someone wrote:


Gets even better - Since we use 120V here, you might be tempted to
connect 120/240V 3-wire as a ring circuit - and now you have some Real
Nasty failure modes. The neutral goes open, the circuit goes into
voltage imbalance, and everything connected on the side that goes high
starts blowing up...

Then once it all goes open on A Phase, the imbalance swings the other
way and the gear on the B Phase starts blowing up...

That has NOTHING to do with loop circuits. From the point of view of
loosing the neutral, the two wires of the loop, look JUST the same as
the one of the radial system. There is no difference.

What the loop does do is provide a more even impedance to a given
point in the circuit. The impedance reaches a peak at 1/2 way round
the circuit, and then starts dropping again.


Another difference is that 'ring circuits' are like small bus bars
and everything that gets plugged in is fused at the plug because the
ring is 30A @ 240 VAC. The British keep bragging about the concept on
some of the electronics groups.

WHich I think is a more reliable system from a safety point of view,
but a real PITA at the plug end.

OUrs are like bus bars too, but without fuses at the terminations.




The only thing I've ever seen that was even close to a ring circuit
that was legal in the US were old commercial fire alarms w


RIng systems are used in the US all the time,.....at medium voltage.


I don't think strictly speaking that it would be a code violation, IF
both ends of the loop were connected to the same branch circuit
device, AND it was listed to terminate multiple conductors, AND the
device was sized to protect the wire size, not the parallel
combination..

Where it COULD be interpreted as a violation is that you are
essentially paralleling two conductors at sizes that may be smaller
than those allowed.

jk