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'[OT]Why 110v vs 220v'
2007\08\06@124546 by jtroxas

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Why do certain countries choose single phse 110v home power and some choose
220v.. is there any advantages of one over the other and vice versa...

Also I've heard of people taking the other half wire of a 220v supply and
discarding the other.. and using ground as the other half to convert to
110v... a bit dangerous I think...



2007\08\06@133306 by John, N5DWI

picon face
jtroxas wrote:
> Why do certain countries choose single phse 110v home power and some choose
> 220v.. is there any advantages of one over the other and vice versa...
>
> Also I've heard of people taking the other half wire of a 220v supply and
> discarding the other.. and using ground as the other half to convert to
> 110v... a bit dangerous I think...
220 reduces power loss in the power transmission grid.

The formula for voltage (E) is current (I) X resistance (R) [E=IR].

The formula for  power  (P) is current^2 X Resistance [P=I^2R].

It follows that if the current flowing through the grid can
be cut in half, the power loss will be only one-fourth.

That's also why cross country transmission lines are sometimes
many hundreds (or even thousands) of volts.  This reduces the
amount of current required to transmit the same power but
greatly reduces the long distance resistance loss.

The US fixed on 110 late in the the 19th century, when consumers
were close to the generating station, and power line loss was no
big deal.

As the generators gradually became more and more remote from
the users, the line loss became significant.  Rather than tell the
consumers they needed to trash their existing appliances, the
power companies, after switching to AC (Edison power was DC),
began to transmit long distance at high voltages, and use
transformers (pole pigs) in the neighborhoods to reduce to
consumer voltages.

But even within a single household, voltage choice can make a
difference.

If you use an appliance that is designed for, say 3,000 Watts, that
would be, at 110V, about 27A.  Since most ordinary circuit breakers
are 20A or 30A, just that one user would max out the capacity of
that circuit.  The same 3,000 Watt user would be only about 14A.

Really high current users would need a dedicated circuit, which
increases wiring and labor costs.


Etc., etc., etc.

vy 73 de john, n5dwi

2007\08\06@134244 by Hector Martin

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jtroxas wrote:
> Why do certain countries choose single phse 110v home power and some choose
> 220v.. is there any advantages of one over the other and vice versa...

110V is safer. 220V is more efficient.

Here are my two theories, both of which may be incorrect:

1. Americans are wussies. Real men use 220V :)
2. (more likely) 110V is older. Once people realized it would be too
wasteful (thicker wires, etc), other countries started using 220V.
America (and Japan) probably already had plenty of 110V appliances, so
it stuck.

> Also I've heard of people taking the other half wire of a 220v supply and
> discarding the other.. and using ground as the other half to convert to
> 110v... a bit dangerous I think...

In 110V areas, it's common for transformers to put out two 110V phases
out of a single winding, tapping the neutral at the center. If you
discard the neutral wire and use both 110V phases, you get 220V. I
believe this is commonly done for dryers and other big appliances that
run on 220V. There are other similar configurations for obtaining other
voltages out of a three-phase supply. I don't think you can get 110V out
of a 220V supply without a transformer, except maybe placing two
identical 110V loads in series.




--
Hector Martin (spam_OUThectorTakeThisOuTspammarcansoft.com)
Public Key: http://www.marcansoft.com/marcan.asc

2007\08\06@134708 by Eoin Ross

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If you run 220/240 you get 1/2 the current, 1/4 the power loss in the wire - and hence you can run a lighter gauge wire for the same job. ($$$)

Your house is wired "exactly the same" as your second question.
Where your power enters the house you have two 120VAC phases (Relative to ground) These are 240 VAC relative to each other. The Neutral and Ground are tied together at the breaker box. The NEC allows this to happen only at one point in the building - all neutrals and grounds must come back to this bus bar to be terminated. From my limited reading, a satellite building such as a garage must have GND and NEU run back to this breaker box as well - even if there are breaker boxes there too.

I agree on the dangerous part - its a good bet that the NEC outlaws it too. The ground wire is only meant to be a return path instead of the neutral IF the neutral connection fails.

>>> .....jtroxasKILLspamspam@spam@gmail.com 06 Aug 07 12:44:31 >>>
Why do certain countries choose single phse 110v home power and some choose
220v.. is there any advantages of one over the other and vice versa...

Also I've heard of people taking the other half wire of a 220v supply and
discarding the other.. and using ground as the other half to convert to
110v... a bit dangerous I think...


2007\08\06@140508 by Cedric Chang
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There is also the issue of safety.  110 is marginally safer than
220.
Cedric
> On Aug 6, 2007, at 10:44 AM, jtroxas wrote:
>
> Why do certain countries choose single phse 110v home power and  
> some choose
> 220v.. is there any advantages of one over the other and vice versa...
>
> Also I've heard of people taking the other half wire of a 220v  
> supply and
> discarding the other.. and using ground as the other half to  
> convert to
> 110v... a bit dangerous I think...
>
>
>
> --

2007\08\06@153843 by Gerhard Fiedler

picon face
Hector Martin wrote:

> 1. Americans are wussies. Real men use 220V :)

While this may be... <g>

> 2. (more likely) 110V is older. Once people realized it would be too
> wasteful (thicker wires, etc), other countries started using 220V.
> America (and Japan) probably already had plenty of 110V appliances, so
> it stuck.

... this one is probably not correct. I'm not sure whether there is in fact
evidence that the USA (definitely not Japan) had historically an edge on
electrification compared to the earlier 220-240V countries. E.g. in Germany
the process occurred pretty much at the same time as in the USA: in the
last years of the 19th century.

Here <http://en.wikipedia.org/wiki/Mains_electricity> they trace it back to
Tesla vs Edison, Tesla favoring 240V AC and Edison 110V DC.

Interesting also <http://en.wikipedia.org/wiki/Mains_power_systems>. The
one information they left out in this page is the phase system.

FWIW, the smaller wire sizes in 230V countries are quite easily
recognizable when working with electrical installations :)

>> Also I've heard of people taking the other half wire of a 220v supply and
>> discarding the other.. and using ground as the other half to convert to
>> 110v... a bit dangerous I think...
>
> In 110V areas, it's common for transformers to put out two 110V phases
> out of a single winding, tapping the neutral at the center. If you
> discard the neutral wire and use both 110V phases, you get 220V.

In 230V areas, I think 3-phase is more common (at least in the EU). 230V is
then the star voltage from phase to ground; phase to phase would be 400V.

I find it practical to have a standard 3-phase system in the home (or in
the shop); if you need a heavier motor, there's no need for workarounds or
special utility contracts, you just connect it.

> I don't think you can get 110V out of a 220V supply without a
> transformer, except maybe placing two identical 110V loads in series.

