CellarPro 4200VSI-B BEER REFRIGERATION SYSTEM, 2177 - Manual (Page 15)

15 V9.14
As shown above, the drain line should drop, then rise (but stay below
the height of the fitting), and then drop again into a drain or bucket.
Then, fill the trap with water. The condensate trap will allow any
excess moisture inside the cooling unit to overcome the static pressure
and flow out of the drain line.