#### Parallel track power busses

Greetings,
I hope this finds each of you staying healthy.

I have a power district that is just over 40 feet long. This power district is divided into five sub-districts protected by four circuit breakers and an auto-reverser. For convenience I want to place the booster and a control panel with the AR and circuit breakers at the middle of the district. If I do this there will be three track busses that run in parallel to the right of the panel before they get to the protected sub-districts. The alternative would be to run a single track bus to the right splitting it and inserting a breaker at each sub-district. This alternative, of course, means that the breakers are not conveniently located at the control panel. What are the potential negatives associated with my preferred arrangement?

As always, be in good health and do good work.

-Michael Boyle

The miracle is this: The more we share the more we have.
Leonard Nimoy

Steve Haas

Michael Boyle inquires,

“I have a power district that is just over 40 feet long. This power district is divided into five sub-districts protected by four circuit breakers and an auto-reverser. For convenience I want to place the booster and a control panel with the AR and circuit breakers at the middle of the district. If I do this there will be three track busses that run in parallel to the right of the panel before they get to the protected sub-districts. The alternative would be to run a single track bus to the right splitting it and inserting a breaker at each sub-district. This alternative, of course, means that the breakers are not conveniently located at the control panel. What are the potential negatives associated with my preferred arrangement?”

Functionally they are both fine.

There are a couple of things to consider:

1. If the centralized approach is used, you’ll have three pairs of wires extending to the right.  Assuming more or less equal spacing of the three districts you will use 1x + 2x + 3x = 6x wire to reach the distribution point for each of those sub districts.
2. If a single bus extends from the booster to the right, you will use only 3x of wire.  That also leads to cleaner wiring underneath the layout.
3. What is the benefit to you of the centralized location? How, in your eyes (after all, you’ll be maintaining this) does centralized vs. distributed design work to your advantage?  What do you see as the advantage of having all the components centrally located?  I’m curious, as this topic doesn’t come up much.

Not arguing here, just trying to ask questions that will help you find the best answer for you and your layout.

Best regards,

Steve

Steve Haas

Snoqualmie, WA

Tom O'Hara

The second method wins. As Steve is suggesting, there is really no need to have the breakers centrally located.
...Tom

On Thu, Dec 30, 2021 at 10:21 PM Steve Haas <Goatfisher2@...> wrote:

Michael Boyle inquires,

“I have a power district that is just over 40 feet long. This power district is divided into five sub-districts protected by four circuit breakers and an auto-reverser. For convenience I want to place the booster and a control panel with the AR and circuit breakers at the middle of the district. If I do this there will be three track busses that run in parallel to the right of the panel before they get to the protected sub-districts. The alternative would be to run a single track bus to the right splitting it and inserting a breaker at each sub-district. This alternative, of course, means that the breakers are not conveniently located at the control panel. What are the potential negatives associated with my preferred arrangement?”

Functionally they are both fine.

There are a couple of things to consider:

1. If the centralized approach is used, you’ll have three pairs of wires extending to the right.  Assuming more or less equal spacing of the three districts you will use 1x + 2x + 3x = 6x wire to reach the distribution point for each of those sub districts.
2. If a single bus extends from the booster to the right, you will use only 3x of wire.  That also leads to cleaner wiring underneath the layout.
3. What is the benefit to you of the centralized location? How, in your eyes (after all, you’ll be maintaining this) does centralized vs. distributed design work to your advantage?  What do you see as the advantage of having all the components centrally located?  I’m curious, as this topic doesn’t come up much.

Not arguing here, just trying to ask questions that will help you find the best answer for you and your layout.

Best regards,

Steve

Steve Haas

Snoqualmie, WA

Steve Hubbard

CBs are not a device that needs to have easy access to if ever.  Whay add additional wiring and work when it's not necessary.

Don Weigt

There are some advantages to having things centrally located. And, what works best for you will depend somewhat on your hardware choices. I prefer having most of my electronics in a few easy to reach locations, and minimal wiring distributed under my layout.

