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I'm done with the benchwork for my new basement layout and am toying with adding a 2nd TIU (it's either that or replace my plethora of lower wattage transformers). If I were to add a 2nd TIU, how does that work with TMCC? Would I need a second command base to connect to the 2nd TIU? 

Also, with DCS remotes becoming as hard to find as plutonium, I've resigned myself to adding a WIU and tablet/smartphone should my one DCS remote fail. How does a WIU work if running two TIUs?

Not an immediate crisis, but thinking in terms of expansion options and obsolescence.

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Sure is a nice feeling having your bench work done.  

It would help if you could give us a idea of how much track you're planing on laying down and what transformers are being used. Good news on the TMCC command base, only one is needed assuming you tie all of the outside rails together. When it comes to the WIU you will need one for each TIU you will be using.

Thanks. Yes, I was happy to finish the benchwork right before the weather started turning nice, so I haven't done anything since then. Looking forward to laying track.

Two U-shaped mainlines connected by switches, each totaling about 75-80' of track.  Outer loop has 54" and 72" curves and inner as 42" and 54". Using good ol' O27 tubular track. Throw in a yard inside the inner loop with 3-4 sidings at 10-12' length. Then an elevated level NOT connected to those with at least one, maybe two (still working on that) which would be about 40' of track. 

I plan to run two trains per mainline on the main level, one train per loop on the elevated.

I was originally planning to dedicate the TIU to the main level and leave the elevated tracks to conventional and TMCC but now I'm thinking about running DCS on the elevated level. For me, I THINK that might mean another TIU.

My challenge, self-imposed, is that I'm unwilling to replace my old PW transformers. Several have suggested I invest in a new ZW with 180W tricks or Z4000, but my PW transformers (a lot of other items) are family heirlooms from my father and grandfather. I know it's impractical, but it's a personal thing. I have all the additional fast-blow fuses and TVSs to protect the electronics using the PW transformers, but I realize using the PW transformers limits me to 100-125W per TIU channel and I'm not confident that I could run two trains on 75-80' of track using, say, an LW or TW transformer.

I THINK I can make that work on the lower level using two TIU channels for the outer loop and two for the inner loop and yard. Of course, the conventionals could only run on the loop with the variable outputs.

With all that considered, I THINK I'd need a second TIU for the elevated level, but if that means a 2nd WIU, too, this is getting a bit pricey.  


Last edited by raising4daughters

I run 2 TIU’s with Wi-Fi and remotes as well as Legacy with remotes and Lionel’s Wi-Fi. While a power supply for each port of the TIU sounds like the way to go. I think it’s overkill in the modern age of can motors and LED lighting in cars. One Lionel 180 brick can power up multiple TIU channels. Depends a lot on what your running as far as a draw. If you run smoke. That will factor in. A yard switcher may draw around 2 amps. Most of my mainline trains draw maybe just a bit more. I run smoke only briefly for guests.  

 I think just running bricks works fine in a command only layout. No need to spend extra money on handles.  I have one power supply on a 22 x 48 space. Not an abundance of trackage. But a good long mainline run. It’s a Big Max put out by Davis Electronics years ago. 2 12 amp supply’s in one unit. Haven’t touched the voltage knobs or buttons in years. It powers 7 channels on my TIU’s. I use  PSX breakers on the channels. A few channels share the same breaker.

If I understand your math you'll have a little north of 200' of track total. It's been some time sense I've had to look at Barry's DCS book for wiring a layout as my track was finished a few years ago. But memory serves me correctly he stated one TIU could handle 1000' of track.   As far as transformers are concerned, start with what you have. You'll know soon enough if they need to be upgraded.  

Thanks guys. My rough math was that I'd need more than 100-125 per mainline that my PW transformers are capable of if running 2 trains. 100-125W / 18V = 5.5-7.0A  Thinking I'd need more than that two trains, especially if passenger cars, on the same mainline. But, as was pointed out, I can try it and see how it works.  If insufficient, I can always break connect 1/2 of each mainline on the main level to a channel and add a second TIU for the elevated track.

Postwar ZWs are fine, but the units you mention are less power.  Before spending bigbux for a Z4000 or new ZW, I'd consider Powerhouse 180s.  The deliver 10 amps, have a very fast electronic circuit breaker, and are reasonably priced (cheap!).  I have one feeding 2 TIU channels for zones where there is little multiple movement.  One could easily power one of my mainlines, where 3 locos running at the same time is commonplace.

You only need on Legacy command base per your layout.  I have 3 TIIUs on my layout  One of the TIUs connects to the Legacy base (separate cable), and the TIUs talk to each other.  Barry's book is mentioned above, and that is a must have and will address everything you want, need and more.  

Yes, you will also need one WIU for each TIU you have.  I would not view this as "resigning yourself" rather freeing yourself.   No more "engine not on track" or other messages that prevented you from running your trains easily.  To me the MTH app is easily one of the best things to happen to this hobby in a long time.


@jbmccormick posted:

I would not view this as "resigning yourself" rather freeing yourself.   No more "engine not on track" or other messages that prevented you from running your trains easily.  To me the MTH app is easily one of the best things to happen to this hobby in a long time.

Very interesting feedback. Thank you!  Maybe it won't be so bad.  I do see it as inevitable.

@RJR posted:

Postwar ZWs are fine, but the units you mention are less power. 

Yes, per transformer, but not if working together, I think.

Maybe I don't fully understand transformers, but if a PW ZW (which I have and currently have dedicated to our seasonal Christmas layout) puts out 275W across 4 outputs, isn't it only putting out about 68.75W per output/channel?  Or, if I'm only using 2 throttles/outputs of a ZW, am I getting 1/2 of the 275 on each?  Even if the latter, that's still only 137.5W per channel, right?

If the former, then a combintation of 2 LWs at 125W each and 2 RWs at 110W each gives me 470W, right? Granted, I need to phase them (done many times) and they take up A LOT more space, but won't 4 single throttle transformers deliver more power than a single ZW?

Not being argumentative, brand new to this DCS thing after years of the "single wire" TMCC and bus wiring

Raising 4, there is a single secondary coil in the ZW.  It is probably capable of putting out a continuous 10 amp. The 4 outputs are simply taps on that coil.  Doesn't really matter how much you draw from each outlet, as long as the total doesn't exceed 10 amp.  How do I get that figure? Rated power is 275 watts.  Lionel laste 40's literature said not to exceed 75% continuously.  That equates to 200 watts.  At the max 20 volt output, this equates to 10 amps.  Regardless of the outputted voltage, 10 amps is the most that the secondary coil, OR ANY PORTION OF IT, can take without overheating.  This pretty much equates to what GunJohn said.

Do not connect transformers in parallel for a single circuit.  When phased, the hots of each are to feed separately insulated blocks.  You can have an RW or LW feed a single channel, and that should be adequate for whatever you will practically be running.  Before my parents gave me a ZW in late 1940s, I had a single type R, 100 watts rating, running two locos, 2 022 switches, and a #97 coal elevator.  I don't recommend emulation.

R4, the subject of remote vs wifi has been beaten to death on this forum, and the flogging of the corpse continues.  Some of us find that with the wifi a single operator can't keep up with a complex layout running multiple trains on intersecting routes.  Other feel wifi is the way to go.  Since my operations are in the former category, and I'd rather watch trains than try to jump among screens, my two WIUs sit in the circuit but never get accessed,  Everyone should use the system they like best for use on their layout.  Happily, I have enough remotes that at least one or two should outlast me

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