Underneath the ice mould, the icemaker has a heating coil.
The icemaker continues its loop when everyone is wired up. A basic electrical circuit and a set of switches typically operate the loop. You can see how the ice maker goes through the cycle in the diagram below.
A timed transition in the circuit sends current temporarily to a solenoid water valve at the beginning of the loop. The water valve is actually located behind the refrigerator in most designs, but it is attached by electrical wires to the central circuit. The charge pushes a solenoid (a form of electromagnet) that opens the valve as the circuit sends current down these wires.
The valve is open for just seven seconds or so; it requires only enough water to fill the ice mould. The ice mould, with many associated cavities, is a plastic well. This cavities usually have a curved, half-circle shape. There is a small notch in one of the cavity walls, so each ice cube can be added to the cube next to it.
The computer waits for the water in the mould to freeze until the mould is filled. The cooling unit in the refrigerator, not the icemaker itself, does the true job of freezing the water (see How Refrigerators Operate for details). The icemaker has a built-in thermostat that controls the amount of water temperature in the moulds. The thermostat closes a turn in the electrical circuit when the temperature declines to a certain amount — say, 9 degrees Fahrenheit (-13 degrees Celsius) — (see How Home Thermostats Operate for information on this operation).
Closing this switch lets electrical current flow under the icemaker via a heating coil. It warms the bottom of the ice mould as the coil heats up, loosening the ice cubes from the top of the mould.
Then, the electrical circuit stimulates the motor of the icemaker. A gear is spinning by the turbine, which spins another gear connected to a long plastic shaft. There are a number of ejector blades in the shaft which stretch out from it. They scoop the ice cubes up and out of the mould while the blades spin, moving them into the front of the ice maker. Since the cubes are bound to each other, as a single entity, they pass.
There are acrylic notches in the casing at the front of the icemaker that complement the ejector blades. The blades move through these notches, and beneath the icemaker, the cubes are moved out to a storage bin.
At its foundation, the rotating shaft has a notched plastic cam. The cam takes hold of the shut-off arm right before the cubes are pulled out of the icemaker, lifting it up. The arm comes back again after the cubes are ejected. It throws a switch into the circuit when the arm hits its lowest resting point, which triggers the water valve to begin another loop. The loop is broken if the arm can’t hit its lowest location because there are stacked-up ice cubes along the direction. This stops the icemaker from loading the whole freezer with ice; if there is space in the collection tank, it can just produce more cubes.
There are a variety of ways for a big, free-standing icemaker to be configured — all you need is a cooling device, a water source and a way to capture the ice that forms.
A large metal ice-cube tray, placed vertically, uses one of the simplest professional systems. In the diagram below, you can see how this method operates.
The metal ice tray is attached to a series of coiled heat-exchanging pipes in this system, like the ones on the back of your refrigerator. You know how these pipes work, if you’ve read How Refrigerators Work. In a constant loop of condensation and extension, a compressor moves a current of refrigerant fluid. The compressor basically causes the refrigerant to condense into a small tube (called the condenser) and then releases it through a larger tube (called the evaporator) where it can spread.
The refrigerant’s compression increases its strain, which increases its temperature. It loses heat to the colder air outside when the refrigerant flows through the small condenser tubes, and it condenses into a vapour. It evaporates as the compressed fluid goes through the expansion valve — it expands to become a gas. The heat energy from the metal pipes and the air around the refrigerant is drawn into this evaporation process. This cools the tubing and the metal ice tray fixed to them.
A water pump is supplied by the icemaker, which pulls water from a collection sump and pours it over the chilled ice tray. It steadily freezes as the water runs over the tray, making up ice cubes in the tray well. It forms transparent ice when you freeze water layer by layer in this manner. You get cloudy ice as in the home icemaker when you freeze it all at once (see How do you make transparent ice cubes? for more information).
The icemaker activates a solenoid valve linked to the heat-exchanging coils after a specified period of time. Switching this valve alters the refrigerant’s route. The compressor avoids pressing the heated gas into the small condenser from the compressor; instead, it pushes the gas into a large tube bypass. Without condensing, the hot gas is cycled back to the evaporator. The pipes and the ice tray heat up quickly as you push this heated gas into the evaporator pipes, which loosens the ice cubes.
The Flake Icemakers
We looked at a typical cube icemaker style in the final segment. On the same basic concept as cube icemakers, flake icemakers operate, but they have an additional component: the ice crusher.
This system uses a series of heat-exchanging coils and a stream of water to build up a sheet of ice, like the cube icemaker concept that we examined in the last segment. But the coils are located inside a large metal cylinder in this device. As well as along the outside rim, water flows into the cylinder. A large column of ice covering the cylinder from the inside and outside is steadily formed up by the passing water.
For a fixed period of time, a solenoid valve releases hot gas into the cooling tubing, as in a cube icemaker. Which loosens the ice column enough that it sinks beneath the ice crusher. The ice crusher splits into tiny parts of the ice cylinder that move on to a storage bin.
The ice bits’ size depends on the process of the crusher. Many crushers grind the ice into fine pellets, while other crushers create larger ice chunks that are irregularly shaped.