[Equest-users] Modeling an Existing Building - Calibrating toUtility Bills

[David Eldridge]

Mike, the below comments assume that you have electricity and steam matched up fairly well. Otherwise you should present all of the discrepancies together as these may provide clues to each other.

1) What are your calibration metrics now, and what are the targets?

2) When you look at the actual building there should be large lab AHUs that will have cool enough air from OA to meet most cooling loads in the winter.

Are there any FCU or other single-zone cooling sources that might be causing the cooling use in the model?

If not, can you run an hourly report showing the AHU cooling demand to verify that these are the source?

3) Verify the range of the client's CHW meters. You may be calibrating to data that has reduced accuracy at low flows.

DSE Mobile

On Jul 9, 2014, at 10:20 AM, "Kathryn Kerns" <kathryn.kerns at bceengineers.com<mailto:kathryn.kerns at bceengineers.com>> wrote:

Michael, I suggest you take the written sequence of operation with a grain of salt. Many years of experience has proved that just because a sequence is written down, doesn't mean the actual controls follow it. Chilled water operation trend logs such as, supply and return loop temperatures, pump status/speed, etc. would be very helpful diagnosing your problem. It is possible that there is an OSA temperature cut off where the chilled water system stops running completely or stops running to a non-critical area that does not show up in the written sequence.  Another problem could be that the 100% OSA heat exchanger doesn't work the same in the winter as it does in the summer. Sometimes, if you are use VAV cooling control, raising the upper temperature limit from 65 F to 70 F on the WARMEST control will lower winter cooling consumption. Then there is the variable infiltration rate due to changing OSA temperature problem. In the end, you may just have to fake something to get the cooling consumption to match. There are just too many unknown variables. One of the reasons I avoid the LEED measurement verification credit.

________________________________
From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael Campbell
Sent: Wednesday, July 09, 2014 7:41 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Modeling an Existing Building - Calibrating toUtility Bills

Hi,

I'm having some trouble calibrating my model to match the utility bills.  The issue I am trying to resolve right now is with the cooling energy.  Below is a table showing the metered chilled water usage for 2013.  As you can see, the usage is minimal in the winter months and much higher in the summer months.  This is a 100% OA laboratory building with fairly high interior loads due to lab equipment.  It is a VAV system with district chilled water cooling and district steam preheat, and hot water reheat coils in the VAV boxes.    The problem I am having is that my modeled chilled water usage is much higher in the winter than expected.  I have tried just about everything I can think of without great results.  I have attached the sequence of operations for the HVAC as well as the modeling files.  If someone can take a look, that would be very helpful.

Thanks,


Start Date

End Date

Chilled Water (KTH)

1/1/2013

1/31/2013

55.8

2/1/2013

2/28/2013

62.4

3/1/2013

3/31/2013

63.3

4/1/2013

4/30/2013

140.5

5/1/2013

5/31/2013

395.5

6/1/2013

6/30/2013

721.3

7/1/2013

7/31/2013

1,277.7

8/1/2013

8/31/2013

850.5

9/1/2013

9/30/2013

448.6

10/1/2013

10/31/2013

266.4

11/1/2013

11/30/2013

65.4

12/1/2013

12/31/2013

52.5




Mike Campbell, E.I.T., LEED AP O+M
Sustainability Specialist
Sustainable Solutions Corporation
Office: 610-569-1047<http://610-569-1047/>
Mobile: 609-923-1743<http://610-569-1047/>
www.SustainableSolutionsCorporation.com<http://www.sustainablesolutionscorporation.com/>
Sustainable Solutions Corporation is WBENC and BCorp Certified.

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