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Re: Moulded mains plug failure

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   And he is in every Dilbert strip.


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Re: Moulded mains plug failure
On Wed, 31 Dec 2008 12:25:45 +0000, Eeyore
composed:

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All other things being equal, I would have thought that a 110V system
was safer than a 240V system.

As for mains plugs, the safest ones I've seen are those with an
integral ELCB. Maybe one day they'll be mandatory ???

- Franc Zabkar
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Re: Moulded mains plug failure
snipped-for-privacy@iinternode.on.net says...

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I recall a friend telling me of the US electricians up near exmouth who
installed the VLF submarine comms system many moons ago, they had the habit
(in USA) of wiping one of the wires across the back of the hand, ostensibly to
find the active - from the inevitable reaction etc, Few yelps when doing that
over here...!

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Along with the intelligent power coupling (trekkie talk for mains socket),
which has optical fibre, other voltages, choice of mains source etc etc...

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Mike
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Re: Moulded mains plug failure



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Why ? Both are lethal voltages and 120V as it actually is requires twice the
current carrying capacity with 4x  increased I2R losses and hotter conductors
that catch fire more easily.


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Give me even ONE example. Aside from British.

It seems to me you know little about electricity. Besides, about 90% of the
world uses 220-240V. As ever it's the USA that's the BACKWARD IDIOT.

Graham


Re: Moulded mains plug failure
On Thu, 01 Jan 2009 02:08:07 +0000, Eeyore
composed:

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Presumably US conductors would be twice the diameter, which means that
the I2R losses would be the same. Maybe someone could confirm this.

As for personal safety, it seems reasonable that there may be
circumstances where 240V may be just enough to kill and 120V may not.
It's not like we're comparing 240kV with 120kV. I've been bitten
several times by 240V, once when I grabbed a fractured light switch in
the dark.

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I didn't say that any country had mandated them, but here is one
example:
http://www.clipsal.com/trade/__data/page/4608/W54.pdf

I'm using several of them myself. They are particularly appropriate
for protecting extension cords which are used with outdoor appliances,
especially when your home's wiring predates the mandatory requirement
for ELCBs in the meter box.

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- Franc Zabkar
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Re: Moulded mains plug failure

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   Other than the fact they are called GFCI in the US, some products
have them in their power cords. The reason the US doesn't use a GFCI at
the main panel is because it is illegal to use one on a refrigerator or
freezer.  We use either a breaker with it built in for circuits with
convenience outlets, or outlets with it built in to protect that outlet,
and anything downstream. The British ring circuit concept makes this
impossible.

   Some items are on dedicated circuits for safety reasons.  A kitchen
with an electric stove will have a 50 A 240 circuit, a dedicated 120
circuit for the refrigerator, and two or more 20 A 120 VAC circuits for
countertop outlets.  We use  14 AWG for 15 A circuits, 12 AWG for 20 A
circuits and 10 AWG for 30 A circuits, unless they are longer than
normal runs.


Here is one of many online charts charts for AWG copper wire.

http://home.earthlink.net/~mike.terrell/RefAWG.html


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Re: Moulded mains plug failure

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Given the price of copper, that is a more expensive option though.

MrT.



Re: Moulded mains plug failure



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You beat me to it. The price has gone through the roof recently. What a
waste of resources.

Graham


Re: Moulded mains plug failure
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twice the diameter gives you 4x the conductor cross section surface
area :)

Actually from what I read some years back, in a USA electrical
installation book a friend brought with him when moving here,  many US
domestic installations have a 240v centre tapped supply, 180 out of
phase, IE 2 x 120v "actives" and a "neutral".  (240v across the 2
"actives")

If you had the 2 "phases" well balanced, there would be theoretically
no current flowing in the neutral, however in real
life this would rarely, if ever happen :)

High wattage things like stoves, fixed heaters, air cons etc are run
from the 240v supply
This used the same looking plug as AUS from the photos, but both pins
would be live, and both would be 120v with respect to neutral. There
was no mention of  15, 20, 32a @ 240v sockets, or their pin size and
configuration either.

standard domestic power points would run at 120v.

I cant remember if they bonded the Neutral and Earth together (MEN)
like AUS.

Another thing that has interested me over the years is that whenever I
have seen US 120v sockets, plugs etc they are all rated at "120v, 15A"
which would imply that the maximum wattage would be 1800w not 2400w as
with an Australian power socket. which is 240v 10A.

There is also a 208v 3 phase industrial supply (ie - same basis as our
3 phase system in AUS but half the voltage.).
I don't think this was used in residences.

Maybe one of our US readers could confirm this ?



The other point, from anecdotal evidence, is that the typical US
household uses a shitload more power, in having more powered
appliances, many more lights etc than typically in Australia.  However
in recent years, I think you will find that we are catching up :).







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Re: Moulded mains plug failure

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   NEMA specifies what connector for each application.
<https://www.hubbellnet.com/max_htm/tech_stuff/NEMA/front.html

 
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   Yes, but at the main panel only.


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   Some homes have 208 three phase, but it isn't common.  I've seen it
where there is an elevator or very large well pump, like for a 8" or
larger well.


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   Compared to the total price of building a new house, the copper costs
are still one of the smallest items on the list.


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Re: Moulded mains plug failure



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IEC states that 30V rms or 42VDC and above is 'hazardous'.

Graham


Re: Moulded mains plug failure

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   You ignorance of electrical codes are a s vast as your knowledge of
electronics, in general.
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<http://www.acehardwaresuperstore.com/cooper-wiring-gfci-grounding-plug-p-16749.html?ref42%
is one made to replace existing, non GFCI plugs, or to replace a damaged
molded on GFCI plug. As usual, Google will reveal things you deny exist.