Yes... not recommended :)

Gerhard

2007\08\06@192305 by Recon

picon face
Eoin Ross wrote:

>If you run 220/240 you get 1/2 the current, 1/4 the power loss in the wire - and hence you can run a lighter gauge wire for the same job. ($$$)
>
>Your house is wired "exactly the same" as your second question.
>Where your power enters the house you have two 120VAC phases (Relative to ground) These are 240 VAC relative to each other. The Neutral and Ground are tied together at the breaker box. The NEC allows this to happen only at one point in the building - all neutrals and grounds must come back to this bus bar to be terminated. From my limited reading, a satellite building such as a garage must have GND and NEU run back to this breaker box as well - even if there are breaker boxes there too.
>  
>

MY Circut Breaker box in the garage is more then 50 FT from my main
entrance CB panel  The code states I need a ground rod connected to the box.

RECON

> I agree on the dangerous part - its a good bet that the NEC outlaws it too. The ground wire is only meant to be a return path instead of the neutral IF the neutral connection fails.
>
>  
>
>
>
>  
>

2007\08\06@235824 by Eoin Ross

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OK - Learned something new. Am I correct in thinking that the code prohibits you connecting the ground and neutral at that box even though it requires the rod?

Eoin Ross
Industrial computer support and design

CHEMSTATION INTERNATIONAL
http://www.chemstation.com

3400 Encrete Lane     Ph  937 294 8265    Ext 1109
Dayton                       Fax  937 294 5360
Ohio
45439
>>> 556reconspamKILLspamcharter.net 08/06/07 19:22 PM >>>
Eoin Ross wrote:

>If you run 220/240 you get 1/2 the current, 1/4 the power loss in the wire - and hence you can run a lighter gauge wire for the same job. ($$$)
>
>Your house is wired "exactly the same" as your second question.
>Where your power enters the house you have two 120VAC phases (Relative to ground) These are 240 VAC relative to each other. The Neutral and Ground are tied together at the breaker box. The NEC allows this to happen only at one point in the building - all neutrals and grounds must come back to this bus bar to be terminated. From my limited reading, a satellite building such as a garage must have GND and NEU run back to this breaker box as well - even if there are breaker boxes there too.
>  
>

MY Circut Breaker box in the garage is more then 50 FT from my main
entrance CB panel  The code states I need a ground rod connected to the box.

RECON

> I agree on the dangerous part - its a good bet that the NEC outlaws it too. The ground wire is only meant to be a return path instead of the neutral IF the neutral connection fails.


2007\08\07@000404 by Eoin Ross

flavicon
face
OK - Learned something new. Am I correct in thinking that the code prohibits you connecting the ground and neutral at that box even though it requires the rod?

Eoin Ross
Industrial computer support and design

CHEMSTATION INTERNATIONAL
http://www.chemstation.com

3400 Encrete Lane     Ph  937 294 8265    Ext 1109
Dayton                       Fax  937 294 5360
Ohio
45439
>>> .....556reconKILLspamspam.....charter.net 08/06/07 19:22 PM >>>
Eoin Ross wrote:

>If you run 220/240 you get 1/2 the current, 1/4 the power loss in the wire - and hence you can run a lighter gauge wire for the same job. ($$$)
>
>Your house is wired "exactly the same" as your second question.
>Where your power enters the house you have two 120VAC phases (Relative to ground) These are 240 VAC relative to each other. The Neutral and Ground are tied together at the breaker box. The NEC allows this to happen only at one point in the building - all neutrals and grounds must come back to this bus bar to be terminated. From my limited reading, a satellite building such as a garage must have GND and NEU run back to this breaker box as well - even if there are breaker boxes there too.
>  
>

MY Circut Breaker box in the garage is more then 50 FT from my main
entrance CB panel  The code states I need a ground rod connected to the box.

RECON

> I agree on the dangerous part - its a good bet that the NEC outlaws it too. The ground wire is only meant to be a return path instead of the neutral IF the neutral connection fails.


2007\08\07@070611 by Howard Winter

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On Tue, 7 Aug 2007 00:44:31 +0800, jtroxas wrote:

> Why do certain countries choose single phse 110v home power and some choose
> 220v.. is there any advantages of one over the other and vice versa...

Not quite that simple - until a few (10?) years ago Europe used 220V and the UK used 240V.  

Then they "Harmonised" it so that we're all using a nominal 230V, but with tolerances such that if you measure it you'll find they're still using those
old voltages!  But by making it a common spec. devices can be designed to work anywhere in the region.  (Looking at my UPS logs for the past couple
of days, it's been between 234 and 247V - so anything designed for the old EU standard of 220V +10% would be out of spec).

> Also I've heard of people taking the other half wire of a 220v supply and
> discarding the other.. and using ground as the other half to convert to
> 110v... a bit dangerous I think...

The voltage is only one difference - the wiring scheme is completely different too.  The US design using a centre-tapped transformer isn't used here.  
3-phase is distributed to the street (and for commercial premises often to the consumer).  This is nominally 400V between phases (somewhere around
that - it used to be 415 here) and 230V between each phase and the star point.  The latter is used as the Neutral and is earthed at the substation
transformer.  The armoured sheath of the cable carries the Earth to the consumer along with one Phase and Neutral.  Consequently the Neutral is
close in voltage to Earth, affected only by the impedance through the ground back to the transformer.  So where you talk about using one half of a
supply and referencing it to Earth, that will only work in places that use the US style of wiring.

They also harmonised the wiring colours - everyone over here should now be using Brown (phase), Blue (neutral), and green/yellow (earth).  Can
you see that this was decided by a committee?  :-)

Cheers,


Howard Winter
St.Albans, England


2007\08\07@074221 by Howard Winter

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John,

On Mon, 06 Aug 2007 12:32:58 -0500, John, N5DWI wrote:

Re: I^2R losses...

> It follows that if the current flowing through the grid can
> be cut in half, the power loss will be only one-fourth.
>
> That's also why cross country transmission lines are sometimes
> many hundreds (or even thousands) of volts.  This reduces the
> amount of current required to transmit the same power but
> greatly reduces the long distance resistance loss.

Indeed!  In the UK "many hundreds" of volts is only used at the consumer level - the lowest delivery voltage to a substation (which may serve a
single street, perhaps a hundred houses or so) is 11.5kV.  The highest voltage is on what's known as the "Supergrid" which is at 440kV.  On a damp
day you can hear the buzzing from those at quite a distance from the pylons!  :-)

Cheers,


Howard Winter
St.Albans, England


2007\08\07@074855 by Gerhard Fiedler

picon face
Hector Martin wrote:

> 1. Americans are wussies. Real men use 220V :)

While this may be... <g>

> 2. (more likely) 110V is older. Once people realized it would be too
> wasteful (thicker wires, etc), other countries started using 220V.
> America (and Japan) probably already had plenty of 110V appliances, so
> it stuck.

