However, for practical reasons, the following applies:
- The mechanical protection mechanisms of the refrigerated circuit should not trigger when the refrigeration unit is at a standstill or as a result of sunlight. So, for example, with ambient temperatures of between 70 - 80°C it should not be possible for a pressure valve to open and release refrigerant. The Carrier Transicold 69NT40 refrigeration unit has, for example, a protection pane with a bursting pressure of 35 bar. According to the vapor pressure curve for the refrigerant R134a, this corresponds to a temperature of approximately 94°C.
- Obviously, other components of the container also should not suffer damage at a temperature of 70 - 80°C, when the refrigeration unit is at a standstill or as a result of sunlight.
- The electronics of the device should not fail when subjected to sunlight. Here also, temperatures of -80°C - 80°C may be considered realistic.
- It must be possible to operate the refrigeration unit under the ambient temperatures that occur in practice. The highest temperatures that can be expected occur when transporting refrigerated containers below deck or when operating on an asphalt surface exposed to the sun. A maximum value of 50°C is generally assumed but this is not specified in any standard.
- Values of -30°C to -40°C are considered realistic values for the lower limits for the ambient temperature. At these temperatures also, no damage should occur.
- All system components must be sufficiently protected to ensure they will operate in the rain or when exposed to salt water when stowed on deck.