NTRAK Modular Railroading Society, Inc

Guidelines for Wiring NTRAK Modules & Layouts to Meet Fire Codes

The following describes the use of Power Strips and Extension Cords with NTRAK Modules and in NTRAK Layouts.

Recent changes in the National Electric Code and International Fire Code restricting the use of Power Strips and Extension cords is concerning us. While aimed more at Home Office and Dorm rooms and their use more as permanent wiring than our weekend layouts use them, we must be aware of the code being enforced by Fire Marshals in public buildings. See the Background, below, for more of the "why" of these requirements.

Modules that have NO NEED for 120 Volts AC should have the Power Strip removed from the module.

Note: The following has been reviewed and accepted by the Eugene, OR Fire Marshal.  Future changes will be made as needed. Jim F.

AC Power distribution on NTRAK Model Train Modules

The following NTRAK guidelines are based upon Chapter 6, Section 605 of the International Fire Code and applicable sections of Underwriters Laboratories Product Standards UL-817 (Cord Sets and Power Supply Cords) and UL-1363 (Relocatable Power Taps), and are believed to comply with most local codes. In the event of discrepancies, local codes will govern. If there are any questions, consult your local fire marshal.

  1. Remove all power strips from modules. Also, remove all AC power cords and outlets from modules.
  2. Use a grounded (3-wire) commercial quality power strip (14 AWG cord, preferably 15 ft long) with 15A circuit breaker to plug into an approved branch circuit wall outlet or power drop.
  3. Although not required, a GFCI adapter or GFCI pigtail inserted between the outlet and the power strip is recommended. Alternately, a GFCI equipped power strip may be used in 2) above.
  4. Grounded, UL approved (no home brew!) multi-outlet extension cords (triple outlet at the end, or multiple outlets along the length of the cord) should be used to distribute 120 VAC from the power strip to points of need on the layout. Extension cords should be 14 AWG minimum for up to 50 ft, 12 AWG for 50 to 100 ft. 

    Extension cords should be placed, wherever possible, in non foot traffic areas but not concealed or covered by equipment. Extension cords can be temporarily attached along the bottom of modules above floor using twist ties, zip ties, S-hooks, etc. No permanent attachment is permitted. Cords should not be routed through clamps and or holes in module frames. This should be done neatly.

    Damaged cords should be discarded and replaced. Repairs should not be attempted.

    Cords that must be placed in areas subject to foot traffic should be at minimum secured to floor along their length with tape.

    In some jurisdictions, Extension cords subjected to foot or equipment traffic must be further protected from damage:

* Cords 3/8" or less in diameter must be covered with hard plastic "office cord covers" or an approved alternate method.

* Cords larger than 3/8" in diameter must use a plywood ramp style cover, or an approved alternate method.

* All cord covers must be secured in place using tape, nails or other methods.

  1. Power supplies for throttles, boosters and accessories must be off-module, either on the floor or a suitable cabinet or shelf under the layout. (This includes "wall-warts").
  2. Throttle, booster and accessory power supply line cords and wall-warts should be plugged directly into the extension cord outlets. "Power cubes", multi-taps or other outlet expansion adapters shall not be used.

Low voltage power distribution

With the loss of the ability to plug multiple wall-warts into a module mounted power strip, the more accessorized modules need a way to get power to their accessories. The following approach is therefore suggested:

  1. The white line remains reserved for layout wide 12 VDC power distribution, and will continue to be used to supply DC throttles. Permissible white line usage, however, may be expanded to also include on-module 12 VDC accessories on a secondary (not to interfere) basis. Such accessories shall be easily disconnected from the white line if necessary. A Powerpole or CJ white line "T" tap to feed accessories is recommended for this purpose.
  2. (Updated 11/4/2006) An optional accessory bus may be implemented within a module set or group for local accessory power (12 AWG, Brown/Black, horizontal Powerpoles, Brown on the left), and may be powered with 14-16 VAC from a separate power supply or transformer as desired. On module rectifier circuits would be used if DC is needed. Note: This bus is NOT intended for layout-wide power distribution!    (Note: The color change to brown from gray (the previous color) is due to the wider availability of brown tape for marking things over gray tape!)
  3. All low voltage supply outputs shall be ungrounded and include over current protection (fuses or circuit breaker) where appropriate.

Background on the need for this change

Early on, NTRAK recognized the need to distribute power for on-module accessories and other miscellaneous requirements. Initially module-mounted outlet boxes and cords were recommended as a way of providing an "AC bus" for such purposes.

In 1988, in recognition of possible safety issues with such "homebrew" approaches, the recommendation was changed to use commercial, UL-approved power strips with each module. While not mounted to the modules, these would be plugged together to extend AC power down the layout as needed.

In July 2004, an amendment was issued to the National Electric Code in UL 1393 concerning the use of such power strips ("Relocatable Power Taps" in NEC parlance), stating that "A cord-connected Relocatable Power Tap is not intended to be connected to another cord- connected Relocatable Power Tap". This technically put the typical NTRAK AC power configuration at odds with the code, even though our power usage was low and presented little danger of the overloads the NEC revision was designed to address.

With the temporary nature of most of our setups, this has not previously been an issue, however in April of this year, the Eugene, Oregon group was flagged by their local Fire Marshall for the use of "daisy-chained" power strips, and although they were allowed to continue the show, they were informed that future setups must be code-compliant. Safety inspectors elsewhere around the country have become more rigorous in their enforcement of this provision as well, and this trend is likely to continue.

As a result of the recent code change, and possible increased enforcement of this provision, NTRAK can no longer recommend the use of power strips in a daisy-chain configuration. Accordingly, and after a review of other applicable codes and standards, our recommendations on AC power distribution via power strips and extension cords are revised as follows:

  1. Power strips must be UL approved 3-wire (i.e., with ground) rated for 15 Amps (14/3 gauge wire or better) and shall include a 15 Amp resettable circuit breaker. For flexibility purposes, a 15 ft cord is recommended. Power strips meeting these guidelines include the Weber/Tripp Lite 6SPDX-15, Hammond 1584H6B1 or similar.
  2. Extension cords must be UL approved 3-wire rated for 15 Amps with outlets along their length or three female outlets at the end. For extension cords of 50 ft length or less, this means 14/3 gauge wire. Cords greater than 50 ft and up to 100 ft in length shall be 12/3 gauge.
  3. Power strips may ONLY be plugged in to an "approved receptacle" (i.e., wall outlet or permanently wired power drop).
  4. Power strips may NOT be plugged into one-another ("daisy chained") or into an extension cord.
  5. Extension cords may be plugged into power strips, but may not be daisy-chained.

Ground fault Circuit Interrupter (GFCI) protection, though not required, is nevertheless recommended, particularly in outdoor venues. As the "first line of defense", GFCIs may be incorporated into a wall-connected power strip, via a wall plug adapter (Grainger 5YL43 or similar) or in-line adapter (Technology Research Corp. # 14880-4-001 or similar).



Credits / Disclaimers / Etc.

Copyright 2002 - 2008 NTRAK, Inc.  All rights reserved. 

Questions?  Comments?  Contact us!