ADDING A SECOND TIU

please explain what benefit we get by adding a 2nd tiu. My board is o gauge 27 ft by 17 ft with two circles, 20 parking tracks, 3 6 foot sidings. dcs signal strength is 10 out of 10. ran 2 engines on 1 circle so far, because I'm still changing the track plan. working on a walkthru lift up with hinges & then the trackplan sb done. My sone & I will likely run 2 engines on each circle, total 4 engines, including some non led passenger cars. so far, have only 1 z4000 with a tiu and aui( no accessories ir landscape has been yet done) and all atlas track. Should we plan on a 2nd tiu. Only rab 1 or 2 engines around the layout to verify no dead spots with the star wiring. so, is it likely we will need a 2nd tiu?  The accessories unit (mth aiu) is not yet set up but I did notice this aiu will connect to and get power from the tiu use a wire to the tiu. Since we have more than 15 switch tracks (most ib the parking track access points), seems like that a lot of power to do our very many accessories & switches powered thru the aiu which gets its power from the tiu, not a separate transformer. Ive included my vlog video here to show you how much track we have. Please advise. we would hate to set it all up, only to find out we need a 2nd mth tiu. see my track layout here: https://www.youtube.com/watch?v=jm6yyi3WELE

I have for command mode 4 of proto 2 or 3 engines, probably 25 proto1 engines for conventional mode, but very much like the speed control of command mode on my inclines. we will probably try to upgrade some of the proto1 engines since they are all mth premier but the upgrade kit is $200 plus $100 or more for upgrade labor. None of my engines have more than 10 hours run time ( health problems kept me away from trains for 8 years, back now) so how would a 2nd tiu help?

Unless you have switches with large incandescent bulbs, the number of switches is meaningless since the AIU will only throw one at a time.  If you power your TIU through a AUX port with a 2-amp wall wart, the AIU relays are getting powered from that.

My layout is about 38x16, and I use 2 TIUs.  This is because the layout was built to run conventional back in 1994 or so, and I needed areas separately powered.  I used 2 TIUs to retain the 6 separate power districts.  But there have been times when I had issues and had all running on a single TIU.

I'd say stick with one and see if you wind up with insufficient signal strength.  Use many relatively sort blocks, each fed via 14-gauge wires, to minimize in-track power & signal losses.

If you have that many premier PS-1 locos, you might want to consider learning ow to do upgrades yourself.  I upgraded everything I have that's can motored.

RJR posted:

Unless you have switches with large incandescent bulbs, the number of switches is meaningless since the AIU will only throw one at a time.  If you power your TIU through a AUX port with a 2-amp wall wart, the AIU relays are getting powered from that.

My layout is about 38x16, and I use 2 TIUs.  This is because the layout was built to run conventional back in 1994 or so, and I needed areas separately powered.  I used 2 TIUs to retain the 6 separate power districts.  But there have been times when I had issues and had all running on a single TIU.

I'd say stick with one and see if you wind up with insufficient signal strength.  Use many relatively sort blocks, each fed via 14-gauge wires, to minimize in-track power & signal losses.

If you have that many premier PS-1 locos, you might want to consider learning ow to do upgrades yourself.  I upgraded everything I have that's can motored.

much appreciated, I feel better since you have been down the path I am just starting. The ability to do command control to move up & down the one incline on my layout makes command control very appealing. and yes, I expect to try some upgrades, just unfortunate to start with my 2 N&W J premier steam or my 2 Daylight steam...I had intended to double head them since 1998. Your opinions were very helpful. This learning curve has been steep, being into trains since 1968, out for last 8 years, back in now. Much appreciated. Yes, I have 16 & 18 gauge feeders every 5 feet, but not in a star pattern and no feeders on the common( which I may add feeeders on common if I see problems). working still on finishing a hinged walkthru so I'm not required to crawl under the board. When done in a few days, I will try a steam upgrade to proto3. I bought an upgrade kit when it first came out but never tried an upgrade myself. Never soldered even once, but am very experienced with building my computers & stereo stuff. I will seek your counsel when I get there. 

file1man aka bucca    gary

Bucca, I recommend that for first upgrade project, try a wide body, long, diesel. They are roomy.