Wiring: Standardizing Color and Connections

A WIRING STANDARD FOR A NEW LAYOUT.

This topic deals with standardizing the wire and the connection system used with the layout wiring. 

If you follow these recommendations you will:

1) instantly identify the purpose of the various power cables running under the layout.  Easy to remember = easy to expand and fix.
2) instantly know your making a mistake if you ever find yourself connecting any 2 wires of DIFFERENT colors DIRECTLY to each other at any time.
3) eliminate track polarity issues as it related to track feeder installation and connection.
4) know what it takes to make a quality connection.

By using just a few wire sizes and connectors, this allows the inventory of just a FEW unique wiring supplies and allow bulk purchasing to lower the overall cost.


This section is divided into two major sections. The first part applies to all layout where the second part applies to larger layouts.

PART A (ALL LAYOUTS)

1) WIRE COLOR CONSIDERATIONS TO BUILD A WIRE PAIR OR BUS.
2) STANDARDIZE ON A WIRE COLOR CODE.
3) WIRE GAUGE CHOICES
4) STANDARDIZE ON WIRE CONNECTORS
5) GET GOOD TOOLS TO INSTALL YOUR CONNECTION SYSTEM
6) DCC CIRCUIT BREAKER WIRE COLOR CONSIDERATIONS (POWER DISTRICTS)
7) REVERSE LOOP WIRE COLOR CONSIDERATIONS
8) SMALL GREEN WIRE FOR FROG POWER WIRE COLOR CONSIDERATIONS

PART B (LARGE OR ADVANCED LAYOUTS)
9) LARGE GREEN WIRE FOR BOOSTER GROUND WIRE COLOR CONSIDERATIONS (BOOSTER DISTRICTS)
10) BLOCK OCCUPANCY DETECTOR INSTALLATION



1) WIRE COLOR CONSIDERATIONS TO BUILD A WIRE PAIR OR BUS.

I use 2 contrasting wire colors to maintain the polarity of the power (DCC or DC) invovled.

The lighter color represents the + polarity or the rail closest to the facia or you the operator.  I call this the hot rail.
The darker color represents the - polarity of the rail farther away from the facia or you the operator.


2) STANDARDIZE ON A WIRE COLOR CODE.

Here is my suggestion based on the most common wire colors and maximum contrast in wire colors in wire pairs.

Red/Black = +12VDC for accessories global around the layout.
Orange/Blue = DCC Bus 1
Yellow/Brown = DCC Bus 2
Gray/Violet = DCC Bus 3
White/Green = DCC Bus 4   (See Note 1)

Note 1:  See item 8 in this Part A and item 9 in Part B for more information about green wire color usage tradeoffs.


3) WIRE GAUGE CHOICES

Generally,

1) Bus wiring that distributes power (DCC or DC) around the layout needs be a large gauge wire 16AWG on up.  Large layouts will need to move up to 12AWG.
2) Track Feeder will be smaller since they only need to support the current of 1 train and must be easily soldered to the rail.  Track Feeders should be 18AWG or smaller.

NOTE:  A good discussion about wire gauge trade offs can be found here:Track Wire Gauge Selection

HOWEVER, if your using any type of connector, Barrier Terminal, IDC (Suitcase) or TwistCap, the wire Gauges chosen MUST be taken into consideration.  This includes the type of connection provided by your DCC system.  Doing a little bit a research can help you in building a reliable wiring system and avoid connection problems.


4) STANDARDIZE ON WIRE CONNECTORS

A good electrical connection involves obtaining clean non oxidized bare wire in contact with non oxidized metal to make a air tight connection that does not fail under normal mechanical stress.  This apples to any type of connection system be it Solder, screw terminal, twist cap, or IDC connector.

There are two type of connection systems used on a layout.  Solder Based and Connector Based.   Each system has pluses and minuses associated with it.  The first thing one should consider before anything else is a honest answer about your wiring skills.   Basically if your soldering skills are not good, then one should consider using a connector system.   Cost should NOT be a prime factor in the choice because wiring is like the foundation of a building.  You can build the best building in the world but it will still fall down because the foundation it is sitting on cannot support it.  In other words, it does not matter how cool the layout is if the electrical system is unreliable.  No body like to operate a layout that does not run well enough to enjoy it.

