How reach-ins, prep tables, display cases and reefers work, and how they fail
By Vimal Bhaya, Founder and Lead Systems Architect · Last reviewed 7 October 2026
Most of the refrigeration in a kitchen, a store or a fleet is not a walk-in. It is the reach-ins and undercounters on the line, the prep table under the sandwich station, the display cases on the sales floor and the reefer in the yard. Each one works on the same loop as a walk-in, and each one fails in its own way.
This is a ten-part tutorial in five pairs: the reach-in cooler, the reach-in freezer, the prep table, the display case and the reefer. In each pair, the first page explains how it works and what normal looks like, and the second goes symptom by symptom through what goes wrong, what to check yourself and when to call.
The 10 parts, in order
By the end you will know four things. How each of the five works, in plain words, and where its machine sits. The normal numbers for each, from the makers' own manuals, and what a healthy one looks like in real readings where we have them. Which symptom points to which cause, and which causes are not broken parts at all, like a prep table rated for a cooler room or a display case overloaded past its line. And what you can safely check before you call.
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1. How a reach-in cooler works
The parts and the five layouts, from bottom-mount to undercounter, the makers' normal numbers, and a real day of readings from a busy restaurant's drinks fridge: a big, steady sawtooth, about twice an hour.
Read part 1 -
2. Reach-in cooler troubleshooting
Seven symptoms, from a warm cabinet and an undercounter cooked by the line to frozen lettuce and water on the floor. Plus the night the same drinks fridge held flat near 46°F (8°C) for 15 hours: the shape of a door left ajar.
Read part 2 -
3. How a reach-in freezer works
The cooler's machine run colder, with heaters on the coil, the drain and the door. Why it heats its own coil a few times a day, and seven makers' defrost schedules side by side.
Read part 3 -
4. Reach-in freezer troubleshooting
Seven symptoms, led by an iced coil and a defrost gone wrong, a door that freezes shut and ice in the bottom of the cabinet. Each with its reasons, the proof and what to check.
Read part 4 -
5. How a refrigerated prep table works
How the cold air moves round the pans on a forced-air rail, and how a cold-wall rail differs. Why food stays cold only below the fill line, why the table is tested in an 86°F (30°C) room, and why the display is not the food's temperature.
Read part 5 -
6. Prep table troubleshooting
Ten symptoms, split by forced-air and cold-wall rails, led by warm food in the pans, which is usually the fill, the lid or the room rather than the machine. Plus nine checks, each with what it should read.
Read part 6 -
7. How a refrigerated display case works
The falling curtain of cold air that keeps an open case cold, the load line, night curtains, defrosts, and why the air can read in the 40s Fahrenheit during one while the food barely moves.
Read part 7 -
8. Display case troubleshooting
Six symptoms, from a broken air curtain and warm top shelves to ice, water on the floor and fogged doors. Plus how to tell a normal defrost from a failing case, and the plastic bag test.
Read part 8 -
9. How a reefer unit works
How a trailer unit blows air over the load and pulls it back underneath, the gaps the load must leave, continuous and start-stop modes, shore power and defrost.
Read part 9 -
10. Reefer troubleshooting
Five symptoms, from a warm load to a parked unit that never restarted, with the Thermo King and Carrier alarm codes behind them. Plus the Boxing Day no-start that TemperatureWise caught in Mississauga.
Read part 10
How to use this
Read them in order if you are starting from scratch. That is the usual path. If you already know which piece you need, jump to it from the list above.
The five pairs stand alone. Start with the equipment that has the problem. The reach-in cooler pages cover undercounters, worktops, drawers and chef bases too, and the reach-in freezer pages build on the cooler pair.
Walk-in coolers and freezers have their own tutorial, how walk-ins work, and how they fail. A reach-in, a prep table and a display case all use the same refrigeration loop, explained step by step there.