Liability & responsibility of electrician?

On Mon, 06 Jul 2009 03:53:52 -0700, Gunner Asch
<gunner@NOSPAMlightspeed.net> wrote:

Long after Ive had the chance to piss on your grave.
Doubtful.

What is that a pussy surfer boy threat?

I will live far longer than a twit like you.
 
On Sun, 05 Jul 2009 17:56:15 -0500, Ignoramus20157
<ignoramus20157@NOSPAM.20157.invalid> wrote:

On 2009-07-05, John E <incognito@xbjcd.com> wrote:
2. Is it normal for electricians to measure the voltage, and "do something"
about it if it's not correct (if only reporting the problem to the
businessman)?

This is the basic question I'm asking. Is it common and regular practice to
inform the owner of a voltage as high as 245? And to suggest that he have
factory personnel come and look at each machine and examine PS taps and such?
And if he had hired a licensed electrician would the electrician likely had
informed the owner of the voltage difference?

I have 245 volts in my garage. Everything works great.

245 volts is a perfectly normal voltage. It corresponds to 122.5 volts
AC from a regular outlet.

There is no causal relationship, as far as I can tell, between
perfectly normal voltage provided in your shop, and your CNC machine
frying after 3 more weeks.

I have not yet seen a more inane discussion thread.

i
Mere ignorance is curable. I have seen worse in this NG. I have seen
far, far worse in other NG. Stick around and learn something, even if
it is only how crazy people get.
 
On Sun, 5 Jul 2009 18:11:46 -0500, "Tim Williams"
<tmoranwms@charter.net> wrote:

"Ignoramus20157" <ignoramus20157@NOSPAM.20157.invalid> wrote in message
news:Y4edneEdUJQSsszXnZ2dnUVZ_r5i4p2d@giganews.com...
245 volts is a perfectly normal voltage. It corresponds to 122.5 volts
AC from a regular outlet.

Oddly enough, that's exactly what I've measured (give or take a few tenths)
in the MSOE power lab (which is equipped with 208V 3 phase), and very nearly
the same at my own bench at home.

Tim
Your apparent conflation of single phase systems and 3 phase systems
only serves to confuse outsiders.
 
On Sun, 05 Jul 2009 12:04:07 -0500, RoyJ <spamless@microsoft.net>
wrote:

Assuming a nominal 240VAC supply, 245V is in no way "not correct" -- it's only
about a 2% overvoltage.

And since there is likely no load in shop when the install was taking
place, the 245 would be a higher than normal reading.

But I question the use of "3phase" and "245 volts" in the OP question.
Around here, 245 volts would be perfectly normal for a single phase
circuit, very high for a "standard" 208/3 phase delta.
Can't say that i have ever heard of 208 V 3 phase delta sources. All
of the 208 V, 3 phase stuff i have seen has been 120/208 V, 3 phase
"Y". Wiring motors for 208 V, 3 phase delta i have seen though, they
typically also have taps for 240 V, 3 phase and other voltages as
well.
 
In article <n6q3551brb2m4ft0q953nv1510n01i6ijl@4ax.com>, "JosephKK"<quiettechblue@yahoo.com> wrote:

Since i am not sure where you are at, and you did not mention. In the
US if the shop owner knowingly hired an non-licensed electrician to do
the install, 'e would have to eat the loss.
Nonsense. There are *many* areas of the U.S. in which there is *no* regulation
of the electrical trade.
 
"Doug Miller" <spambait@milmac.com> wrote in message
news:2Qn4m.6913$iz2.1189@nlpi070.nbdc.sbc.com...
Nonsense. There are *many* areas of the U.S. in which there is *no*
regulation
of the electrical trade.
Such as....?
 
On Sun, 5 Jul 2009 11:31:43 -0700 (PDT), rangerssuck
<rangerssuck@gmail.com> wrote:

On Jul 5, 2:11 pm, PlainBil...@yahoo.com wrote:
On Sat, 4 Jul 2009 23:40:18 -0700, John E. <incogn...@xbjcd.com
wrote:



I have been asked to offer an opinion in a sensitive situation.

A machinist moved his shop across town and required some rewiring (3-phase
outlets, conduit, etc.) in order to locate some machines where he wanted
them.

He hires a guy who's not a pro (and later discovers is not insured) but has
done shop wiring before and had a good attitude and track record. The guy
does good work. No complaints about the quality of his work.

Owner throws the switch, all works fine.

