Sunbelt is an insulated metal hall on Phoenix's year — 25 m² of skylight, 20 kW of day gains, a 28 / 15 °C band with a setback — on three two-stage evaporative units: a water coil cooled by a small tower pack on its own fan and pump, then a direct pad on its own sump, then a 5 m³/s supply fan, 100 % outside air. Three units are about 3.4 air changes, the low end of what such installations are sized at.

The units lead, on fan AUTO; a gas rooftop sits behind them for winter nights and the hottest afternoons. The pad's sump matters: plumbed into the tower loop, as the app's template once was, it ran as a water cooler on 25 °C water and supplied 27 °C air into a 28 °C hall.

On Phoenix's year the hall reads 463 MWh of evaporative coil duty for 38.4 MWh of fan-and-pump electricity — most of the duty is the 40 °C outside air the units bring in and cool, not the room's load — with the rooftop adding 18.3 MWh of DX trim and 2.1 MWh of gas, and no unmet cooling hour in the hall (three unmet heating hours on winter nights; the office's own split leaves it six). The hall's 1 091 hours above 0.012 kg/kg are what evaporative cooling is.

What it reads on Phoenix

Evaporative duty / electricity	463 MWh / 38.4 MWh
Rooftop	18.3 MWh of DX trim, 2.1 MWh of gas
Hall	no unmet cooling hour, three unmet heating hours on winter nights; 1 091 humid hours — evaporative cooling, declared

What it taught

• A direct pad on its own sump is adiabatic; on tower water it is a water cooler, which is a different machine.
• Fan AUTO is the thermostat's switch: a unit that is not the rooms' outside air should not ventilate an empty hall on ON.
• A machine with nothing to heat with derives an off stage for winter, or it blows 5 °C air into the hall at 15 m³/s.

The machines

• Two-stage evaporative unit, 5 m³/s — open in the builder
• Packaged rooftop with gas furnace, 3 m³/s — open in the builder
• DX split, 12 kW class — open in the builder

Sources

• Munters CELdek 7090/7060 published effectiveness curves
• DOE Commercial Prototype Building Models — Warehouse (shift schedule)
• PVGIS TMY, Phoenix

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.