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CI-2009 EAc1.3:Optimize Energy Performance—HVAC

Energy Modeling

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Charles Nepps
NH Green Consulting
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We received a review comment back, on Energy Modeling report use to document EA cr1.3, that stated the following: "The Proposed design air cooled chiller COP for office is indicated 2.5 does not comply with the requirements of ASHRAE 90.1-2007, Section 6.4.1.1 which requires the minimum efficiency requirement of air cooled chiller per Table 6.8.1.C. This will preclude the project from using Alternate Baseline method" The reviewer goes on to recommend using the Baseline method of modeling instead. My question is if the design chiller COP used in the model was too low to meet the requirements, couldn't we just simply rerun the model using the min. efficiency COP from Table 6.8.1.C. ...which should generated even better savings? Am I missing something here?

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Thu, 05/22/2014 - 13:33

Chiller efficiency is "mandatory" provision (6.4) which specify the minimum for each cooling epuipment. Failing to comply will lead to not meet requirement of credit EAp2 which is a prerequisite. I am not sure with or have heard of the "alternate baseline method". Also waiting to see other comments.
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Charles Nepps
NH Green Consulting
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Thu, 05/22/2014 - 14:56

Sorry, I believe to reviewer meant to say "Alternative" Baseline Method The project can demonstrate the installed equipment meets the mandatory requirements, I believe the low COP value of 2.5 was entered in error during the modeling. It just concerns me that the reviewer's solution was to change to the "Baseline Method", rather than correct the input data for the model. Is it a case of once you've submitted a design chiller COP, are you stuck with it; so changing the existing model is not an option? Or is it because since the project is just a portion of an existing building, the Baseline Method is more applicable?

Thu, 05/22/2014 - 15:40

You can change the model and simulate again. Simply write the narrative to explain the reviewer about the input mistake. However, please make sure the matching COP with the comissioning data EAp1 and EAc3.
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Charles Nepps
NH Green Consulting
LEEDuser Premium Member
80 thumbs up

Fri, 05/23/2014 - 08:59

Thanks for your help Jatuwat! I've found some of the USGBC review comments confusing and I'm not entirely sure they will accept us simply changing the COP number. One of their comments seemed to question if the model was consistent with ASHRAE 90.1.2007 requirements at all. Unfortunately I do not have a lot of experience with energy modeling; can you recommend any resources that would help me understand them better?
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Fri, 05/23/2014 - 17:12

Download the Advance Energy Modeling Guide for LEED from the USGBC web site. If you are concerned about changing the COP provide additional documentation (product literature perhaps) to verify the correct COP.

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