... this one is probably not correct. I'm not sure whether there is in fact
evidence that the USA (definitely not Japan) had historically an edge on
electrification compared to the earlier 220-240V countries. E.g. in Germany
the process occurred pretty much at the same time as in the USA: in the
last years of the 19th century.

Here <http://en.wikipedia.org/wiki/Mains_electricity> they trace it back to
Tesla vs Edison, Tesla favoring 240V AC and Edison 110V DC.

Interesting also <http://en.wikipedia.org/wiki/Mains_power_systems>. The
one information they left out in this page is the phase system.

FWIW, the smaller wire sizes in 230V countries are quite easily
recognizable when working with electrical installations :)

>> Also I've heard of people taking the other half wire of a 220v supply and
>> discarding the other.. and using ground as the other half to convert to
>> 110v... a bit dangerous I think...
>
> In 110V areas, it's common for transformers to put out two 110V phases
> out of a single winding, tapping the neutral at the center. If you
> discard the neutral wire and use both 110V phases, you get 220V.

In 230V areas, I think 3-phase is more common (at least in the EU). 230V is
then the star voltage from phase to ground; phase to phase would be 400V.

I find it practical to have a standard 3-phase system in the home (or in
the shop); if you need a heavier motor, there's no need for workarounds or
special utility contracts, you just connect it.

> I don't think you can get 110V out of a 220V supply without a
> transformer, except maybe placing two identical 110V loads in series.

Yes... not recommended :)

Gerhard

2007\08\07@075252 by Gerhard Fiedler

picon face
Howard Winter wrote:

> The voltage is only one difference - the wiring scheme is completely
> different too.  The US design using a centre-tapped transformer isn't
> used here. 3-phase is distributed to the street (and for commercial
> premises often to the consumer).  This is nominally 400V between phases
> (somewhere around that - it used to be 415 here) and 230V between each
> phase and the star point.  The latter is used as the Neutral and is
> earthed at the substation transformer.  The armoured sheath of the cable
> carries the Earth to the consumer along with one Phase and Neutral.

In Germany it is customary to have all three phases at the consumer. Not at
a very small consumer, but something like a normal one-family home would
have three phases.

Gerhard

2007\08\07@075352 by Howard Winter

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Gerhard,

On Mon, 6 Aug 2007 16:33:00 -0300, Gerhard Fiedler wrote:

>...
> In 230V areas, I think 3-phase is more common (at least in the EU). 230V is
> then the star voltage from phase to ground; phase to phase would be 400V.
>
> I find it practical to have a standard 3-phase system in the home (or in
> the shop); if you need a heavier motor, there's no need for workarounds or
> special utility contracts, you just connect it.

I don't remember where you are, but here in the UK it's incredibly expensive to have a 3-phase supply run to a house - it would cost thousands, and
usually it's cheaper to have an inverter to convert single to three phase if you have a workshop machine that needs it.  Or to change the motor to a
single-phase one!  You can get single phase plug-and-socket up to 32A (say 7.5kW) and hard-wired connections up to twice this, so although three
phase is a nicer solution, it's generally not used even by the most ambitious amateur workshop owner!  :-)

Cheers,


Howard Winter
St.Albans, England


2007\08\07@080254 by Russell McMahon

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I've been puzzled by mention of 110 VAC / 220 VAC here and 230V 3
phase in other documents referring to USA mains power, as this does
not translate logically into what is done here. Now, after some
Gargoyling,  I think I know why.

In NZ the residential mains voltage is invariably 230 VAC nominal.
This is distributed along streets as 3 phase 400 VAC nominal. In  3
phase system the 3 phase vectors are 120 electrical degrees apart and
simple geometry shows that the phase to phase voltage is sqrt(3) x the
phase to neutral voltage. Thus 230 VAC x sqrt(3) = 398V ~= 400V. The
400 VAC is derived from local transformers, usually ground mounted
cabinets of a cubic metre or so volume, and much less commonly from
"pole pigs". The street transformers are usually fed from 11 kV or 33
kV AFAIR.

The US does it differently. From my reading I understand the
following:
Local distribution is typically from pole mounted transformers ("pole
pigs") a relatively short distance from homes. The output secondary
voltage is typically 220VAC centre tapped with both halves of the
output being distributed as two "phases" 180 degrees out of phase.
Thus using one "phase" gives 100 VAC nominal and connecting across 2
phases gives 220 VAC nominal as the two halves are directly opposing.
This is quite unlike the NZ situation where each phase is the phase to
neutral connection of a true 3 phase supply. A home may receive two
phases (as mine does) and one could connect equipment phase to phase
to receive a 230V x 1.732 =~ 400 VAC supply BUT this is seldom done.
The next "step up"  is to full 3 phase connection allowing equipment
to be connected in start or delta configurations as appropriate.

When running motors on a NZ 3 phase supply a true 3 phase squirrel
cage induction motor may be used, making use of the "phase rotation"
of the 3 phases. In the US the 2 phase system with it's diametrically
opposed phase system does not allow use of a true 3 phase motor
directly and motors would have to either synthesise a virtual 3 phase
system or use single  induction motors with start winding and run
windings, or capacitor start and run windings to regenerate the
rotating vector.

The US 3 phase system is 230 VAC providing 3 true phases but this is
(apparently) seldom or ever used as multiple single phases. If it was
each phase would be about 230/1.732 =  133VAC. Presumably this is the
reason for substantial internet mention of xxx to 135 VAC equipment.

A 110 VAC single phase system would have a phase to phase voltage of
110 x 1.732 = 190 Vac and 115 per phase gives 200 V phase-phase.
Gargoyling "200 VAC 3 phase" gives only a modest number of hits
suggesting that this system is used but not as commonly as 230 VAC.

How does it look so far ... ? :-)

_____________

FWIW Edison went with DC as, amongst other things,  it was more
efficient over longer distances. BUT Westinghouse went with AC as the
ability to transform voltage with passive non mechanical copper and
iron technology made it more practical in the real world. Westinghouse
won, effectively. Edison promoted his DC systems as safer but for
practical purposes they weren't and AFAIK he had a higher fatality
rate amongst his workers. DC at equivalent voltage is generally more
lethal as it has no cyclical muscular effect which can give the victim
a chance to let go in some cases. Once muscles are activated by DC
they stay that way. I've had a few HV DC shocks (up to 1200 VDC!) but
they were not associated with "fingers clamp on conductor" scenarios
but more "arm is thrown violently away and knuckles are skinned on
chassis etc".  I haven't managed a major DC shock for decades and my
AC shocks are nowadays few and far between. I can't remember with
certainty when I had the last one, so maybe they affect the brain :-).
RF can be nasty but the last of those was long long ago.




