Most sizing mistakes are not calculation mistakes. They are sequencing mistakes — the equipment gets chosen before anyone wrote down what the rooms have to do.
Product type decides more than temperature: meat needs hygiene zoning, vegetables need air movement and humidity control, ice cream needs a much colder evaporating temperature.
One building usually contains several different rooms — a blast freezer at −30 to −35°C, frozen storage at −18°C, a chilled room at 0 to 5°C, sometimes a 10 to 15°C processing room. List them separately, not as "a cold room".
Tonnes in and out per day, and how many hours the shift has to do it in. Two rooms of identical size behave completely differently at 5 t/day and 50 t/day.
A room list has one line per room: name, temperature, product, tonnage, daily throughput, and what happens at the door (pallet truck, forklift, hand carts, personnel only). This is the document the equipment selection is read against — and the one that catches the classic mistake of a frozen store sized for tonnage but with a door that a forklift has to pass through every twenty minutes.
Unit type follows duty: continuous heavy load suits screw or parallel piston sets; small rooms suit packaged units. Air cooler fin spacing follows room temperature — roughly 4.5 mm for chilled duty, 6.0 mm for −18°C storage, 9.0 mm for −25°C and below — because the wrong spacing means either a starving coil or a defrost cycle every hour.
Electric, hot gas or water defrost — chosen at design stage. Changing it after the room is built usually means new coils.
Frozen rooms need underfloor protection against frost heave. It is invisible until it becomes a demolition job.
Condensate has to leave the room without freezing or letting air in. Poor layout shows up in month two, not day two.
Chilled, frozen and blast freezer walls are not the same. Using one thickness everywhere is either expensive or ineffective.
Installed capacity, voltage and phase; and whether a second phase of rooms is coming. Both are cheap now and costly later.
A local service team changes the sensible answer: fewer, larger units versus distributed packages.
Product(s) · room list with temperatures · tonnage and daily in/out · room dimensions or a layout drawing · local summer design temperature · power supply (voltage / phase / frequency) · whether the product is for export · target commissioning date. With these, a first room list and an indicative price usually takes one working day.
Temperature bands and what each one implies: Cold room temperature zones explained. Sector specific room lists: meat processing · poultry & slaughter.
No obligation until you approve a drawing and a price.