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After a basement flood and demand for more space for our youngest in 2011, I had to tear down one of the legs in my U shaped layout leaving me with an L.  One leg is 4X12 and the other is 3X10. There's a yard inside the wider leg and a few sidings and town scene inside the other with a straight bumper-to-bumper trolley line. All "toy train" perspective.  I started working on it again last year, but had to stop due to back surgery.  This year, I'm back on it and completed the track work last weekend.  Now onto power.

 

I have number of PW transformers for power:  2 RWs, 2 LWs, and a 1033.  I also have a 175W TW and a new Williams transformer from a new set, but I'm using the last two for the Christmas layout upstairs. I figure on putting the 90W 1033 on the trolley line.  That's the easy part.

 

My question is on the loops.  I'm thinking of putting the 2 RWs in parallel on one loop with the sidings and the 2 LWs in parallel on the other loops with the yard.  I'll run one bus line per transformer (4 total) and then a common neutral (if that's the right term) for each transformer to use.  I've got drops planned every 5-6'.  I recall this working (instead of two bus wires per transformer) if I properly phase the transformers.  Sound right?

 

If that sound right, I've got 4 other questions.

 

1.  Which post (A or U) do I connect to the center rail and which goes to an outer rail?

 

2.  If my 2-transformer-per-loop is right for conventional operation, will this cause a problem for TMCC? My meager electrical skills tell me this increases wattage and amps but not voltage.

 

3.  I recall reading, however, that I should add a diode or something else to protect TMCC engines from potential problems from a PW transformer.  What do I need to do?

 

4.  Lastly, what if I want to add powermasters to allow for Cab-1 control of my conventional engines?  I've used powermasters on our simple Christmas layout, but not with 2 transformers (and presumably two powermasters) connected in parallel to the same loop.  My guess is that powermasters are a no-go with this "power plan" and that I should divide my loops into separate power blocks and go one transformer and one powermaster per block.

 

Any input would be much appreciated.  Thanks!

 

 

 

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While I'm not familiar with your particular Transformers, Putting 2 power sources in parallel is always a BAD idea. One will pull more of the load and overload while the other idles.

Go with one for Sidings, One for Loop and isolate the sidings from the loop by using an insulating pin in the middle rail right after the switch.

 

Adding a Transorb across the power wires and from each power wire to Earth ground will protect engines from spikes. Use bi-directional ones, they cover positive or negative spikes.

"Adding a Transorb across the power wires and from each power wire to Earth ground will protect engines from spikes."

 

DO NOT add anything from the power wires to earth ground.  There should be no electrical connection between the floating outputs of the transformers and earth ground, especially if you are running TMCC/Legacy.  A TVS (Transient Voltage Suppressor) across the transformer output or from center to outer rail is sufficient.

 

OK, thanks for the replies.  I'll dispense with the idea of hooking up two power sources to the same block.  Someone on this forum gave me that idea 3-4 years ago when I indicated I had broken my loops/mainlines into blocks with a single transformer per block.  I was lamenting the voltage drops due to trackside accessories, and the forum responder suggested piggybacking two transformers in parallel.  Live and learn, I guess.

 

Buiding on Andy's idea, I'll go back to my original idea of breaking each loop in half, or 2 separate blocks, and run one transformer to each. Then, I can put a powermaster on each as well.  Requires 2 more powermasters but I like that price tag better than new bricks.

 

I think that answers my questions #2 and #4 above.

 

Any input on whether the A post or U post goes to the center or outer rail?  Or, should I just dig out the old instruction sheets?

 

Lastly, Dale, can you explain more about the TVS you're suggesting?  I'm not familiar with that at all.  I'm a bit of an electrical novice.  Can I get one at, say, Radio Shack?  And, what do you mean "across the transformer output or from center to outer rail"?

You want to buy some 1.5KE36CA Transient Voltage Suppressors.  At Mouser.com they are P/N 511-1.5KE36CA.  I suggest you buy a dozen while you are at it.  Be sure to get the CA type, which is the bipolar type for AC voltages.

 

The TVS is connected in shunt across the output of the transformer - one lead to A, the other to U.  Or you can connect them where your transformer leads connect to the track.  Do not connect the TVS in series with a power lead.

 

The TVS provides a bypass path to clamp any surge voltage spikes that exceed the 36 volt rating of the TVS.  Only the tips above 36 volts flow through the TVS.  This avoids an overvoltage spike from reaching the electronics of the locomotives.

 

If you are using a Powermaster, include a TVS at the transformer's output and another at the Powermaster output.

The only practical, effective way to parallel transformers is with a pair of fixed voltage transformers such as the Lionel Powerhouses when linked to a TPC [Track Power Controller]. With variable voltage transformers it is virtually impossible to accurately match voltages on the two units.

 

TVS??--see photo below including one wired accross ZW A and U posts.

IMG_1764

IMG_1762

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Last edited by Dewey Trogdon

Thanks so much Dale for the description/specs and Dewey for the picture.  My layout is looking like it'll have 6 transformers, 5 with powermasters and 1 purely for conventional operation.  Plus, with 2 transformers and 2 powermasters on the Christmas Tree layout, Dale's estimate of 12 TVS' was 1 shy of what I need.  At $0.55 each for a 10pack, I'll buy an even 20 for about $11.00 and keep a few extras around.  Seems like a VERY small investment to protect hundreds of dollars of train electronics.  THANKS SO MUCH for the tips and tricks.  I wish my Grandpa was still around.....he was an electrical genius in the electro-mechanical era, and I should've picked up more from him while he was alive.

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