This interactive 3D model is a dedicated deep-dive into a central chiller plant room — two 300-ton water-cooled chillers, the primary and secondary chilled-water pumping loops that decouple them from the building, the decoupler bypass line that makes primary-secondary pumping work, the condenser water loop, and the rooftop cooling tower that rejects the heat. Click any component to see what it does and how it's sized. It's a visual learning tool for HVAC designers, mechanical engineers, plant operators, and students learning how a real chiller plant is built and pumped — built to match the numbers used in this site's Chiller Plant Sequencing Simulator.
The viewer is a dedicated central plant room, modeled in real 3D detail rather than as a whole-building schematic:
• Two 300-ton water-cooled centrifugal chillers, built as real evaporator/compressor/condenser barrel shells rather than simple boxes. • Primary CHW pumps — constant-speed, one dedicated to each chiller. • Secondary CHW pumps — VFD-driven, serving the variable-flow building distribution loop. • The decoupler / bypass line connecting the primary and secondary loops — the defining feature of primary-secondary pumping. • Condenser water piping and pumps running between the chillers and the rooftop cooling tower. • The cooling tower itself, modeled with fill media, fan deck, and propeller blades. • Local chiller control panels, the plant BAS, and pressure/temperature gauges at key points in both loops.
Primary pumps run at fixed, constant speed and guarantee each chiller always sees its design flow — protecting the evaporator from the low-flow trip conditions that can occur if flow drops too far. Secondary pumps carry VFDs and vary speed to match actual building demand, which saves significant pump energy at part load. The decoupler bypass line sits between the two loops so they never have to fight each other's pump head: when secondary demand is below what the primaries deliver, the surplus simply recirculates through the decoupler instead of forcing the building distribution system to absorb full primary flow. This plant stages a second chiller on once the first crosses roughly 85% of its 300-ton capacity, matching the staging logic in this site's 2D Chiller Plant Sequencing Simulator.
1. Drag to orbit the plant room, scroll to zoom, and pan to move around. 2. Use the VIEW buttons to isolate the ground-level plant room or the rooftop cooling tower platform. 3. Click any component to highlight it and read its function and applicable standard. 4. Follow the chilled-water path (chiller evaporator → primary pump → decoupler → secondary pump → building) and the condenser water path (chiller condenser → CW pump → rooftop cooling tower → back) to see how the two loops connect.
Primary-secondary pumping uses constant-speed primary pumps to maintain design flow through each chiller, and variable-speed secondary pumps to distribute chilled water to the building at varying flow rates. A decoupler (bypass) pipe between the two loops lets flow recirculate when building demand is below what the primaries deliver, so the two pumping systems never fight each other's head.
Without it, the constant-flow primary pumps and the variable-flow secondary pumps would be hydraulically coupled — secondary pump speed changes would directly affect flow through the chillers, risking low-flow trips at part load. The decoupler isolates the two loops so each can be controlled independently.
In this model, Chiller #2 stages on once Chiller #1 reaches roughly 85% of its 300-ton capacity — the same threshold used in this site's Chiller Plant Sequencing Simulator. Staging too early wastes energy running two machines at low part-load; staging too late risks insufficient capacity.
Chilled water leaves the evaporator at 44°F design (resetting up to 46°F at low load) and returns around 54°F. Condenser water leaves the cooling tower at 85°F design supply and returns from the chillers at 95°F — a 7°F approach at 78°F outdoor wet-bulb.
ASHRAE 90.1 §6.8.1 sets minimum full-load kW/ton and IPLV/NPLV efficiency requirements by chiller type and capacity. AHRI Standard 550/590 defines the certified performance rating and testing procedures chillers are tested against.