How to solve the refrigerator’s internal or external sweating?

According to international standard ISO 7371 household refrigeration appliances must not have water dripping on their external surface. But when installed in places where it’s very humid and hot, there may be interior or exterior sweating in the system. Besides environmental factors, some changes in the refrigerator’s proper functioning may be associated with these problems.

Frequently opening the door or leaving it open for too long can cause internal sweating in the refrigerator.

When does sweating occur?

The sweating process occurs when water in the air finds the right condition to transform itself from vapor (gas) into moisture (liquid), causing sweating (water condensation process). The condition for this to occur is related to two main factors: The concentration of water in the air (relative humidity) and the temperature of the surface where there is condensation (called the dew point temperature). To illustrate, imagine a glass on the table with a cold liquid. Due to higher humidity on rainy days, there is more sweating than on dry days. Now, imagine instead that heated liquid was placed in the glass this time. Since the glass wall temperature would be above the dew point temperature, there would be no sweating.

Understand the external sweating process

On rainy and cold days, even with the cooling system working properly, sweating on the refrigerator’s outside surface is possible, especially at the height of the freezer. This is likely to occur due to the high relative air humidity, but also because of the refrigerator’s external surface temperature being too close to the dew point temperature. In this case, it’s recommended to set the thermostat to the hottest position (minimum), which will also provide an energy consumption reduction.

Please note, if external sweating is noticed on days with normal humidity and temperature, take care! This is a sign that the refrigerator needs adjustments or maintenance. External sweating may be due to poor or damaged thermal insulation, causing the refrigerator’s wall temperature to become too low so as to generate condensation. Another possible cause is the rubber gasket drying out or needs to be changed, which allows cooled air leakage to the refrigerator wall, generating a sweating point there. Or still, it could be from an electric source, such as a defective thermostat, causing the compressor to work 100% of the time, or the thermostat bulb installed in an incorrect position, deregulating the cooling cycle.

Causes of internal sweating

Internal sweating is typically caused by moisture infiltration that can also be due to the door rubber gasket drying out, which allows hot air into the refrigerator. Excessive door openings, especially in refrigerators that are not frost-free, also increases sweating.

Storing hot food as well as liquid and food containers without lids also generate increased humidity inside the refrigerator, increasing internal sweating.

 How to avoid sweating:

• Avoid placing food and liquids in containers without lids in the refrigerator.
• Remember, on cold days, set the thermostat to the warmest position (minimum), and on hot days, set the position of the thermostat at the coldest point (maximum), which will ensure better refrigerator performance and energy savings.
• In some cases it will be necessary to perform system maintenance like changing the thermostat or door gasket.

However, on very humid and colder days the sweating process may actually occur and should be considered normal.