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The cool physics of ice makers

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You might think that making ice is a simple business: just throw water into the freezer and it turns to ice. Simple, right? That’s true if you just want to make a single tray of ice, but most of us prefer to have ice available on demand. That’s why we have ice makers, devices that can make ice consistently for the many years that you will own your fridge. That takes a bit more engineering than a simple ice tray. Let’s take a closer look at how the humble ice maker creates the ice to keep your summer drinks cool.

The basic ingredient of ice is, as you might expect, water. But you can’t just throw any old water into an ice maker: good ice needs clean, fresh water. So, the first part of the ice maker is a filter that removes all of the solids (dust and dirt particles) and most of the dissolved chemicals as well. What comes out of this filter is crisp, clean, clear water that will make crisp, clean and clear ice. Assuming that you remember to change the filter, that is…

Now that we have clean water, we can start freezing it. Most ice makers are built around a tray that has semicircular or rectangular depressions in it. A valve above this controls the flow of water, filling the tray with enough water to fill the depressions, forming the shape of the ice cube. Because this tray is inside the freezer, it gets cold, and the water begins to freeze. Nearby is a sensor which is measuring the temperature of the water, waiting for it to reach a certain temperature (usually about -12°C/10°F).

Once it reaches this temperature, the water is solidly frozen and ready to remove. Ice is tricky, though: it sticks tightly to most surfaces, so you can’t just tip it out. Instead, ice makers use heat to loosen the ice. Under the ice tray is a small electric heating element, which is triggered to heat the the tray slightly, creating a very thin layer of water between the ice and the tray. This is not enough to melt most of the ice, but the thin layer of water provides enough lubrication to allow a motorized arm to push the ice out, into the ice holding bucket.

The tray is then filled again, and the cycle continues until the ice bucket is full. On most cheap refrigerators, a wire pokes down into the bucket, and the ice piling up pushes this triggering a switch that stops the ice maker cycle. When you remove some ice, the wire falls down again, disengaging the switch and restarting the ice maker cycle. More expensive refrigerators will use infrared or other sensors that don’t need a wire, but the principle is the same: they detect the level of the ice and disable the ice maker when it reaches a certain level.

Most of you will also be familiar with the curse of the cheap ice maker: you get a big block of ice because the ice cubes have stuck together. On the lower-end models that just dump the ice into a bucket, the ice cubes will stick together over time, eventually forming a solid lump of ice. This is a phenomenon called accretion, where the moisture in the air passing over the ice cubes bumps into the ice, and joins it. It’s the same phenomenon that makes icicles on tree branches on a cold night: moisture in the air freezes and sticks together, forming ice crystals that then pick up more moisture, and so on.

Inside your ice maker, the ice cubes that are in contact will join together as they accrete new ice, forming a solid block. If you have a particularly bad refrigerator (or an old one), the ice cubes may also be melting slightly as the temperature of the freezer compartment rises. This creates a thin layer of liquid water on the surface of the ice cubes, which flows together, only to be refrozen when the freezer.

More expensive fridges deal with this problem by including a stirrer, a metal rod that is turned occasionally inside the ice bucket, separating the ice cubes. This also explains the mysterious noises that you may hear from your expensive fridge in the middle of the night: it isn’t haunted, it is just stirring the ice. These more expensive fridges also separate the freezer and ice maker compartments, limiting the flow of cold air into the ice bucket so there is less moisture in the air to be captured.

So consider this the next time you grab a chunk of ice to chill your soda: the ice that you take for granted is the result of some sophisticated engineering and some basic science.

HOW TO TROUBLESHOOT A KITCHENAID ICE MAKER

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If you enjoy serving cold drinks and iced cocktails to your friends and family, having an ice maker already built in with your freezer could prove to be a good investment. Luckily, KitchenAid offers a line of freezers that offers this very convenient feature. However, just like any other appliance inside your kitchen, the ice maker may eventually break down. If this happens, do not be too hasty in calling a repairman. Follow these simple steps in troubleshooting the KitchenAid Freezer ice maker first before calling in a professional.

  • If the freezer is plugged in but the ice maker is not functioning, check the on/off lever. The switch arm can be seen right above the ice bucket. There are instances when somebody dispenses too much ice, the ice cubes in the bucket pushes up the lever and it gets stuck in that position. If this happens, the ice maker is switched off automatically. Simply push on the lever one more time and listen if the motor will start running again. If the ice maker does not respond, proceed to the next step.
  • Check if the water hose supplies the trays with enough water. The water supply that feeds the trays comes from an outlet or faucet near the freezer unit. Impurities in the water can buildup in this hose causing the line to get blocked. If not enough water reaches the trays, the ice maker will not be able to produce ice. If you suspect that this is the problem, try to inspect the water hose from one end to the other. If there are parts that are bent or pinched, the water will not be able to pass through. Replace the hose if it has signs of wear or is damaged or punctured. Smooth it out if it has kinks. Push the hose firmly into the slot if it is hooked up loosely. This should solve the water supply problem and help your ice maker function properly again.
  • Pinch the ice maker’s filling hose to check if it is frozen. The filling hose is the tube that supplies water to the individual ice trays. If the water inside this tube freezes, water will not flow into the trays and the ice maker will not have any ice to dispense. To check if this is the issue with your ice maker, squeeze the hose and see if it still bends. If it feels hard, switch of the freezer and ice maker and wrap the hose with a washcloth or towel dipped in very hot water. You can also use a hair dryer to thaw the ice stuck inside the tube. Avoid using too much heat as the filling hose could melt.
  • Make certain that your freezer is set at 10 degrees Fahrenheit. Even though water freezes at 32 degrees Fahrenheit, the KitchenAid freezer ice maker requires that the temperature inside the system stay above 10 degrees in order for the ice cubes to freeze quickly. Your ice maker might encounter problems in dispensing ice as quickly as needed if the freezer temperature is higher than the prescribed setting. Lower the temperature setting and observe the performance of your ice maker for a few hours and see if the problem has been addressed.

 

Once you have addressed any damage or defects in the ice maker, make sure that you maintain a clean and hygienic refrigerator to avoid contaminating the ice. If the ice starts to taste and smell funny, check the coating of the ice bucket. With frequent use, the interior coating of the ice bucket might erode and get mixed with the ice. This can affect the smell and taste of the ice being dispensed. If you see any peeling inside the bucket, go to the department store or any home improvement centers and purchase a brand new ice bucket.