Internal wiring of USA v UK mains plug

You can certainly get higher-quality plugs in the U.S., it just requires going to a real hardware/home improvement store rather than the supermarket or dime store. :-)

Keep in mind that, in the U.S., since we don't use ring circuits, a shorted plug is perhaps a skosh safer than the U.K. where the plug and circuit fuse are all in the same connector.

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So the USA has separate fuse for each radial spur to each wall outlet ? each such wiring run requiring more than twice the weight of copper (110V v

I have never seen a house here in the US wired with stranded wire, except for one built in 1906. Generally #14 solid copper. BTW the 3 wire UK plug reminds me of what is used on a clothes dryer or stove here. Would you actually use one of these on a lamp?

Tam

Yes, fitted with a 3 amp fuse...

No, it's just that each radial spur in the U.S. (which typically would serve one room, although I don't know what the actual law requires here) is limited to ~1.8W (120V, 15A), whereas my understanding is that each ring in the U.K. is generally fused at 30A or 32A, allowing a shorted outlet to pull as much at

Yes, this is true, and supposedly it was the cost of copper that drove the U.K. to use ring circuits.

I don't know how much power cabling sells for in the U.K., but I have done some low-voltage (12V) wiring in New Zealand, and it was truly painful to be purchasing, e.g., 2.5mm cable compared to the prices in the U.S.

---Joel

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We have no choice in the matter, by law, we can use 1,2 or 3 amp fuses inside these plugs but thats the only choice

The USA cannot have the equivalent of RoSPA (Royal Society for the Prevention of Accidents), AFAICS none of the USA ones have child preventers on them unless the mouldings on the wall outlets preclude that eventuality of small fiongers touching both pins. The other notable difference is the insulated pins that have been necessary refinement, again by law, for 20 years or so You can just see the orange plastic bits extending up the brass pins on the first pic on this wiki and the black bits on the one lower down on

as an aside someone told me that per million houses there are more house fires in the USA due to wiring faults than any other country, partly due to a lot of timber construction and partly due to the higher current for a given KW of power transfered - is that the case?

SNIP

Have you seen the way they connect their wires? They just twist them together and put a plastic cap over the bare wires! Multiply that by double current and it's no wonder they have fires :)

All heavy loads are connected across 240 Volts. 120 is basically used for things that can be moved from room to room. There seem to be two main causes for electrical fires in the US. One the improper use of extension cords; for example, a 10 foot length of 5 amp wire with a refrigerator and microwave plugged in at the far end. This comes about because older houses and apartments tend to have an insufficient number of wall outlets. Two, there was some problem with houses built about 30 years ago that uses aluminum wire; these require special connection methods. When a home owner replaces a switch or an outlet with a standard device, you have problems. Most home owners here tend to do their own electrical repairs.

I think there is an inherent safety factor in a system where neither side of a 240V circuit is more than 120 V above earth potential. Never heard of a person being electrocuted who was not standing, or otherwise submerged, in water. This costs money. For instance the wiring to an electric clothes dryer will have two 20 Amp hot wires, a 20 Amp neutral wire (from center tap of transformer), and a 20 amp earth ground wire connected to a cold water pipe or ground rod. In some localities, the neutral and ground wires can be tied together at the appliance. I think the only reason for the heavy neutral and ground wires is to make sure the circuit breaker trip in case of a short. As recently as about 20 years ago, a much smaller earth ground wire was used.

The electric use meter must be more expensive than an unbalanced single phase one.

Tam

A colleague in Maryland said that he'd attended a safety talk from what sounded like the equivalent of a Health and Safety guy, who advised that the best way to reduce the probability of fire in the house was to rewire the kitchen sockets using decent ($3) sockets rather than the $0.25 ones the builders use. Apparently it's something to do with quality of the bits of bent metal that make contact... And he also advised to not unplug appliances if possible, since that wore out the sockets faster. Out of curiosity, I bought a double socket for $0.44 at the local Walmart, and was somewhat dismayed by the apparent lack of robustness. No comparison with our 230V 13A sockets, but maybe that's why they are around $4+ each instead. hth Neil

They are called wire nuts, and contain a threaded metal insert. Sort of an inverse of a self tapping screw. I understand the hesitance, but they don't seem to be a problem

Tam

Tam/WB2TT wrote: > someone wrote

We used to have a similar thing but made of ceramic, called a scruit (sp?) (pronounced screw-it) I understand that they may be outlawed these days.