The story continues 4 weeks later when the very expensive CNC fries its
controller PCB to the tune of $4000.

Turns out the voltage in the shop was upward of 245 and the taps in the CNC's
power supply were set for 220.

What is the legal and moral responsibility of each party?

What will not be helpful are replies about the character or intelligence of
either of the players or their actions.

Thanks.

First of all, 245 VAC is a common AC voltage in the US.  Yes, I know
we say 110 / 220, but it is more like 120 / 240.  

Second, what was the 'handyman' hired to do?  If he wired a number of
1 and 3 phace 110 / 220 volt  outlets, he has no liability.  If he
hard-wired (ran conduit directly to) the equipment, it is open to
discussion.  If he adjusted wiring taps, etc than he MAY be
responsible.

Just to muddy it up even further, we recently put a medical device
through CE approval and were advised by the examiner that our label
should read "110/240", and that's the label we passed with.

Ah!! More of the old 'nominal' vrs 'actual' nonsense. 3/4" iron pipe
isn't. Neither is 3/4" copper because it has the same flow
characteristics as 3/4" iron. Except there are three ratings of
copper water pipe with the same OD, but different IDs. And 2 x 4s
haven't been 2" x 4" since they started planing them. The latest
change in size was to bring them in line with metric lumber sizes, but
metrification of the US is dead....

PlainBill

However, every controller I have ever seen uses a regulated power
supply.  Decades ago my employer built them.  We tested the supplies
at full load while varying input voltage from 20% below nominal to 20%
above nominal voltage (90 - 130 VAC).  If the equipment operated for 4
weeks, I would say the 'handyman' is not responsible.

Fully agreed.


PlainBill
 
John,
Sounds like no formal contract was in effect. The shop owner hired labor,
not a licensened electrician. In point of fact the owner should have had the
service inspected and certified by law in most areas. He didn't. Secondly,
even if he had, the conformability of his equipment to the new installation
would never be the responsibility of the electrician, unless it was
specifically mentioned in a formal contract. So, the owner and receiver of
this service, owns the sole burdon of responsibility., no question. There is
no such thing as a free lunch. If the owner wanted this level of assurance,
he would have hired a firm that does this professionally and his price would
naturally reflect the cost of the necessary insurance and the maintenance of
all the appropriate license costs. By lo-balling the job, he assumed all the
risks and consequences. This should be a lesson for all of us.
Steve

"John E." <incognito@xbjcd.com> wrote in message
news:0001HW.C67598E2001051EEB08A39AF@news.sf.sbcglobal.net...
I have been asked to offer an opinion in a sensitive situation.

A machinist moved his shop across town and required some rewiring (3-phase
outlets, conduit, etc.) in order to locate some machines where he wanted
them.

He hires a guy who's not a pro (and later discovers is not insured) but
has
done shop wiring before and had a good attitude and track record. The guy
does good work. No complaints about the quality of his work.

Owner throws the switch, all works fine.

The story continues 4 weeks later when the very expensive CNC fries its
controller PCB to the tune of $4000.

Turns out the voltage in the shop was upward of 245 and the taps in the
CNC's
power supply were set for 220.

What is the legal and moral responsibility of each party?

What will not be helpful are replies about the character or intelligence
of
either of the players or their actions.

Thanks.
--
John English
 
"Tom Horne" <hornetd@gmail.com> wrote in message
news:7b5b2666-7da3-4f8d-a61d-d4471dc5c155@r33g2000yqn.googlegroups.com...
On Jul 5, 1:04 pm, RoyJ <spaml...@microsoft.net> wrote:
Assuming a nominal 240VAC supply, 245V is in no way "not correct" --
it's only
about a 2% overvoltage.

And since there is likely no load in shop when the install was taking
place, the 245 would be a higher than normal reading.

But I question the use of "3phase" and "245 volts" in the OP question.
Around here, 245 volts would be perfectly normal for a single phase
circuit, very high for a "standard" 208/3 phase delta.
Roy
Three phase delta would not produce 208 volts unless it was a customer
provided special purpose transformer. Three Phase Delta can be wired
as corner grounded, grounded center tap in one phase with the opposite
phase being the odd higher voltage to ground known as the wild leg or
stinger, or completely ungrounded with or without ground fault
detection. The way you end up with three phase 208 is to wire the
transformer in a wye or star configuration with the transformer
primary taps set to produce 120 volts to ground on each of the three
secondary legs.
--
Tom Horne

The sole exception to that is if the wild leg is wired to ground. It then
yields 208 volts, at least on my panel.