Three parallel buses use more wire, but the loads are less and the voltage drops for the same gauge wire will be reduced. The current in the nearest section of a single bus would on average be three times what's in each of three parallel ones, and the voltage drop for the same wire size also tripled. Larger layouts benefit more from saving multiple buses, but the longer runs mean the wires need to be heavier gauge, and then multiple summed currents mean it needs to be even heavier. What is the maximum voltage drop you will accept in your track power? What's the maximum current your system would have in that single bus, and how long will it be? Look up the wire resistance, work out the total resistance out and back and the resulting voltage drop at the maximum design operating current. You may be shocked at the wire gauge you should use.

If there's anything that needs to be sensed and reported, it's easier to do that in a central location than bringing back signal wires from all over the layout. And, "signal" type lower currents and voltages are more easily corrupted by higher power nearby circuits, so it's a very good idea to separate signal wiring from track power wiring, not route them in the same cable or even two parallel cables a few inches apart.

My track wiring was begun 40 years ago, for DC power and a computer interface. My layout measured 10 x 20 at the time. It has since grown a foot or two in each direction. But, it's still "medium size", although a central aisle means wires run about 30 feet in two opposite directions to the farthest points. The bulk of my railroad's electronics are centralized near the main control panel. I didn't want to have a bunch of complex electronics scattered all over under the layout.

All my blocks have current detection, on cards that also have relays for switching track power. This is still needed for detection with DCC, and the relays are handy for for locating and isolating short circuits. My cards have the relays and detectors for four blocks on each card, and the cards are mounted side by side in a rack. The railroad control computer is right below them, all connected through a 50 conductor ribbon cable that acts as the backplane for the cards.

It works for me. If the layout were much larger, I'd probably have multiple nodes like this one, and have them communicating wirelessly now, or over ethernet cabling. In summary, I'd say it's a system design decision. Not many of us probably think about our railroads' wiring and electronics that way, but it's a good analysis tool..

Don Weigt
Connecticut

--
Don Weigt
Connecticut

Thanks to each of you for your help.
As the layout host (during ops sessions), having a centralized, easily visible control panel will help direct me to where the "problem" is. (Each breaker has a light that flashes when tripped.) An added benefit (as Don points out) is the decrease in voltage drop. For the three track buss runs to the right, using 14 AWG will keep the voltage drop acceptable. If I use a single run that splits the first stretch of the run will need to be at least 12 AWG.

As always, be in good health and do good work.

-Michael

The miracle is this: The more we share the more we have.
Leonard Nimoy

Steve Hubbard

The AR's have a buzzer option that you can solder n the board.  This would let you know it tripped.  I used #12 to 2 of my AR's and then branched off with #14 after the breakers.   I dought the #12 was necessary however I had it in stock.  I found the cheapest wire to buy is your standard Romex.  I strip it and then twist the conductors together with a drill.  Also gave me bare copper wire to ground the 3 NCE Power pros (2 in Booster Mode) together.  Works quite well for me.

Dale Gloer

You didn't say which circuit breakers you are using so maybe this suggestion isn't practical, but here's what I have done on my personal
layout and our club layout.  Both use multiple Digitrax PM42s.  I have added remote indicators to the PM42s (Digitrax Knowledge Base has an article on how to do it easily).  In the club case there is a specific display panel with all the remote indicator LEDs suitably labelled.  On my personal layout the PM42s are widely separate so I mount the remote indicators in the Facia near each PM42 location.