           Russell


2007\08\07@081234 by Russell McMahon

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> I don't remember where you are, but here in the UK it's incredibly
> expensive to have a 3-phase supply run to a house - it would cost
> thousands, and
> usually it's cheaper to have an inverter to convert single to three
> phase if you have a workshop machine that needs it.  Or to change
> the motor to a
> single-phase one!  You can get single phase plug-and-socket up to
> 32A (say 7.5kW) and hard-wired connections up to twice this, so
> although three
> phase is a nicer solution, it's generally not used even by the most
> ambitious amateur workshop owner!  :-)

I have 3 phase cabling to the switchboard but only 2 phases live. A
prior owner had a large shed in the backyard and ran a plastic
moulding business 2 shifts per day with 3 phase power to moulders and
lathes etc in basement. The neighbours were unimpressed. Only the
empty switchboards remain.



       Russell


2007\08\07@082902 by Alan B. Pearce

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>This is quite unlike the NZ situation where each phase is the phase to
>neutral connection of a true 3 phase supply. A home may receive two
>phases (as mine does) and one could connect equipment phase to phase
>to receive a 230V x 1.732 =~ 400 VAC supply BUT this is seldom done.

The common reason for supplying two phases to a house is to supply an
electric stove. Where the power connection is made to the stove there is
generally a strap to allow a single or two phase connection to be made. A
two phase connection is made to even out the high current load of the oven
and hotplates across phases, rather than putting all the load on one phase,
and potentially have large current imbalances between phases. However it is
allowable to have the whole stove wired to a single phase, where
(presumably) the cost of providing the extra phase is prohibitive, or
perhaps all stoves in a local area are electric, with the houses spread
across the three phases, hence reducing the need to load balance and thereby
reducing the requirement for two phases into a premises.

2007\08\07@085945 by Chris Smolinski

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I recall that years ago, during a visit to my aunt and uncle's house,
they had problems with the lights being too bright and too dim in
various parts of the house. Turns out the incoming neutral had come
loose. As a result, the various 120V circuits in the house were
acting as a voltage divider, variable of course depending on what the
loads were. I don't recall anything getting blown up, so the loads
must have fortunately been fairly close to matched ;-)

We live in an "all electric" house, our furnace is a heat pump,
electric stove and water heater, even an electric water pump for the
well. All 240 volt powered.  Yes, a real bear when the power goes
out. I've got a 7.5 kW generator which can power the well pump and
water heater, as well as various small appliances. Although not the
toaster oven and microwave, while the well pump and running and the
water heater is heating, as my wife has discovered ;-)

A few years ago, the power went out on a very cold winter day. We've
got a kerosene heater for such occasions as well. It finally came
back on at around midnight. When I switched back to the grid, I
noticed the lights were very dim, and the ceiling fan was turning
rather slowly. I got out the voltmeter, and was only getting around
100V. Everyone here uses heat pumps, so I suspect that the demand
created by everyone running their resistance heat (heat pumps don't
work well when it is very cold, and if the difference between the
actual room temperature and thermostat setpoint is too large, they
switch to resistance heat) was causing massive voltage drops on the
power lines in the neighborhood.

--

---
Chris Smolinski
Black Cat Systems
http://www.blackcatsystems.com

2007\08\07@091831 by Russell McMahon

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>I recall that years ago, during a visit to my aunt and uncle's house,
> they had problems with the lights being too bright and too dim in
> various parts of the house. Turns out the incoming neutral had come
> loose.

Friends had someone wire their house up with phase and neutral
reversed.

Cold water boiled in the pipes with moaning noises as the mains went
to ground via the water pipes :-).
Nothing blew - pole fuse must have been "bigger than usual".

Worms crawled out of the ground (really!).

I suspect somebody lost their job.
Someone could easily have died.


           Russell

2007\08\07@093415 by Chris Smolinski

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>Friends had someone wire their house up with phase and neutral
>reversed.
>
>Cold water boiled in the pipes with moaning noises as the mains went
>to ground via the water pipes :-).
>Nothing blew - pole fuse must have been "bigger than usual".
>
>Worms crawled out of the ground (really!).
>
>I suspect somebody lost their job.
>Someone could easily have died.

Ouch. That's pretty bad.

Shortly after I moved into this place (new construction), I noticed
the lights in one upstairs room would sometimes flicker. I went down
to the panel, wiggled the breaker, and the lights flickered. So I
opened up the panel, and noticed the wire was loose. Tightened the
screw on the breaker. No, not part of a turn, or one turn, but lots
of turns. It had never been tightened. Checked other breakers. Same
thing, on the entire left side of the panel. Not a single screw had
been tighted, the wires were just shoved in. Must have taken a month
or two for oxidation to finally start to affect the connection from
the wire resting against the terminal.

I'm figuring that code inspection in this county involves the
inspector counting and verifying that the contractor has indeed given
him a full dozen donuts.

--

---
Chris Smolinski
Black Cat Systems
http://www.blackcatsystems.com

2007\08\07@095417 by Hector Martin

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Gerhard Fiedler wrote:
> FWIW, the smaller wire sizes in 230V countries are quite easily
> recognizable when working with electrical installations :)
Or power strips. When I first bought a power strip in the US, I was
wondering what the heck was up with the huge cord. Then it hit me.

Also, even though wiring is supposed to be thicker, it still performs
worse than in Europe, at least where I've been. In the USA dorm where I
stayed (I study in the US), every time the fridge compressor turned on
the lights dimmed slightly. I've yet to see anything like that here in
Spain, although I've heard it's common in the US.


--
Hector Martin (EraseMEhectorspam_OUTspamTakeThisOuTmarcansoft.com)
Public Key: http://www.marcansoft.com/marcan.asc

2007\08\07@101926 by Howard Winter

face
flavicon
picon face
Russell,

On Wed, 08 Aug 2007 01:17:54 +1200, Russell McMahon wrote:

> Friends had someone wire their house up with phase and neutral
> reversed.
>
> Cold water boiled in the pipes with moaning noises as the mains went
> to ground via the water pipes :-).

This is confusing me - why would it get to the ground connection in the first place?  Do you know what type of earthing system they had (TT, TN-C,
TNC-S, etc) ?  I'm trying to work out a circuit diagram that would have that effect, and so far failing miserably...

At one time it was common to use the incoming water pipe as an "earth rod" but since a lot of water pipes are plastic now - nobody lays metal pipes
from the main into the house these days - so this was banned some time ago.

> Nothing blew - pole fuse must have been "bigger than usual".

It would only blow if excessive current was flowing, not necessarily if it was flowing to the wrong place.  Even a short to earth would only blow the
fuse if the earth-loop impedance was low enough, and certain wiring faults could mean that it wasn't.

> Worms crawled out of the ground (really!).

I believe that's fairly common in situations like this - "they don't like it up 'em!"  :-)

> I suspect somebody lost their job.

I hope so...

> Someone could easily have died.

Quite!

