How many TIUs for new layout

I would recommend to go by the number of amps needed in each block. Even then, you should consider going passive mode if you require more power for older pass cars for example. How many trains (x # engines in each) will run at once? Does each block see engines at the same time on the same loop? Do you run more than 4 engines in a train with smoke on and/or old lighted pass cars?

 When someone already has wiring done like buss wiring, I'd recommend trying it first as is. If it's starting fresh, then it's easy to do the star pattern out to each block. Remember you don't have to go to the farthest point on each block. Block wiring is for keeping power strong, (and killing sidings), as much as anything else. If the power is good, I find the DCS signal will be good as well.

 If you plan on running large consists of engines in each train, you may need more shorter blocks, or passive wiring.

I my layout I have two main lines with 8 block per line. Each line is powered by one side of a ZW (A and D handles) and each line has it's own TIU channel (Fixed 1 for the inner, Fixed 2 for the outer). So in your case I would wire each of the 3 lines to it's own TIU channel, with the yard getting it's own TIU channel. So that's 4 channels, and you'll just need 1 TIU.

You really don't need a channel for each block.I have 22 blocks running off 2 channels of my TIU.Unless you need more than 10 amps per block or combination of blocks, 1 TIU should be fine. My two lines on Fixed 1 and Fixed 2 are bout a scale mile each. I run four engines on each and don't get to 5 amps with smoke on. I think Barry recommended 10 to 12 blocks per channel.

OK, guys, thanks a ton, but I'm officially lost. I do have Barry's book and probably need to re-read.  I was wondering about passive mode.

I think the amp question and # of trains per mainline are where I need to start. Again, I'm going back to my old conventional and TMCC days. I plan to run 2 trains per mainline on the first (with DCS) level and, yes, some PW passenger trains with incandescent bulbs.  In prior basement layout (which was similar, but perhaps a bit smaller), I had two mainlines and I broke each into two separate power blocks consuming 4 transformers.

Maybe my basic question is whether more than one transformer (assuming single throttle) can be connected to an input channel on a TIU.  I was assuming no.

In my experience with TMCC, none of my transformers were able to sufficiently power a mainline by itself with 2 trains. Things were sluggish. Granted, I was using track-powered switches (have moved to aux powered switches).  So, in my only TMCC mind, I see my first level as 7 transformers (2/mainline + 1 yard), so I figured I'd need 7 input connections or 2 TIUs.  

I think an 80 foot mainline will be easily handled by a single TIU channel.  I also can't see needing more than 10 amps on an 80 foot mainline, so in my eye, one TIU should do the trick.

I'm curious about the comment about not powering two trains with one transformer.  My experience with 180W bricks is quite different.  The only time I can see it being a problem is two large passenger trains with incandescent lighting and Pulmore motors.

gunrunnerjohn posted:

I'm curious about the comment about not powering two trains with one transformer.  My experience with 180W bricks is quite different.  The only time I can see it being a problem is two large passenger trains with incandescent lighting and Pulmore motors.

Agreed. But my PW transformers deliver about half the output of a 180W brick. Last layout mainline struggled with roughly that much track using a single PW RW or LW. When I broke up each main and used 2 per main, it was fine. 

I know one option is to upgrade my transformers but really dont want to go that route. I own a lot of total power, just spread across about 10 single throttle transformers.

Transformers don't struggle with track, unless you have poor connections. They struggle with supplying current over their capacity. You're better off spending the money you were ready to fork over on another TIU for a better transformer.

raising4daughters posted:

gunrunnerjohn posted:

I'm curious about the comment about not powering two trains with one transformer.  My experience with 180W bricks is quite different.  The only time I can see it being a problem is two large passenger trains with incandescent lighting and Pulmore motors.

Agreed. But my PW transformers deliver about half the output of a 180W brick. Last layout mainline struggled with roughly that much track using a single PW RW or LW. When I broke up each main and used 2 per main, it was fine. 

I know one option is to upgrade my transformers but really dont want to go that route. I own a lot of total power, just spread across about 10 single throttle transformers.

I guess I don't see why not have optimum power and control.  The costs of upgrading the transformers will be similar adding TIU's as adding good transformers, but the end result will be a simpler power scheme and less electronics to go south.  Also, operating with one TIU is simpler than having multiple TIU's.  I'm a K.I.S.S. fan.  You're making decisions you'll have to live with for years, why not do it the best way now?

If you are insisting on using your PW transformers to power your trains with electronic circuit boards, you will need to invest in some quick acting circuit breakers. The ones found in PW era transformers are designed to protect the TRANSFORMER, not the electronics! They will not trip fast enough, if at all. I highly recommend you add fast tripping CBs to your transformer outputs to protect the electronics. Not cheap, but far cheaper than board replacements!

But frankly, I'd go the route GRJ has suggested and buy new transformers with both sufficient power and quality circuit protection.

My 2 cents.

Chris

LVHR

Thanks. In preparation, I did buy some fast blow fuses and fuse holders from Digkey so I'm good there.

It'd be hard to put with my PW transformers. Family heirlooms. Might have to happen, though. 

Sounds like if I keep them, I'm looking at a 2nd TIU.

We have DCS and agree with the others. Update your transformer and your job just got tremendously easier. The more individual things there are, the greater the chance of problems.

A ZW-L and one TIU with about 20 blocks and the ability to easily run four trains has been trouble free, easy to wire, lots of room to expand, and no hassle with circuit breakers or any of that stuff. We have 3-4 ZW transformers and several others in the attic and didn’t bother to check them out. 

Good luck.