How to Stock a Walk-In Cooler for Good Airflow

How you load a walk-in affects how well it cools as much as the refrigeration does. A walk-in that's packed wrong develops warm corners, frozen product next to the fan and an iced evaporator, even when every part is working.

How air moves in a walk-in

The evaporator, the fan-coil unit on the ceiling or high on a wall, pulls warm air from the box through its coil and blows cold air out the front. That cold air has to travel across the room, wash over the product and return to the back of the coil. Product doesn't get cold from the setpoint; it gets cold from that moving air.

Block the loop in either direction and three things happen:

• Air short-circuits back into the coil, so the controller sees cold air and shuts off while the far corners stay warm.
• Areas behind stacked cases get almost no air and run warmer than the thermometer shows.
• The coil sees less airflow, runs colder and frosts faster, which leads to a frozen evaporator coil.

The page on the evaporator coil explains the unit in more detail.

The most common stocking mistakes

The exact clearance a unit needs in front of and behind the evaporator is in the evaporator manufacturer's installation manual. Heatcraft, for example, publishes evaporator options and specifications for its unit coolers. If you don't know yours, ask the installer.

A stocking layout that works

1. Keep a clear zone around the evaporator. Nothing on the top shelf directly under or in front of it, and nothing blocking the coil's intake side.
2. Shelving off the walls. Leave a gap between shelving and the wall panels so air can travel down the walls and back.
3. Everything off the floor. Bottom shelves or dunnage racks, never cases stacked on the floor.
4. Gaps between cases. Air should be able to move between cases, not just around the outside of a solid block.
5. Warm-sensitive product in the middle, frost-tolerant product near the fan. Delicate produce and items that shouldn't freeze go away from the discharge.
6. First in, first out. New product goes behind or under older product. The Food Code limits most ready-to-eat TCS food held over 24 hours at 41°F or below to 7 days, counting the day of preparation as day 1, so clear date labels and rotation also cut waste.
7. Keep the path to the door and the inside release clear. Nobody should have to climb over cases to get out. See inside safety release.

Hot food and big deliveries

The FDA Food Code requires every establishment's cooling and holding equipment to be "sufficient in number and capacity" to keep food at safe temperatures. A walk-in holds cold food well; it isn't designed to cool a big batch of hot soup.

The Food Code's cooling standard is 135°F to 70°F within 2 hours, and to 41°F within 6 hours total. Getting there usually means shallow pans, ice baths, ice wands or a blast chiller before food goes into the walk-in. Food Code 2026 lists placing food at a depth of no more than 2 inches as a cooling method. Your local health department's adopted code governs the details.

A delivery of room-temperature product is a smaller version of the same problem. Break it into batches if possible and expect the box temperature to rise for a while afterward. Log it so a technician can tell a delivery bump from a failing system. See temperature fluctuating.

Door habits

Every opening lets in warm, humid air. The moisture freezes on the evaporator coil and the heat has to be removed all over again. DOE rules require walk-ins built since 2009 to have automatic door closers and strip doors, spring-hinged doors or another way to reduce warm-air infiltration. They only work if nobody defeats them.

• Never prop the door open with a case, a wedge or a hook.
• Don't tie back strip curtains. Replace torn strips.
• Close the door between trips when loading.
• If the door doesn't close on its own, fix it. See walk-in door won't close.

When stocking isn't the problem

If you've cleared the airflow and the walk-in still can't hold temperature, or runs almost all day and never catches up, the cause is probably mechanical. Start with walk-in cooler runs constantly and keep a temperature log to show the technician. A box that's permanently too small for your volume is a capacity question, and the site's guide to commercial walk-in coolers covers sizing for replacement.