I'm designing a building on a college campus that has a DES. We opted to model option 1 for EAc1 (Building Stand-alone scenario). Our original baseline system was System 3, and we have district heating and cooling, so we shifted our baseline to 4-pipe CV AHU. The USGBC manual for treatment of District Thermal Energy says that any system parameters not specifically referenced in Table 3 (the baseline system revisions table) are modeled as specified in Appendix G.
Here lies the question: Appendix G doesn't specifically recognize a 4-pipe CV AHU system. My original system 3 was DX cooling and Fossil Fuel heat. There are several parameters that I need to model that aren't addressed by Appendix G's system 3 such as Hot Water design temps, HW Temp reset, Hot Water pump efficiencies, Chilled water design temps, Chilled water reset, and Chilled Water pump efficiencies.
Should I just use the values for other systems? It seems a little unfair because those other systems are more efficient that what System 3 would normally be. Any input would be appreciated.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
July 31, 2012 - 1:58 pm
Yes you use the values for the other systems that translates to a 4-pipe CV system (all of the hot water and chilled water baseline parameters). The chillers may be more efficient but the boilers are about the same efficiency in the baseline. I think the DES is just requiring an apples-to-apples comparison of HW/CW systems.