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N scale DCC and Blocks

Started by Fish, January 23, 2019, 04:50:08 PM

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I want to double check what I believe I read in the Forum:  I am switching a DC operation to DCC.  I currently have about 9 blocks.  While blocks are not necessary in a DCC operation, there is no physical reason I need to remove the block controls (plastic rail joiners and wiring).  And it may be advantageous to have blocks if a short occurs?  I am going to also throw in a question about turnouts:  remote control turnouts I have currently will work just fine using a separate AC hookup to one of my DC power packs.  Sorry if this question has been asked and answered.  Thanks.


Replace the DC power pack with your choice for DCC system and set all blocks the same and you are ready to test  You will quickly find out if the present track wiring is good enough for DCC and if additional power connections are needed.

You should be able to continue to control the turnouts as is.


Thanks.  What I am still unclear on, is do I need to replace all the wiring from my controller to each block, with a heavier gage wire? I believe I used 22 gage wire.  Should it be replaced with 16or 18 gage wire?  And what does "bus" stand for?


The NMRA says to use 18 gauge wire for HO and smaller scales.

"Bus" is a contraction of the Latin word omnibus.


Wiring in DCC sounds a lot more complicated than DC.  Do you think using the 6 blocks I have on my small 4x6 layout, I will have a good enough power distribution? Or will more feeder wires be necessary?


Personally, I think DCC simplifies the wiring:  Left bus to left rail, right bus to right rail, and reverse loop modules take care of shorts for uninterrupted running.

Which DCC system are you using?

How many locomotives will you be running at once and do they have sound?

How are the feeder wires currently spaced?


Thanks for replying again. I have a small n scale layout, 4x6.  simplified it is inner and outer loops connected by turnouts; I have several sidings off of the inner loop.  I have broken this layout into 9 separate blocks, controlled by several Atlas selectors.  I can currently run 2 trains via a 2 cab set up.  My confusion comes from reading the frequently DCC may require for feeder lines.

I recently purchased an NCE Power Cab system.  At this point I am expecting to run 2, possibly a 3rd loco in time.  Since I am new to DCC my first 2 locos will not have sound.

I don't have evenly spaced feeder wires.  I have  assumed the feeder wires to the 9 blocks serve the purpose of adequately distributing power.  From your previous post I understand that I can keep the blocks but may need to change the gage wire from 22 gage to 18 gage.  Hopefully I have helped in giving a better understanding.


I also use the NCE Power Cab system.

Ideally you should connect a feeder to each rail segment, but my On30 E-Z Track layout has feeders every 3-5 feet along a 90 foot bus, and the Power Cab has no trouble keeping up with that length.

Non-sound locos tend to draw half an amp to a whole amp when active, and the Power Cab can handle up to two amps at a time, so you shouldn't need a booster.

You can remove the blocks to simplify the wiring if you like, or rewire them so they control individual sidings so you can 'turn off' locomotives to save power.


For the size layout you are describing and the number of N scale locos you say you will run, the Power Cab and 22 gauge feeders should work OK.  I have basically done the same thing with Kato sectional track and their feeder wires (24 gauge) without using a bus when I set-up temporary track arrangements.

One thing to be aware of is that this might cause the electrical resistance to the location of a distant short circuit to be too much to allow enough current to flow to cause the Power Cab protective breaker to trip.  So, if that is the case, and you get a short circuit at that distance from the Power Cab, you would get a continuous current of up to somewhat less than 2 amps through that short circuit.  That could eventually cause a lot of heat build-up at the location of the short circuit contact, and that might melt plastic parts and/or damage electronics.

The "quarter test" that you have probably read about in model railroad wiring publications is basically a test to see if that can happen.  By using a quarter (or anything else) to deliberately create short circuits one-at-a-time all around your layout, you can find any places where the track power breaker does not trip.  If you find such a place, and that section of track is fed directly, then you know that you need heavier gauge wire feeding that location.  On the other hand, if the rails at that location are fed only by rail joiners to other sections that are fed directly, then adding a new feeder to that point is probably needed, although you might be able to just solder the linking rail joiners if they are not already soldered and have corroded a bit over time.

One thing to understand about the Power Cab is that it has a lower circuit breaker trip current setting (somewhat less than 2 amps) than most DCC circuit breakers that can be bought separately.  That includes NCE's EB1 breakers.  The PSX Power Shield breakers do have adjustable setpoints that allow current trip values as low as 1.27 amps, so that it would just barely trip before the Power Cab.  but, that really doesn't do much with respect to lowering the threat of an uninterrupted short circuit.

