---
kind: "section"
citation: "49 C.F.R. § 238.425"
title: "49"
number: "238.425"
heading: "Electrical system."
url: "https://uscodex.org/cfr/49/238.425"
---

# §238.425. Electrical system.

- (a) **Circuit protection.**
  - (1) The main propulsion power line shall be protected with a lightning arrestor, automatic circuit breaker, and overload relay. The lightning arrestor shall be run by the most direct path possible to ground with a connection to ground of not less than No. 6 AWG. These overload protection devices shall be housed in an enclosure designed specifically for that purpose with the arc chute vented directly to outside air.
  - (2) Head end power, including trainline power distribution, shall be provided with both overload and ground fault protection.
  - (3) Circuits used for purposes other than propelling the equipment shall be connected to their power source through circuit breakers or equivalent current-limiting devices.
  - (4) Each auxiliary circuit shall be provided with a circuit breaker located as near as practical to the point of connection to the source of power for that circuit; however, such protection may be omitted from circuits controlling safety-critical devices.
- (b) **Main battery system.**
  - (1) The main batteries 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) Battery circuits shall include an emergency battery cut-off switch to completely disconnect the energy stored in the batteries from the load.
  - (4) If batteries are of the type to potentially vent explosive gases, the batteries shall be adequately ventilated to prevent 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.
  - (2) Power dissipation grids shall be designed and installed with sufficient isolation to prevent combustion between resistor elements and combustible material.
  - (3) Power dissipation resistor circuits shall incorporate warning or protective devices for low ventilation air flow, over-temperature, and short circuit failures.
  - (4) 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 can be achieved through equipment design or changes to the operating environment.
  - (2) The electronic equipment shall not produce electrical noise that interferes with trainline control and communications or with wayside signaling systems.
  - (3) To contain electromagnetic interference emissions, suppression of transients shall be at the source wherever possible.
  - (4) Electrical and electronic systems of equipment shall be capable of operation in the presence of external electromagnetic noise sources.
  - (5) 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.

## Notes

### Authority

Authority: 49 U.S.C. 20103, 20107, 20133, 20141, 20302-20303, 20306, 20701-20702, 21301-21302, 21304; 28 U.S.C. 2461 note; and 49 CFR 1.89.

### Source

Source: 64 FR 25660, May 12, 1999, unless otherwise noted.