Our project is one of three major healthcare projects: the Orthopedic Ambulatory Building (OAB), Atrium extension, and garage/central plant building. The central plant will be located in the basements of the garage building, providing chilled water and steam for all three buildings and part of the existing facility, the Kellogg Building. The central plant will include phased chiller and boiler installations. As requested by the client, the central plant has to provide N+1 capacity for redundancy at each phase. See Chart 1 and Chart 2 below: Chart 1: Chillers Phasing Plan Phase Date Building___Phase Load__Tot. Loads__Instl. Capacity _______________________(Ton)_______(Ton)_____(700 Ton and _______________________________________________1400 Ton chiller) A____8/1/2008 OAB_________732_______732________Two 700 Ton B____6/1/2011 Atrium Ext.__2333_____3065________5600 C____10/1/2013 Atrium_____1800______5300________5600 C____10/1/2013 Kellogg____600_______5905________7000 Chart 2: Boilers Phasing Plan: Phase Date Building____Phase Load__Tot. Loads__Instl. Capacity _______________________(Lbs/Hr)______(BHP)_____(412 BHP and _______________________________________________712 BHP chiller) A____8/1/2008 OAB___________6860_____205_______Two 412 BHP B____6/1/2011 Atrium Ext._____33297____120_______2268 C____10/1/2013 Atrium________27490____2021______2900 C____10/1/2013 Kellogg/other__51820____3570______5155 The Atrium Extension, Phase B, will be the building seeking LEED certification. It is a new 1,120,000 square foot hospital addition consisting of two basement levels for logistics and ancillary services, five floors of diagnostic and treatment functions, one lab floor, and five inpatient bed floors. The Atrium Extension Building will receive primary chilled water (38F) and high pressure steam (140PSI) from the central plant, which will be three blocks away. The Atrium Extension Building will only be using one quarter of the total central plant capacity. When we simulate the building energy performance for Atrium Extension building, should we include the central plant in the models? If so, how much of the total capacity do we include? Alternatively, could we just use "purchased chilled water and steam" for both the baseline and proposed design models? The central plant is producing 38F of chilled water for the entire facility. This operation is not covered in the nonstandard operation, stated in ASHRAE 90.1-2004 6.4.1.2 C). Should we set up our baseline model based on 44F chilled water and 3 GPM/Ton of condensing water? Or should we use the 40F with 2 GPM/Ton condensing water, which is close to the proposed design condition?
The project team is requesting clarification regarding the modeling of separate campus buildings served by a campus central plant. Based on the information provided, the central plant appears to be a new central plant, which will add chillers and boilers as additional phases of the project are completed. The following clarifications are requested regarding the central plant: [1] Should the energy models reflect the design of the central plant, or be modeled using purchased chilled water and steam? If the central plant is modeled, how should the capacities of the central plant be modeled? [2] What circulation loop temperatures and condenser water flows should be used in the base case? [1] It should be noted that if the project is pursuing credit under EAc1, the project must be modeled using ASHRAE 90.1 2004 Appendix G requirements. Section G3.1.3.7 states that for systems 7 and 8, electric chillers shall be modeled in the baseline building regardless of the cooling energy source. However, if the project is only seeking compliance with EAp2, the budget building may be modeled with purchased chilled water when the design energy case is also modeled with purchased chilled water. The USGBC is in the process of preparing a document describing the modeling protocol for individual buildings serviced by a central plant with Combined Heat & Power. If the project would like to reflect energy savings achieved from the central plant, they may apply the modeling methodologies described in this document (which will be available some time after January 2007). If the project is completing documentation prior to the release of this document, then the Proposed design for the central plant should be modeled using purchased energy rates, and the Baseline design should be modeled using ASHRAE modeling protocol. If purchased energy rates are used, documentation should be provided justifying how these rates were determined. [2] For the Baseline (or budget) building, chilled water circulation loop temperature must be modeled in accordance with Note 5 of Table 11.3.2A (if using the Energy Cost Budget Method to show minimum compliance) or G3.1.3.8 (if using the Performance Rating Method to show credit). Condenser water temperature rise must be modeled using Note 5 of Table 11.3.2A (if using the ECB method) or G1.3.11 (if using the Performance Rating Method).