When everything is hooked up, the icemaker begins its cycle. The cycle is usually controlled by a simple electrical circuit and a series of switches. In the diagram below, you can see how the icemaker moves through its cycle.
- At the beginning of the cycle, a timed switch in the circuit briefly sends current to a solenoid water valve. In most designs, the water valve is actually positioned behind the refrigerator, but it is connected to the central circuit via electrical wires. When the circuit sends current down these wires, the charge moves a solenoid (a type of electromagnet), which opens the valve.
- The valve is only open for about seven seconds; it lets in just enough water to fill the ice mold. The ice mold is a plastic well, with several connected cavities. Typically, these cavities have a curved, half-circle shape. Each of the cavity walls has a small notch in it so each ice cube will be attached to the cube next to it.
- Once the mold is filled, the machine waits for the water in the mold to freeze. The cooling unit in the refrigerator does the actual work of freezing the water, not the icemaker itself (see How Refrigerators Work for details). The icemaker has a built-in thermostat, which monitors the temperature level of the water in the molds. When the temperature dips to a particular level -- say, 9 degrees Fahrenheit (-13 degrees Celsius) -- the thermostat closes a switch in the electrical circuit (see How Home Thermostats Work for details on this operation).
- Closing this switch lets electrical current flow through a heating coil underneath the icemaker. As the coil heats up, it warms the bottom of the ice mold, loosening the ice cubes from the mold surface.
- The electrical circuit then activates the icemaker's motor. The motor spins a gear, which rotates another gear attached to a long plastic shaft. The shaft has a series of ejector blades extending out from it. As the blades revolve, they scoop the ice cubes up and out of the mold, pushing them to the front of the icemaker. Since the cubes are connected to one another, they move as a single unit.
- At the front of the icemaker, there are plastic notches in the housing that match up with the ejector blades. The blades pass through these notches, and the cubes are pushed out to a collection bin underneath the icemaker.
- The revolving shaft has a notched plastic cam at its base. Just before the cubes are pushed out of the icemaker, the cam catches hold of the shut-off arm, lifting it up. After the cubes are ejected, the arm falls down again. When the arm reaches its lowest resting position, it throws a switch in the circuit, which activates the water valve to begin another cycle. If the arm can't reach its lowest position, because there are stacked-up ice cubes in the way, the cycle is interrupted. This keeps the icemaker from filling your entire freezer with ice; it will only make more cubes when there is room in the collection bin.
This system is effective for making ice at home, but it doesn't produce enough ice for commercial purposes, such as restaurants and self-service hotel ice machines. In the next section, we'll look at a larger, more powerful icemaker design.