In refrigerator and freezer energy efficiency testing, test packages are commonly used to simulate the thermal characteristics of food products and evaluate temperature performance under controlled test conditions.

However, there is often confusion about the different test packages, especially the -1°C and -5°C freezing-point packages. Some users may assume that the two packages represent different operating temperature ranges. In fact, the distinction is primarily related to their freezing points and intended testing applications.

In this article, we explain the basic classification, composition and structure of refrigerator energy efficiency test packages to help laboratories and test engineers select the appropriate solution.

1. What Are Refrigerator Test Packages?

A test package is a standardized simulated food load used in refrigerator and freezer testing.

Instead of placing actual food products inside the appliance, laboratories use test packages with controlled thermal properties. These packages help create a repeatable test load and allow the temperature behavior of the appliance to be evaluated under defined test conditions.

The filling material is formulated to provide thermal characteristics similar to specific food products. The package is enclosed in a material with negligible water-vapor exchange with the surrounding environment, helping maintain stable test conditions.

2. -1°C Test Package: A-Class Package

The -1°C freezing-point test package is commonly referred to as the A-class test package.

An important point is that “-1°C” refers to the freezing point of the filling material, not the operating temperature range of the refrigerator compartment.

This distinction is important when selecting test packages.

For general refrigerator and freezer testing, the A-class (-1°C) package is commonly used, making it one of the most widely used test package types in laboratory applications.

Composition of the -1°C Filling Material

For every 1000 g of filling material, the formulation is:

The freezing point of this filling material is -1°C, and its thermal properties are designed to be equivalent to lean beef.

This carefully controlled formulation is important because the thermal behavior of the test package directly affects the reliability and repeatability of the test.

3. -5°C Test Package: B-Class Package

The -5°C freezing-point test package is referred to as the B-class test package.

Again, the -5°C value represents the freezing point of the filling material, rather than meaning that the package is suitable for all refrigerator compartments operating around -5°C.

Compared with the A-class package, the B-class package has a different formulation and therefore different thermal characteristics.

Composition of the -5°C Filling Material

For every 1000 g of filling material:

The higher sodium chloride content is one of the formulation differences between the -1°C and -5°C packages.

Where Is the B-Class Package Used?

For typical refrigerator and freezer energy-efficiency testing, the A-class package is generally the more common choice.

The B-class (-5°C) package is mainly associated with intermediate-temperature or variable-temperature compartments, where the corresponding test requirements call for this type of test load.

Therefore, laboratories should not simply select a test package based on the compartment's nominal temperature. The applicable testing requirement should be checked first.

4. A-Class vs. B-Class: What Is the Difference?

The simplest way to understand the two packages is to focus on their freezing point and application, rather than treating -1°C and -5°C as operating temperature ranges.

The freezing point does not mean the test package can only be used at that temperature.

This is one of the most important concepts for laboratories purchasing or preparing refrigerator test packages.

5. What Is an M Package?

Another term frequently encountered in refrigerator testing is the M package.

The “M” does not represent a different freezing-point class. Instead, it refers to a test package equipped with a temperature-measuring device.

A typical 500 g M package has dimensions of:

50 mm × 100 mm × 100 mm

A thermocouple, or another equivalent temperature-measuring device, is installed at the geometric center of the package.

The thermocouple should be in direct contact with the filling material, while appropriate measures should be taken to minimize heat conduction from the outside.

The thermocouple is specified as 3.5 m long.

Why Is the M Package Important?

During refrigerator testing, simply placing a temperature sensor somewhere inside the appliance does not necessarily provide representative information about the temperature experienced by the simulated food load.

By positioning the thermocouple at the geometric center of the M package, the temperature of the simulated product load can be monitored more consistently.

This makes the M package particularly useful when the test procedure requires temperature measurement of the test load.

6. Why Does the Test Package Material Matter?

The test package is more than just a container filled with liquid or gel.

Its composition, dimensions, mass, packaging material and temperature-measuring arrangement can all influence the thermal response of the package.

For example, the filling material needs to have controlled thermal characteristics, while the outer packaging should have negligible water-vapor exchange with the surrounding environment.

This helps ensure that the test package behaves consistently from one test to another.

For laboratories performing comparative or repeatability testing, consistency of the test load is especially important.

7. Common Misunderstandings About Refrigerator Test Packages

Misunderstanding 1: “A -1°C package is only used at -1°C.”

Not necessarily.

The -1°C value identifies the freezing point of the filling material. It should not be interpreted as the operating temperature range of the refrigerator compartment.

Misunderstanding 2: “The -5°C package is simply for any compartment below 0°C.”

Not necessarily.

The B-class package is mainly associated with specific test applications, such as intermediate or variable-temperature compartments. The applicable test requirement should determine which package is needed.

Misunderstanding 3: “An M package is another freezing-point class.”

No.

“M package” describes a test package with an integrated temperature-measuring device. The M package concept is related to temperature measurement, rather than simply defining a separate freezing point.

8. Choosing the Right Test Package for Your Laboratory

When preparing a refrigerator energy-efficiency test system, laboratories should consider several factors:

• Which refrigerator or freezer compartment is being tested?
• What test standard or test procedure applies?
• Is an A-class (-1°C) or B-class (-5°C) package required?
• Is temperature measurement through M packages required?
• What package mass and dimensions are specified?
• What type and length of thermocouple is required?
• How many test packages are needed?
• Does the laboratory need pre-filled packages or empty packages for on-site filling?

These details are particularly important for laboratories performing repeated energy-efficiency tests, because standardized and consistent test loads help improve test repeatability.

9. Sinuo Refrigerator Energy Efficiency Test Packages

For refrigerator and freezer testing laboratories, Sinuo can provide test packages designed according to the required freezing point, dimensions, mass and temperature-measurement configuration.

Depending on the testing application, solutions can include:

• A-class (-1°C) test packages
• B-class (-5°C) test packages
• M packages with thermocouples
• Different package quantities and configurations
• Customized test package arrangements for laboratory testing

If you are setting up a new refrigerator energy-efficiency laboratory or replacing existing test packages, it is recommended to confirm the applicable standard and test compartment first, rather than selecting the package solely according to the nominal temperature.

Need Help Selecting the Right Refrigerator Test Package?

If you are unsure whether your application requires an A-class, B-class or M package, feel free to contact Sinuo and provide the relevant test standard, refrigerator type and compartment being tested. Our technical team can help you determine the appropriate test package configuration for your laboratory.