From this point on, I will assume you have chosen to use a connector system.

The Benefit of a implementing a connector system allows one to

1) work under the layout without getting burned
2) Speed up the installation of all the connections
3) get a reliable connection system once you master the steps and requirements

Furthermore, if you buy the connection system in quantity, you can lower the cost of the wiring system.

There are many connections systems.

1) Barrier Screw Terminal strips and bare wire.
2) Barrier Screw Terminals and wire crimp Lugs.
3) European Screw Terminal strips and bare wire.
4) TwistCaps
5) Wire Taps
6) IDC Connectors.
7) Soldering Bare Wire.

What is in common with all of these connection system is the limitation on the wire AWG that can be used reliably.  Going ABOVE or BELOW these wire gauge limitation will result in a poor connection.  A poor connection is a time bomb that takes time to develop but will go off.  You may or may not notice it depending if the connection is redundant or not.

EXAMPLE: 567 Scotchlok IDC (SUITCASE) Connector made by 3M.

This high current IDC creates a wire tap to "tap off" power from the main wire run without breaking the main wire run.  Specification are as follows:

Only 10AWG - 12AWG (4.0 - 3.0mm^2) wire run is acceptable.  Run means the wire that passes through the 567 non stop to the next 567 and so on.
Only 14AWG - 18AWG (1.5 - 0.75mm^2) on the wire tap.  So you can use any wire size between 18AWG and 14AWG such as 16AWG (same with metric wire)
Wires can be solid or stranded.   

So if one want to build a HO or larger scale layout using the 567, then use 12AWG for the track bus wiring and 18AWG for the track feeder*.  It will be both fast and reliable and you only need to stock 2 type of wire and 1 type of connector.  

*Use 18AWG solid is small enough to solder to HO rail and disappear when painted.


5) GET GOOD TOOLS TO INSTALL YOUR CONNECTION SYSTEM

Get the best tools for the Job.  The cheapest version of a given tool is very often not the best solution in the long run.  Good tools are an investment into obtaining high reliability.  A cheap/poor tool is a device that can help you build a bad electrical foundation without you knowing about it until its too late.  This often lead to the person blaming the connector when it is actually his fault for not doing it right.  Ignorance is no excuse.

EXAMPLE:  Wire Crimper for Lugs

PROBLEM: There are many low cost crimping pliers on the market and they all have on thing in common, there is no indication of when you have properly crimped the connector.  Most model railroaders stop when their hand hurts.  Everyone has a different definition of pain too which means no consistent pressure person to person.   Since proper crimping pressure involves more force than model railroaders think, most connections fail. The failure will be on or both of the following:

1) loose wire that eventually falls out of the crimp connector
2) high resistance connection builds up of time.  Why? The lack pressure prevents an air tight connection to be establish between the wire and the connecting metal. A non conductive oxidization builds on the bare wire.  In other words a poor insulator grows with time.  Oxidation is one of the reason why we clean our track to re-establish good electrical pickup again.

SOLUTION:    Buy a ratcheting version of a crimp tool and it will prevent mistakes.  First time you use this tool, your hand will hurt and you cannot complete the crimp by hand.  You may give up thinking there is something is wrong with the tool or you may have to use your body weight to crimp all the way down to make the ratcheting crimper release.  This is especially true on large gauge wire connections.  But I know from experience, your hand will get stronger and your hand will learn how much force is require resulting in you pain threshold going down and crimp rate going up.


6) DCC CIRCUIT BREAKER WIRE COLOR CONSIDERATIONS (POWER DISTRICT)

A) DCC bus Color pairs can change pair colors at a DCC circuit breaker (Power District) but you must retain the same Light/Dark color polarity through the breaker.    Light Color to Light Color and Dark color to Dark color.   That fact you are using a DCC cricuit breaker means you need to separate the wires pair to eliminate any confusion.

B) If you use a color pair to act as a raw DCC booster power distribution bus to feed multiple DCC breakers, then that bus color pair should be a unique color pair between the given booster and all of it associated DCC Circuit Breakers.   This same color pair can also be used as a DCC accessory bus color pair for the layout area the booster is responsible for.   (This type of DCC accessory bus is not recommended if you are doing signals.


