your primary/secondary
CHW pumps, and not the power of each pump.

Regards,

Bill

 

William Bishop, PE, BEMP, BEAP, LEED AP | Pathfinder Engineers &
Architects LLP

Senior Energy Engineer

 

 

134 South Fitzhugh Street                 Rochester, NY 14608

T: (585) 325-6004 Ext. 114            F: (585) 325-6005

bbishop at pathfinder-ea.com <mailto:wbishop at pathfinder-ea.com>            
www.pathfinder-ea.com <http://www.pathfinder-ea.com/> 

P   Sustainability - the forest AND the trees. P       

 

 

From: bldg-sim-bounces at lists.onebuilding.org [
mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Christian
Kaltreider
Sent: Friday, December 20, 2013 9:15 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Appendix G Secondary Pump Control

 

I have a question regarding 90.1 2004 Appendix G baseline chilled water
pump control.  Section 3.1.3.10 says that baseline CHW systems must be
primary/secondary, with a constant flow primary loop and a variable flow
secondary loop.  The secondary pump will either ride the curve or be
controlled by a VSD depending on square footage.  In the case I
currently have in my hands, the pump rides the curve.  No questions yet.


 

Section 3.1.3.11 goes on to state that each chiller shall have its own
condenser water and chilled water pumps, interlocked to operate with the
chiller.  This is clear and reasonable for the condenser water and
primary chilled water pumps, but what about secondary chilled water
pumps?  For my current application (one chiller, pump riding curve), my
question simply boils down to whether I should turn the secondary pump
off when the chiller is off, or if I should run it all of the time.  

  

But to get into it a little more, here are three approaches I see:

 

1.      Model one secondary pump for each chiller, and turn each pump
off when its associated chiller turns off.  Section 3.1.3.10 is titled
Chilled Water Pumps, and that section includes both primary and
secondary pumps, so when the next section references "chilled water
pumps" that should include both primary and secondary.  However, this
does not reflect the typical reality of one secondary pump serving
multiple chillers, and the common interpretation that only a primary
pump has one single associated chiller.

 

2.      Model one secondary pump regardless of how many chillers there
are, and turn it off when all chillers are off.  This is perhaps most
similar to what you might expect in a 'real' system.  If you only have
one chiller (as I currently have), this is exactly the same as approach
1.  

 

3.      Model one secondary pump regardless of how many chillers there
are, and never turn it off.  Many buildings are unfortunately operated
this way.  This approach significantly increases baseline energy when
the pump is riding the curve.

 

I have always used approach 2 without putting much thought into it.  But
now my results are highly dependent on which approach I take, and I see
enough ambiguity that arguments could be made for approach 3.  

 

Your thoughts?

 

Thanks,

Christian

 

 

Christian Kaltreider, LEED AP | Energy Analyst

Sud Associates, P.A. | T 828.255.4691 | F 828.255.4949 | 
www.sudassociates.com

 

      

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