Hi All,

I am working on 137,000 SF Recreation Center (ARC) expansion project which is LEED v4 New Construction+ Renovation project. The building is partially served by a 250 TON Heat Recovery chiller (HRC) which provides heating and cooling to the building. However, the HRC doesn’t have enough capacity to fulfil 100% of the cooling load. During peak load, the building is supplemented by campus CHW. The building peak cooling load is estimated to be 500-550 Tons. The campus CHW provides cooling for approximately 1065 hours in a year, accounting for 12% (100,550 TON-hr) of the total cooling Tonnage. HRC capacity is enough to take care of the building cooling load rest of the time (7695 hrs, 762,000 TON-hr). When there is no cooling demand for the building, the HRC feeds back the campus CHW system. An estimated cooling ton back to the campus is ~ 450,000 TON-hr. The project also has a PV array of 250 KW on the roof. I am looking for clarifications regarding selection of baseline system and how to model the baseline HVAC plant for the following scenarios if the project must follow DES guidelines.

  1. As per ASHRAE 90.1 2010, based on the building type, and all electric HRC system, the Appendix G baseline system would be System 6. Since, the CHW from the campus is supplemented for peak load only (12%) and the HRC adds capacity back to the campus CHW system, Does the project have to follow District Energy Guidelines (DES) or use System 6 for the baseline system?
  2. If DES Guidelines must be followed:
    1.  Option1 Path2, The HRC is connected to the campus CHW system and adds capacity to it when there is no building cooling load. Am I correct in assuming the HRC is modeled as upstream equipment and staged according to the percentage of load (HRC- 88% and Campus CHW system -12%)? Then the baseline system would be VAV Fan Powered boxes and electric reheat (System 8) with water cooled chillers.
    2. Option 1 Path 1: As per option 1 Path1, both the proposed and baseline design use purchased CHW. Then, the baseline system would be VAV Fan Powered boxes and electric reheat (System 8) with purchased CHW for cooling. And the proposed is similar to the previous case with HRC + Campus CHW, however instead of modeling chiller, we would be using purchased CHW.
    3. For both Option1 & 2, Could I use the percentage reduction from onsite renewable generation (PV)?

Any help is much appreciated!

Regards,

Harshana