How many tiu do I need????

There are two ways a TIU can be applied to an existing layout.  Direct wire with the track circuits through the TIU, or Passive mode, where only the DCS signal is applied to the layout.   You might want to explore Passive mode wiring.

Unless the 2 “loops” have extreme power requirements, I would power all 3 sections of each loop with a single brick, 1 brick powering as loop’s 3 sections.

That would require a total of 8 channels for a total of 2 TIUs.

I'm inclined to agree with Mr. B.  3 PH-180' for a loop of that size is overkill, unless you've got some weird rolling stock.

Gentlemen,

   Barry is correct as usual, I have 2 TIU's powered by 3 Z4K's each has it's own side receiver for running Conventional Engines, this covers about all I will ever need for my Train Room.

PCRR/Dave

On earlier layout, I added a TIU channel each time the amps got above 6 amps (to permit faster speeds, turning on smoke and whistles without going over 10 amps - 4 - 6 engines per loop).  Do not forget to put the variable channels to fixed.  On my current layout I have a TIU channel for each parking siding so that when I turn on the power to that section of track the DCS watchdog signal is caught by the engines on that siding.  Each main loop (currently six) have a separate channel each with 4 to 6 blocks fed by  a 180 brick, a Z4000 handle or a PurePower handle.  With 5 TIU's, that is another reason I am not going the Wifi route.  The main reason is that I have 9 DCS handhelds, 3 CAB2s, and 3 CAB1s and no desire to add to my home Wifi network.