Cheers,





2007\08\07@105208 by Tony Smith

picon face
> Friends had someone wire their house up with phase and
> neutral reversed.
>
> Cold water boiled in the pipes with moaning noises as the
> mains went to ground via the water pipes :-).
> Nothing blew - pole fuse must have been "bigger than usual".
>
> Worms crawled out of the ground (really!).
>
> I suspect somebody lost their job.
> Someone could easily have died.
>
>             Russell


A plumber acquaintance was once asked "Is plumbing a hard job?", to which he
replied (verbatim) "Nah, poofters job.  A bit smelly at times."

A while later he added "...dodgy earths can make life exciting".

That situation is on the exciting side of exciting.  Usually it's a case of
making an earth by attaching wire the nearest convenient piece of pipe,
house gets renovated, power off, rusty pipes removed, power back on, plumber
suddenly discovers he's the earth.  Exciting for the plumber...

Tony

2007\08\07@105429 by Russell McMahon

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>> Friends had someone wire their house up with phase and neutral
>> reversed.

>> Cold water boiled in the pipes with moaning noises as the mains
>> went
>> to ground via the water pipes :-).
>
> This is confusing me - why would it get to the ground connection in
> the first place?  Do you know what type of earthing system they had
> (TT, TN-C,
> TNC-S, etc) ?  I'm trying to work out a circuit diagram that would
> have that effect, and so far failing miserably...

On the switchboard ground and neutral are connected by a link.
Ground is connected to a waterpipe ground connection.

Phase is now connected from the street to where neutral ought to be.
Current flows from mains phase to switchboard neutral to switchboard
ground to waterpipe ground to true ground and thence back to utility
supply transformer ground. The are "problems".

Current flow SHOULD be massive as it's limited mainly by loop
resistance. The thing that probably caused the fuse not to blow would
be the two ground resistances at house and transformer. If these were
eg 1 ohm each them Imax is about 100 A. That's still 23 kW which would
give the water pipes a good heating. If the pipes are steel and the
ground resistance a bit lower than above then the pipe resistance
could be a significant part of the loop resistance and "heating may
occur". It did. Steam came out the cold taps when turned on.



       Russell









2007\08\07@111529 by Russell McMahon

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>> Friends had someone wire their house up with phase and
>> neutral reversed.

>> Cold water boiled in the pipes with moaning noises as the
>> mains went to ground via the water pipes :-).
>> Nothing blew - pole fuse must have been "bigger than usual".

> That situation is on the exciting side of exciting.

Sadly I didn't see it happen. I arrived minutes after it had been
fixed and got told all about it.




               Russell





2007\08\07@125127 by Matthew Bajor

picon face
It was my senior year in high school and the school was being renovated.
Because of this, we were put into some shody, makeshift classrooms in one of
the school gyms. Anyway, one of the kids in my pre-engineering class decided
to remove a temporary light switch panel and shove a paperclip inside. Well,
on the way out of class, I ended up touching it with a large rolled up piece
of drafting paper by accident. Sparks flew out of the wall like a fireball
and the lights went out in the entire school..... and the entire group of
houses around the school. All of the students were evacuated to the football
field. In all, about a .5 square mile radius of power outage. Eventually the
principle with the help of the electrical contractors found out it was me
(not sure how, no one saw me bump the switch) and I got called down to the
office. Expecting to be slapped with a heavy punishment I was suprised to
hear the principle ask " Is your hair naturally curly?" and thats it,  which
it is.

>From that day on, I knew I was meant to be an electrical engineer.

The contractors were eventually fired for poor work. Though I am still
unsure how such an area was effected by one little switch. The principle
mentioned a temporary high voltage wire going through the wall for
contruction, but that seems beyond unusual.



On 8/7/07, Russell McMahon <apptechspamspam_OUTparadise.net.nz> wrote:
{Quote hidden}

> -

2007\08\07@145900 by peter green

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> I don't remember where you are, but here in the UK it's incredibly expensive to have a 3-phase supply run to a house - it would cost thousands
I think the issue is not so much that three phase supplies are much more
expensive as that having stuff changed in the leccy boards network is
always very expensive and most houses are not fitted with 3 phase at
build time.

all but the smallest commercial buildings here in the UK tend to have 3
phase though.

2007\08\07@164224 by Spehro Pefhany

picon face
Quoting peter green <@spam@plugwashKILLspamspamp10link.net>:

>
>> I don't remember where you are, but here in the UK it's incredibly  
>>  expensive to have a 3-phase supply run to a house - it would cost  
>>  thousands
> I think the issue is not so much that three phase supplies are much more
> expensive as that having stuff changed in the leccy boards network is
> always very expensive and most houses are not fitted with 3 phase at
> build time.
>
> all but the smallest commercial buildings here in the UK tend to have 3
> phase though.

Aside from the cost of a drop and meter board for 3-phase, in North America,
the phases are not necessarily brought down residential streets. On larger
streets you can see all three phases where overhead wires are present,
but I think they just bring a single phase at relatively low voltage
(4kV?) down smaller residential streets. All industrial and I think
most commercial
buildings have 3-phase, often at 600VAC for the former in Canada (480V
in the US)

Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
KILLspams...KILLspamspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




2007\08\08@095642 by Gerhard Fiedler

picon face
Howard Winter wrote:

>> In 230V areas, I think 3-phase is more common (at least in the EU). 230V
>> is then the star voltage from phase to ground; phase to phase would be
>> 400V.
>>
>> I find it practical to have a standard 3-phase system in the home (or
>> in the shop); if you need a heavier motor, there's no need for
>> workarounds or special utility contracts, you just connect it.
>
> I don't remember where you are, but here in the UK it's incredibly
> expensive to have a 3-phase supply run to a house - it would cost
> thousands, and usually it's cheaper to have an inverter to convert
> single to three phase if you have a workshop machine that needs it.  

I'm now in Brazil. Here, in most areas it depends on the registered
consumption (amount and type) how many phases the utility company "grants"
you :)

Probably similar in Germany, even though most normal houses there have 3
phases. (The house where I live now has 2, but would have 3 in Germany.)
There is not really a reason not to - where you get your 1 or 2 phases
from, there's the third right there :)

> so although three phase is a nicer solution, it's generally not used even
> by the most ambitious amateur workshop owner!  :-)

Yes, but that's for political/bureaucratic reasons and not technical ones.
Of course, in a place where 3-phase supply is very rare (and expensive) in
workshops, workshop equipment for sale won't generally be 3-phase. But if
the bureaucratic hurdles went away for some odd reason, you probably would
see 3-phase equipment enter the market. It's better for the stability of
the grid, too.

Gerhard

2007\08\08@105426 by Herbert Graf

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On Tue, 2007-08-07 at 15:53 +0200, Hector Martin wrote:
> Gerhard Fiedler wrote:
> > FWIW, the smaller wire sizes in 230V countries are quite easily
> > recognizable when working with electrical installations :)
> Or power strips. When I first bought a power strip in the US, I was
> wondering what the heck was up with the huge cord. Then it hit me.
>
> Also, even though wiring is supposed to be thicker, it still performs
> worse than in Europe, at least where I've been. In the USA dorm where I
> stayed (I study in the US), every time the fridge compressor turned on
> the lights dimmed slightly. I've yet to see anything like that here in
> Spain, although I've heard it's common in the US.

