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

[Kathryn Kerns]

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
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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