Still, the Power Cab current rating is not as dangerous to your equipment as a 5 amp system. If you are watching your trains, then you can probably notice and clear a fault before anything melts.  On the other hand, if you like to just let trains run in circles while you may be distracted, then you are probably asking for trouble with track sections that will not trip the protective circuit.  The most dangerous locations would be switches ("turnouts") that cannot trip the breaker, because that is where most short circuits are going to occur.


I know the answer to this one.  :) This is what I did:

1. Disconnect all of your DC power packs from the track wiring and don't connect them ever again (unless you wire in a DC/DCC switch, but that should be connected in such a way that when the switch is thrown to DCC it disconnects all DC power packs from the track wiring. You do NOT want to have the DCC and DC power packs hooked up to the track wiring at the same time, bad things will happen).

2. Hook your + wire up to the Cab A connection on your control panel and the - wire to the common rail.

3. Throw all of your block switches to Cab A.

4. Run two trains at a time with a big smile on your face, but be aware, you can now crash them into each other so you will really want to be aware of what your turnouts are doing...just as if you were driving a real train.

If you ever want to get away from using the DC packs for turnout power NCE makes a device called a Snap-It that uses track power to switch the turnout directions, you can wire it in with the Atlas turnout control or operate it from your NCE hammer.


Thanks to everyone who has offered help.  I spoke with a tech person from NCE.  Really helpful person.  I've decide to remove the old block system, and run a bus line with feeders @ every 3 feet.  I will use 14 awg for the bus and 22 gage for the feeders.  One question I still have is:  a preliminary marking of feeder points from the bus line, show that the spacing can be a little more than exactly 3 feet.  I am assuming that +- a few inches will not be significant.  Also if I reuse existing wires for feeder lines can I get away with 20 gage vs 22 gage? Is it dangerous or does it create a potential problem if feeder wires are a mix of 20 or 22 gage? Thanks again for any additional help.


The 3 feet spacing of feeders connection to track came about in part because a HO flex track section is 36 inches long. This eliminates depending on rail joiners to carry DCC power.  Same thing can be accomplished, close enough, by soldering the rail joiners if feeders spacing is more than 3 feet.

Ideal -  Rule of Thumb - feeder is connected to each rail at the center of a track piece so there is equal distance to the rail joiner at each end. This is not always practical so close is good enough.   This center rule of thumb is not applicable to turnout wiring.
The voltage and amps the wire is required to carry determines its gauge and maximum length.  Keep feeders length about 12 inches or less you can mix the use of 20 and 22 AWG wire for feeders just do not use 20 to one rail and 22 AWG wire to the other rail on same track piece.


I'm new to this could some one show me a picture of how your doing your feeder wires on EZ track. Just got started on my n scale ez track layout. I too am wanting to go DCC. Thanks for any help.


There is really a lot of flexibility in how you do feeders.  So, no need to obsess on  getting exactly the same spacing between connections from the bus to the track, or even using the same gauge wire for all connections, or even to the opposite sides of the same connection point.  (I have no idea why Hunt thinks that you should not use 20 gauge to one rain and 22 to the other - unless 22 is too small for the connection, it doesn't make any difference, because the current flows up one and down the other, then reverses if DCC.)

Regarding soldering rail joints.  It is not a bad idea to solder most rail joints.  But, you don't want to solder all rail joints because that removes their ability to let the rails slip in an out as the wooden platform expands and contracts slightly with changes in humidity over the year.  Completely rigid rails lead to kinked straight track and/or curves that are pushed off the roadbed.  Typically, people solder the rail joints on curves to make sure that the curves don't kink at the joints, and leave unsoldered joint on the straight sections between curves at intervals of six feet or so.  If you manage to get a feeder wire attachment to every piece of track, then it is not really necessary to solder any rail joiners from an electrical point of view - but you would still probably want to solder the joints on curves from the mechanical/kinking point of view.


Maletrain thanks again.  My bus wires are running parallel (of course) around the layout. Is there any concern if the bus wires touch or do they need to be separated a certain distance.  I am not planning to  twist them as I saw in some videos.

Bigal232 - search YouTube. There are numerous helpful videos.