Express delivery worldwide. ISO17025 Accredited & Compliant to FDA

Why is the temperature fluctuating in my cooling equipment?

Temperature fluctuations are quite normal and always occur to a greater or less extent in cooling equipment. This guide gives you an introduction to dealing with different types of temperature fluctuations as well as a short guide to what you can do to adjust your equipment and to avoid temperature fluctuations that can lead to deviations.

Fluctuations in temperature

As said, temperature fluctuations are quite normal and will occur to a greater or less extent in all types of equipment.

Below is an example of the temperature in a freezer:

Eupry example on conducting temperature mapping of refrigerators

The temperature rises and falls in the freezer due to the control that the freezer is equipped with. Based on the setting, the freezer will cool until it reaches a limit value. When reached the compressor turns off and the temperature rises gradually due to the ambient temperature – the temperature in the surroundings.

The size of the temperature fluctuations depends partly on the quality of the equipment. Expensive equipment will typically have better control and will be able to keep temperatures more constant. Also, the number of goods in the equipment will influence stability. The more goods, and thereby thermal mass, the more constant the temperature will be. 

Adjustments of the equipment

Temperature fluctuations as such are not harmful as long as the temperatures in the equipment stay within the specified limits.

Although the temperature of the goods in the equipment may not be outside the specified limits, it is still advisable to adjust the equipment. The adjustment can be done by slowly adjusting the cooling setting and wait for a minimum of 2 hours. Then look at what effect this had, and re-adjust if necessary. This ensures that the adjustment has not been too extreme. Always check again after 1-2 days to ensure that the equipment is still set correctly.

Additionally, take note of where the temperature monitors are located in the equipment since some areas may be warmer or colder than the rest of the equipment. Read our article about temperature mapping to learn more about this.

Different fluctuations

Equipment sometimes has temperature fluctuations that do not follow the graphs above. We have included some of the most common ones here.


Some types of equipment have a built-in feature where they regularly raise the temperature for a short period of time (typically every 6 and 24 hours). This function removes ice from the heat sink in order to optimize the efficiency of the equipment both in terms of cooling and power consumption.

An example of defrosting can be seen below:


In the example, you see a refrigerator that runs a defrost program every 6 hours. As seen, the temperature of the equipment is raised 1 degree for a short period of time.

Defrosting is not necessarily harmful even if it results in temperatures in the equipment that exceed the specified limits. If you use a grey-zone temperature monitoring system, these can be used to avoid alarms and deviations when the defrost program runs. It is always an assessment, but it can usually be argued that if the equipment only exceeds the specified limits in short periods of time the goods usually do not get heated above the specified limits.

However, if the defrosting causes the temperature of the goods to exceed the specified limits to a critical level, it may be worth considering changing the settings of the equipment or introducing thermal mass as explained later in this article.

Usage patterns and equipment filling

When cooling equipment is used for general goods or general use where goods are unboxed and dispatched, temperature fluctuations may occur as shown below:

In the example, the door of the cooling equipment had stayed open for too long which resulted in an alarm from the wifi temperature data logger.

It is important to remember that the door can only be opened shortly, otherwise, the temperature may exceed the critical specified limits and a deviation that needs to be handled will occur.

Likewise, it may be problematic if you place too many goods in the cooling equipment. If the temperature takes a long time to restore after the goods have been placed in the equipment, it may indicate that too many goods have been stored in the equipment or that the goods have not been properly cooled beforehand.

To avoid this, it is advised to limit the amount of goods in the equipment or make sure that the carrier transports the goods at the right temperature.

What can be done to reduce temperature fluctuations?

Fortunately, it is relatively easy to limit temperature fluctuations in equipment.

•  The easiest solution is to increase the thermal mass in the cooling equipment. This can be as simple as adding some bottles of water and placing them at different places in the equipment. The water will reduce temperature fluctuations even when new goods are placed in the equipment.

•  Make sure to have equipment that logs continuously and sends data continuously. The best way to reduce the risk of deviations is to continuously monitor the temperature of your equipment. As seen in the above examples, logging once a day is not enough to detect fluctuations that occur several times per hour.

•  Systems with continuous data readings are clearly preferable. If you use a manual reading system (e.g. USB data loggers) you cannot detect temperature fluctuations in time, which may have major financial and quality consequences.

Need help?

Eupry optimizes how organizations monitor, and document temperatures. Using the Internet of Things (IoT), Eupry changes the way organizations approach compliance, quality, and efficiency. We have a wide variety of customers in several sectors. If you have any questions regarding how to secure temperature sensitive goods, you are welcome to contact us.