Section 154.702 - Refrigerated carriage(a) Each refrigeration system must:(1) Have enough capacity to maintain the cargo vapor pressure in each cargo tank served by the system below the set pressure of the relief valves under ambient temperatures of 45 °C (113 °F) still air and 32 °C (89.6 °F) still water with the largest unit in the system inoperative; or(2) Have a standby unit with a capacity at least equal to the capacity of the largest refrigeration unit in the system.(b) For the purpose of this section, a "refrigeration unit" includes a compressor and its motors and controls.(c) Each refrigeration system must:(1) Have a heat exchanger with an excess capacity of 25 percent of the required capacity; or(2) A standby heat exchanger.(d) Where cooling water is used in a refrigeration system: (1) The cooling water pump or pumps must be used exclusively for the system;(2) Each pump must have suction lines from sea chests on the port and starboard sides of the vessel; and(3) There must be a standby pump, that may be used for:(i) Non-essential purposes on the vessel; or(ii) Essential purposes on the vessel, if the pump is sized to simultaneously provide for the capacity requirements for the essential purposes and the refrigeration cooling water.(e) Each refrigeration system must use refrigerants that are compatible with the cargo and, for cascade units, with each other.(f) The pressure of the heat transfer fluid in each cooling coil in a tank must be greater than the pressure of the cargo.