Preventing Icing in Walk-In Freezers
August 17, 2010
There are two typical icing conditions in a walk-in freezer, and both can be eliminated by finding and correcting the root cause, according to Russell Coil, Ellicott City, Md.
- Frost or snow ice caused by warm moist air infiltration forms when water goes directly from a vapor to a solid by deposition. Normally, this condition is due to a walk-in door that is not sealing properly or to air leaks where conduit and piping penetrate the enclosure. The solutions are not difficult. A simple door adjustment may solve the problem; if that does not work, a new gasket, hinge or latch may do the trick. If the freezer door must be left open for extended periods of time, install a strip curtain to keep air-leaking to a minimum. Check out all penetration areas and be sure they are properly sealed.
- Hard clear ice forms when water vapor coming out of the evaporator during defrost cycles condenses to liquid droplets on the fan blades, fan guard and ceiling, then freezes to solid ice. This can be due to incomplete defrosts or poor drainage. If the defrost timer is set for too short a time, the cycle will terminate according to time instead of temperature. Sometimes, although less frequently, the fan’s delay switch, defrost termination switch or heaters may be faulty. All drain heaters must be working properly so the condensate drains completely. It is important that air infiltration problems are corrected first. After the walk-in freezer is free of frost and snow, the defrost timer should be set to provide three to four complete defrosts every day. At the end of a defrost cycle, the coil should be free of water and ice, and the condensate drain pan should be empty. The fan delay should prevent the fans from coming on until the coil has pulled down below freezing.