A district plant serving three buildings through a manifold

Lakeshore is a water-cooled plant — four ZHT300KCE scrolls from the catalog on R513A, a coaxial evaporator and condenser, a condenser-water pump and a cooling tower with a Eurovent 35/30/25 rated point on Braun's enthalpy-basis model — holding 6.5 °C for three chilled-water handlers, each with a gas-boiler stand-in for heat and ten cubic metres of loop water declared as a buffer on its intake.

On New York's year the plant delivers 558 MWh on 176 MWh of electricity — a seasonal COP of 3.2 with its tower fans and pump, honest about the fact that fixed-speed scrolls cycle where a centrifugal would unload on vanes — and every room is held to within eight hours. The plant carries a waterside economiser: a plate exchanger between the tower loop and the chilled-water return, ahead of the evaporator, with a free-cooling stage the controller tries before the chiller. On this campus it is worth about 9 MWh a year — modest, because the handlers' airside economisers already take the load on the hours the tower is cold; a waterside economiser earns more on loads that persist in cold weather, a data hall or a laboratory without outside air. The boilers burn 435 MWh of gas, 150 of them the reheat the humidity ceilings ask for.

The finding the case leaves open is the one it states: 616 / 1 639 / 1 005 humid hours across the three rooms. A 0.012 kg/kg ceiling on an 8 m³/s handler with a boiler-fired reheat is not held on New York summers; the cleanroom's answer — face-and-bypass — is the next thing to measure here.

What it reads on New York

What it taught

• A plant this size on scrolls over-states part-load electricity a little; the case says so rather than borrowing a centrifugal curve it does not have.
• A loop's thermal mass is a configuration, not a default: 10 m³ a receiver costs comfort hours because the plant answers a load step later.
• A humidity ceiling with reheat is a finding to measure, not to hide.

The machines

• Example water-cooled plant, 600 kW class — open in the builder
• Example campus AHU, 8 m³/s, boiler heat — open in the builder

Sources

• Copeland PSS rating database (ZHT300KCE, R513A)
• EVAPCO LPT bulletin and Marley Aquatower tables (tower model anchors)
• Braun, Klein & Mitchell 1989 (tower ε-NTU)
• PVGIS TMY, New York

Readings of the shipped model on the building's own PVGIS typical meteorological year; engineering estimates from catalog data and published correlations. The building runs on every plan, including Free, a few times a day.