Moulded mains plug failure

On Thu, 01 Jan 2009 02:08:07 +0000, Eeyore put finger to keyboard and composed:

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.

I didn't say that any country had mandated them, but here is one example:

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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.

- Franc Zabkar

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Reply to
Franc Zabkar
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Great, you know a 'pointy headed dunce'. I'll bet he has a 154 IQ, too?

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Reply to
Michael A. Terrell

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.

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Reply to
Michael A. Terrell

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.

Reply to
Mr.T

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

MrT.

Reply to
Mr.T

For him, it might have sentimental value. I have a Portable CTV (Akai) purchased in 1995. Works like brand new. I would'nt part with it.

Reply to
Qanset

Have worked with.

One of the most able engineer-directors I've ever met.

Probably more actually.

Graham

Reply to
Eeyore

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

Graham

Reply to
Eeyore

I agree. And this type removes the need to rewire a plug.

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Ideal for use with one these.

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Graham

Reply to
Eeyore

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

Graham

Reply to
Eeyore

And he is in every Dilbert strip.

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Reply to
Michael A. Terrell

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 :).

Reply to
kreed

NEMA specifies what connector for each application.

Yes, but at the main panel only.

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.

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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Reply to
Michael A. Terrell

You ignorance of electrical codes are a s vast as your knowledge of electronics, in general.

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.

shows 'Results: about 273,000 for gfci plug'.

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

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Reply to
Michael A. Terrell

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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 ?

o

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.

Reply to
kreed

"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

Reply to
Phil Allison

and

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conductors

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.

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.

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.

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.

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

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.

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

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Reply to
Michael A. Terrell

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