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Do I need an insulated gap with DCC?

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  • Member since
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  • From: Anaheim, CA Bayfield, CO
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Do I need an insulated gap with DCC?
Posted by Southwest Chief on Thursday, December 16, 2010 1:29 PM

I'm in the process of removing several of my old (over 30 years old) Atlas turnouts with Peco.  Still sticking with code 100.

My question is about an insulated joint where a crossover is located.  Here's what it looks like:

Our layout used to be regular (DC) track power.  Track A and Track B had their own separate power packs.  The insulated gap was needed due to a short circuit when the direction of power pack A was different than power pack B.  The arrows indicates the typical direction of travel

But we are now DCC.  And now I'm not sure if I still need this insulated gap.

The new turnouts are Peco Insulfrog which replace comparable Atlas turnouts which also had insulated frogs.

So do I still need this insulated gap?

Matt from Anaheim, CA and Bayfield, CO
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Posted by retsignalmtr on Thursday, December 16, 2010 1:40 PM

Yes you still need the insulated joiners there. If you don't put them in there you will be creating a short circuit.

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Posted by Vail and Southwestern RR on Thursday, December 16, 2010 1:44 PM

Well, it actually depends on the rest of the layout, and how it's wired.  If there are no reversing sections, and both mains are wired with the same phase, there's no need for the gap.

If it is a dogbone configuration, then there is a need for the gap.

Jeff But it's a dry heat!

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Posted by DigitalGriffin on Thursday, December 16, 2010 1:57 PM

As long as your divergent frog rail and through frog rail are isolated from one another you are good to go.  If they touch then you will need to isolate them.  (See picture below for which rails I'm talking about)

 

Don - Specializing in layout DC->DCC conversions

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Posted by selector on Thursday, December 16, 2010 2:12 PM

Your big arrows may be doing much to confuse you...or me.  Smile   Do you mean to signify that the parallel tracks are on opposite sides of an oval or loop?  If so, you need the gap as you have shown.  If they are twinned tracks running parallel to each other on one side of a loop or oval, then the area in question is merely a cross-over, and no gaps are needed.  As the last poster says, though, a lot depends on the nature of the turnouts, how/if they route power, and if the frogs are live or isolated, etc.

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Posted by Southwest Chief on Thursday, December 16, 2010 4:31 PM

Sorry for the confusion on the arrows.  This is just the normal direction trains travel on our layout, and how our signals are set up for directional running.

But the layout is just two main tracks (double track) that are separate loops.  No reverse loop.  The separate mains only meet at this cross over.  There are around four power feeders on each main line scattered around the layout.  All come from one power port on our DCC system (Digitrax Zephyr).

All of the turnouts have isolated frogs.  All used to be Atlas #6?  Possibly #4 I'm not sure (Code 100).  They are being replaced with Peco Large Radius Insulfrogs.

 

Here is a quick and ultra rough rendering of the layout:

 

 

Matt from Anaheim, CA and Bayfield, CO
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Posted by richhotrain on Thursday, December 16, 2010 5:04 PM

Given your drawing, you should not need the gaps unless for some reason Track 1 and Track 2 are not wired in phase.

Rich

Alton Junction

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Posted by mfm37 on Thursday, December 16, 2010 6:40 PM

Do you need an insulated gap? Maybe, maybe not. Why not just put the gap in anyway. If it's not needed, you just connect the wires from each loop together. Gap is bridged by wire and it will be electrically the  the same as no gap. Down the line, maybe you would want to break the layout into two power districts using circuit breakers. Required gap is already in. You would just need to separate the wires.

Martin Myers

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Posted by rrinker on Thursday, December 16, 2010 11:17 PM

 Gap or no gap, the two loops have to be wired in phase. With no gap, it would short immediately, with the gaps, it will short when a train tries to cross over.

 By "in phase" it means both loops should be connected to the DCC system the same way. Using the close-up view of the crossover, and assumign the terminals on the DCC syste, are labeled Rail A and Rail B, you'd want the wires to the rails, in order, fromt he bottom, to be Rail A< Rail B, Rail A, Rail B. The rail to the bottom of both loops should be Rail A, the rail to the top, Rail B.