No, I don't use it that way. Just tested voltage out of curiosity.

Harold
 
Paul Hovnanian P.E. wrote:

"John E." wrote:

[snip]

Turns out the voltage in the shop was upward of 245 and the taps in the CNC's
power supply were set for 220.


So far, no problem.

A nominal 240V service can vary +/- 5% and be within power quality
specifications. Equipment (nameplate) ratings are normally lower to
acount for voltage drop. A 120V service powers 110V appliances. A 240V
service powers 220V loads.

Paul, I take my hat off to you sir...

I knew some one here would finally get it right! :)
 
"Steve Lusardi" <stevenospam@lusardi.de> wrote:

John,
Sounds like no formal contract was in effect. The shop owner hired labor,
not a licensened electrician. In point of fact the owner should have had the
service inspected and certified by law in most areas. He didn't. Secondly,
even if he had, the conformability of his equipment to the new installation
would never be the responsibility of the electrician, unless it was
specifically mentioned in a formal contract. So, the owner and receiver of
this service, owns the sole burdon of responsibility., no question. There is
no such thing as a free lunch. If the owner wanted this level of assurance,
he would have hired a firm that does this professionally and his price would
naturally reflect the cost of the necessary insurance and the maintenance of
all the appropriate license costs. By lo-balling the job, he assumed all the
risks and consequences. This should be a lesson for all of us.
Steve
A few thoughts. Wiring inside an industrial facility gets pretty sketchy at times. Using
Michigan for an example, there is nothing saying plant personnel can not run circuits.
I've worked for two firms that were big enough to be concerned about this and could not
find anything stopping us from running power inside the plant ourselves. (Gunners Temp
worker exception)

New machine installations, we hire a licensed electrician, and have the sellers or
manufacturers technical staff commision it. That means they make sure the line voltage
and taps are correct. They throw the switch. Put a million dollars or more of machinery
on the floor, you want the warranty to be in effect.

Now repositioning machines, we tend to do our own wiring assuming we have the manpower to
do it. If not, we hire a licensed electrican.

Recently we aquired used machining centers from a plant the corporation closed down, those
we wired ourselves after making sure we knew how the taps were set.

Earlier this year, my brother, a licensed master electrican with a michigan electrical
contractors license wired up an used CNC near where I live. My brother is pretty good,
knew I worked with CNC's and lucky for him, he was installing the same model we have on
the plant floor. Had he not had me for a resource, he would have depended on the customer
to tell him what the machines electrical requirements are.

In the case of this machine, it does have a transformer, not all CNC's do. Quite often
you get 2xx v machines and step down 480v to match it. 480v is pretty much the standard
in US manufacturing facilites of any decent size. Copper and switch gear adds up at half
the voltage. Now if the japs would just design around 480V nominal, life would be very
nice.

Since it was my brother and he likes to give more than expected, I went over to check
things. Most electricians don't have CNC techs to call on. Btw, shock loads that our
troll ridiculed? Somehow a breaker on the spindle drive managed to trip during the move.
It wasn't from an overload or overvoltage. It was from rigging and transporting.

There was some slack jaws concerning their investment when it powered up with a spindle
alarm. Some of those drives go for 5-12 grand. BTDT.

Smiles all around when I found the problem and made it spin and move.

I'd really like to hear the handymans side of the story. I wonder if the OP can get him
to post?


Wes
 
"John E." wrote:
[snip]

Turns out the voltage in the shop was upward of 245 and the taps in the CNC's
power supply were set for 220.
So far, no problem.

A nominal 240V service can vary +/- 5% and be within power quality
specifications. Equipment (nameplate) ratings are normally lower to
acount for voltage drop. A 120V service powers 110V appliances. A 240V
service powers 220V loads.

--
Paul Hovnanian mailto:paul@Hovnanian.com
------------------------------------------------------------------
Steinbach's Guideline for Systems Programming
Never test for an error condition you don't know how to
handle.
 
On Mon, 6 Jul 2009 04:44:03 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@mendelson.com> wrote:

Doug Miller wrote:
Yes, I'm afraid you are missing the point. Different locations, even though
attached to the same local grid, may have different supply voltages because
they are receiving those supplies through different transformers.

I got that. What is wrong is that the person who wrote that originally (was
it you?) used that to explain why a regular house outlet could be 220 volts
on one side of town, and 240 volts on another, both connected to the same
"grid".

There's going to be some variation, but not that much.

