How Ice Makers Function

A century ago, ice was a rare commodity in most parts of the world. In warmer regions, you had to buy ice from delivery services that transported large blocks from colder areas or industrial refrigeration plants. It was costly, but if you wanted to keep your food chilled, there weren't many options. In the hottest areas, ice was a luxury you might never experience in your lifetime.

This all changed in the early 1900s. Compact, affordable refrigerators brought refrigeration and ice-making technology into homes and local stores. By the 1960s, automatic icemakers further revolutionized the process. Today, most Americans rarely think twice about having ice, even on the hottest summer days.

In this article, we’ll explore the inner workings of a standard home icemaker, as well as the larger commercial versions found in hotels or grocery stores. While the basic principle of making ice is straightforward — freezing water — producing perfectly shaped ice cubes involves a more intricate process.

Before the home icemaker, there was the plastic ice tray. The mechanism is simple: You fill the mold with water, freeze it until solid, and then remove the ice cubes. An icemaker operates in the same way, but the entire process of filling the tray and removing the cubes is done automatically. A home icemaker is essentially a small-scale ice production line.

Most icemakers rely on an electric motor, a water valve controlled by electricity, and a heating element. To power these components, the icemaker must be connected to the electrical circuit that runs your refrigerator. Additionally, it needs to be linked to your house's plumbing to supply fresh water for making ice. Both the power cable and water intake line pass through a hole at the back of the freezer.

Next, we will explore the process an icemaker goes through to produce ice.

Making Ice

Once everything is connected, the icemaker starts its cycle. This cycle is generally controlled by a simple electrical circuit and a set of switches. The diagram below illustrates how the icemaker progresses through its various stages.

This system works well for creating ice at home, but it doesn't generate enough for commercial use, like in restaurants or hotel ice machines that offer self-service. In the next section, we'll explore a more robust and larger icemaker design.

Commercial Icemakers

There are various configurations for a large, free-standing icemaker — all that’s needed is a refrigeration system, a water supply, and a method to collect the formed ice.

One of the most basic professional setups uses a sizable metal ice-cube tray placed vertically. The diagram below illustrates how this system functions.

In this setup, the metal ice tray is connected to a series of coiled heat-exchange pipes similar to those found on the back of your refrigerator. If you are familiar with How Refrigerators Work, you'll understand how these pipes operate. A compressor drives the refrigerant fluid through a cycle of condensation and expansion. The compressor pushes refrigerant through a narrow tube (called the condenser) to compress it, then releases it into a wider tube (the evaporator), where it expands.

Compressing the refrigerant increases its pressure, which raises its temperature. As the refrigerant travels through the narrow condenser coils, it releases heat into the cooler air outside and condenses into a liquid. When the compressed liquid passes through the expansion valve, it evaporates and transforms into a gas. This evaporation process absorbs heat from the metal pipes and the surrounding air, cooling both the pipes and the ice tray.

The icemaker features a water pump that pulls water from a collection sump and distributes it over the chilled ice tray. As the water flows over the tray, it gradually freezes, forming ice cubes in the tray’s cavities. Freezing water layer by layer results in clear ice, while freezing it all at once, as in home icemakers, produces cloudy ice (see How do you make clear ice cubes? for more details).

After a predetermined time, the icemaker activates a solenoid valve connected to the heat-exchange coils. This action redirects the refrigerant's path. The compressor halts the flow of heated gas into the narrow condenser and instead forces it into a broad bypass tube. The hot gas cycles back to the evaporator without condensing. By pushing this heated gas through the evaporator pipes, the pipes and ice tray heat up quickly, loosening the ice cubes.

Typically, the individual ice cube cavities are slanted so the loosened cubes can slide out on their own into a collection bin below. Some systems include a cylinder piston that gives the tray a little nudge, helping to release the cubes.

This system is favored by restaurants and hotels as it produces uniform ice cubes in standard shapes and sizes. Other industries, like grocery stores and scientific research firms, require smaller ice flakes for packing perishable goods. In the next section, we will explore flake icemakers.

Flake Icemakers

In the previous section, we explored the design of a typical cube icemaker. Flake icemakers operate on the same fundamental principle, but with one key addition: an ice crusher. The diagram below illustrates how a standard flake system works.

Similar to the cube icemaker system, flake icemakers use heat-exchanging coils and a stream of water to form a layer of ice. However, in this case, the coils are housed inside a large metal cylinder. Water flows through the cylinder and also around its exterior. As the water circulates, it gradually forms a thick layer of ice both inside and outside the cylinder.

Just like the cube icemaker, a solenoid valve introduces hot gas into the cooling pipes after a designated time. This action causes the ice layer to loosen, allowing it to fall into the ice crusher below. The crusher then breaks the ice into smaller chunks, which are transferred to a collection bin.

The size of the resulting ice pieces depends on the type of crusher used. Some crushers produce fine ice flakes, while others generate larger, irregularly shaped chunks of ice.

While there are various versions of these systems, the core concept remains consistent across all designs. A refrigeration system forms a layer of ice, and a harvesting mechanism ejects the ice into a collection bin. At its simplest, this is the fundamental operation of any icemaker.

To learn more about icemakers and related topics, explore the following links for additional information.