The time it takes for the temperature in an upright freezer to reach its maximum low can vary depending on several factors, including the initial temperature of the freezer, the ambient temperature of the room, the freezer's insulation and cooling efficiency, and the quantity and temperature of the items you place inside.
Generally, when first setting up an upright freezer or after adding a significant amount of new items, it may take several hours (around 4 to 6 hours) for the freezer to reach its maximum low temperature. During this initial cooling phase, the freezer has to work harder to bring the internal temperature down to the desired level.
Once the freezer reaches its maximum low temperature, it should maintain that level as long as the door remains closed and the unit is functioning correctly. Modern upright freezers are designed to maintain a stable temperature and will cycle on and off to regulate the internal conditions.
Keep in mind that frequently opening the freezer door can increase the time it takes to reach the maximum low temperature, as warm air from the room enters the freezer, causing the cooling system to work harder to compensate.
For accurate information on the specific time it takes for your upright freezer to reach its maximum low temperature, refer to the manufacturer's guidelines or user manual. It should provide more detailed information on the cooling time and how to optimize the freezer's performance for efficient and effective cooling.