Heatcraft | The Cold Front | Supermarket Edition | Summer 2012 | 5 Steps to preventing surface condensation on your display cases
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5 Steps to preventing surface condensation on your display cases

In summer months, ice cream and frozen foods for grilling fly off the shelves as consumers look for ways to relax and stay cool. And that means frozen food aisles are seeing a lot of extra traffic.

While the frozen food rush is great for the bottom line, the continual opening and closing of freezer aisle glass doors presents an interesting paradox. That’s because when doors are left open too long, and the temperature of the glass surface interacts with the store air, surface condensation starts to occur.

When this happens, the glass viewing area on freezer door cases begins to fog, impacting product visibility so consumers can no longer see what’s inside. As a result, shoppers hold the doors open longer when selecting products. This, coupled with the doors being opened more frequently due to high seasonal traffic, causes energy consumption to rise—and utility costs to quickly follow. Finally, when doors are opened too many times, it causes the temperature inside the cases to rise, making food spoilage more likely to occur.

How can store owners prevent surface condensation? While it cannot be prevented entirely, the steps below can help to minimize the occurrence:

1.  Right size your HVAC system.
This is the first line of defense in maintaining a favorable store environment. It should also be equipped with a dehumidification system to decrease the amount of moisture in the air based on the air percent relative humidity. If the HVAC system is designed properly to not exceed ASHRAE test conditions, it should prevent surface condensation from forming.
2.  Maintain proper store air moisture levels.
In addition to installing an effective dehumidification system, it’s important to ensure the store temperature is continually adjusted to work with changing outside air conditions. In summer months, the condition of the air outside is usually warmer and more humid, with more water vapor entering the store from the outside air. Therefore, if humidity is not controlled within the store, the chances of surface condensation are greater.
3.  Rule out air conditioning performance issues.
When moisture from ambient store air condenses on a cold surface, and the temperature of the cold surface is below the dew point temperature of the air that surrounds that surface, surface condensation will occur. If store air conditions meet do not exceed ASHRAE test conditions (75° F dry bulb and 64° F wet bulb), with a corresponding dew point temperature of 58.5° F, surface condensation will be prevented. Therefore, store owners can verify proper system performance by finding an accurate reading of dew point temperature based on wet and dry bulb temperatures. Once these temperatures are measured, they can be used to determine the dewpoint temperature by using a psychrometric chart.
4.  Verify proper case performance.
In the event that store conditions are favorable and air conditioning and dehumidification systems are working properly, surface condensation issues are more likely related to performance issues on the freezer cases. This could be due to glass door heaters not working, coils freezing or other factors and will merit a visit from a service tech.
5.  Prevent other moisture-related problems from occurring.
Generally, as a matter of the way a door case operates, the built-in air curtain reduces moisture entering the case from the outside store air. But when freezer aisles experience increased traffic, and the cases are opened more frequently, store air mixes with the air inside the case, causing moisture to form on the evaporator coils and inside the case. Store owners can alleviate this by defrosting evaporator coils at least once a day—and sometimes more often—depending on store conditions.

Kysor/Warren STRATUS freezer door cases are designed to help customers save energy, with features that help to prevent surface condensation. For more information, visit www.kysorwarren.com.

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