Frequently Asked Questions:

Here are some common questions about Electronic Power Protection for DCC Layouts:

Auto Reversers:

Don't all Auto Reversers also act as circuit breakers? Which ones don’t?

Frog Juicers are Auto Reversers that don’t usually have circuit breakers embedded in them. I'm sure there are others.

Does an AR need to be directly connected to a DCC power Buss? Can't it be connected directly to a Circuit Breaker?

Auto reversers with circuit breakers built in can be connected directly to the DCC Buss or they can be after a Circuit Breaker.

I've done it both ways and it works equally well. If you connect an AR directly to the DCC Buss it makes troubleshooting a bit easier since you can isolate the problem because you can turn off each CB and AR one at a time. I like to attach a switch to the CB and AR inputs so I can quickly turn them On and Off.

I also like to add a power Green LED light and a trip LED Red light connected directly to the CB circuit board and place it out next to the switch. Same on an AR except the Red Trip light will also flash when it reverses polarity.

Why does the CB response time need to be made longer then the AR response time?

When you enter an auto reverse zone the AR senses a short and quickly flips the track polarity so that you can't even tell it happened. If the short trips the Circuit Breaker first, before the AR flips the polarity, your train will stop, the sounds will stop and the transition will be noticeable. On a PSXX and PSXX-AR set the AR to trip at a lesser amperage than the PSXX. On an older model PSX and PSX-AR, change the PSX-AR trip time to a smaller value. Works the same way with NCE EB1 and AR10.

With older AR's that use relays it will be very noticeable.

What is the symptom that a circuit breaker is tripping before the AR?

The Train entering the reverse loop will short, it will stop momentarily, and will loose sound momentarily.

Don't many reversing sections have multiple entry/exit points? Why shouldn't they be connected to the same Power Booster?

Multiple AR's can connect directly to the DCC Buss but its not good to have an AR connect directly to another AR.

For circuit breakers shouldn't you mention that one good reason for using a circuit breaker is to limit the short circuit current of a 10A or even 5A booster to a less potentially damaging 1-3Amps?

Yes. You want to minimize the trip level to a point where you start seeing nuisance trips and then raise it slightly. So generally CB's at 3 amps and AR's at 1 or 2 amps, but each layout differs. The built in Power Booster Circuit Breaker or DCC System’s built-in Circuit Breakers purpose is to first protect the DCC System itself from damage. The newer the DCC System and Boosters the faster their built in CB’s trip which can lead to a dilemma when upgrading DCC systems. What if your DCC System CB is faster than the layout Circuit Breakers and Auto Reversers?

Manufacturers of Circuit Breakers and Auto Reversers have the same issue. If a new DCC system comes out that is faster than their CB/AR's then then need to redesign their product.

What about using an auto-lamp? (cheap, but what are the draw-backs)?

Light bulbs (typically auto bulbs like #1156) are used in DCC model railroad systems primarily as simple, inexpensive current limiters for short-circuit protection, not for voltage spikes.

They are wired in series with the track power feed between the booster and track, or just for frog power on turnouts. This older technique is still used on smaller layouts, though modern electronic DCC circuit breakers are now more common and have far better performance.

Limitations:

• Not instant: High current flows briefly until the bulb heats up. Fast boosters may trip before it fully limits.
• Voltage drop: Under load, it can dim trains slightly or reduce performance if multiple locos draw current.
• Multiple shorts: Can cause the booster to shut down and stay off until cleared.
• Best for low-current systems, single-engine districts, or frog protection—not high-power multi-train layouts.

Modern best practices replace bulbs with fast electronic breakers to minimize the risk shorts and spikes. If you loose one $100+ DCC sound decoder to a lightbulb you could have bought one or two modern circuit breakers. But if it works for you go for it.

What should the Circuit Breaker District be limited to? How many locos are running in a district and what is the needed current ?

If too many locos are running in a district and it overwhelms your CB or Booster divide the district into another district by adding another CB or move the AR's attached to that district, directly to the main buss taking that load off that CB.

Why 2-4 districts? Doesn't is depends on layout size?

A small home layout with one or two operators could use the built in DCC System breaker, if it's modern and fast enough. On a bigger layout where multiple people are operating I usually put a breaker on each yard, also one for each of the main line districts attached to the yard(s). Most shorts happen during yard operations which annoys the rest of the operators when their power goes down all the time. On one large layout that I've worked on over the past 6 years, the owner failed to separate out the 4 rail yards. After multiple Operating Sessions we've added CB's to 3 of the yards. For AR's I've used all of the methods listed in the table plus Tortoises. The Tortoise internal switches work well on the tail end of Y's when used to turn single engines.

Do you really need a separate circuit breaker for a siding? What about a section of the layout including mainline, siding and industrial spurs?

No on the siding. Long stretches of mainline with sidings and spurs should usually get their own CB. You don't want to shutdown the Yards. 

Why heavy wire size if the circuit breaker is limiting the current to ~3A? Our club has Three 8A boosers, 20+ PSXs and uses 18g wire.

This page is about DCC Power Protection.

I recommend asking AI and/or searching on these Buss wiring questions:

• What wire gauge is advised for small medium and large DCC HO layouts and why?
• Should the buss wires be twisted and if so why?
• Should Buss wires be run parallel and close to power cords and lines?
• If all of my Circuit Breakers are located in one place and they all need to run out through a conduit to the layout should they all run through the same conduit?
• What type of connections should I use to connect the different parts of my wiring Buss and what are the pros and cons of each type?

Why don't you mention the older PSX breakers? They are still available used?

PSX is the previous version to PSXX. They are distributed directly through Tony's Trains to other stores. PSX is no longer made so I didn't mention them.

I suspect that a new DCC System came out that was faster or they could no longer get parts. Our large Lockheed club layout uses these exclusivly and they're bulletproof. I use 4 on my own small layout. I've used the PSXX on two other layout's and NCE EB's on another. The PSX & PSX-AR work well.

One drawback of the PSX/PSXX circuit breakers is that they use red LEDs to indicate both that the track is powered and that the breaker has tripped.

On our club layout we add a Switch to the PSX and PSX-AR inputs to be able to turn off each CB and AR. We wire a Green LED directly to the PSX and PSX-AR boards to show that the CB or AR is powered up. We add a red LED to show when the CB or AR trips. The LED will also show when the AR has changed polarity. The LED's solder directly to the PSX or PSXX boards.