Geoff.
Depends entirely where you are. I've seen wider variations than that.
GENERALLY the power company will correct if the voltage is "out of
tolerance" but you don't count on it in some third world countries. Or
some older inner-city areas.

My current line voltage is 116. I have seen 123, and 108 and just
about anything in between in sites seviced by the same power utility
here in Ontario - but generally 117 is pretty standard.
 
In article <9mg5555mlclpatbfm0nf6p45dhq1tpvq3v@4ax.com>, clare@snyder.on.ca wrote:
On Mon, 6 Jul 2009 04:44:03 +0000 (UTC), "Geoffrey S. Mendelson"
gsm@mendelson.com> wrote:

Doug Miller wrote:
Yes, I'm afraid you are missing the point. Different locations, even though
attached to the same local grid, may have different supply voltages because
they are receiving those supplies through different transformers.

I got that. What is wrong is that the person who wrote that originally (was
it you?) used that to explain why a regular house outlet could be 220 volts
on one side of town, and 240 volts on another, both connected to the same
"grid".

There's going to be some variation, but not that much.
Sorry, but that's not correct. Suppose you have two nominally identical
transformers, each specified to produce a secondary voltage of 230VAC when
4KVAC is applied to the primary. If the tolerance is +/- 5%, one could have a
secondary voltage as low as 218.5, and the other as high as 241.5, without
there being anything wrong with either of them.

Moreover, it's entirely possible to have connected to the same local
distribution grid 30-year-old transformers that are designed and speced to
produce a secondary voltage of 220VAC, and brand-new transformers that are
designed and speced to produce 240VAC. Throw in a small tolerance, and you
might see service entrance voltages ranging from 215 to 250 at different
services on the same local grid.

There simply is no support for your notion that service voltages must be the
same at different locations attached to the same local distribution grid. The
power company distributes the same voltage everywhere, true -- but the service
entrance voltage is determined by the individual transformer at each
individual point of service. There is _no reason_ to suppose that will be the
same everywhere.
 
Tim Shoppa wrote:

On Jul 5, 2:40 am, John E. <incogn...@xbjcd.com> wrote:
I have been asked to offer an opinion in a sensitive situation.

A machinist moved his shop across town and required some rewiring
(3-phase outlets, conduit, etc.) in order to locate some machines where
he wanted them.

He hires a guy who's not a pro (and later discovers is not insured) but
has done shop wiring before and had a good attitude and track record. The
guy does good work. No complaints about the quality of his work.

Owner throws the switch, all works fine.

The story continues 4 weeks later when the very expensive CNC fries its
controller PCB to the tune of $4000.

Turns out the voltage in the shop was upward of 245 and the taps in the
CNC's power supply were set for 220.

What is the legal and moral responsibility of each party?

What will not be helpful are replies about the character or intelligence
of either of the players or their actions.

From my past experience in industrial environments, it's 100%
guaranteed that the electrician will wire the 3-phase feeds wrong.
Either the phases will be out of sequence (motor spins backwards), or
it'll be Delta instead of Wye, or wrong voltages, or something. It has
absolutely nothing to do with how much specifying you try, it'll get
hooked up wrong every single time.

Tim.
You need to dump the outfit you are using and use a competent electrician.

--
Paul Hovnanian paul@hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.
 
On Jul 5, 2:40 am, John E. <incogn...@xbjcd.com> wrote:
I have been asked to offer an opinion in a sensitive situation.

A machinist moved his shop across town and required some rewiring (3-phase
outlets, conduit, etc.) in order to locate some machines where he wanted
them.

He hires a guy who's not a pro (and later discovers is not insured) but has
done shop wiring before and had a good attitude and track record. The guy
does good work. No complaints about the quality of his work.

Owner throws the switch, all works fine.

The story continues 4 weeks later when the very expensive CNC fries its
controller PCB to the tune of $4000.

Turns out the voltage in the shop was upward of 245 and the taps in the CNC's
power supply were set for 220.

What is the legal and moral responsibility of each party?

What will not be helpful are replies about the character or intelligence of
either of the players or their actions.
From my past experience in industrial environments, it's 100%
guaranteed that the electrician will wire the 3-phase feeds wrong.
Either the phases will be out of sequence (motor spins backwards), or
it'll be Delta instead of Wye, or wrong voltages, or something. It has
absolutely nothing to do with how much specifying you try, it'll get
hooked up wrong every single time.

Tim.
 
