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NC-2009 EAp2:Minimum Energy Performance

Fans broken out at ARI-rated conditions

Profile picture for user o_osama
Omar Elrawy
Green Building Consultant | Researcher
GreenA Consultants
LEEDuser Basic Member
38 thumbs up

Dear all, I've got the following reply during my preliminary design submittal stage: "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 the simulation tool's 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. My question is: should I proceed with the submittal with the zero fan power to this psz system, and report it as zero also in table 1.4.7A, or I must provide any extra documentation?

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Mon, 06/08/2015 - 15:45

Since you are including the fan power in the cooling EIR, it won't show any fan power in the SV-A report. 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.
Profile picture for user o_osama
Omar Elrawy
Green Building Consultant | Researcher
GreenA Consultants
LEEDuser Basic Member
38 thumbs up

Mon, 06/08/2015 - 16:54

Thanks Gaston, I need more clarification just on the dividing part. Now I understand that I can report the SV-A report with zero fan power, but I must model the indoor fan separately from the system. But this is a baseline case that is not referring to an actual design; so where do I separately input the indoor fan power (kw), and what value should it be? Thanks

Tue, 06/09/2015 - 17:15

You should read this thread: http://energy-models.com/forum/energy-modeling-software/equest/901-app-g-fan-power-and-eer-calculations#comment-22467 Most of the information you need is in there. Hope it helps.

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