§ 238.225 Electrical system.

All passenger equipment shall comply with the following: (a) Conductors. Conductor sizes shall be selected on the basis of current-carrying capacity, mechanical strength, temperature, flexibility requirements, and maximum allowable voltage drop. Current-carrying capacity shall be derated for grouping and for operating temperature. (b) Main battery system. (1) The main battery compartment shall be isolated from the cab and passenger seating areas by a non-combustible barrier. (2) Battery chargers shall be designed to protect against overcharging. (3) If batteries are of the type to potentially vent explosive gases, the battery compartment shall be adequately ventilated to prevent the accumulation of explosive concentrations of these gases. (c) Power dissipation resistors. (1) Power dissipating resistors shall be adequately ventilated to prevent overheating under worst-case operating conditions as determined by the railroad. (2) Power dissipation grids shall be designed and installed with sufficient isolation to prevent combustion. (3) Resistor elements shall be electrically insulated from resistor frames, and the frames shall be electrically insulated from the supports that hold them. (d) Electromagnetic interference and compatibility. (1) The operating railroad shall ensure electromagnetic compatibility of the safety-critical equipment systems with their environment. Electromagnetic compatibility may be achieved through equipment design or changes to the operating environment. (2) The electronic equipment shall not produce electrical noise that affects the safe performance of train line control and communications or wayside signaling systems. (3) To contain electromagnetic interference emissions, suppression of transients shall be at the source wherever possible. (4) All electronic equipment shall be self-protected from damage or improper operation, or both, due to high voltage transients and long-term over-voltage or under-voltage conditions. This includes protection from both power frequency and harmonic effects as well as protection from radio frequency signals into the microwave frequency range.