On Wed, 8 Jul 2009 08:04:32 -0700 (PDT), Tim Shoppa
<shoppa@trailing-edge.com> wrote:

On Jul 5, 2:40 am, John E. <incogn...@xbjcd.com> wrote:
I have been asked to offer an opinion in a sensitive situation.

A machinist moved his shop across town and required some rewiring (3-phase
outlets, conduit, etc.) in order to locate some machines where he wanted
them.

He hires a guy who's not a pro (and later discovers is not insured) but has
done shop wiring before and had a good attitude and track record. The guy
does good work. No complaints about the quality of his work.

Owner throws the switch, all works fine.

The story continues 4 weeks later when the very expensive CNC fries its
controller PCB to the tune of $4000.

Turns out the voltage in the shop was upward of 245 and the taps in the CNC's
power supply were set for 220.

What is the legal and moral responsibility of each party?

What will not be helpful are replies about the character or intelligence of
either of the players or their actions.

From my past experience in industrial environments, it's 100%
guaranteed that the electrician will wire the 3-phase feeds wrong.
Either the phases will be out of sequence (motor spins backwards), or
it'll be Delta instead of Wye, or wrong voltages, or something. It has
absolutely nothing to do with how much specifying you try, it'll get
hooked up wrong every single time.

Tim.

Your name Shoppa or Lammeh? Just wondering, because that is a pretty
lame outlook.
 
On Jul 5, 11:39 am, "Geoffrey S. Mendelson" <g...@mendelson.com>
wrote:
Doug Miller wrote:

Incorrect. Distribution voltages are on the order of a few thousand volts,
stepped down by transformers at the point of service to a few hundred. New
location = different transformer = possibly different service voltage even if
the distribution voltages are exactly the same.

Yes, BUT, a power company attempts to keep a constant voltage through their
service area. While the voltage fluctuates due to equipment, load, etc, I don't
think you can honestly say that if it is 220 volts on one side of town, the
same "grid" produces 240 on the other side of town. It might be 242 in one
place and 239 in another, but even that's a big difference unless there is
a heavy load in one location and not another.

The EU spec allowing household line voltage to be 240 volts while claiming 230
was to allow the UK to keep their current system while being "in spec" but I
doubt it was intended to allow variations from as much as 220 in one place
and 240 in another within the same country.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel g...@mendelson.com  N3OWJ/4X1GM
Was going to ask someone knowledgeable to post the percentage voltage
variation allowed in the USA (or wherever it is) for 'normal service'.
For example if one were to look at European and similar so-called 230
volt systems might find that plus 10% to minus 5% (or some such thing)
quite normal? Just using those as an example that is around 218 to to
253 volts!
The question posted states "Upwards of 245 volts, whereas the machine
taps were set for 220 volts".
That is only a 12% difference! And when was the voltage found to be at
245? Immediately upon installation or several days/weeks later?
To answer the question as asked; I don't think the workman who did the
wiring is/was responsible. More so the owner who should take
responsibility for not using the proper trade/profession. If it was
say an insurance or warranty situation surely whoever has to repair or
supply the 'blown' part would ask "What tests or checks were made
after the machine was moved here and hooked up anew? There is also
nothing to say that the machine had not been working on 245 volts, or
whatever , at the old location. Also what was the agreement or
contract with the worker about testing the machines at the new
location once hooked. Maybe? Maybe not? Maybe more a task for the
people who regularly operate and service the machines regardless of
whether they are in the old or new location? Did the owner get a
cheaper job by taking the risk of using a non-registered electrician.
Two cents fom here based on what's provided!
 
On Jul 5, 12:34 pm, o...@uakron.edu wrote:
I work on lasers that use a buck/boost with 16 tap possibilities  on 3
phase all the time, and I used to use the same units in theatrical
touring service until more modern solid state lasers dominated the
laser show industry. .  From that perspective,  I'm amazed at the
replies here that have failed to ask two simple questions.  I will
state that I never met a house electrician who ever looked at the
rating plate on the gear, although I did have a few that asked about
phase sequences.

    Two, I never met a house electrician who ever checked anything
hooked to the pigtail I gave him to connect, including "professional"
rental generator technicians (actually they were the worst)  In the
theatrical business, it is up to the touring operator to check the
local guys work, and in most cases, we preferred they stand in a
corner and watch us, after your first blown passbank with 3 or 4 out
of 22 power  transistors blown in the laser, you get the idea to check
the taps both preshow and under load condition.   In one case I asked
for 220/3, went to lunch,  and came out to find 380V European power
from the generator  in my distro box, which is why the box had its
own"tagged out"  disconnect switch. Its a rotary switch in big modern
generators, easy to mess up.