                           --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by gondola1988 on Thursday, December 16, 2010 11:36 PM

Depends on if you are using a booster for each loop, If you are then it has to be double gapped . Might be something to think about before  you continue.  Jim.

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Posted by Southwest Chief on Friday, December 17, 2010 12:34 AM

Tracks are definitely wired in phase.

No separate booster either.  Just the Zephyr.  Pretty basic operations with two trains running.  Passenger train on Track 1 (A) and a freight on Track 2 (B) so nothing really advanced was needed.

I tested the crossover without a gap this evening and observed no problems.  Running over it is fine with a single loco or a multi-unit lashup.

I also figured that if there was a short I would have noticed it right away after tuning on the track power.  After seeing none I tested some locos and everything ran perfectly.  Actually a lot smoother compared to the old Atlas turnouts.

Thanks for the info.

Matt from Anaheim, CA and Bayfield, CO
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Posted by richhotrain on Friday, December 17, 2010 5:49 AM

rrinker

 Gap or no gap, the two loops have to be wired in phase. With no gap, it would short immediately, with the gaps, it will short when a train tries to cross over.

 By "in phase" it means both loops should be connected to the DCC system the same way. Using the close-up view of the crossover, and assumign the terminals on the DCC syste, are labeled Rail A and Rail B, you'd want the wires to the rails, in order, fromt he bottom, to be Rail A< Rail B, Rail A, Rail B. The rail to the bottom of both loops should be Rail A, the rail to the top, Rail B.

                           --Randy

 

Randy,

Not to be argumentative, but the the two loops do not "have" to be wired in phase.  In that particular layout, they should be wired in phase to avoid the need for gapping the resulting reversing section if they are not wired in phase.  However, if Track 1 and Track 2 are not wired in phase, either Track 1 (Black) or Track 2 (Red) becomes a reversing section and the rails between the two turnouts that form the crossover need to be gapped and dealt with as a reversing section.

Rich

Alton Junction

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Posted by MisterBeasley on Friday, December 17, 2010 6:32 AM

By the normal definition, there is no reversing section here.  There is no way that a train can turn around and end up going the other direction on this layout.

As for the insulators, I would put them in.  I would wire the rest of the layout with a separate track power bus for the inner and outer loops.  Then, I would run each bus through its own circuit breaker.  It may be overkill, but it will isolate the two loops and make troubleshooting easier in the long run, as the layout develops further.  It will also allow trains to keep running on one loop after a derailment on the other.  If you don't want the expense of breakers right now, simply wire the two power buses together at one point, and wire that to the Zephyr.

Since this was a DC layout, I would suspect that you already have it wired this way.  By keeping the insulators in the track, you'll maintain the isolation and be a step ahead of the game if you decide to install breakers later.

It takes an iron man to play with a toy iron horse. 

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Posted by richhotrain on Friday, December 17, 2010 7:06 AM

MisterBeasley

By the normal definition, there is no reversing section here.  There is no way that a train can turn around and end up going the other direction on this layout.

LOL  There is something to be said about not seeing the forest for the trees.  Nevertheless, reversing section or no reversing section, the gaps would be necessary if Track 1 and Track 2 are not wired in phase.

Rich

Alton Junction

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Posted by retsignalmtr on Friday, December 17, 2010 7:39 AM

It would be nice to have the I.J.'s there if you ever want to run a loco on DC (not on address 0) on one or both of the tracks

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Posted by galaxy on Friday, December 17, 2010 8:07 AM

I have a similar layout with two such switches {opposing directions} wired on DCC. I have no inulating gaps, and you should be fine without one too.

UNLESS you don't have the same polarity on red track and black track. If the red left rail is wired the same DCC pole as the black left rail you will be fine.

My layout is very small, but of similar design, I can basically run it with just two wires connected to it with no blocks and no inulation gaps anywhere  and can run one train one way on the outer loop and one the opposite or reverse direction on the inner loop. {I have added a few feeder wires}.

You will not need isulating gaps on the spurs either UNLESS you intend to store "idle" engines there waiting for a call up to play, then you will want to insulate the spur so as not to draw unnecessary amps  and drag down your DCC system.

-G .

Just my thoughts, ideas, opinions and experiences. Others may vary.

 HO and N Scale.

After long and careful thought, they have convinced me. I have come to the conclusion that they are right. The aliens did it.

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