Part load conditions

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Hi all,

How do you show this method on Trace 700 for System 6?

[cid:image001.png at 01CDFA10.42964EE0]

Thanks,

Catalina Caballero, AIA. Assoc., LEED GA.

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Catalina,

You can define a custom fan curve based on the 90.1 cubic equation, but I would recommend that you use the 90.1 fan curve library member that comes with the program. The curve is the same for 2004 and 2007 versions of 90.1.

[cid:image003.png at 01CDFA11.18A5F5D0][cid:image002.jpg at 01CDFA11.46446D50]
Scott

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Can the software calculate it automatically with the following feature on?

[cid:image001.png at 01CDFA11.A1109920]

Regards,

Catalina

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Duncan S. McClellan's picture
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Catalina,

I would guess that you are working on a LEED project. From my experience the LEED reviewer will not accept the automatic fan calculation within Trace. You need to manually calculate the maximum break HP for each fan for the baseline systems. I recommend putting them in units of kW/CFM. You will need to manually do the fan power calculations according to 90.1 and adjust for any "allowances" per 90.1. Please don't use the Full Load Energy Rate numbers I have used. You'll need to calculate these for your specific conditions per 90.1 requirements.
[cid:image004.png at 01CDFA13.4EB94620]
Scott

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To create a custom curve, go into your curves library and create a new curve, be sure the load units are set to "curve". Enter the coefficients from Table G3.1.3.15 as follows:

[cid:image001.png at 01CDFA12.4A6809E0]

The help menu goes on to describe how to enter coefficients:

[cid:image004.png at 01CDFA12.4A6809E0]

Duncan McClellan PE, BEMP, LEED AP

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Joined: 2012-06-22
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We have submitted multiple projects using the automatically calculated fan energy. They will ask you to printout the report that shows how Trace calculated the consumption of each fan but that has been satisfactory in the past. The Trace help desk can tell you how to print out this report.

Rick

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Scott,

What we have seen is that the Trace700 PRM Sizing works correctly and you just need to submit the PRM report but I don't know if that particular requirement for G3.1.3.15 Part 2 can be done using it.

Thanks.

Catalina Caballero, AIA. Assoc., LEED GA.

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To All

We have submitted the trace report fan power calcs to LEED on multiple
jobs and we had no problems.

The calcs are accurate.

Houcine Tlemsani

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A diligent engineer should know if the calcs are performed correctly by performing back-checks. You shouldn't depend on a LEED reviewer to determine the accuracy of your methodologies. The fan power calcs are not always right. Sometimes they work, sometimes they don't. If want to be sure, always back-check via hand calcs. Scott's comment regarding "kW/cfm" is very important. Don't input anything as "horsepower". If you enter a 10hp fan, you're going to get a 10kW fan. It's not a unit display issue, it's actually using 10kW. Motor efficiency is already included in the Appendix G calc if you are performing it correctly. Here is a message I received from CDS several years ago regarding Horsepower units:

Duncan,

You're right. 3 HP does not equal 3 kW however when you select units of HP in TRACE, the program automatically assumes 75% efficiency and that 75% basically cancels the conversion between HP and kW (0.746).

Eric Sturm

Duncan S. McClellan's picture
Joined: 2012-06-22
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Here is a spreadsheet that can be used to back-check the software.

Duncan S. McClellan's picture
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A diligent engineer should know if the calcs are performed correctly by
performing back-checks.

Trace calcs are as good as the data that was interred. That's why
back-checking all the outputs is a must.

Never take software outputs for granted.

My point is that the trace output is accepted by leed reviewer as long
as it's done correctly.

Houcine Tlemsani

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Catalina,

The check box for "Apply ECB/PRM rules to fan sizing?" just sets the design fan power. The fan curve must be applied separately as I showed on the "Fans" tab under Systems section of Trace. Every project will have the exact same baseline fan curve, but the design fan power for the baseline is unique for each project, and that checkbox allows the program to calculate it rather than you doing it manually. I leave it up to you as whether you trust the output from Trace or not on the fan power design power. You can see the originally input value and the corrected kW value for each fan on the Equipment Energy Consumption report if you allow Trace to calculate the fan power.

Scott

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Hi all,

Under Ashare 90.1 2007 , what do the mean by Return and or exhaust airflow devices specifically... dampers?

[cid:image004.png at 01CDFA45.6C00C690]

Thanks.

Catalina

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Hi all,

Under Ashare 90.1 2007 , what do the mean by Return and or exhaust airflow devices specifically... dampers?

[cid:image004.png at 01CDFA45.6C00C690]

Thanks.

Catalina Caballero, AIA. Assoc., LEED GA.

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