Wiring Reverse Loops On A DCC Layout

Reverse Loops, Auto-Reverse Loop Modules/Switches and Unitrack/ Other Track

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If you decide to add one or more reverse loops to your Unitrack layout using DCC, One should use one reverse loop module/switch for each reverse loop on your layout. It isn't advisable to piggyback two reverse loops on one reverse loop module/switch.

One might say that I'm only running one train at a time on my layout. However there will come a time when two trains might be running on the same layout at the same time. If both trains enter the two reverse loops at the same time and both loops are wired with one Auto-Reverse Loop Module, the result will be a short circuit with a complete shut down of the system. What are the results of such a shut down? In some cases blown out decoders could result and worse, blown out locomotive motors if your system doesn't shut down quickly.

To avoid this situation, each reverse loop should be wired to its own reverse loop module/switch. The cost to buy a second reverse loop module/switch is but a small price to pay to avoid a short circuit and blown out decoders.

On the "Original" JJJ&E, I had four reverse loops plus a turntable so that makes five reverse loops. Each reverse loop was wired with its own individual reverse loop module/switch. In over nine years of operation, reverse loops never caused a short circuit on the "Original" JJJ&E. I used five Lenz LK100 Auto-Reverse Modules on the "original" JJJ&E.

 Lenz today offers the LK200 Auto-Reversing Unit instead of the LK100. When trains entered the reverse loop, the auto reversing module automatically changed the polarity inside the loop. When trains started to leave the reverse loop, the polarity was again reversed by the auto-reversing module.

The added security of knowing that each reverse loop has its own reverse loop module/switch is more than enough to justify the added cost of these switches on a layout? 

Now some facts about reverse loops. If you have more than one reverse loop on a layout, each reverse loop must be long enough to accommodate the longest train/trains you expect to run on your layout. If a train is longer than a reverse loop, the train will short out the DCC system as it passes in and out of the reverse loop.

Diagram Of A Reverse Loop And Its Wiring To An Auto-Reversing Module  From Allan Gartner's Wiring For DCC

 Its also important to have metal wheel sets on your rolling stock. The metal wheel sets enhances the performance of the Auto Reverse loop module. If you don't want to outfit all your rolling stock with metal wheel sets, use metal wheel sets on the first car after the locomotive and the last two cars of each train.

Wiring of a reverse loop is extremely important but in reality very easy to do In DCC.

 The reverse loop module/switch changes the polarity of the track when trains enter and leave the loop.

The wiring of reverse loops is easy with Unitrack using DCC. You only need one set of feeders (black and red wires) in the reverse loop. This set of feeders is wired directly to the reverse loop module. You then must wire a set of feeders to the track adjacent to and outside the reverse loop. This set of feeders is also wired to the appropriate terminals on the reverse loop module. These four wires are all that is needed to wire a reverse loop in DCC using Unitrack and any other brand of track. It is an very simple installation.

Again let me reiterate that only one set of feeders need to be soldered to the rails inside the reverse loop.

The track inside the reverse loop is isolated from the rest of the layout by using two pairs of plastic rail joiners, one pair of plastic rail joiners inserted at each end of the reverse loop.

You must use one reverse loop module/switch for each reverse loop. You can't wire two reverse loops to one reverse loop module/switch. This type of wiring will inevitably cause a short circuit. This occurs when two different trains enters two different reverse loops wired to the same reverse loop module/switch.

 Tony's Trains, Digitrax, Lenz and MRC make Auto-Reverse Modules. You have an excellent selection of Auto-Reverse Modules at various prices.

All the information and photographs below were obtained from each manufacturer's website and provide the N scale modeler with an excellent choice of Auto-Reversing Units at various prices.
 

Photo  #  1  Digitrax AR-1  Auto-Reversing Unit

AR1 Features:

• Cost effective automatic reversing for one reversing section or subdistrict
• User selectable trip current lets you adjust the AR1 to work with any scale or equipment on your layout
• Auto-Reversing manages polarity mismatches on the reversing track section without manually throwing electrical toggle switches or adding another booster
• 8 amp peak, 6 amp continuous Auto-reversing control for a single reversing district.
• Simple to wire 4 wire hookup, no locomotive wiring required
• No external power required, runs off track power
• AR1 operates with or without LocoNet, so it is compatible with all DCC systems.

  Photo  # 2  MRC  AD520 Auto-Reversing Unit

The MRC AD520 Auto-Reversing Unit automatically changes polarity of your reverse loop or reversing section. Easy 4-wire hookup. Up to 5 amp output. Not for use on non-DCC layouts or with non–decoder equipped locomotives.

Photo  # 3  Lenz LK200 Auto-Reversing Unit

Wiring is very simple. Two wires connect into the track in the loop and two wires go to the main line, before the gaps. That’s all you need to do, simply install it and forget about it. There is no need for additional control connections, sensor tracks or user adjustments. The maximum load is 5 amps.

Photo  # 4 Tonys Trains PSX-AR Auto -Reversing Unit And Circuit Breaker

Tony's Trains PSX-AR Auto-Reversing Unit is easy to set up and wire.