CONDENSER

  Condenser construction must be rigid and rugged, and the fin surface should be treated for corrosion resistance unless the metal is corrosion resistant. The area in which the condensers mounted on the skirt of road splash, while those mounted high on the nose of a truck or trailer are in a somewhat cleaner atmosphere. If the condenser is mounted beneath a trailer facing in the direction of travel, a mud guard should be provided. The type of tube and fin construction affects the allowable fin spacing, but n general, fin spacing of no more than 8 fins to the inch is recommended, although as high as 10 and 12 per inch.

  Since the unit will operate for extended periods when the vehicle cannot be considered in designing  for adequate air flow, but the condenser fan should be located so that the ram air effect aids rather than opposes condenser air flow. It also should be born in mind that often many trucks will be operating side by side at a loading dock, and the air flow pattern should be such that one unit will not discharge hot air directly into the intake of the unit on the next vehicle.

  Since the space available for condenser face area is limited in transport refrigeration applications, the condenser tube circuiting should be designed for maximum efficiency.

  Low head pressure during cold weather can result in lubrication failure of compressors. With trucks operating or parked outside or in unheated garages in the winter months, this condition can frequently occur. A decreased pressure differential across the expansion valve will reduce the refrigerant flow, resulting in decreased refrigerant velocity and lower evaporator pressure, permitting oil to trap in the evaporator. Frequently the feed will be decreased to the point that short-cycling of the compressor results. The use of a reverse acting pressure control for cycling the condenser fan, or some other type of pressure stabilizing device to maintain reasonable head pressure is highly recommended.