Zone Loads, Ventilation, and Autosizing using the Loads Data Spreadsheet
Overview
Pre-defined prototype ApacheHVAC systems can be imported and autosized at both the zone and system levels. These two levels of loads analysis and autosizing can also be applied successfully to a broad range of user-modified variants of the pre-defined prototype systems. All systems, including any user-defined configuration, can be autosized with respect to system coils, fans, water loops, and plant equipment.
For pre-defined systems and variants thereof, the autosizing process sizes a broad range of system elements in two stages—first at the room/zone level, then at the system/plant level—with opportunity for user intervention between the two. ASHRAE Loads calculations are linked to target ApacheHVAC systems for both stages of the sizing process:
- Zone-level loads and sizing must be completed either manually or through the autosizing procedure described below. The resulting values for airflows and other controller settings must be assigned to the HVAC system in order for the spaces to be adequately conditioned.
- System-level loads and sizing, which applies to coils, fans, water loops, chillers, DX cooling, boilers, heat pumps, and other heat sources, must be completed in order to appropriately scale equipment capacities and performance data to obtain appropriate performance and energy consumption (unless the equipment sizing/capacities are otherwise manually set).
While any pre-defined prototype system can be modified without losing autosizing capabilities, retaining the zone-level autosizing capability requires maintaining pre-defined controller applications, controller reference name prefix with colon (e.g., “MC4: ….” ), and relationships to the Loads Data spreadsheet for each system. The use of the Loads Data spreadsheet is further described below.
System-level autosizing for coils, fan components, DX Cooling, HW and CHW loops, Heat transfer loops, boilers, chillers, heat pumps, and most other heating and cooling sources that “see” a load during the sizing run, applies to all ApacheHVAC systems, regardless of how and when they were created.
Systems setup and sizing toolbar in ApacheHVAC.
From left to right, the toolbar buttons in Figure provide the following functions.