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I have a layout that consists of 2 physically separate loops. The outer loop is controlled by the left-hand throttle of a Z400 and the inner is the right-hand. So, the loops are both physically and electrically separate. I also run DCS. If I add a double crossover (like a Ross #175) will I end up electrically connecting one loop to the other? I would assume the crossover would isolate each loop, but, what happens when a locomotive crosses from the outer loop to the inner? Especially if it's a long locomotive and would have multiple power pickups?

Thanks,

Rick

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More info needed.  Are you running conventional or TMCC/DCS?

Assuming that the center rail is insulated from that of each loop at some point within the crossover:

If you run purely DCS/TMCC, the voltages from both Z-4000 outputs are likely to be set the same and the short connection between them via the locomotive or passenger car pickup rollers won't matter.

If you are running conventional, then you need to take care to have the voltages of both loops set the same when the train is crossing over.  And you wouldn't want a step-change in speed then, either.

Because the source for both tracks is the same Z-4000, no phasing issue exists.

It's not a problem.  Anyone that runs DCS faces the same situation if they have more than one power district.  I have four bricks powering the four channels of my TIU.  Obviously, trains regularly cross over the boundaries for the DCS signal from a different channel.  As long as the voltage input to the TIU is the same for all channels, it'll work fine.

DCS will momentarily lose connectivity to the engine as the two power districts are connected, but a DCS engine if it loses connectivity simply continues what it's doing.  Once it has transitioned the boundary, it's back in contact and continues on it's way.

@Rick posted:

I would assume the crossover would isolate each loop, but, what happens when a locomotive crosses from the outer loop to the inner? Especially if it's a long locomotive and would have multiple power pickups?

Thanks,

Rick

All very good advice so far.

One more point however.  When you insert the crossover it won't automatically continue the electrical isolation that you have presently have with the two independent loops.  You'll need to insert plastic (also called fiber) pins in the center rail between track sections at the appropriate point where they meet, in order to do the job.

This sketch will show you where they should be placed if your crossover is made up of two independent switches:

And, as @KarlDL has mentioned make sure that your two throttles are at about the same position as your train makes its way over those joints fitted with the plastic pins.  If you don't your engine's rollers will be connecting the center rails, across the plastic pins, with two different voltages.  This will create a momentary short circuit until the train completely passes through.  The "strength" of the short circuit depends on how different in position the throttles are.  Widely different means a big short, which could trip a breaker or blow a fuse; closely means a very small one, which will go unnoticed.

Mike

Last edited by Mellow Hudson Mike

Each loop of my layout is split into 4 Power Districts. Each Power District is power by it's own PW ZW. Each ZW has a volt meter and ammeter for me to monitor voltages and amps. I experienced problems once when a powered car straddled 2 Power Districts. A lighted passenger car straddled 2 Power Districts for a few minutes and the wiring in the car literally burned up. I have an emergency disconnect that kills all power immediately. As a result I make sure no cars and no engines especially straddle Power Districts. I installed poles with blue LEDS on top to show where the insulated pins are installed for each loop. That way I can visually see where engines/cars are paused in relation to Power District insulation points are located.

Last edited by Junior
@Junior posted:

A lighted passenger car straddled 2 Power Districts for a few minutes and the wiring in the car literally burned up.

That indicates you clearly had a significant difference in the voltage feeding the two power districts!  If you're going to use PW-ZW or similar transformers, I'd set them to the same voltage (measured), and then don't ever change the handles.  I'd also have improved circuit protection on every output, the circuit breaker in the PW-ZW or most other PW transformers is not up to the task!

If you're going to use PW-ZW or similar transformers, I'd set them to the same voltage (measured), and then don't ever change the handles.

Agreed whole-heartedly for command control, but you can't run conventionally that way.

Need a way to automatically (using PowerMasters instead of PW-ZW's?) force both loops to the same voltage as the train approaches the cutover from one loop to the other.  Follow this with a way to allow them to return to their previous settings once the entire train clears the cutover and is safely into the other loop.

Mike

That indicates you clearly had a significant difference in the voltage feeding the two power districts!  If you're going to use PW-ZW or similar transformers, I'd set them to the same voltage (measured), and then don't ever change the handles.  I'd also have improved circuit protection on every output, the circuit breaker in the PW-ZW or most other PW transformers is not up to the task!

Oh yeah…..I watch that like a hawk John. One incident was enough for me. And it didn’t take much for voltages to be off to cause the meltdown.

I’m seriously considering moving to Lionel 180 Watt Powerhouse bricks to alleviate this issue.

Junior,

Make sure that your ZWs are phased identically.  How do you do that?  I'm going to assume that the U terminals of all of the ZWs are tied together, whether at the transformers or at connection points, which is essential.  With no engines on the tracks of your power districts and the ZW variable voltages feeding the tracks set identically on all 4 transformers (say, 16V), then measure voltages between center rails in different districts, using a general-purpose multimeter in AC voltage mode.  So, if one labels each district as AA, BB, CC, DD, then you would first measure AA to BB center rails.  If the voltage is around 0V, all is well.  If it is around 32V, reverse the BB transformer's power plug in its source socket - the measured voltage should reduce to near 0V.  You do the same for AA to CC and AA to DD.  Then, just for confirmation, measure BB to CC and CC to DD, which should both be near 0V. After ensuring matched phasing, mark all of the ZW power plugs with a painted dot or adhesive dot (nail polish can be handy, if wife cooperates) on the same side of each, to ensure proper phasing should you ever disconnect them from the power strip and plug them back in again.

My Torch Lake Central uses 3 Powerhouse 180s.  One of the three needed the phase reversal output adapter connector provided with the unit, in order to ensure matched phasing.  I assume that the cause was a manufacturing variation in that Powerhouse, flipping the two primary or secondary wires with respect to the other two units.  The Powerhouse 180s use modern plugs with dissimilar prong widths, so plugging the "source" side in backwards is not possible.  I use a PW 1033 for accessory power, which has identically-sized power prongs.  I marked the "top" side of the power plug to ensure that it is phased the same as the track power from the Powerhouse units, whenever it is disconnected and reconnected.

@KarlDL….

Thanks for the tip. I learned a long time ago the importance of properly phasing all transformers.

This practice also applies to Accessories that provide power to track sections.

When I was connecting power to my Coal Tipple, I inadvertently reversed the wires. The Tipple itself worked just fine (the Tipple was standalone at the time. I shove a car into it to test the action).

Literally months later, I was running a bunch of bathtub ore cars into the Tipple and “pop”;  a big spark! What the…..?

The power to the Tipple (for operating the Tipple) also supplies power to the track section within the Tipple; which is isolated from the track meeting the Tipple by a gap on either side.

Because of my mistake, the Tipple track was out of phase with the rest of the layout! Fortunately, it was a rail car and not an engine that bridged that gap! The spark did leave a mark on the car’s wheel.

Last edited by Junior

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