[Bldg-sim] LEED Treatment of District Systems Pump Energy

Corinne Benedek corinne.benedek at arup.com
Wed Oct 12 14:07:08 PDT 2011


All,

We're running into a similar issue on a project using the newer guidance and the default standard cooling system COP of 4.4 as we know very little about our plant itself - though they do seem to be using variable speed secondary pumps.  Our building itself has no pumps - all pumping is central.

The COP of 4.4 is meant to include the central plant pumping - but it's unclear whether this would also cover the case where all pumping is central.  Do we model the total central plant at a COP of 4.4 and include no pumping energy in our building or do we add pumps equal to the baseline in our building assuming that this 4.4 wasn't allowing for that extent of pumping?

We'd like to meet the intent of the guidance, but also not unfairly penalize the project by being overly conservative.  As we're not sure how the 4.4 was derived, it's difficult to know where to go.

What do you think?

Thanks for any thoughts
Corinne


From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Christian Kaltreider
Sent: Wednesday, October 12, 2011 2:07 PM
To: 'Christopher Schaffner'; 'Quitadamo, Bob'
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] LEED Treatment of District Systems Pump Energy

That makes perfect sense to me.  This is the approach which seems to best follow the intent of the LEED modeling process.

Thanks for your input,
Christian

From: Christopher Schaffner [mailto:chris at greenengineer.com]
Sent: Wednesday, October 12, 2011 1:51 PM
To: Christian Kaltreider; 'Quitadamo, Bob'
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] LEED Treatment of District Systems Pump Energy

You need to have an apples to apples comparison, and you need to account for the pump energy.

As you indicate, the Step 2 baseline, is a standalone building, System #7, with pump energy included.

Your step 2 Proposed Case should account for the all pumping energy in some way. You have variable primary pumping, so the requirement to model secondary pumping in the building is not applicable, but you still need to account for all the pumping energy. Whether it is modeled in the plant or building is irrelevant. I'd probably model it in the building for simplicity sake.

Your step 1 models should have identical plant conditions. If all the pumping is in the plant, then I would leave the pump energy out of both  Step 1 cases.

--

Chris Schaffner, PE
LEED Fellow
Founder and Principal

The Green Engineer, LLP
Sustainable Design Consulting
50 Beharrell Street
Concord, MA 01742
T: 978.369.8978
M:978.844.1464
chris at greenengineer.com<mailto:chris at greenengineer.com>
www.greenengineer.com<http://www.greenengineer.com>

The Green Engineer, LLP is a Certified B Corporation

From: Christian Kaltreider <ckaltreider at sudassociates.com<mailto:ckaltreider at sudassociates.com>>
Date: Wed, 12 Oct 2011 08:47:15 -0400
To: "'Quitadamo, Bob'" <bquitadamo at RDKEngineers.com<mailto:bquitadamo at RDKEngineers.com>>
Cc: <bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>>
Subject: Re: [Bldg-sim] LEED Treatment of District Systems Pump Energy

Thanks for this information, Bob.  You are correct that I'm referring to the earlier guideline (Required Treatment of District Thermal Energy in LEED Version 2.2 and LEED for Schools, Version 1.0, 2008).

I should have been clearer in my post:  This is a LEED 2.2 project, and the model was originally created using the Version 1 guidance referenced above.  This project was started before the newer 2010 document (Version 2).  The model was submitted using the Step 1, Step 2 method of Version 1.  I am now trying to address the reviewer's comments.  I did not create the original model, but I have inherited it since the original modeler is not here any longer.  For addressing the comments, I think I should maintain the Version 1 format in which we submitted.

I'll do what seems to be most fair and accurate based on what I read in both documents and the main intent of apples-to-apples comparisons.  I was just hoping someone else out there had come across this situation.

Thanks again,
Christian

From: Quitadamo, Bob [mailto:bquitadamo at RDKEngineers.com]
Sent: Tuesday, October 11, 2011 5:19 PM
To: Christian Kaltreider
Subject: RE: [Bldg-sim] LEED Treatment of District Systems Pump Energy

I think you may be referring to an outdated USGBC guideline...The most current is here http://www.usgbc.org/ShowFile.aspx?DocumentID=7671 You should only have to model option one OR option two, whichever you believe to be more beneficial.

Bob Quitadamo | Mechanical Energy Engineer

RDK Engineers
Seaport Center, 70 Fargo Street, Suite 800, Boston, MA 02210
P: (857) 221-5927 | F: (617) 345-4226 | M: (978) 482-5629
bquitadamo at rdkengineers.com<mailto:bquitadamo at rdkengineers.com>
http://www.rdkengineers.com<http://www.rdkengineers.com/>

[cid:image001.png at 01CC8901.236A3F80]



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 Christian Kaltreider
Sent: Tuesday, October 11, 2011 2:44 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] LEED Treatment of District Systems Pump Energy

Hi Everyone,

I have not seen my specific situation adequately addressed in the LEED documentation, so I would be interested to hear others' opinions on the matter:

I am modeling a building which relies on a central plant for heating and cooling.  The plant serves only a few buildings.  Heating enters the buildings as HW, not steam.  My building is designed such that there are no hot water pumps...the BAS communicates back to the central plant pump system, which adjusts flow appropriately.  All flow within the building is controlled by valves.  My basic question is, in which models do I include HW pump energy (that's 4 models...Step 1 Baseline and Proposed, and Step 2 Baseline and Proposed)?

Here are my thoughts.  For certain I need to include HW pumps in the Step 2 Baseline, as for any Baseline using System 7.  That leaves only 3 models to ponder.  The LEED guidance I have read leads me to believe I should include HW pumps in Step 1 Baseline as well.  The intention of Step 1 is to model the buildings independent of the central plant, which would lead me to not include the HW pump energy in my Step 1 Proposed model.  Am I now cheating by including the pump energy in the Baseline but not the Proposed for Step 1?

For Step 2, LEED documentation indicates that secondary pump energy needs to be modeled in the proposed aggregate building/DES model.  This would lead me towards not modeling the central plant pumps, but again, is that cheating?  A portion of the central plant pump energy is certainly being used to push water through my building...

Thanks for any thoughts/opinions you may have,
Christian







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