Dale Gloer

PS.  I use JMRI on both layouts so have set up a routine that sounds a siren when one of the sections is shorted.  Makes the operator look at the display instead of throwing up their hands and saying "why is my train stopped?" :-)

JimD - G&J--BKRR

Great conversation and similar to one I had on the NCE group recently. I'm not an expert nor engineer (though an RPI graduate!)but am in the process of addressing this identical issue by doing the following:
1. 5amp NCE Power-Pro system on a perfectly U- shaped 24" wide 60ft long shelf layout. The command center is dead center 30' ft from each end of this point to point RR.
2. This "main" track bus comes directly out of the booster where it immediately divides into two with one "leg" running down the back of the "right and left" shelves. This "back bone" is 10 AWG twisted wire pair.
3. The layout is divided into 5 districts, A terminal yard (part visible part staging) at each end with 3  towns in the middle.
4. At each district I have two (2-wire) drops  (4 suitcase connectors). One is 12 awg and goes to a PSX circuit breaker then out to the track feeders. One is 14awg and acts as an "auxiliary track bus" that feeds my NCE switch-8's. (BTW I provide the Switch-8's with 12 v DC to take the load off the track bus)
5. So far, as I build out the layout my tests show this works well. I have not tested the voltage yet (I have Tony's rrmeter) but the loco response seems superb.
6. My plan seems to combine the best of many ideas (I'm biased and will shortly be proven wrong by the smart folks here!).
a. I have every district's track, circuit breaker protected for safety,  and no other district is affected by a local short.
b. I have a strong "backbone" track bus using the LEAST amount of wiring (I'm aware 2*60'=120' of 10 awg wiring isnt free but...and running a stable 12 v DC bus isn't free either but it is very easy to do .
c. I have auxillary "track" buses in each district that WILL NOT crash with a short circuit, so a turnout can be thrown and more importantly, programming will less likely be corrupted/lost.
d. As mentioned above, I see no reason to centralize Circuit breakers. I went ahead and soldered little buzzers (soft sound NOT annoying!) into the PSX exactly as the manual suggests. I will hear where the short occurred! Perhaps humorously, if there are 5 operators, one at each district, everyone will know who has the short and adds an incentive to my guests and I to "pay attention" going through that turnout!
Happy New Year to my friends in a wonderful hobby!
Jim

Hi Dale,
Just checked and I think this (connecting remote indicators) will work very nicely. An excellent alternative.
However, if I use the second method (run a 10AWG track buss to the right then split to the breakers) I'll need to find a source for 20' of yellow and brown stranded 10AWG. This is because the colors for this Power Bus are yellow and brown.
The big box stores won't be of help but perhaps the local electrical supply will have what I need.
Thanks,
Michael

Don Weigt

I've found auto parts stores are good sources of heavy stranded wire, and the larger currents and lower voltages of automobile wiring make their wiring supplies well suited to our similar model railroad requirements.

Don Weigt
Connecticut, USA

--
Don Weigt
Connecticut

Steve Hubbard

Hmmm!  #10 wire is way overkill, harder to work with and expensive.   Just sayin.

Steve,
You are probably correct. At the 10-12 level I find little difference in the workability and there is a slight decrease in voltage drop. I'll just need to see what the local electrical supply has.
Thanks,
Michael

Bill Wilken

I've been replace 12 gauge with 14 as I rewire to support signaling on a 4-track main, but have had no problems.  Indeed, in one section, I've even been able to get away with exceeding the maximum recommended buss length with no problems.

On 1/1/22 8:22 AM, Steve Hubbard via groups.io wrote:
Hmmm!  #10 wire is way overkill, harder to work with and expensive.   Just sayin.

Greg Harter

I'm either lucky, or it doesn't matter.......

After 20+ years, I am replacing my EB3 circuit breakers on my HO layout.  I have an NCE ProCab system.

I replaced them with six PSX circuit breakers.  I've wired it (hopefully) correctly.  And have run a loco through three of the blocks powered by the PSX units, with no problem.

I know polarity doesn't matter with AC circuits, and there's nothing but AC circuits on the six blocks........but.........when a loco goes from one block to another, and the AC rails are reversed in the new block, does it matter?

Wish I knew more about this stuff, but at 80, I'm still learning!

