You’re watching a great movie on TV. You go to the upright freezer to take out a lolly, but in your hurry to get back to the action, you forget to close the door. The following morning, you come back to the kitchen to see the freezer door hanging wide open, and quickly shut it. You’re nervous about how the freezer has been open, and put a thermometer in it to check the temperature. You find that it’s only -4°C, against the -18°C that it should be. You figure that if you leave it properly closed for a few hours, it’ll get back to where it should be.
The following morning, it’s still only at -10°C, and you’re worried about keeping your food in good condition. What’s going on? Is your freezer broken? Should you call in a professional?
It’s actually a common problem
To begin, you don’t need to throw out all your food — not as long as it’s still frozen. A few hours of moderate subzero temperature levels won’t spoil food. You do need to get your freezer back to normal, though. It isn’t okay to keep your freezer this way. The solution isn’t well-known.
Here’s how freezers work
In most upright freezers, the cooling coils are at the very top. A little fan draws air from lower down, forces it pass the cooling coils, and blows it down the front of the freezer. This design works well because it puts a curtain of cold air past the door as a way to keep the warm air outside from coming in when the door is opened.
The air in any home tends to contain much more moisture than the air inside a freezer. When you open the, moist air gets into the freezer, and gets on the cooling coils. The moisture quickly freezes on the coils, creating a coating of ice.
Usually, the freezer’s frost-free mechanism is able to periodically kick in, heat the element briefly, and get rid of any smattering of ice. With a freezer that’s been left open all night, this brief heating interlude proves inadequate. Ice being an excellent insulator, a covering of the stuff on the cooling coils lets little of the deep cold produced by the coils get through. The freezer doesn’t cool properly for this reason.
How do you defrost the cooling coils?
You might consider turning off the freezer for a few hours to completely clear all the ice out, but you would have to find another freezer to put your food in. There’s a clever alternative. You only need to get a hairdryer and play hot air at the cooling coils to quickly melt the ice.
You’ll need to look for a few screws to gain access to the cooling coils. Once you see them, you’ll find that they are covered in ice. When you use the hair dryer, your freezer will be back to normal. A tech would do the same thing.