7) REVERSE LOOP WIRE COLOR CONSIDERATIONS

IF the Auto-Reverser (AR) that does NOT also perform a DCC Circuit Breaker function, then the color wire pair going into the AR shall be the same color pair leaving the AR.  
If the AR DOES perform a DCC circuit breaker function too, then is should follow the color considerations of a DCC Circuit Breaker.

A reverse loop does not prevent you from still following the near versus far rail/wire color polarity rules.   Just pick the part of the reverse loop track that closest to the facia and start there and ingore the fact that the rule breaks down on the other end of the reversing section.  Why?  It is impossible to solve this problem and it is more important for you to keep the rail/wire polarity correct inside the reverse loop.  Just remember the reversing section wiring start and ends between the double gaps or double insulated rail joiners that you install to electrically isolated the reverse loop track.


8) SMALL GREEN WIRE FOR FROG POWER WIRE COLOR CONSIDERATIONS

One may want to consider using the green wire track feeder wire gauge size if one uses live or powered frogs.  It runs between the Frog and the device (Tortoise) that selects the correct polarity for the Frog from the given DCC bus that is powering the track.  It typically will be very short (less than 18") and be a different color than anything else near it.

Chances are with a small layout, you may not have a White/Green bus nor a second booster.  Hence using a single green wire for frog power will not create any color code conflict.   However if you do need to create a White/Green bus, then you should find another UNIQUE color for the Frog power wire if you can find it.   There are out there but not commonly stocked colors.

Suggestion:  Green with a Yellow stripe.  Even if you use this same color wire for a Booster common, see section 2 item 5, the two wires will never get close to each other since one has nothing to do with the other nor routed the same way.   You will never see a Green-Yellow stripe wire related to the booster common coming out a hole in the wood directly under a turnout.



PART TWO (LARGE OR ADVANCED LAYOUTS)


9) LARGE GREEN WIRE FOR BOOSTER GROUND WIRE COLOR CONSIDERATIONS (BOOSTER DISTRICTS)

This only applies if you have MULTIPLE BOOSTERS which create booster districts.

Some DCC systems that support multiple booster require the user to install a single dedicated wire often called a "Booster Ground" that runs between the boosters.  (Technically this is not a ground but a "Booster Common" since it has no relation to Earth Ground nor the Ground wire/connection on any other device on your layout.) 

Normally the current of a SINGLE engine will flow down this wire when the given engine is crossing between booster districts.  This become VERY important is you run any locomotive with offset wheel pickup.  (Many older steam locomotive had the engine pick up one rail while the tender picked up the other rail.)   The current will flow between the two booster over this wire as the engine crosses the Booster District boundary.  On the other hand, many all wheel pickup engines are less sensitive to this problem.   However if you do not want you headlights to even flicker the slightest or engine to even hesitate, you need to install this wire.   It should be a large gauge wire that is the same gauge as the track bus wires

Why a large gauge wire?

a) HIGH CURRENT:  Full booster current can flow if their is a short circuit as a given engine crosses the booster district boundary and derails creating a short.

b) LONG WIRE RUN:  Boosters are supposed to be installed DISTRIBUTED around the layout as opposed to a single location.  Given locomotive current will be flowing, you want to be consistent in the voltage drop performance as offered by your track bus wire.

Booster District Boundary?  The location where you installed two rail gap or a pair of Insulated Rail joiners to isolated the two booster from each other on the layout).

What is you need the Green wire for the Green/White 4th bus?

Suggestion:  Get a large gauge Green with a Yellow stripe for the Booster Common.  Green and Green with a yellow stripe are two common colors used in the Electrical Power Industry for Earth Ground connections.  My point is that it available if you look for it.  So you have you plain green for the White/Green bus and Green with Yellow strip for the booster common.


10) BLOCK OCCUPANCY DETECTOR INSTALLATION

Install any block occupancy detectors on the Light color wire.  This make it easy to know which rail needs the gap/insulated rail joiner and which wire it is installed on.  The wire and rail closest to the facia.


Page written 9/27/14.