Greg Harter

Tim

On Wed, Jan 5, 2022 at 05:30 PM, Greg Harter wrote:
I know polarity doesn't matter with AC circuits, and there's nothing but AC circuits on the six blocks........but.........when a loco goes from one block to another, and the AC rails are reversed in the new block, does it matter?
Hi Greg. Yes, it matters. If the rails are connected backwards in one power district compared to the next it will create a short circuit when the wheels cross the gap. Even with AC, a short circuit is still a short circuit.

If your trains run around the layout with no hesitation and you're not tripping the PSXes then everything's OK.

Tim Rumph
Lancaster, SC

Duff & Polly M

Assuming I am understanding correctly, polarity does matter with AC, but not the same way for train operation.
Let's consider two of the  six blocks for simplicity, the train rinning from left to right, and crossing from one block to the other.  The rails in each block are marked + and -.  Yes, for AC, they alternate, but at any instance of time, the the labels are as shown.

In this first example, as the wheels cross the gap, they connect + to +, and - to -.  No problem.

+ ____________________________________  ________________________________ +
- _____________________________________ _________________________________ -

In this second example, the wheels connect + to -, and - to +.  This is a short circuit.  And is what happens with reversing loops.

+ _____________________________________ ________________________________ -
- ______________________________________ ________________________________ +

If each block has its own auto reverse, things will correct themselves, and it may not matter.  However, if there are no autoreversers, a short will be detected.

This is how I understand it, given my limited experience with DCC.

whmvd

Duff or Polly,

That's almost correct as far as it goes, except for the statement about auto-reversing. Only ONE of the two blocks would need one. In fact, auto-reversers that are adjacent will not work happily together unless there is a piece*() of track between them that does not autoreverse.

Wouter
(*) volumes have been penned about how long a "piece" is, often when the subject is string. This is not the place for that discussion.

On Thu, 6 Jan 2022 at 15:04, Duff & Polly M via groups.io <dpmeans=yahoo.com@groups.io> wrote:
Assuming I am understanding correctly, polarity does matter with AC, but not the same way for train operation.
Let's consider two of the  six blocks for simplicity, the train rinning from left to right, and crossing from one block to the other.  The rails in each block are marked + and -.  Yes, for AC, they alternate, but at any instance of time, the the labels are as shown.

In this first example, as the wheels cross the gap, they connect + to +, and - to -.  No problem.

+ ____________________________________  ________________________________ +
- _____________________________________ _________________________________ -

In this second example, the wheels connect + to -, and - to +.  This is a short circuit.  And is what happens with reversing loops.

+ _____________________________________ ________________________________ -
- ______________________________________ ________________________________ +

If each block has its own auto reverse, things will correct themselves, and it may not matter.  However, if there are no autoreversers, a short will be detected.

This is how I understand it, given my limited experience with DCC.

Duff & Polly M

Yes.  Thank you for the correction and clarification.

Jim Zarnick

Welcome to DCC.   You want to rails to match and not be reversed, otherwise everytime an engine truck crosses the gap it will create a short back to the main power supply.

Use a voltmeter set to AC, to make certain both sides of the gap are the same polarity…

From: w4dccqa@groups.io <w4dccqa@groups.io> on behalf of Greg Harter <greg1462@...>
Sent: Wednesday, January 5, 2022 5:30 PM
To: w4dccqa@groups.io
Subject: Re: [w4dccqa] Parallel track power busses

I'm either lucky, or it doesn't matter.......

After 20+ years, I am replacing my EB3 circuit breakers on my HO layout.  I have an NCE ProCab system.

I replaced them with six PSX circuit breakers.  I've wired it (hopefully) correctly.  And have run a loco through three of the blocks powered by the PSX units, with no problem.

I know polarity doesn't matter with AC circuits, and there's nothing but AC circuits on the six blocks........but.........when a loco goes from one block to another, and the AC rails are reversed in the new block, does it matter?

Wish I knew more about this stuff, but at 80, I'm still learning!

Greg Harter

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