Frozen storage
Also known as: freezer room, low-temperature room, frozen store
Short definitionA room where product that arrives already frozen is held for months at −18 °C and colder. It does not do the freezing; it only protects what is frozen.
Customers often expect to freeze product in this room as well; it does not work. The calculation assumes goods come in at −12/−15 °C at the warmest. Fresh product put inside does not freeze for days, warms the box next to it and fills the evaporator with ice. Freezing is the blast freezer’s job. The reason for the −18 °C limit is simple: at this cold, microbes cannot multiply and chemical spoilage slows right down. It is also the legal limit for quick-frozen food.
In practice the set point is −20/−22 °C; ice cream needs −25 °C and oily fish an even colder room. A steady −20 °C is better than a swinging −24 °C, because fluctuation leaves snow inside the pack and a dry surface. The quote is heavier than for a chill room: 120–150 mm panels, an insulated floor heated from below, a heated door frame, and an evaporator with defrost and 7–10 mm fin spacing. Evaporating at around −30 °C, the compressor produces far less cooling.