[Trace-users] Fan power

Christian Kaltreider ckaltreider at sudassociates.com
Fri Apr 11 13:55:49 PDT 2014



I see two things which are likely culprits.  


1.       As Alex pointed out, the fan power in the Proposed model seems
high.  Looking at your "Equipment Energy Consumption" output report, I see
that the fan kW for the Proposed model is more than twice as high as that
for the Pretend model, though the supply CFMs are similar.

2.       Looking at the same report, I notice that the fans never come close
to drawing their full power (looking at monthly demand) in the Pretend
model, which is unusual.  This indicates that the energy model is never
seeing close to design conditions.  Meanwhile, the Proposed model does reach
its maximum fan kW or close to it at some point in every month of the year.
Looking through your model, I think a reason for this difference could be
your 'people' schedules.  They are set to 0% in the Pretend model.  Since
your fans are set to cycle with occupancy, this will have a large effect on
run time as well as cooling load.  I would suggest taking a close look at
all of your schedules to make sure they are the same between models.



I hope that helps,




Christian Kaltreider, LEED AP | Energy Analyst

Sud Associates, P.A. | T 828.255.4691 | F 828.255.4949 |




From: trace-users-bounces at lists.onebuilding.org
[mailto:trace-users-bounces at lists.onebuilding.org] On Behalf Of
AChapin at sriregistrar.com
Sent: Friday, April 11, 2014 10:04 AM
To: john.s.eurek at usace.army.mil; trace-users at lists.onebuilding.org
Subject: [Trace-users] Fan power


Hi John, 

I wasn't able to make any changes to the model to correct the difference in
fan power. However, I noticed a couple of things. 

1.	The Baseline Case "Pretend" doesn't include any pressure drop
adjustments from Table This will help increase the baseline fan
power. Note that credit for heat recovery devices may not be taken unless it
is required in the Baseline Case system (see note under Table G3.1.2.9). 

2.	The Proposed Case "Actual" fan power seems high. See attached pdf
for a range of BHPs for a sample TRANE AHU at 3,000 cfm. They range from
0.88 to 3.08 depending on the system total static pressure. The system in
the model has a nominal HP of 10 which is being modeled as 7.46 kW. 


Hope that helps, 
Alex Chapin 

Alex N. Chapin 
Sustainability Program Engineer 
SRI Green Building Certification, LLC 
300 Northpointe Circle . Suite 304 
Seven Fields, PA 16046 . USA 

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Date: Thu, 10 Apr 2014 18:01:15 +0000
From: "Eurek, John S NWO" <John.S.Eurek at usace.army.mil>
To: "'trace-users at lists.onebuilding.org'"
                <trace-users at lists.onebuilding.org>
Subject: [Trace-users] Fan power (UNCLASSIFIED)
<E777FD5A41D3B04A83296213737A85D7092442FB at EIS-MB0501WPC.eis.ds.usace.army.mi
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Classification: UNCLASSIFIED
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I need a little help.  The fan energy usage of the Actual/Purposed building
is 4.5X more than the Pretend building.

I've looked and looked and looked for something that is causing such a huge

One thing I tried that really confused me was to set the system for the
pretend building as 'same as Alternate 1' and the pretend building fan
energy usage went up....  So then I went tab-by-tab and matched Alternative
1 to the setting that the Pretend building was using and the fan energy for
Alternate 1 was still over 2 times the Pretend building.


Classification: UNCLASSIFIED
Caveats: NONE

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