A: The number of trains you can run with a ZW depends on the locomotives and what they’re pulling. Large steamers and dual-motored diesels use about 50 watts for each motor; small engines use about 35 watts. And don’t forget to add 5 watts for each light bulb. That’s why passenger trains increase wattage in a hurry.
Using the information given here, add up the total wattage for your trains. One more thing: Experience has taught me that for locomotives to perform at their best, never increase the load beyond 140 watts.
I have 4 ZW’s and 2 KW’s on my layout. I usually run one large consist and one medium size train on Cab A&B. On C&D, I’ll run something small like a trolley or a service vehicle