On Sat, 28 Apr 2018 23:46:08 -0400, wrote:

On Sat, 28 Apr 2018 19:56:21 -0700 (PDT), trader_4
wrote:

On Saturday, April 28, 2018 at 10:09:06 PM UTC-4, Jack wrote:
On 4/28/2018 8:33 PM, trader_4 wrote:
He's not obsessed with code, he merely pointed out to you that you
don;t know WTF you're talking about,*again*, and Edison circuits
are normal, safe, and MEET CODE. The neutral current will never be
greater than the breaker rating. For example, a 20A circuit will
have 20A breakers and use 12g wire. There will never be more than
20A flowing in the neutral.

Yes, Edison circuits MEET CODE but because of the potential mayhem lurking with an unbalanced load and a loose neutral, you won't find one in my house. Too much risk, not enough reward.

Yes, that's a different question, whether they are worth it or not.
I don't necessarily disagree with you. Another issue is that some homeowner
who knows something about electricity, but like JWS doesn't understand
how they work, screws around with it in the future. But the point here
was that they do work, they don't somehow overload the neutral and that
is recognized by them being described in the code and acceptable.

The main advantage is reduced voltage drop on a circuit that goes to
the far end of the house. You might even find them that you don't know
about because they were not required to be on a 2 pole or handle tied
breaker until fairly recently.

Previous to 1974 in Canada. Had pullouts in my old fuse panel -
house built in 1974. Helped my dad wire houses in the sixties and thry
were all paired then too. That was for not only single yoke but any
time the 2 circuits existed in the same box (lighting switch on one
circuit and recepotacle on the other in a ganged box, as an example -
or two lighting switches on different circuits)
The requirement to have a common trip was applied to multiwire
circuits in 1987 but only if both sides landed on the same yoke. (a
split receptacle) There was no requirement before that. It was not
until 2008 that the NEC required all multi wire circuits to have a
common trip. When you understand that most jurisdictions take a while
to adapt the new code. you can have a pretty new house with a
multiwire circuit landing on 2 single pole breakers that are not even
required to be grouped, much less handle tied.
The typical multiwire circuit in a house will feed bedrooms or general
lighting loads on the far end of the house and be split out in a
ceiling box so they never land on a single yoke. .