DIN 27165:2025-04

This document has been prepared by Working Committee NA 087-00-07 AA "Heizung, Lüftung, Klima" ("Air conditioning, heating and ventilation") at DIN Standards Committee Railway (FSF). Railway air conditioning systems are used for conditioning the air of driver and passenger compartments and for battery conditioning. In normal operation the air conditioning system heats, cools, and ventilates the driver's and/or passenger compartments in accordance with the specified air conditioning requirements or regulates the temperature of the battery system. This document applies to mainline vehicles and urban rail vehicles. This document is applicable when ready-to-use refrigeration units with flammable refrigerants of class A2L, A2, A3 according to ISO 817:2014 are operated for air conditioning in rail vehicles. The systems shall be designed to be permanently leak-tight in technical terms. The operation of the refrigeration machine for air conditioning includes heat pump operation. This document specifies procedures for identifying and assessing hazards caused by leaks in refrigeration circuits with flammable refrigerants that may occur during operation, due to incorrect handling, technical defects, or accidental events. The risk assessment in the life cycle with the anticipated operating modes is recorded by the OMRA (Operational Mode Risk Assessment), which uses methods such as HAZOP (Hazard and Operability Studies), FMECA (Failure Mode, Effects, and Criticality Analysis), or FTA (Fault Tree Analysis), or a combination of these methods. Based on this, this document prescribes specific and targeted procedures and principles for risk assessment of railway air conditioning systems and for risk management, as well as the associated validation steps and procedures. Taking into account DIN EN 50126-1 (VDE 0115-103-1):2018-10, and DIN EN 50126-2 (VDE 0115-1032), this document specifies requirements for the air conditioning system, the vehicle manufacturer, and the responsible operator that arise from the use of flammable refrigerants.