That has more to do with the age of the building and the codes used for
it's construction (i.e. wire gauges used, number of outlets per circuit,
etc.). My parent's house in Austria was built in the 70s and experiences
slight dimming when something "big" starts up. My house here in Canada
was built in the late 80s and I've never seen a "dim" occur.

TTYL

2007\08\09@093131 by Russell McMahon

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> Yes, but that's for political/bureaucratic reasons and not technical
> ones.
> Of course, in a place where 3-phase supply is very rare (and
> expensive) in
> workshops, workshop equipment for sale won't generally be 3-phase.
> But if
> the bureaucratic hurdles went away for some odd reason, you probably
> would
> see 3-phase equipment enter the market.

The market here in NZ is pretty much an open one. If you want 3 phase
you can pay for it at the going rates. It's widely (almost
universally) used commercially and homes can have it if they want it.
I still have the circuitry connected and the empty spaces in the
switchboard where the 3 phase meters used to be. 3 phase motors are
common and 2nd hand ones are often cheaper per kW (or HP) than single
phase ones. *

I have two phases running with single phase meters but nothing
connected phase to phase, but I could have. At one stage the home was
used as a (small) rest-home which explains the existing divided phases
and dual meters.

One phase roughly serves the main residential part of my house and
some of "downstairs". The other serves a rear wing where I have an
office and much of downstairs where my workshops are. Occasionally we
lose one only phase - usually the residential one. More rarely we lose
both. Outages are usually minutes rather than hours in this area when
they do occur. I have a small petrol alternator which could provide
core power for a few PCs and internet if I wished to use it. 2 PCs and
internet run on a small UPS for graceful shutdown. Others take their
chances so far :-(.



       Russell

* eg $NZ35 (about $US27) buy now

     I have 5, 4 kw 3Phase motors in good order. All are used but are
in great working order with good bearings. the shaft diameter is 28mm
with an 8mm key and base monuted 6" between hole centres . If you have
any quiries please ph Garry 0211579111 or 098283123 wrk you are
bidding on one motor only



       http://www.trademe.co.nz/Business-farming-industry/Industrial/Engines-motors/auction-112386300.htm?p=3

Zillions of 3 phase motors

       http://www.trademe.co.nz/Browse/SearchResults.aspx?searchType=all&searchString=3+phase+motor&searchRegion=100&type=Search


$NZ15 buy now 3 HP !!!

       www.trademe.co.nz/Business-farming-industry/Industrial/Other/auction-112216671.htm?p=47

2007\08\09@104049 by Tomas Larsson

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Here in Sweden we can't get anything but 3-phase, it's sort of standard
regardles if it is for domestic use or professional use.
All homes (apart for some few built long time ago) is wired for 3-ph, same
goes for shops, offices etc.

With best regards

Tomas Larsson
Sweden
http://www.tlec.se
http://www.ebaman.com

Verus Amicus Est Tamquam Alter Idem

2007\08\10@073108 by Howard Winter

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Russell,

On Wed, 08 Aug 2007 02:54:37 +1200, Russell McMahon wrote:

> On the switchboard ground and neutral are connected by a link.
> Ground is connected to a waterpipe ground connection.

With no earth conductor back to the substation?  OK, this is TNC-S: Earth ("Terre") / Neutral Combined, then Separated.  It's not the best scheme, but
it is getting more common now as it's cheaper than having a separate earth conductor.

> Phase is now connected from the street to where neutral ought to be.
> Current flows from mains phase to switchboard neutral to switchboard
> ground to waterpipe ground to true ground and thence back to utility
> supply transformer ground. The are "problems".

Got it!  The only consolation is that it would be rather hard to get a fatal shock in the house, as everything metal is connected to Phase - you'd need
an independant path to Earth to get much to flow through you.  I'm not saying it's safe, but it's slightly safer than it sounds at first... anything outside,
or in a shed, though, has a good chance of being fatal.

> Current flow SHOULD be massive as it's limited mainly by loop resistance.

...which can be massive in a situation like this.  The connection via the pipe to Earth is dodgy, at best - depending on the pipe it could be that rust and
paint would the majority of the conducting surface, and the dampness of the ground plays a big part.  I've seen cases where Earth Loop Impedance
using an earthing rod varied from a few ohms to a few k, depending on the weather.  Anything more than a few ohms and you're not going to blow
any fuses.  Of course, in this case the only fuse in circuit is the distribution one at the transformer, so you'd need hundreds or thousands of amps to
blow that!

>The thing that probably caused the fuse not to blow would
> be the two ground resistances at house and transformer. If these were
> eg 1 ohm each them Imax is about 100 A. That's still 23 kW which would
> give the water pipes a good heating. If the pipes are steel and the
> ground resistance a bit lower than above then the pipe resistance
> could be a significant part of the loop resistance and "heating may
> occur". It did. Steam came out the cold taps when turned on.

LOL!  The water itself will conduct somewhat, of course, so some heating may be direct.  But the fact that someone could turn on a tap and live to
tell the tale supports what I said above about it being "slightly safe"!  :-)

This would not happen here if the current wiring regs. were followed - a TNC-S setup has to have "Protective Multiple Earth" in place, which
basically means that the supplier has to provide a real connection to the ground at a lot of places down the wire from the substation to the
consumers - such as having earthing rods at each tap.  This brings down the earth impedance, so ensuring that there's enough current to blow
fuses/trip breakers when a short to earth happens.  Further, Residual Current Devices (RCDs) have to be in place to protect any sockets that may be
connected to something outdoors, and this is taken to mean any ground floor socket, as people run extension leads outside from any convenient
point.  This would certainly have tripped in the situation above, and although it wouldn't have disconnected the mains itself, it would at least have
alerted the sparky that there was something wrong.  Finally, the circuits should have been tested (and results recorded) before being released to the
user, and that would have shown the fault pretty quickly - I'd like to have seen the results of an Earth Loop Impedance test...

A lot of people think that the wiring regulations are a nuisence, and are being over-protective because doing the job properly means they "aren't
needed", but they aren't designed to protect people from a job well done!  :-)

Cheers,


Howard Winter
St.Albans, England


2007\08\10@073254 by Howard Winter

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Russell,

On Wed, 08 Aug 2007 03:13:40 +1200, Russell McMahon wrote:

> >> Cold water boiled in the pipes with moaning noises as the
> >> mains went to ground via the water pipes :-).
> >> Nothing blew - pole fuse must have been "bigger than usual".
>...
> Sadly I didn't see it happen. I arrived minutes after it had been
> fixed and got told all about it.

