Reply to "Post war ZW transformer circuit breaker pops after 5 - 10 minutes of running 3 trains simultaneously; what's up?"

I run four trains on four loops on my layout but use two post war ZW transformers for power. Also use a 90 w transformer for lighting.  Never had a breaker blow except for a dead short.  If you wish to know if you keeping within the transformers specs measure the current  (in amps) that each train draws, then multiply that number by the running voltage (volts).  That gives you the wattage draw.,  If its 12 volts and 4 amps that's 48 watts and three trains = 144 watts. While a ZW is rated at 275 watts thats the transformer input draw wattage and not the wattage that it puts out. I would estimate that a ZW can deliver about 150 Watts on the output and at 12V on three transformer legs you are probably a bit over what that transformer can handle.