[Equest-users] Indoor fan separation at ARI

Tue Jun 9 06:23:49 PDT 2015

Omar,

I wrote the following fan power email previously so it is not specific to your case, but it may be helpful and includes an important caution on defaults. To your specific question, fan power is calculated per G3.1.2.9. There are static pressure allowances for baseline PSZ if applicable to your case, listed in 6.5.3.1.1. There are a few tools available to help calculate the fan power for Appendix G if you don’t create your own, such as EMIT from Rocky Mount Institute<http://www.rmi.org/ModelingTools>.

There are two ways to enter system fan power – using either SUPPLY-STATIC and SUPPLY-EFF, or using SUPPLY-DELTA-T and SUPPLY-KW/FLOW. These inputs are shown here:

[http://ARCHIVER.PATHFINDER-EA.COM:8080/cgi-mod/getstubbedattachment.cgi/image004.jpg?charset=utf-8&cid=image004.jpg%4001CDEA94.E3CF3780&delivery=1357351320&len=35534&md5=6075eb6dd225742240674662c0eec1c0&mid=45c6611a05a825b62347e012aae8664ad408abdbe8db2cb944d695b0c4aa42ef2ade843d]

I have found that it generally makes sense to enter SUPPLY-KW/FLOW (in kW/cfm), because it can be easily calculated if you have the fan BHP, and because baseline ASHRAE 90.1-Appendix G system fan power is calculated the same way.
The eQUEST wizard generates values for static and efficiency. You can see in the screen shot above that I have created and applied a user-defined default value of 0.0003 kW/cfm. However, I have not “restored default” to the static and efficiency values assigned by the wizard. Since the static and efficiency values are red, these are considered user inputs, which override user-defined defaults. In the example above, my user-defined default value has not been used, resulting in lower-than-intended fan power. To remove the unwanted values in red above, you can right-click and “restore default”, which in this case will leave an empty box for static and “n/a” for efficiency. The quicker way to do this for a model with many systems is to do a find-and-replace in the input file and delete all the lines with “SUPPLY-STATIC” and “SUPPLY-EFF”.

This concludes this episode of D’oh! How could I miss that?!

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Omar ElRawy
Sent: Tuesday, June 09, 2015 5:26 AM
To: equest
Subject: [Equest-users] Indoor fan separation at ARI

Dear all,
               I've got the following reply for a psz system in the baseline case during preliminary LEED design submittal:

"Note that section G3.1.2.1 requires that where efficiency ratings, such as EER and COP, include fan energy, the descriptor shall be broken down into its components so that supply fan energy can be modeled separately. Because the efficiency ratings are calculated at ARI-rated conditions, the fans should also be broken out at ARI-rated conditions. Most simulation software programs have the capability to perform this step automatically. Provide documentation showing that this calculation has been performed by the software automatically or provide calculations consistent with the ASHRAE 90.1-2007 User’s Manual showing that the calculation has been performed at ARI-rated conditions."

What I did is that I referred to eQuest library, and documented the following paragraph to the reviewer:

"COOLING-EIR:
The Electric Input Ratio (EIR), or 1/(Coefficient of Performance), for the cooling unit at ARI rated conditions..... This EIR is at ARI rated conditions, i.e., without correction for different temperature or part load. Note: If you include fan electric energy consumption in your value of COOLING-EIR, then you should set SUPPLY-KW/FLOW to zero. Otherwise, the supply fan electrical energy will be double counted........ Imbedding the fan energy into the COOLING-EIR is valid only if the fan is constant volume and INDOOR-FAN-MODE = INTERMITTENT; i.e. the fan cycles on/off with the compressor. If the fan runs continuously during occupied hours, or the fan is variable volume, then the fan energy cannot be included in the COOLING-EIR (or HEATING-EIR)."

And I did set fan kw/cfm to zero, intermittent, and constant volume, but I've got the SV-A report reporting zero kw power demand, and zero fan (kw) for the system and its zones.

Then I got an advice stating that:

"You should do what the reviewer mentions, divide the indoor fan from the efficiency rating at ARI-rated conditions and model it separately; this way you will be able to report the appropriate fan power"

My question is: where do I separately input the indoor fan power (kw), and what value should it be?, knowing that this is a baseline case that do not refer to an actual design.

Thanks,
Omar ElRawy, LEED AP BD+C
LEED Project Manager
EA Sustainable Building Consultants
http://www.ea-buildingconsultants.com<http://www.ea-buildingconsultants.com/>
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