Did they offer you a cup of tea, straight from the cold tap?  :-)

Cheers,



Howard Winter
St.Albans, England


2007\08\10@075445 by Howard Winter

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Peter,

On Tue, 07 Aug 2007 19:59:05 +0100, peter green wrote:

>
> > I don't remember where you are, but here in the UK it's incredibly expensive to have a 3-phase supply run to a house - it would cost thousands
> I think the issue is not so much that three phase supplies are much more
> expensive as that having stuff changed in the leccy boards network is
> always very expensive and most houses are not fitted with 3 phase at
> build time.

Well yes, it's obviously cheaper at build time, but I don't think ordinary houses would ever have three phase installed - first there's no point (only an
amateur engineer with heavy workshop machinery would need it) and secondly it's more dangerous, because a shock across phases is a much higher
voltage than a phase-neutral one.  In offices which have more than one phase supplying single-phase sockets, there are strict regulations on how it's
done, with minimum distances between sockets on different phases and things like extension leads and long cables banned, to make it "impossible" to
get yourself across phases.

But there's no need to change the network - it's just a case of replacing the 1-phase cable from the road to the house with a 3-phase one - the
cable in the road is 3-phase.  But making a live connection is always expensive, not to mention all the digging up of the road.  When I was a student I
worked on a building site during the holidays, and saw how the connection is made - we laid the cable from the house to the path (the cable wasn't
under the road as such, luckily) and dug a trench around the point where the cables met.  It was about 9" clear under the main cable, and about 18"
wide, and wet!  The men from the electricity board arrived (one to do the work and a mate standing by for safety), threw a rubber mat into the
trench, and standing on the mat (also wearing Wellies) he unwrapped the outer sheath, separated the armour and pulled the conductors apart,
unwrapped the insulation around the appropriate phase and neutral (not at the same time!), and soldered our cable to it, then re-insulated and
sealed it all up - all with the power live!  It occurred to me that if someone had tapped him on the shoulder at the wrong moment, it could have gone
spectacularly wrong!  But what surprised me was the apparent lack of safety precautions - I would at least have flicked my finger on the conductor
before getting hold of it, just in case...  I heard that the fee for making the connection - which took less than half an hour - was about what I was
getting paid for a week's work.  I understand it's rather a lot more (relatively) than that nowadays.

Cheers,


Howard Winter
St.Albans, England


2007\08\10@082834 by peter green

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Howard Winter wrote:
>
> In offices which have more than one phase supplying single-phase sockets, there are strict regulations on how it's
> done, with minimum distances between sockets on different phases
There is a minimum distance given but you can put them closer so long as
you use danger 415V labels.

>  and things like extension leads and long cables banned,
there are lots of places where there are single phase sockets on
multiple phases and extention leads are everywhere. Ever been into the
non public areas of a theatre or a typical university lab?

>  
> But there's no need to change the network - it's just a case of replacing the 1-phase cable from the road to the house with a 3-phase one - the
> cable in the road is 3-phase.
In other words a minimum of replacing all the kit in the premisis
digging up to the road, disconnecting the old supply cable from the main
cable (live), connecting the new cable (also live). If you need a new
transformer or a third wire adding to some 11KV lines then the price
will be even higher.

>  But making a live connection is always expensive, not to mention all the digging up of the road.  When I was a student I
> worked on a building site during the holidays, and saw how the connection is made - we laid the cable from the house to the path (the cable wasn't
> under the road as such, luckily) and dug a trench around the point where the cables met.  It was about 9" clear under the main cable, and about 18"
> wide, and wet!  The men from the electricity board arrived (one to do the work and a mate standing by for safety), threw a rubber mat into the
> trench, and standing on the mat (also wearing Wellies) he unwrapped the outer sheath, separated the armour and pulled the conductors apart,
> unwrapped the insulation around the appropriate phase and neutral (not at the same time!), and soldered our cable to it, then re-insulated and
> sealed it all up - all with the power live!
nowadays i belive they tend to use insulation displacement connectors to
avoid exposing too much live metal.
>  It occurred to me that if someone had tapped him on the shoulder at the wrong moment, it could have gone
> spectacularly wrong!  But what surprised me was the apparent lack of safety precautions - I would at least have flicked my finger on the conductor
> before getting hold of it, just in case...  I heard that the fee for making the connection - which took less than half an hour - was about what I was
> getting paid for a week's work.  I understand it's rather a lot more (relatively) than that nowadays.
>  
Of course the person doing the work and taking the risk does not get
most of that :(

2007\08\10@231609 by Peter Todd

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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Fri, Aug 10, 2007 at 12:54:32PM +0100, Howard Winter wrote:
{Quote hidden}

Reminds me of how I felt watching the gas company replace all the pipes
going from the gas mains to the houses on my street a few years back.
Everything was done live, the workers simply chopped the existing copper
line in half with a non-sparking tool, manually bent it to stop too much
gas leaking out, and replaced it with a plastic pipe. The whole
neighboorhood stunk of gas for weeks.

Probably a lot less dangerous than live splicing though, natural gas
floats for one, so it dissipates very quickly.

Now that said... I've read that lineman will do *full-tension*
resplicing of HV cables on towers, via chopper... Couldn't find any
details on exactly what that involves, sounds fun!

- --
http://petertodd.org
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2007\08\10@234917 by Nate Duehr

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On Aug 10, 2007, at 9:15 PM, Peter Todd wrote:

> Reminds me of how I felt watching the gas company replace all the  
> pipes
> going from the gas mains to the houses on my street a few years back.
> Everything was done live, the workers simply chopped the existing  
> copper
> line in half with a non-sparking tool, manually bent it to stop too  
> much
> gas leaking out, and replaced it with a plastic pipe. The whole
> neighboorhood stunk of gas for weeks.

Well, technically natural gas is odorless, and the neighborhood stunk  
of the additive they add to allow you to know you have a gas leak.

> Probably a lot less dangerous than live splicing though, natural gas
> floats for one, so it dissipates very quickly.

It dissipates so quickly, it stunk for weeks.  ;-)

> Now that said... I've read that lineman will do *full-tension*
> resplicing of HV cables on towers, via chopper... Couldn't find any
> details on exactly what that involves, sounds fun!

Well, here's some guys doing inspections:

http://youtube.com/watch?v=9tzga6qAaBA

And this guy looks like he might be doing a small repair:

http://youtube.com/watch?v=uEKbMMHAwm0

--
Nate Duehr
RemoveMEnateTakeThisOuTspamnatetech.com



2007\08\10@235628 by Jake Anderson

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>
> Now that said... I've read that lineman will do *full-tension*
> resplicing of HV cables on towers, via chopper... Couldn't find any
> details on exactly what that involves, sounds fun!
>  

saw a video of it once.
The crew wear metallised suits (like a normal set of overalls with metal
threads woven in including gloves). They stand on a platform out the
side of the chopper and clip the helicopter itself onto the line with
this big metal clipy type thing (it wouldnt hold the helicopter on to
the line or anything, looks like a bent coathanger with some more of
their fancy cloth hanging off it in a strap) the "clipping on" procedure
threw arcs about 30cm long and the guy doing the clipping was hanging
onto the thing while the big arc was being made like it was nothing.
Then helicopter then hovers next to the bit that needs repair and the
person wraps new conductors on or whatever needs doing.

