How Do Frost-free Fridges Work?

For many of us, defrosting a refrigerator or freezer is still a fairly vivid memory. Whether you removed the build-up of ice via melting or chiselling, it’s always an annoying and time-consuming task. While it may seem counter-productive to have a heater inside a fridge, frost-free fridges use this relatively recent innovation to help eliminate this problem. Frost forms in a fridge because the moisture in the air condenses against the cooling coils and then freezes. The more frequently the door is opened, the more moisture is let in and the faster frost builds up. As it accumulates, you’ll quickly find less and less space is available to store food. In a frost-free fridge, the solution is simple. That is, periodically raise the temperature to melt the ice. The execution, however, is slightly more complicated. For a frost-free system to work, a fridge needs a heating coil, timer and temperature gauge. The timer starts the heating coils typically every 6-12 hours to start the process. Since the rate of frost accumulation can vary depending on how much moisture is allowed in during that period, the temperature gauge is there to ensure the heating coils turn off just as all the defrosting is completed. If it was determined by the timer and stayed warmed for a set period, it becomes likely that frost builds up faster than it can be eliminated, or the fridge be heated for longer than necessary. All the liquid water from the melted ice then gets drained to an evaporator tray to dry up, typically located at the bottom or back of the fridge. Occasionally, this drain can itself become frozen, causing the water to pool at the bottom and freeze over again. Left unchecked, this can be just as big a problem as normal frost, though most fridges will come with tools to easily correct the situation. It’s also worth noting that a frost-free fridge regularly raises the temperature slightly above 0°C by necessity. This means that the cabinet, especially areas closest to the heating coils if food isn’t properly stacked, will go through cycles of relative warmth. For most foods, the effect is negligible but it’s always worthwhile to arrange the contents of your fridge to facilitate the flow of air within. Some frost-free fridges try to mitigate this by installing a fan which blows moist air out, meaning slower frost build-up and less heating time.

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