This document specifies requirements and test methods for factory made thermally insulated flexible pipe-in-pipe assemblies for directly buried district cooling distribution systems, comprising a service pipe from DN 15 to DN 200 and a casing of polyethylene. The pipe assembly may also include the following additional elements: measuring wires, spacers and diffusion barriers. This document is intended to be used in conjunction with prEN 17414-2 or prEN 17414-3. This document applies only to insulated pipe assemblies, for continuous operation with water at various temperatures (1 to 30) °C and a maximum operation pressure of 25 bar dependent on material specified. The design is based on an expected service life with continuous operation of a minimum 50 years. This document does not cover surveillance systems. NOTE For the transport of other liquids, for example potable water, additional requirements may be applicable.