If its a long repair and the wires are suitable (IE 3 cables carrying
the one phase all bundled together) they dropped the person off on the
cables and he walked along the bottom one holding the other two.

2007\08\11@001202 by Nate Duehr

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flavicon
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On Aug 10, 2007, at 9:15 PM, Peter Todd wrote:

> Reminds me of how I felt watching the gas company replace all the  
> pipes
> going from the gas mains to the houses on my street a few years back.
> Everything was done live, the workers simply chopped the existing  
> copper
> line in half with a non-sparking tool, manually bent it to stop too  
> much
> gas leaking out, and replaced it with a plastic pipe. The whole
> neighboorhood stunk of gas for weeks.

Well, technically natural gas is odorless, and the neighborhood stunk  
of the additive they add to allow you to know you have a gas leak.

> Probably a lot less dangerous than live splicing though, natural gas
> floats for one, so it dissipates very quickly.

It dissipates so quickly, it stunk for weeks.  ;-)

> Now that said... I've read that lineman will do *full-tension*
> resplicing of HV cables on towers, via chopper... Couldn't find any
> details on exactly what that involves, sounds fun!

Well, here's some guys doing inspections:

http://youtube.com/watch?v=9tzga6qAaBA

And this guy looks like he might be doing a small repair:

http://youtube.com/watch?v=uEKbMMHAwm0

--
Nate Duehr
spamBeGonenatespamBeGonespamnatetech.com



2007\08\11@045247 by Russell McMahon

face
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> Well, technically natural gas is odorless, and the neighborhood
> stunk
> of the additive they add to allow you to know you have a gas leak.

To see your picky picky and raise you a nit-picking rebuttal.

What they sell you is "gas". It happens that the gas has more than one
component. One of the components is added to give it a malodorous
odour. But, the gas as a whole is what stinks, even though it's
principally one component that cause this. To start having to qualify
"X does Y" about products or substances by saying "Component Z of X
does Y when conditions qqq apply except when sss applies or on bank
holidays, but ..." is a path to confusion.

:-)


       Russell


2007\08\11@045247 by Russell McMahon

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flavicon
face
> Reminds me of how I felt watching the gas company replace all the
> pipes
> going from the gas mains to the houses on my street a few years
> back.
> Everything was done live, the workers simply chopped the existing
> copper
> line in half with a non-sparking tool, manually bent it to stop too
> much
> gas leaking out, and replaced it with a plastic pipe. The whole
> neighboorhood stunk of gas for weeks.

Stopping gas flow can be dangerous - air can leak back into the pipes
and ... .
So having a bit of positive flow at all times is more desirable.


       Russell


2007\08\11@081828 by Gerhard Fiedler

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Russell McMahon wrote:

>> Well, technically natural gas is odorless, and the neighborhood stunk of
>> the additive they add to allow you to know you have a gas leak.
>
> To see your picky picky and raise you a nit-picking rebuttal.
>
> What they sell you is "gas". It happens that the gas has more than one
> component. One of the components is added to give it a malodorous odour.
> But, the gas as a whole is what stinks, even though it's principally one
> component that cause this. To start having to qualify "X does Y" about
> products or substances by saying "Component Z of X does Y when
> conditions qqq apply except when sss applies or on bank holidays, but
> ..." is a path to confusion.

I saw the smiley, but couldn't really tell what it means (besides the
smiley :)

E.g. couldn't it be that while the burning part of the gas floats and
dissipates quickly, the stinking part doesn't, which could explain the
stinking neighborhood? Don't know whether this is the case, but looking at
what's in things is often an eye opener. (Highly recommended with food...
not all bread is made alike :)

Gerhard

2007\08\11@084712 by Jake Anderson

flavicon
face

> I saw the smiley, but couldn't really tell what it means (besides the
> smiley :)
>
> E.g. couldn't it be that while the burning part of the gas floats and
> dissipates quickly, the stinking part doesn't, which could explain the
> stinking neighborhood? Don't know whether this is the case, but looking at
> what's in things is often an eye opener. (Highly recommended with food...
> not all bread is made alike :)
>
> Gerhard
>  
I find it most interesting to take a look at the ingredients list on my
other half's wakeup.
She still whacks me over the "peel off face mask = wood glue" incident ;->

2007\08\11@221732 by Peter Todd

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On Sat, Aug 11, 2007 at 01:55:47PM +1000, Jake Anderson wrote:
{Quote hidden}

Ahh, yeah I've seen a number of video's of that sort of operation. Very
impressive piloting. The company website that I saw the "full tension
splicing" mentioned had some video's like that as well, but not one of
the splicing operation.


A neat twist is aparently a number of those outfits are beginning to use
standard rock climbing gear instead of helicopters, especially for
rescue operations. Turns out nylon climbing rope, if stored carefully,
is sufficiently insulating that you can rappel down from some tied to
the upper ground wire to the lower energized conductors. Probably much
less expensive and safer than messing around with closely hovering
formations of spare parts...

- --
http://petertodd.org
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2007\08\11@221732 by Peter Todd

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On Sat, Aug 11, 2007 at 09:18:02AM -0300, Gerhard Fiedler wrote:
> E.g. couldn't it be that while the burning part of the gas floats and
> dissipates quickly, the stinking part doesn't, which could explain the
> stinking neighborhood? Don't know whether this is the case, but looking at
> what's in things is often an eye opener. (Highly recommended with food...
> not all bread is made alike :)

Sadly, the explanation is really simple:

It took the guys about 2-3 weeks to completely replace all the pipes in
the neighboorhood. All done incrementally, so there was always somewhere
with gas leaking out.

- --
http://petertodd.org
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2007\08\11@221734 by Peter Todd

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On Sat, Aug 11, 2007 at 06:57:45PM +1200, Russell McMahon wrote:
{Quote hidden}

Ahh, good point...

So when they bring major new gas pipelines into operation what do they
do? Purge them with nitrogen/co2 first?

- --
http://petertodd.org
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2007\08\15@194500 by Barry Gershenfeld

face picon face
>>There is also the issue of safety.  110 is marginally safer than 220.

The electrocution hazard is lower at 110.  But the risk of fire is greater
due to the correspondingly higher currents needed. (If there's a wiring
fault).  Even more surprising is that it's more difficult to "let go" at
60Hz than at 50Hz.  My EE friends told me this; you may want to check up on
them.

Barry

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