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With Fall upon us, I can finally get back to my basement layout. Long story, but this is a re-build of a former layout in the same spot but with a bit more real estate and the incorporation of DCS for the first time for me (I connected a TIU to our Christmas layout in 2019 to learn more about DCS).  Two questions as I forge ahead.

FIrst, my two concentric U-shaped loops will be roughly 75' - 100' of track, and I plan to use the "Star Wiring" method.  What's a good rule of thumb for the length of each section running back to a terminal block?  25' gives me 3-4 segments, but 10' gives me 7-10 segments with a whole lot more wire consumption.

Second question, what's a good rule of thumb for power required to run TWO trains, say 8-10 cars long.  As I recall from my old layout, a single postwar LW wasn't sufficient for two trains. Back-of-the-envelope math says 100-120W / 18V gives me 5-7 amps among two trains.  Thinking that's barely enough for a non-lighted freight train let along a string of lighted passenger cars (haven't made the jump to LEDs yet). Thinking 3-5W along per passenger car.

Seems like my options are, as others have advised me before on prior posts,  to invest in some 180W bricks from Lionel or breaking each of my loops into two separate power blocks and use four transformers (since I have a plethora of 90 - 120W transformers). The latter, of course, means the two loops consumes all four TIU channels.

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Seeing no one else replied yet.... ???

the track is a function of length, and the number of track joints. If it's solid rail and soldered, I believe you can have a big amount on each TIU channel. I would guess 150' per channel max? Problem is the wire, track, joints, etc., change what is possible. So the number of pieces of track or total length per terminal block is tuff for me to answer. I would throw a guess there using ideal stranded feed #14 (or #12?) wire to the block, 25' per segment with 4 segments should be fine.

I run two segments at around 50'+ (maybe 70'?) rail each? and I'm 2 rail! So again, 4 at 25 should be no problem.

I like to figure 2.5 to 3 amps per engine and the cars depend on LED or bulb?

I use the Lionel PH180s on each half of my mains, so I have 4 of them now.

I have a Z4000 that runs the same length of single 3 rail track on a single handle.

If that helps or I can help you further with any more guesses, just ask.

This is from The DCS Companion (second edition):

  • Limit the number of track blocks from a single TIU channel to no more than 12-15.
  • Limit track blocks to no more than 11 or 12 track sections where sections (long or short) all count. If sections are short, consider soldering connections between sections to make longer ones.
  • Track blocks should not exceed 100 feet in length.
  • Use 16 gauge or higher stranded wire (for wire runs less than 50 feet).
  • Use home run or star wiring.

Power requirements depends on what you are running.  John Will told me the following: I suspect with dual can motored diesels with smoke and six incandescent passenger cars, you would be knocking on the door to kicking a 3A breaker. Usually, a dual diesel will be pulling around an amp or a bit more with smoke with a light load, and incandescent passenger cars are in the .3 to .4 amp range each.

My layout is U shaped with 4 loops.  Each loop is around 100 - 120 feet in length.  Each loop is fed by one TIU channel.  I use two PW ZWs for power with each TIU channel fed from a ZW terminal with external fuses and breakers.  Each loop has four blocks with power feeds in a star pattern.  I use mostly Gargrave flex (37” long) track.  DSC signal strength is good throughout.

The one time I tripped a 4 amp breaker under load, I had a Williams GG1, 2 unlighted baggage cars, 5 LED lighted passenger cars and 5 incandescent lighted passenger cars.

Great input from both of you, thanks

Bob, I should've opened my DCS Companion book. I guess I just got lazy sitting here by my computer.

Question for Bob @Lehigh74.  When you say you're using 2 PW ZWs, that's 8 outputs from transformers. I'm pretty sure you can't run more than 1 to a TIU Input, so can I assume you're using 2 outputs per ZW for other purposes (accessories, etc.)?

I have several PW transformers (bought fast-blow fuses and TVS diodes for this layout), including a ZW, 1 modern Williams transformer from a set, and a 1 modern Lionel BW, also from a set.  I run traditional, not scale.

I'd really like to reserve my ZW for our Christmas layout since I can power 2-3 loops and some accessories with a small footprint. With the permanent basement layout, I have space to accommodate all the single throttle/output transformers and plan to connect 1 transformer per TIU input channel. Probably will use my 2 LWs, modern Williams, and modern BW to power the TIU (and 2 loops and yard) and then use my 2 1033s and 2 TWs for accessories and switches.

Thinking, based on your design and comments , I should use 2 TIU channels per loop on my main level since my input will only be 100-120W.  I know how to phase transformers.

That's not a problem until I consider my upper level with intentions of 1, maybe 2 loops. I might leave it as TMCC only (with powermasters for conventional) OR I might just add a 2nd TIU.  I realize the 2nd TIU is a more expensive option than adding modern Lionel 180W bricks, but I don't see having a 2nd TIU as a back-up as a waste given their potential demise.

Make sense?

I use two outputs (the A and D terminals) from each ZW to power track loops through the TIU.  The B and C terminals power accessories.  Previously, I used just one ZW with each terminal going to a track loop via the TIU, but there were times (when I was running 8 trains) that it got hot, so I bought the second ZW.

The LWs (125W), TWs (175W) or 1033s (90W) would all be good for track power.  I don’t know much about the BW or Williams transformers.  If you are running MTH locomotives, they might be a problem.  I don’t see them on the MTH transformer compatibility chart.  I have heard the CW (also not on the MTH chart) does not play well with MTH locomotives.

I don’t see a need to have 2 TIU channels for each 75-100 foot loop.  You will have two loops on level one and will have two on level two if I got it right.  One TIU should handle that (one TIU channel for each loop).  But getting a second TIU is not a bad idea.  I use one TIU for my layout and I have one spare that I sometimes use on a test track.

Last edited by Lehigh74
@Lehigh74 posted:

The LWs (125W), TWs (175W) or 1033s (90W) would all be good for track power.  I don’t know much about the BW or Williams transformers.  If you are running MTH locomotives, they might be a problem.  I don’t see them on the MTH transformer compatibility chart.  I have heard the CW (also not on the MTH chart) does not play well with MTH locomotives.


Yes, I do have MTH engines (all new to me....I fell in love with my brother-in-law's MTH's last Christmas and decided to add some Rail Kings to my stable).  I do recall reading that MTH engines prefer a pure sine wave, and it's possible the BW and Williams have chopped.  Either way, that's an easy switch for me.  I also have 2 RWs right now in service in a bedroom around-the-ceiling setup with only TMCC. I could put the modern ones there and go with LWs, RWs, or TWs in the basement.

My biggest reason for putting 2 transformers and, therefore, 2 channels per loop is to provide enough power for 2 trains. It's more about the power than the TIU.  I envision a single LW (my highest-output PW transformer) with, maybe, 100W output, getting overly taxed by 2 trains. Guess I could try it, but to me the math doesn't add up, especially not with passenger cars.

Last edited by raising4daughters

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