Our project is located on a University campus with two separate DES buildings. One DES building houses all the chilled water equipment including chillers, pumps, cooling towers, etc. and only provides chilled water. There is a separate DES building which houses all the steam equipment. The DES Guidance indicates that for EAc3 we must commission all upstream equipment if "the DES supplies energy constituting more than 20% of the project building's annual energy cost, as determined using the Proposed Case energy modeling run of either the EAc1 Option 1 or Option 2." Should we be viewing the chilled water plant as one DES and the steam plant as a separate DES? In our case, the CHW plant accounts for 19% of the energy cost of the building and the Steam plant accounts for 9% of the energy cost of the building. Separately, these two plants are less than 20% of the energy cost but combined they would be greater than 20% and thus require commissioning of the DES. Because these are separate systems, should we be required to commissiong both even though separately they do not account for 20% of the cost? Is there a reason to commission the Steam Plant in this situation? The guidance document does not get detailed enough to answer this question nor are there any CIRs addressing this. Any thoughts? Also, even if the steam(or HHW) and CHW equipment are located in the same physical building, should they be viewed as separate plants?
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James Del Monaco
Sustainability Director, PEP2S Engineering, Inc.
64 thumbs up
September 10, 2012 - 12:35 pm
As a follow-up on this item, we received a CIR ruling on this question. In our case we have CHW from one plant and steam from a 2nd plant. In the eyes of the USGBC, the DES plant is the combination of the CHW plant and steam plant. Since this is how they view it, we would need to commission both plants. Here's the CIR ruling:
"The applicant is requesting clarification as to whether the project meets the enhanced commissioning exception for the DES energy contributing less than 20% of the building’s annual energy cost based on a three separate DES plants contributing less than 20% individually or if the exception applies to a total DES contribution of over 20% of building annual energy cost. Per the “Treatment of District or Campus Thermal Energy in LEED v2 and LEED 2009, August 13, 2010” a DES is “a central thermal energy conversion plant and transmission and/or distribution system that provides thermal energy (heating via hot water or steam, and/or cooling via chilled water) to more than one building…” In this case, the DES system is the steam and chilled water. Therefore, if the project building’s gross floor area is greater than 50,000 square feet, the DES’ total contribution as a whole contributes to more than 20% of the project building’s annual energy cost and either the project building is pursuing points under EAc1 using the performance path or the project building’s connected load is 50% or more of the DES total connected load or expected connected load at the date of the project building’s substantial completion, all upstream equipment associated with serving the project building must be included in the scope of EAc3."