Temperature Controlled Loads & Reefer Loads: Meijer Refrigeration Units
It’s important to remember the procedures for reefer and temperature-controlled loads to be sure we’re following guidelines for safe transport. Meijer has requested that we leave the refrigeration units running while doing peddle stops at stores. This practice generates some challenges for refrigeration equipment.
The outside air (which is higher in humidity) enters the trailer while the doors are open and is drawn through the evaporator by the fan where the water in the air condenses on the evaporator coil. This is similar to condensation that occurs on the outside of a glass of ice cold lemonade on a hot summer day. With that picture in mind the temperature of the evaporator is cold enough that the moisture that condenses freezes on the cooling coil. This continues to build up ice until the air no longer can pass through the evaporator coil and the unit can't pick up the heat and transfer it outside making the unit incapable of keeping the load in the trailer cool. Given the desire of the customer, and the objective to create an environment of care for the product, we have developed a plan.
As long as the unit is running, let's make the best use of that time by manually putting the unit into defrost mode whenever the trailer is at the dock with the door open. The unit closes down the circulation of air in the trailer to prevent heating up the trailer and puts the evaporator into heat mode until the evaporator is thawed out or until the timer times out (which could be as much as 45 minutes) and puts the unit back into cool whichever comes first. In either case, the coil will be more efficient when it is in the “cool” mode after it has been defrosted. If the coil is clear it will only take a few minutes to cycle. It should automatically go back into cool at the completion of the defrost cycle. But as always I would watch to make sure it returns to cool at the end of the defrost cycle and returns the temp to the set point.