Walk-in cooler not cooling

What to do with the food

The Conference for Food Protection's Emergency Action Plan for Retail Food Establishments, which many health departments use, sets out how long refrigerated food can sit above 41°F before it has to go:

While the walk-in is down, the same plan says to record food temperatures every 2 hours, move product to working refrigeration or pack it in ice, and never put hot food into the failing box. It also recommends telling your health department when an interruption starts. Your local food code and inspector have the final word; this table is a guide, not a ruling.

First: which half has failed?

A walk-in has two halves. The evaporator (unit cooler) is the fan box inside, near the ceiling. The condensing unit — compressor, condenser coil and fan — sits on top of the box, on the roof, or outside. Two quick observations narrow things down a lot:

The checks, in order

These are the things a technician looks at before reaching for gauges, roughly in this order. Everything up to step 6 is safe for an owner or manager to look at.

1. The thermostat and the display

Check the set point has not been changed. Then check whether the system is simply in defrost: Kolpak's manual gives a default air-defrost of every 6 hours for 30 minutes, and electric-defrost timers set at the factory to four cycles a day of 45 minutes each. A walk-in that is warm for half an hour and then recovers is often just defrosting.

2. Power

The evaporator and the condensing unit are often on separate breakers or disconnects. Check both. A tripped breaker that trips again immediately is a technician job — do not keep resetting it.

3. The door

Walk-ins built since 2009 must have automatic closers that pull the door shut from within an inch of closed, and strip curtains or another way of limiting warm air coming in. Push the door to within an inch and let go: it should close and seal by itself. Look for a torn gasket, a missing or tied-back strip curtain, and anything propping the door. Warm, humid air coming in is also what ices the coil.

4. Product blocking the evaporator

Heatcraft says to keep a gap equal to the unit's height below the unit cooler and never stack product in front of the fans. Kolpak asks for clearance at least equal to the coil height on all sides. Cases stacked to the ceiling after a delivery are one of the most common causes of a walk-in that "suddenly" can't hold temperature.

5. Ice on the evaporator coil

Shine a light into the unit cooler. A coil that is a solid block of white ice can't move air, and the box warms up while everything sounds normal. See the next section.

6. The condenser coil

Look at the outdoor coil. Matted dust or grease stops it rejecting heat; Kolpak warns that a dirty condenser causes poor performance and compressor failure. Kolpak's schedule is to clean it every 3 months, or monthly near cooking equipment. Kitchen exhaust is why rooftop units over a fryer line clog so fast.

7. Technician territory

If all of the above is fine, the remaining causes need gauges and a licence: low refrigerant from a leak, an expansion valve or superheat problem, a failed defrost heater or termination control, a bad contactor or compressor, or high head pressure. Heatcraft's instruction on low refrigerant is to find and repair the leak before adding refrigerant — a technician who only tops up is likely to be back.

Ice on the coil: why it happens

An evaporator runs below freezing and collects frost; defrost cycles melt it off. When frost wins, the coil ices over. The causes Heatcraft and Kolpak list:

• Too much warm, humid air coming in — a door left open or not sealing, or a unit cooler mounted too close to the door.
• Defrost not doing its job — too few cycles a day, cycles too short, a failed defrost heater, timer or termination thermostat.
• Low refrigerant — Heatcraft lists an iced coil among the causes of low suction pressure.

Uneven frosting, with ice heavier on one side, usually points to the unit cooler being too close to the door or the defrost ending too early.

To clear it, the coil needs a manual defrost: turn the cooling off and let it melt, with towels or a tray ready for the water. Don't chip the ice off — the fins and tubes are thin, and a puncture turns an ice problem into a refrigerant leak. If the coil ices up again within days, the underlying cause is still there.

Water on the floor

Defrost water runs from the drain pan out through a drain line. If the pan overflows, the line is blocked, frozen or not pitched properly. Heatcraft specifies a fall of at least 1/4 inch per foot, a trap in a warm space, and an open drain rather than a direct sewer connection. In freezers the line needs a heater. Ice in the drain pan points to a frozen line or a failed heater; standing water points to a blockage or bad pitch. Clear standing water quickly — a wet walk-in floor is a slip hazard and a health-inspection finding.

What this costs

86 Repairs reported an average vendor invoice of $1,000.42 for walk-in repairs across its customers, against $519.09 for reach-ins — almost twice as much. Some of the most common causes cost very little: a door closer adjustment, moving product off the evaporator, or a condenser cleaning. Checking those first is what keeps a call-out from becoming the average invoice.

What to tell the technician

• The make of the box and of the refrigeration system — often different brands (a Kolpak or Norlake box with a Heatcraft, Bohn or RDI system, for example).
• Product and air temperatures, and when you first noticed.
• Whether the inside fans and the outside unit are running.
• Whether there is ice on the coil, and how much.
• Water on the floor, or ice on the ceiling around the unit cooler.
• When the condenser was last cleaned.

Refrigerant work in the US needs an EPA Section 608 certified technician.

Running a freezer? It has problems a cooler doesn't — ice on the ceiling, a door frozen to the frame or hard to open, a frozen drain. See walk-in freezer problems.

Maintenance the manufacturers specify