Conventional Block Wiring & Phasing Two Or More Transformers?

[lionelsoni]

I didn't mean to suggest rewiring the transformers' cords, but just to get the benefit of the equipment ground that wasn't available when they were made.  One easy way to do this is to put a single wire into a 3-wire plug, connected to the round equipment-ground pin, leaving the other blades unconnected.  Then connect this single wire to the layout common, that is, the outside rails of 3-rail track or the American-Flyer "base".  Other possibilities are to connect to a grounded handy box, if you have one exposed, or to metal plumbing.

That said, I have in fact replaced the original 18-AWG ungrounded cords on my type-Z and 30B transformers with 16-AWG with ground, not just to get the ground, but also because the original cords are a little light by modern standards, especially when plugged into the 20-ampere circuits that the NEC allows.  Years ago, equipment grounds in the building wiring were allowed to be 2 AWG sizes smaller than the current-carrying conductors, but now must be the same size, presumably to assure tripping.  The same consideration applies to power cords, which are almost always smaller than the building wiring and can benefit from at least being closer to the size of that wiring.

[Timboy]

 

[lionelsoni]

You've got it.  The ground wire doesn't need to be insulated; but, if it is, it should be green.

If the electrons tried to flow into that wire, the accumulation of excess electrons on the earth and the positive charge from the unpaired protons in your layout wiring would produce such a voltage difference that they would be stopped in their tracks by the opposing electric field.  The effect is so strong that no significant charge can ever flow.  Now, if the layout common becomes connected to the 120-volt side of the power circuit, then electrons can flow freely through the ground wire in one direction and through the power wire in the other direction, with no accumulation of charge.  The current that flows would quickly trip your house's circuit breaker or, even faster, trip the GFI, which would sense the imbalance in the power circuit--current in the black wire, none in the white wire--and disconnect the 120 volts before anyone could get hurt.