using track ground instead of trannie to trannie???

Common is common no matter how it gets connected.  As long as the transformers are in phase the common outside rail of the track can act as the common buss for both.

That is true about using the common rail to connect 2 transformers but if it is a long distance the power loss has to be considered, because the track connections will cause some resistance and distance of track might cause some resistance as well.

Most track usually has the capacity of a # 16 gauge wire.

It would be best to just go ahead and use a # 14 gauge wire to connect the 2 transformers.

The other thing to consider are both transformers on the same 120 volt plane from the circuit breaker box? Turn off power to the outlets in the room and see if all outlets lose power, if not you may have an issue on the 120 volt side.

Lee Fritz

I agree with Lee, track joints are a wild card here, and the wire between commons removes any doubt.

Since the primary windings of the transformers are totally isolated from the secondary windings, the only "problem" of the opposite phases of the 120V outlets would be a phasing issue.  Reverse one plug and that goes away.  Obviously, you'll have to actually check the phasing of the transformers to determine if that is the case.

Well if your track joints are that bad I suspect using it as a common would be the least of your worries.  But whatever.  Having done it in the past, I've had zero issues.

For a 5 to 8 foot run it might be decent to do that.

But like I mentioned before "check your wall outlets" or you may fry something! Go to the breaker box and shut off power for the wall outlets in the room, if they all go off you are in good shape, otherwise you may have a voltage issue on the 120 side.

I was almost a journeyman in electrical work, so I have seen some wild wiring practicess in both residential & commercial work, that's why I say check your 120 volts outlets if using 2 different outlets even in the same room!

Lee Fritz

Marty, 

The last house I lvied in that we owned was wired sort of strange, the guy who built the house wired it, I didn't touch it. There was a group of 2 duplex outlets back to back in one room and the one side was wired from leg one of the circuit box and the other side of the outlet group was wired from leg two, so if I was to use two different duplex outlets to phase a transformer and not check my input voltages I may end up with close to 45 volts on my layout instead of 23 volts. The voltage between the two duplex outlets was 250 volts AC.

Lee Fritz

Lee, I don't find that particularly unusual. In order to run my layout and lighting, I installed a 4 gang box with 4 different 20A circuits, 2 on each phase. The opposing phases are wired with the typical common neutral with a 3 conductor 12 gauge romex going back to the panel.

Back to Walt's question: I would say just bite the bullet and use a wire. If it's that much of a hardship, let me know the length you need and I'll send you a chunk of 12 gauge stranded that will solve all your problems. Personally, I have six, 20 amp supplies, 3 each on side of the room, about 20' apart. I ran 2, 12 gauge common wires between them to handle any imbalance.

Thanks guys.  A couple of comments.

I did check that the 2 trannies are in phase even though they are using separate wall outlets.  That was my first action.

I set up a test.  I laid down some track between the 2 trannies with a switch at the one end.  I powered the track with the ZW.  I put a lockon near the MRC and connected the track ground to the fixed ground on the MRC.  Then I connected the switch + to the MRC fixed +.  I powered up the ZW, turned on the MRC, and it all seemed to work.

When I said WAY apart I wonder if I left a bad impression and that's why some comments came in about track joints.  The trannies are 15' apart and I will be using 36" straights in the area between them, creating only 3 or 4 track joints. 

Thank you Marty for saying that you've successfully done it.  Now I KNOW for sure that it will work. 

If I land up with a problem I can always still run a wire between the 2 trannies.  It's just that with a floor layout and having as many wires as I already have running everywhere, I try to reduce/eliminate where I can.

Since no one brought up any issue other than phasing (which I already checked) and the track joints, I feel it's safe.  I was concerned that there might be other hidden reasons why it would be a bad idea but none has surfaced - at least not yet.

As always, thanks

Walt