Power Districts

Power Districts.

Power Districts are not compulsory for successful DCC operation of a layout, it just makes life easier as there are no total layout shutdowns when there is a short. Layout “division” on all but the smallest layouts is for:

1. Troubleshooting the inevitable short that occasionally happens and would be very difficult to locate if the layout was only ONE area. In DC, the blocks could be switched off to help locate the short. With DCC it is suggested that there only needs to be one block. As your layout grows, there may be other reasons to divide the layout – see next items.

2. When there are more locos and other loads on the original booster than it can supply, there needs to be extra boosters to supply this current. The layout will then be divided for each booster.

3. With any layout that is being operated by a few operators, when there is a short, the booster’s internal circuit trips, removing power to the entire layout. This results in interruptions to ALL the operators and this becomes very annoying. To eliminate these interruptions, add power districts that are controlled by DCC circuit breakers or in my case 1156 lamps. When an operator creates a short that normally is running against an incorrectly set turnout, ONLY that operator is affected, all other operators operate as normal and most probably never new there was a short on the layout.

Dividing the layout up into Power Districts can be done by:

Boosters, but at over $150, this is an expensive way. Using Boosters is only really necessary when the power capacity of the original booster is near it’s limit and more current is required.
DCC circuit breakers like NCE’s EB3 and Tony’s Power Shields at about $25 per district, are the way to go. There are a couple of problems with DCC Circuit Breakers and these are:

They must operate quicker than the booster’s internal circuit breaker. Only use circuit breakers that provide a “response time” and a “current limit” adjustment. Digitrax’s PM42s require a Digitrax DT400 throttle to adjust the breaker, so non Digitrax users would be advised to use another brand of circuit breaker.
Sound locos with their larger Inrush Current requirements have resulted in the circuit breaker NOT resetting after the short has been cleared, on some layouts (mine included). See Circuit Breakers & Boosters not resetting with sound

· For HO, use the cheap $2 12 volt 27 watt 1156 automotive tail (stop) light lamp. For N scale use an 1141. Using 1156s does not remove the power from the layout in the event of a short like the booster or circuit breaker, they just restrict the current to 2.1 Amps. See later for more details. I like using 1156s due to their easy installation and because of their operating limitation of only being able to allow approximately 1.0 amp of current per power district, requires the layout builder to make his power district zones even smaller, that in the end gives the best operating performance. The 1156 has the advantage in that it illuminates brightly, providing a very visible warning of a short that should not go un-noticed by any operator if the lamp is suitably “locally” located in the area of “control” in a line side building or other suitable place to get the operator’s attention.

My double deck Main North 500 square feet per deck layout, has been divided into 14 Power Districts and each district is “controlled” by an 1156.

If the loco stops, it is easy to see why:

– NO bright illumination of the 1156, it is dirty track.

– Illumination of the 1156, it’s a short.

Shown below is the way I have divided my Main North into power districts that are in “Operator Areas”. This could include a double main line and sidings/loops, as it does on my layout. Shorts are commonly caused by running against an incorrectly set point/turnout and if the “division” is in local “Operator Areas” then only THAT operator will be effected. All other operators will not be affected, in fact they most probably did not know there was a short on the layout.

If you divided the layout into areas of Main line 1, Main line 2, Industry/Town 1, Industry/Town 2 etc, then when there is a short on a mainline point/turnout, this could affect other operators. This essentially would negate the reason for adding power districts (reducing the annoying power interruptions).

Locate the “Gaps” between power districts, in between “industries/towns” away from any points/turnouts. The chance of a short here is very minimal.

The red/blue Power Buses are runs to the local areas are twisted, 3 twist per foot, shown in dotted red/blue lines, to reduce the chance of excessive inductance having an effect of DCC operation, when the Power Bus length are greater than 30 feet. A few of my Power Bus runs are 60 – 70 feet long by the time you go over the top of the layout.

At the local area, the red power bus wire goes directly to the 1156 lamp suitably located for a visible warning then with the blue power bus wire, they run parallel under the “industry/town”, 3 inches apart, for easy track feeders (droppers) connection.

All power bus wiring “fans out” like the spoke of a wheel from the centrally located DCC system/booster.

My layout designed for 5 – 8 operators and will only need one 5 Amp system. For example my club layout using a NCE Power Pro 5 Amp system, operating 10 locos (some sound) and double headed by 6 to8 operators, the installed Ammeter only showed 1.5 to a maximum of 2.0 Amps while everyone was running. Remember not all the locos are running at the same instance in time. Some are stationary waiting to enter yards or at stations etc, so the current is lower.