Cold traps are used to condense and freeze or “trap” water vapor. They are often used in a drying process for substation electrical transformer oil. A vacuum pumping system is used to lower the pressure in the transformer case and allow the water to vaporize. The water vapor travels into the vacuum chamber where it condenses and freezes onto the surface of the cold plates. When the drying process is complete, the cold plates are heated and the trapped water can be collected from a drain located at the bottom of the chamber.