Worked cases · Houston

A supermarket floor dried at the door, and a freezer held at −20 °C

Display cases as a negative gain, three gas rooftops, a dedicated outside-air unit that takes the sales floor's humid hours from 1 126 to 0, and a frozen store on a remote low-temperature condensing unit.

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Bayou is a 2 000 m² sales floor on Houston's year with a 0.0095 kg/kg humidity ceiling, a prep room on a split, and a frozen store at −20 °C. The display cases are modelled as what they are — a negative gain, 35 kW sensible and 8 kW latent taken out of the room — which is why a supermarket's rooftops heat in the shoulder seasons and its night latent is negative.

Three gas rooftops with 22 % outside air each could not hold the ceiling against some 80 kW of outside-air latent: 1 126 humid hours. A dedicated outside-air unit on the modular chiller — the DOAS scaled to 2.7 m³/s with a gas reheat — now leads the floor and the three rooftops recirculate behind it under the priority rule, so the unit carries the latent and the rooftops are asked only for the rest. Humid hours: 1 126 → 0, at a measured price the page states rather than hides.

The frozen store is a unit cooler with both refrigerant ports open, fed by a Copeland ZF49K5E condensing unit on R404A drawn as its own block — the refrigerant coupling. A ZF25 was tried first and ran short on a 35 °C afternoon; the ZF49 holds −20.0 °C every hour of the year at a seasonal COP of 1.45.

What it reads on Houston

Cooling	938 MWh (most of it the outside air the unit brings in)
Electricity / gas	359 MWh / 152 MWh
Sales-floor humid hours	0 (1 126 before the outside-air unit)
Frozen store	−20.0 °C every hour; 56.4 MWh of unit-cooler duty on 38.7 MWh at the condensing unit
Prep room	117 unmet cooling hours — a split whose own outside air is a third of its capacity on a humid afternoon

What it taught

Ventilation air is where the moisture arrives; drying it once at the door beats asking every rooftop to do it.
A machine that leads a room carries its latent; the ones behind it are asked for the remainder — the priority rule has a moisture side.
A cold store's condensing unit is sized for the hot afternoon, not the annual mean; pull-down margin of two to one is ordinary.

The machines

Sources

Copeland Product Selection Software rating database (ZF49K5E on R404A)
ASHRAE 55 humidity bound; ASHRAE 62.1 ventilation rates
PVGIS TMY, Houston

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.