As you can imagine, having a big chunk of ice in your walk-in freezer is not safe. Not only could someone slip on the ice when trying to wrangle a box down from the stack, but also the ice could chip away and contaminate foods. It also takes up space, leaving you less room for storage. There's no doubt about it; if your walk-in freezer is forming icebergs, you need to do something about it. The first step is to figure out what's causing the ice formation. Here are some common culprits.
Lack of Insulation
Lack of insulation is especially common in older walk-in freezers. The insulation may have become compacted over time, or someone may have accidentally removed some of it while doing some remodeling near the freezer. Without proper insulation, one or more walls of the freezer may get a little too warm, allowing frost to melt when it hits that wall. Then, the freezer's cooling mechanism kicks back on and lowers the temperature, refreezing the water into ice. This happens over and over again, so the iceberg grows larger and larger.
Luckily, the solution to this problem is simple. You can add insulation around the exterior of the freezer. Having spray foam applied may be the most effective since spray foam insulation is impervious to moisture, but cotton insulation is also a smart choice. It does not release particles like fiberglass, so it's better for food service areas.
Clogged Drain Lines
Walk-in freezers do generate some condensation as they pull humidity from the air. When everything is working well, the condensation should go down the condensate drain. If this drain becomes blocked by crumbs, dust, dirt, or even mold accumulation, the water won't go down it. Over time, the water builds up and freezes. If your ice formation is primarily over the drain, this is probably the issue you're contending with.
Unfortunately, to clean the drain, you will first have to remove everything from the freezer and let the ice thaw. Then, you can scrub the drain clean. You may need to hire a professional to clean down inside the drain line if the blockage is deeper. In either case, work to keep the freezer cleaner, going forward, as this will prevent future blockages.
Your freezer's fan is meant to propel the cold air over the evaporator coil and through the freezer. If the fan is not working properly, the evaporator coil might get too cold and may ice over. If the ice buildup is located primarily on your evaporator coil, this may be the problem you're contending with. Listen to see if the fan turns on or if it seems like it's running slowly.
Fan problems are complicated. The motor may be ailing, or the fan blades may have been damaged by hitting ice or another hard object. A commercial refrigeration contractor may simply recommend removing and replacing your fan to prevent future ice buildup.
Lack of Defrost Cycle
Most freezers are designed to run a defrost cycle from time to time. The freezer warms up just enough to melt the frost, and then the humidity is discharged from the air via a fan. If the defrost cycle has been turned off or is not functioning for some reason, this could be why you're getting ice buildup. Your contractor may have to make some electrical repairs to trigger the defrost cycle to run as intended.
Don't ignore ice buildup in your walk-in freezer. It won't go away on its own. Consider the causes above, and reach out to a commercial refrigeration repair professional if you need assistance.