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Very interesting reading! Yes, I know, I'm an extreme geek!


Aren't we all at ECN? [Linked Image]

This does indeed make for interesting reading.

The "Crowfoot" receptacle has cropped up every so often in threads before, so I did a little searching. Here's what our own Bjarney had to say about it in this thread :

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similar to what in the US used be called - in slang - a 'crowfoot' device - for its shape. Both were rated 125/250V 3-wire, non-grounding, but the grounded-neutral pin was improperly used as an equipment-ground connection.


Just to complicate things further though, take a look at the receptacle from this thread :

[Linked Image]

It's clearly designed to take either a "crowfoot" plug or an NEMA 1-15 type (but not a 5-15), yet the flat blade is clearly labeled as as ground, not a neutral.

Paging Bjarney....... [Linked Image]


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The US method of wiring appears to use something like our M.E.N system so the neutral and earth would be at virtually the same potential.


Yes, the American system is equivalent to your MEN or the British PME arrangement. In fact at the main panel there can be a single neutral/ground busbar, bonded to the case and to which both the incoming supply neutral and the grounding electrode are connected. At sub distribution panels though, neutral and ground are kept distinct and separate.

There are still many American installations in which the dryer and range use a 3-wire connection (using the 10-30 and 10-50 receptacles), and the appliance frame is grounded to the neutral. This was allowed only where the circuit was fed directly from the main panel. If the circuit came from a sub-panel, then the 4-wire hookup was needed so that the ground was completely separate.

New installations now have to use the 4-wire system exclusively.