Are your commons wired together?

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

Assuming all transformers are phased then YES.

UNLESS for some reason you want to isolate a run then it doesn't matter so long as there is no metal contact between those lines..

Er, . . what'sa common?  Is it the so-called neutral wire connected to the outside rail?

If so, I have 6 power districts, and all of mine are wired together at a terminal block near the transformer.

Mannyrock

Your commons are already wired together by default. They are tied together internally in the transformers and via the outside rails.

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.)

@Mannyrock posted:

Er, . . what'sa common?  Is it the so-called neutral wire connected to the outside rail?

If so, I have 6 power districts, and all of mine are wired together at a terminal block near the transformer.

Mannyrock

Since we are talking AC, The correct terms are Neutral and Hot.  Common is the term used for the DC guys.

Tomato tamato, Potato patato. IMO neutral refers to house wiring where the neutral is connected to earth ground. Common is a good term for our AC powered track. It's not connected to earth ground, unless you install TMCC or Legacy. ⇐text removed

@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.

**************

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.

@Rich Melvin posted:

Your commons are already wired together by default. They are tied together internally in the transformers and via the outside rails.

Thanks Rich!  That thought actually had occurred to me a little while after I posted the question.

George

@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.

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.

@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:

...I copied this from http://www.trainfacts.com/trainfacts/?p=298

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.

@AmFlyer posted:

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.

Well, there's a very specific reason they DON'T have the transformer common connected to the earth ground (3rd prong)!  TMCC would cease to function if they did.

@Oman posted:

It's not connected to earth ground, unless you install TMCC or Legacy. ⇐text removed

Sorry people. If I hadn't included "unless you install TMCC or Legacy", then this debate most likely would not have taken off. I corrected my original post.

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.

That ship has sailed Keith, we're going to keep beating you up!

Just kidding.