3 Potential Causes For A Warm Walk-In Freezer

An air conditioning system that won't keep your home cool is an inconvenience, but a walk-in freezer at your business that can't maintain its temperature is potentially a disaster. Not only do inadequate temperatures put your inventory at risk, but thawing food can pose a potential health hazard for your customers.

It's crucial to monitor your freezer's temperatures closely to recognize when trouble may be brewing. The FDA recommends maintaining a temperature of 0 degrees Fahrenheit for food safety, and upwards deviation likely indicates an ongoing failure. Once you notice your freezer beginning to warm, it will likely be due to one of these three common causes.

1. Stuck Defrost Clock

Commercial freezers share much of their DNA with standard air conditioning systems, but several notable differences exist. Since the evaporator coils must cool the freezer to well below freezing, frost on the coils is a significant concern. Too much frost build-up will eventually cause the refrigerant to slug, forcing the compressor to shut down or even causing damage.

All commercial refrigeration units use a defrost system with a defrost clock (or timer) to switch between refrigeration and defrost modes. These timers use physical gears that can become stuck, leaving the unit in defrost mode and not cooling. While it may be possible to temporarily free up a stuck clock, it's often best to replace the timer and prevent future issues.

2. Faulty King/Service Valve

"King" valves are special multi-position service valves found primarily in refrigeration systems. These valves allow technicians to access the refrigerant system for testing, but they're also a common source of leaks. The typical king valve includes a normally-closed access port accessible by turning a valve at the top of the assembly.

These valves allow multiple positions so technicians can adjust the valve for testing, charging, and recovery. However, it's also possible for the valve to become stuck or for a previous technician to leave it in the wrong position. These situations can potentially result in leaks, which will impact the performance of your walk-in freezer.

3. Bad Temperature Controller

Finally, the temperature controller is always a potential culprit. A faulty temperature controller can exhibit numerous symptoms, ranging from over-cooling to under-cooling. The two types of controllers found in walk-in freezers are conventional electromechanical controllers and more modern electronic controllers. Each can fail in its own unique ways.

However, since electronic controllers typically include additional controls for fan speed and variable-speed compressors, these units often have more potential failure modes. In either case, it's best to allow a trained HVAC technician to investigate the problem and determine if the temperature controller is actually at fault for your high freezer temperatures.

For more information, contact a local company like NuAire Mechanical Engineering.