Like air conditioners, freezers use a refrigerant to transfer heat out of the freezer compartment and into the air. This cools the freezer compartment until it reaches temperatures low enough for water to freeze. Sensors and a thermostat monitor temperatures and run the freezer system as needed. Ordinarily this system works well, but sometimes problems occur and the freezer can collect water in the bottom compartment.
The most common cause for water collecting and freezing on the bottom of the freezer is a leak. This leak may occur in the tubes and valves that direct water into the freezer for making ice, if the freezer system uses an automatic ice maker. If this is the case, owners can replace tubes and valves to solve the problem. If the freezer is built below a refrigerator, water may be leaking in from the bottom of the refrigerator.
The heat exchanger is the system that transfers heat away from the freezer. The sudden changes in temperature in the heat exchanger tubing can cause condensation to form very easily. Sometimes this causes leaking outside the freezer, and sometimes the condensation can leak into the freezer itself, especially in humid areas where there is a lot of moisture in the air.
Another very common cause of water at the bottom of the freezer is a drain problem. Freezers have drain tubing and a drain in the bottom compartment to get rid of any excess water that occurs when the freezer goes through a defrost cycle. If the drain becomes blocked or the drain tube becomes clogged, the water will have nowhere to go and will sit on the bottom of the freezer, freezing there.
If the thermostat or sensors in the freezer malfunction, they can make the freezer constantly run or constantly go through defrost cycles. Timer and temperature problems can cause the freezer to produce too much water for it to deal with, or freeze water at the bottom of the freezer before it can drain away.
The freezer uses condenser coils to gather heat and pass it into the air, which allows the refrigerant to cool so it can gather more heat from the freezer compartment. If these condenser coils become dirty or covered in frost, they can cause a wide number of problems, including water problems and excess frost.