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I am looking for informed opinions.  Here are the pertinent facts:

  • 8 power districts 18 VAC wired as buses with 12 AWG wire pairs (red & black); all districts have isolated center rails where they meet other power districts.  No commons are connected, although 1 outside rail is reserved for common.  The other is reserved for insulated rail activation purposes where applicable.
  • 3 switch buses 15 VAC wired with 16 AWG wire pair (red, black and white for the DZ-2001 Data Wire Driver).  Each switch bus is powered by a separate K-Line 120F PowerChief transformer;  no commons are connected.

IMG_3300

Here are the questions:

  1. Should I tie all the power district commons together?
  2. Should I tie all the switch bus commons together?
  3. Should I tie all of the commons (power district and switch bus) together?

Thanks!

George

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George

1. yes  2. yes  3. yes    Technically that's the safest and most productive convention.

If you have #10 stranded wire you run that all around the layout and tap off that for all commons depending on your load calculations.

mannyrock, the Common is the outside rails wire, neutral, white wire in house wiring, black wire, negative in DC, etc.

(My website is temporarily having technical difficulties.)

Last edited by Susan Deats
@Oman posted:

In posts where the poster is experiencing TMCC/Legacy running issues, it has been stated that both outside rails should be connected to common.

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Common is a good term for our AC powered track. It's not connected to earth ground, unless you install TMCC or Legacy.

Keith, please don't offer any more faulty TMCC advice!

It is certainly not necessary to connect both outside rails to common with TMCC.  Many of us have one outside rail wired to common and the other insulated and segmented for use as signal detection blocks.  TMCC works great.

Also NEVER, NEVER, NEVER connect AC common from your transformer to earth ground unless you want to completely kill the TMCC signal.

And George, track common has to be connected to switch machine and signal common for occupancy detection to work with DZ equipment.  Like AlanHN says, make sure the transformers are in phase with each other.

@Bob posted:

Keith, please don't offer any more faulty TMCC advice!

It is certainly not necessary to connect both outside rails to common with TMCC.  Many of us have one outside rail wired to common and the other insulated and segmented for use as signal detection blocks.  TMCC works great.

Also NEVER, NEVER, NEVER connect AC common from your transformer to earth ground unless you want to completely kill the TMCC signal.

And George, track common has to be connected to switch machine and signal common for occupancy detection to work with DZ equipment.  Like AlanHN says, make sure the transformers are in phase with each other.

Do you disagree with the following? I copied this from http://www.trainfacts.com/trainfacts/?p=298

The power source is a special “wallwart” AC transformer with a 3-pin molded AC power plug. Unlike most wallwarts, the Lionel unit connects one leg of the low-voltage AC outlet to the “U-ground” safety grounding pin on the AC plug. THIS CONNECTION IS NECESSARY FOR THE TMCC SIGNAL TO PROPOGATE PROPERLY!! This link from the Base to the house wiring is an essential part of the antenna system for TMCC.

@Oman posted:

Do you disagree with the following? I copied this from http://www.trainfacts.com/trainfacts/?p=298

The power source is a special “wallwart” AC transformer with a 3-pin molded AC power plug. Unlike most wallwarts, the Lionel unit connects one leg of the low-voltage AC outlet to the “U-ground” safety grounding pin on the AC plug. THIS CONNECTION IS NECESSARY FOR THE TMCC SIGNAL TO PROPOGATE PROPERLY!! This link from the Base to the house wiring is an essential part of the antenna system for TMCC.

This is absolutely correct.  The TMCC base is a radio transmitter.  It broadcasts a 455 kilohertz radio signal using two halves of an antenna.  The outside rail is one half (transmitted by the wire attached to the lug on the command base) and the ground wire in a 3-wire house electrical system is the other half (transmitted by the U-ground pin on the command base power plug).

Your post above mine said, "Common is a good term for our AC powered track. It's not connected to earth ground, unless you install TMCC or Legacy."  Our AC track common is NOT connected to earth ground.  The track and the earth ground are the two legs of the antenna for the TMCC signal.  Connecting these two legs together would prevent them from broadcasting the signal.

@Bob posted:

This is absolutely correct.  The TMCC base is a radio transmitter.  It broadcasts a 455 kilohertz radio signal using two halves of an antenna.  The outside rail is one half (transmitted by the wire attached to the lug on the command base) and the ground wire in a 3-wire house electrical system is the other half (transmitted by the U-ground pin on the command base power plug).

Your post above mine said, "Common is a good term for our AC powered track. It's not connected to earth ground, unless you install TMCC or Legacy."  Our AC track common is NOT connected to earth ground.  The track and the earth ground are the two legs of the antenna for the TMCC signal.  Connecting these two legs together would prevent them from broadcasting the signal.

I do not want to belabor a point but AC is AC regardless of the voltage.  There is in electrical theory a need for the difference in terms between "Neutral" and "Common".  If there is no difference Between DC and AC, try running one engine of one kind on the others Electric.  It is Neutral because the current goes plus and minus from the Neutral reference point and DC depending on your wiring is either always on the Plus side or Minus side of Common.  Just because Our venerable Postwar ZW's have "COMMON" emblazoned on the Back Above the "U" posts does not make it Right.  Interesting the Prewar Z's do not have "COMMON" above the "U" post.  I have not looked at the various versions of the Modern ZW's.

My Final $.02.

@Bob posted:
Also NEVER, NEVER, NEVER connect AC common from your transformer to earth ground unless you want to completely kill the TMCC signal.
@Bob posted:

That is not a direct connection, but instead, a capacitive coupling in the TMCC base. You can see in the schematics that there is no direct connection between the house ground and the layout through the "U" output post.

@AmFlyer posted:

The ZW-L has COMMON emblazoned above the 4 U terminals. Even as a degreed EE I have decided to accept modern usage of common to be anything that is wired together.

I know I stated my final $.02, but look in your electrical distribution box. The neutrals are tied together and unbeknownst to most the gnds are tied together and then the neutrals and Gnds are tied together.

Jim, I am aware of house wiring practices and codes. I just give up on trying to correct the semantics of people who use the terms incorrectly. What does concern me is train people who insist on connecting what is called the Common terminal on the transformer secondary to true ground. If the transformer were designed to be safely operated that way the manufacturer would have submitted it for UL testing and certification with that connection made internally.

I never answered the original question. All my track power is supplied by two ZW-L's so the U terminals are all connected together. I did run two wires from each output Channel around the layout, wire is cheap. Plus as a 2 railer I have 5 reverse loop controllers to power and all Power District feeds and reverse loops need a .1microfarad coupling capacitor across the connections to put the Legacy signal on both rails. Its just easier to run a separate pair of color coded and tagged wires for each Channel. I also have six other power supplies for accessories, frog polarity relay coils, lighting, LCS etc. Some are DC, some are AC, all are different voltages. Each of these supplies has two independent wires to their loads, no shared cabling.

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