The time it takes for a chest freezer to cool down after adding food and closing the lid can vary based on several factors, including the starting temperature of the food, the size and efficiency of the freezer, the surrounding ambient temperature, and the initial temperature setting of the freezer.
In general, a chest freezer is designed to cool down relatively quickly due to its efficient cooling system and good insulation. It can take anywhere from 30 minutes to a few hours for the freezer's internal temperature to reach its optimal cooling level, typically around -18°C (0°F) or lower.
Keep in mind that opening the lid frequently or adding a large amount of warm food can increase the time it takes for the freezer to cool down. For the most efficient cooling, it's recommended to pre-chill the food items before placing them in the freezer and avoid overcrowding the freezer with too much warm food at once.
To be sure that your chest freezer has reached its desired cooling temperature, you can use a thermometer to monitor the internal temperature. Once the freezer reaches the desired temperature, you can store your food with confidence that it will be properly frozen and preserved.