Smokey The Bear [RE-wrenches]

[August Goers]

Matt -
 
I'm still chuckling after reading through your very thorough response. 
 
Regarding your option C below where you state "...You have
a 50-50 chance of "nothing" happening if the buildings are connected to the
same side of a single-phase 120/208 or 120/240 utility transformer..."
 
Could you explain the logic here? I'm having a hard time understanding why it wouldn't create a short probably because I don't have a deep understanding of how the grid works.
 
-August

----- Original Message ----
From: Matt Lafferty <mlafferty at universalenergies.com>
To: RE-wrenches at topica.com
Sent: Wednesday, October 24, 2007 10:50:42 PM
Subject: RE: Smokey The Bear [RE-wrenches]


Hi Mark,

Don't take this wrong. I know you're in solar and all... But some part of me
wants to not explain these possibilities just for the sake of seeing if the
smoke is visible from my house.  I'm right across the Bay from you. Let me
know when you are going to do this so I can get up on the roof for the best
view... 

As long as you only ran the cord between the receptacles and didn't actually
plug it into either one, you would probably only create a trip hazard.  If
you were able to actually plug the cord into both receptacles by using, say
for instance, a don't-try-this-at-home-double-male-ended-danger-cord, any
number of things could happen. Determining the answer to "what would happen"
and the sequence in which it does, can be achieved by applying a flowchart.
Similar to a logic path chart you may or may not have heard about in school.
I missed that lesson personally so I didn't learn it until later. Telling
time, too. That really screwed me up as a kid. But back to the matter at
hand before it becomes an emergency... The flowchart... Simple version.

Disclaimer: The following is for hypothetical purposes only. All case
examples assume that both receptacles are properly configured and intended
for 120 VAC and all neutral conductors and paths to ground are intact. Case
examples assume that utility service has not been interrupted for lack of
payment.

The events and order in which they occur will be first determined by whether
or not either or both of the receptacles is energized at the time you plug
the cord in. Second tier on the flowchart of possibilities is whether or not
one or both of the receptacles are served by a Zinsco breaker... Followed
immediately by whether or not the wiring behind the receptacles happens to
be aluminum.  Beware of aluminum wire if the building was built around 1972.


Let's recap the first three tiers:

Option A: Recept #1 is energized; Recept #2 is not energized. Both circuits
are served by Zinsco breakers. Do NOT plug the cord into either receptacle.
Go to the hardware store and buy a new Zinsco breaker to replace the one
serving Recept #2.

Option B: Recept #1 is not energized; Recept #2 is not energized. Relax.
Light a candle. Go for a walk.  The power is off in the neighborhood.  If
you do plug the cord in, nothing will happen until the power comes back on.
When it does, there is a 50-50 chance that it will go right back off again
immediately following a loud "bang" noise coming from one or both load
centers.

Option C: Recept #1 is energized; Recept #2 is energized. Both circuits are
served by Zinsco breakers. The building was wired with copper wire. You have
a 50-50 chance of "nothing" happening if the buildings are connected to the
same side of a single-phase 120/208 or 120/240 utility transformer. If the
buildings are connected to the same side of a three phase utility
transformer, your odds of "nothing" happening drop to 33%.  If the two
buildings are connected to different utility transformers, you have a 100%
chance of something happening.  No matter what transformer situation there
is, if something happens, it will not be good. It can range from "a loud
bang coming from the load center followed by the lights going out" to all
kinds of undesireable things like: starting fires, blowing the guts out of a
load center or two, knocking the power out to the neighbors, hurting
somebody, going to jail, or even death.

Basically, I hope my message is clear that this is NOT A GOOD IDEA. There
are combinations of conditions that might create a "less dangerous"
situation compared to other combinations.  In general, if you don't already
know what those combinations are, it's certainly not appropriate to discuss
them in a public forum. Who knows who will read this stuff and whether or
how they would apply the information?  Nobody's meter is going to run
backwards if that's what you were thinking.

I've seen two cases personally and heard of numerous others where this very
situation has happened with bad results... In all cases, it happened when
one neighbor got their power shut off and the other neighbor tried to help
them out. One case ended up with a neighbor kid getting shocked by the
danger-cord when playing at the house without power. The parents complained
to the landlord, who called me to "fix the outlet".  Needless to say, all I
could do was tell the neighbor to unplug the cord, be thankful the kid
wasn't hurt badly, and report the findings to the landlord. Who turned
around and evicted the tenant who had lost their power.

The other case I saw was when I had to replace a panel that blew up on the
poor meter guy who came to turn the power back on. They had not unplugged
the cord and he didn't know it was there. When he flipped the main breaker
back on, the receptacles were on different phases and powee! Zinsco panel,
by the way. I've heard numerous cases from utility guys and a few from
contractor buddies and building inspectors. It's always the same. There's
nothing good to tell.

If somebody wants to help out a neighbor who is having a tough time paying
the bills, get a heavy duty extension cord and have them plug in what they
really need to. Just don't plug it directly into receptacles on both ends.
Too much wrong with that picture. Too much Smokey Bear in CA right now
anyway. 

Pray for Sun!

Matt Lafferty 


-----Original Message-----
From: Mark Frye [mailto:markf at berkeleysolar.com] 
Sent: Wednesday, October 24, 2007 4:22 PM
To: RE-wrenches at topica.com
Subject: Smokey The Bear [RE-wrenches]


What would happen if I ran a cord between recepticals installed under
separate meters in the same building (say for instance between two
apartments within an apartment building)?

Berkeley Solar Electric Systems


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