Ron(UK)

"Tam/WB2TT" wrote in news:vtadnShIELmCTB_bnZ2dnUVZ snipped-for-privacy@comcast.com:

Actually a typical US clothes dryer uses a 120/240V 30A circuit. And the ground wire always connects back to the services neutral, where things are grounded with rods and/or plumbing.

They way is was, is that it was permitted to run just a grounded conductor (neutral) to the appliance, and bond that to the case.

Since 1996 or so, that has been prohibited, so separate neutral and grounding conductors must be supplied to a 120/240V appliance.

For the safety ground, yes. For neutral it is assumed, to the terminals in the appliance, that the appliance could draw the full current on the neutral.

If you mean the US ones, 2-wire 120/240 ones are the norm, so are made in quantity enough not to be expensive.

"N Cook" wrote in news:f5u30d$c0e$ snipped-for-privacy@inews.gazeta.pl:

The trick for the screws is to twist the strands anti-clockwise.

Good plugs will have cord grips, and a mechanism you insert the (twisted) conductor into and screw down (although rather different from typical European/UK plugs)

"N Cook" wrote in news:f5u73r$231$ snipped-for-privacy@inews.gazeta.pl:

For general purpose recepticle and lighting circuits, they are wired as radial, but one fuse or breaker per radial circuit.

Yes, but not as much KWs are delivered to GP recepticles as there is in the

Larger appliances that need more power have their own dedicated recepticle (or are hard wired) and circuit.

Sounds dodgy!

I've spent time in the US and Japan, and I have to say that those flat blade sockets are an atrocious design. They suffer sloppy fit problems very easily . Those countries don't seem to have switched wall sockets either, which the Uk standard has, so you get more arcing if plugging in live equipment (which degrades the contacts even further). The UK plugs are more complex, and expensive, but a damn sight safer and a lot more sturdy and resist wear better -only ever had to replace one or two fittings over the years.

I suppose all this is because it is a more recent standard - like the German PAL TV system - which, since it was introduced later, had the edge.

-B.

Most US electric meters, at least the electromechanical kind, have one voltage coil (240 volts, l-l) and two current coils, one in each of the 120 volt phases. That computes power based on an assumption of voltage symmetry, usually a reasonable bet.

John

Done correctly, a quality wire nut is a very secure and long lasting connection. It's not simply a plastic cap, but a plastic casing over a threaded springy metal insert which grips the wires very well. I have some UK terminal blocks, and the problem with them is that there's no mechanical bond between the wires, the contact point is small, and they can and do work loose or corrode over time. They generally are ok, but neither method is greatly superior to the other.

The double current isn't really much of an issue, our large loads are 240V too, it's handy to have both voltages readily available.

You can get quality US style receptacles, problem is they're expensive so few houses come with them. I like many things about the UK plugs, but the thing I don't like is they're *huge* so things like power strips and multi-gang outlets are really cumbersome.

Having discussed this in length with a friend in the UK, we've both come to the conclusion that both systems have many advantages and disadvantages and neither one is a clear winner.

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Could someone direct me to pics of the 2 different types of plug/socket system used in the USA to differentiate for medium and high power use, I didn't even realise 220 or 240V was used residentially anywhere in the USA.

There are several kinds depending upon the current rating and if 120 volts is used too. Before 1996, the ground pin was also used for neutral for things like clothes dryers that had a 120 volt motors and timers and

In 1996, it became illegal. If your device has a mixture of 120 and 240 volt components, you need to have a four wire plug. I left the U.S. in

The simplest kind is used for air conditioners and is similar to a 120 volt grounded plug, with two flat blades and a rounded ground pin below them in the middle. The difference is that the flat blades are the same size and are horizontal instead of vertical.

I remember walking into an electronics store in SoHo (in Lyle Street?) around 1983 and talking to the owner for a while. We got on to discussing the differences in power cords and he showed me the 240 volt cords they sent to the U.S. He was surprised that I was familar with them.

He also showed me a catalog from a U.S. company called Herbach and Rademan that sold surplus electronics. He imported items from them. It was my turn to be surprised, I lived less than 2 miles from them and was a frequent customer. :-)

By 1989, the store was gone, it had become a Chinese grocery. In 2001 I was given a stack of U.K. radio magazines and an article about the store was in one of them. It was written by the nephew of the man I spoke to. Unfortunatley he had no pictures of the store near the end, and although I took many photographs of London that trip, I never thought to take one of the store or his uncle. :-(

Geoff.