Reply to "Protecting a Lionel KW transformer."

Remember that the ampacity isn't the whole story.  There is also a table of voltage drop per amp per foot that may indicate that a wire run is too long for the amount of current and allowable voltage drop, especially when you are starting out with only 12 or 18 volts.  A similar table for house wiring may allow a 5% drop for a run, but at 120 volts that is a 6 volt drop.  That amount of drop would be disastrous on a train layout!!