On Mon, 22 Mar 2021 19:09:28 -0700 (PDT), DerbyDad03
wrote:

On Monday, March 22, 2021 at 9:43:51 PM UTC-4, wrote:
On Mon, 22 Mar 2021 15:17:09 -0700 (PDT), DerbyDad03
wrote:

On Monday, March 22, 2021 at 5:53:13 PM UTC-4, Clare Snyder wrote:
On Sun, 21 Mar 2021 16:22:03 -0700 (PDT), DerbyDad03
wrote:
On Sunday, March 21, 2021 at 4:33:18 PM UTC-4, J. Clarke wrote:
Please forgive me--this is a bit of a rant.

I went to put a new fixture at the top of the stairs--the old one is
physically too small to hold anything bigger than a 60w incandescent
(by physically I mean you can't put the globe on if anything bigger is
in it, and that includes CF and LED that are larger than 60W
equivalent and in that location a 60 just isn't enough light.

Well, went to kill the power to the circuit and discovered chaos.

First:
Turned the switch off
Checked socket with a voltage sensor
Still voltage on the circuit
Par for the course in this house
Switch is in the neutral leg
Add to list of stuff to fix.

Next:
Screwed adapter into socket and plugged in tracer
Traced signal in breaker panel
Not one, but _two_ breakers showed signal
Turned both off
Went back upstairs
Checked for voltage again
No voltage--good
Flipped switch--checked again
Voltage--not good
Back to the panel
Identify third breaker, turn off
Now no voltage

Replaced fixture, turned breakers back on, everything works, I didn't
die.

But now I have the real mystery--how is this effing light managing to
be connected to not one, but _three_ separate branch circuits?


It's possible that you are dealing with an Edison circuit, also known as
a "shared neutral" or "multi-wire branch circuit". Granted, Edison circuits
usually only involve 2 breakers, but I think I could imagine one with 3.

In a typical Edison circuit a cable with 2 hots and a single neutral has the
2 hots tied to separate breakers. That 3 wire cable runs to a junction box
from which a pair of 2-wire (hot and neutral) cables emerge. Those 2 circuits
share the single source neutral from the 3 wire cable.

If you only turn off one breaker, you will often get some voltage that bleeds
back through the neutral at the supposed-to-be-dead fixture. If you used a
meter as opposed to a voltage sensor, I'll bet that it's not the full 120 VAC.

Now - although this is not something that I have ever seen - expand that to
a 4 wire source cable (3 hots and a single neutral) to the first junction box
and you've brought that 3rd breaker into the picture.

I don't know if a "super-Edison" (I made that up) would be allowed by code,
but I can certainly imagine someone grabbing some 12/4 Romex and running
one.


Could only occur on a 3 phase circuit - and BY LAW all edison circuits
MUST use a "tied breaker" - and in a fused panel a "ganged pull-out"
which makes it IMPOSSIBLE to shut off power on one side only.

By *law* or by *code*?
They're the same in many/most jurisdictions. The NEC is written into
the law.

I'll agree that many jurisdictions *mandate* that the NEC be followed, but
that doesn't make the NEC itself a law, under the legal definition of a law.

No, it *is* law, with all of the responsibilities and penalties of any
similar law.

When an amendment or clarification or even a whole new version comes out,
these jurisdictions aren't running it through their legislatures for approval.

Nope. The *LAW* delegates that to the NFPA. The law incorporates the
NEC (and NFC) as law.

I'm pretty sure that no one ever challenged the NEC in their state's Supreme Court. ;-)

It would stand as much as any other regulation (law). There are far
more such regulations than there are laws and all have the force of
law. In fact, it's damned rare that legislatures pass laws anymore,
other than to give powers to administrative departments.

...