<http://www.google.com/search?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&hs=rdB&resnum=1&q=gfci+plug&um=1&ie=UTF-8&sa=N&tab=iw
shows 'Results: about 273,000 for gfci plug'.


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   Only in your pathetic, America hating, little mind.  It is you who
knows nothing about electrical safety.


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Re: Moulded mains plug failure
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Its more likely that way because the US was one of the first with
public electricity distribution.
Its more likely that the reason it was 120v was to

1> No set standards for voltage, current or anything else at the time
- it was all new - what was it supposed to run on ??

2> limitations on the the insulating materials available at the time
(ie, types of rubber compounds that had been developed at the time,
transformer & alternator winding insulation coatings etc.

3> Loads (compared to now) were probably a lot less, therefore the
currents that flowed were not
considered a problem. The relatively high cost of providing
electricity probably helped minimise wastage and excess usage.
(Remember a lot of homes in Australia only had 32A wiring from the
street. One stove with a few elements/ oven on at the same time could
use up nearly all of that now !!)

4> Might have been more difficult to manufacture light bulbs etc that
lasted as long with higher voltages. These - I think would have been
the main original intended use of electricity - lighting.
IIRC they used other materials for filaments before settling on
tungsten, such as carbon and osmium these might not have been suitable
for higher voltages at the desired wattage needed ?

By the time all these things were sorted out, it was probably too late
to change the standard mains voltage, as too many things were using
it ?  Those who came later settled on 240v based on observations of
past experiences in the US ?.
Its also possible that the different voltages and frequencies were
chosen to provide "trade barriers" to imported appliances too.

Even now - I think it would be a costly and problematic nightmare to
convert the entire US to a 240v system like here. - even worse if it
had to go to 50hz as well.

just my 2c worth - but if there were ever to be a standard for a world
power socket - why not wire homes with the IEC type system like used
on computers and just about everything else these days and even has a
15a version ?




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I will admit, I didn't know that the US used Earth leakage units (GFI)
though it isn't really a surprise that they do.
They are however, now mandatory in some (if not all) states of
Australia.


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Re: Moulded mains plug failure

"kreed"

just my 2c worth - but if there were ever to be a standard for a world
power socket - why not wire homes with the IEC type system like used
on computers and just about everything else these days and even has a
15a version ?


** First you gotta have a world standard for domestic AC voltage and
frequency.

And that just  AIN'T  gonna happen.

No more than world standard for rail gauge or the use of bits of  the VHF
and UHF spectrum.

BTW:

Even now, lotsa gear made for the US and Japanese market has a 3 pin IEC
inlet fitted and one uses an IEC to US mains plug adaptor lead with it  -
but no easy way exists to change the 120V rating to 240V.

Causes  MASSIVE  trouble when the same gear travels outside the US.

Bloody  STUPID  idea.



.....   Phil




Re: Moulded mains plug failure

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and
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and
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the
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conductors
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   Some early US electrical installations were a single 120 V 15 amp
circuit to power light bulbs only.  Of course that was when electricity
was a new thing to most people.

 
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   The range of 90 to 120 volts was considered the best for long lamp
life.  Just like 12 volt is for automotive use.  The planned conversion
to 42 volt systems didn't take this into consideration.


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   part of it is the way that electricity is distributed. A transformer
generally only feeds about four homes. If a home is isolated, it has its
own transformer.  This minimizes distribution losses.   The only
drawback is that the higher the line frequency, the shorter the
distribution network can be before the lines become radiators,
increasing the losses.  That is why long haul HV lines are DC.


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   Some of the early power plants were 16 to 20 Hz, to power huge motors
in mining operations.  Lights flickered a lot.  Some radios were built
for mining towns.  the transformers are huge, to cope with the higher
iron losses at lower frequencies. 60 Hz allows for smaller transformers
and motors than in 50 Hz systems.  Power supplies need smaller filter
capacitors, and the ripple frequency is higher, as well.


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   We already use 240 for high current applications.  Lighting and wall
outlets are 120 VAC.  Everything else is 240.


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   Is there a need for a world wide standard?  A lot of things have
detachable cords, and versions are available for any country they are
likely to be used in.


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   We also have arc fault circuit interrupters that monitor the load for
arcing and trip.

<http://ecatalog.squared.com/techlib/displaydocument.cfm?id48%840-122-03&action=view


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Re: Moulded mains plug failure

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Since ELCB's are already mandatory on new house mains supplies, forcing
every device to have another seems unnecessarily expensive/wasteful IMO.
And even if you're house doesn't have one, fitting them to power boards
rather than every device plug top is a cheaper alternative.

MrT.



Re: Moulded mains plug failure



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I agree. And this type removes the need to rewire a plug.
http://www.wiki.diyfaq.org.uk/index.php?title=Image:PlugInRCD.jpg

Ideal for use with one these.
http://www.play.com/PC/PCs/4-/615685/Belkin-F9E609U3M-6-Way-Economy-Power-Strip-3m-Cable/Product.html?cm_mmc=Froogle-_-PC-_-Accessories-_-Belkin%2BF9E609U3M%2B%2F%2B6-Way%2BEconomy%2BPower%2BStrip%2B%2F%2B3m%2BCable&source50%66&engine=froogle_pc&keyword=Belkin+F9E609U3M+%2F+6-Way+Economy+Power+Strip+%2F+3m+Cable

Graham



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