Questions:

 One,  Did the "electrician" hook straight to the machine's tappable
control transformers, or did he meet a simple  junction box on the
side of the machine.  If it were the later, I'd say he's off the
hook.  On the other hand if he was staring at a tap strip , he should
have asked. There is also the possibility of a "cascade" of
transformers in some machines, ie little CTs all over the place in the
machine, that need tapped. ??????

Two, Did anybody bother to read the manual chapter on setup? Machine
shop gear needs leveled and "trammed"  when moved, its not a simple
matter of tossing a CNC off the truck onto any old pad of concrete and
expecting good parts to tolerances, and the first paragraph usually
reads, something like "check settings" and have appropriate safety
gear. ??????

The fault occurred months down the road, a instant  ":poof and shower
of sparks:" would point to the electrician, but months down the road
is lack of due diligence on the part of the owner.
BTW just measured our North American domestic single phase here!
Leg A = 119 volts, Leg B = 121 volts. Leg A to b = 232 volts.
119/115 = 3.4% high
121/115 = 5.2% high
232/230 = 0.8% high
It's about 02.00h in mid summer so system load is probably light and
utility will have adjusted. No AC loads here; not needed.
 
On Wed, 15 Jul 2009 21:48:36 -0700 (PDT), stan
<tsanford@nf.sympatico.ca> wrote:

On Jul 5, 12:34 pm, o...@uakron.edu wrote:
I work on lasers that use a buck/boost with 16 tap possibilities  on 3
phase all the time, and I used to use the same units in theatrical
touring service until more modern solid state lasers dominated the
laser show industry. .  From that perspective,  I'm amazed at the
replies here that have failed to ask two simple questions.  I will
state that I never met a house electrician who ever looked at the
rating plate on the gear, although I did have a few that asked about
phase sequences.

    Two, I never met a house electrician who ever checked anything
hooked to the pigtail I gave him to connect, including "professional"
rental generator technicians (actually they were the worst)  In the
theatrical business, it is up to the touring operator to check the
local guys work, and in most cases, we preferred they stand in a
corner and watch us, after your first blown passbank with 3 or 4 out
of 22 power  transistors blown in the laser, you get the idea to check
the taps both preshow and under load condition.   In one case I asked
for 220/3, went to lunch,  and came out to find 380V European power
from the generator  in my distro box, which is why the box had its
own"tagged out"  disconnect switch. Its a rotary switch in big modern
generators, easy to mess up.

Questions:

 One,  Did the "electrician" hook straight to the machine's tappable
control transformers, or did he meet a simple  junction box on the
side of the machine.  If it were the later, I'd say he's off the
hook.  On the other hand if he was staring at a tap strip , he should
have asked. There is also the possibility of a "cascade" of
transformers in some machines, ie little CTs all over the place in the
machine, that need tapped. ??????

Two, Did anybody bother to read the manual chapter on setup? Machine
shop gear needs leveled and "trammed"  when moved, its not a simple
matter of tossing a CNC off the truck onto any old pad of concrete and
expecting good parts to tolerances, and the first paragraph usually
reads, something like "check settings" and have appropriate safety
gear. ??????

The fault occurred months down the road, a instant  ":poof and shower
of sparks:" would point to the electrician, but months down the road
is lack of due diligence on the part of the owner.

BTW just measured our North American domestic single phase here!
Leg A = 119 volts, Leg B = 121 volts. Leg A to b = 232 volts.
119/115 = 3.4% high
121/115 = 5.2% high
232/230 = 0.8% high
It's about 02.00h in mid summer so system load is probably light and
utility will have adjusted. No AC loads here; not needed.
Except for the fact that the NA standard is 120/240 volts (there are a
number of authorative references, feel free to Google them). So your
two 'phases' are almost dead on (probably measurement error) and the
240 is slightly low (measurement error, seems odd that it can be off
consdiering that it is supposed to be the sum of the two 120 legs.)

The reason that it was standardized at 120 volts was because of the
massive interconnecting done in North America in the past 25 years.
Old standards included the 115 volts you mention, and 117 volts in
some areas, and even some with 110 volts. It was determined that it
would be necessary to standardize all voltages (just not the low
voltages we are discussing here) to allow interconnection, and direct
substitution of equipment.

 

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