Internal wiring of USA v UK mains plug

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

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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.

I fixed a Weller TCP iron a couple of weeks back that was running cold. A 'wire nut' inside was loose and a connection to the element had become iffy.

Graham

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.

Just to add more aspects to this discussion. In Germany, practically all houses have 400V three-phase electricity, which is three 230V phases 120° degrees apart. So all the normal 230V outlets are just a single phase out of those three plus neutral.

Big appliances in a fixed location like electric ovens and water heaters get all three phases but are not required to use them in balance.

The nice thing about this is that if you want to set up a workshop in your house, all you need is some extra fuses and cable and a couple those nice big, red CEKON sockets.

robert

Leaving aside the joining wires/terminal blocks issue, on the subject of the plugs and sockets, the UK one to me is superior in many ways.

1. fused plugs.
2. cord grip in plugs
3. screw terminals in plugs -no wrapping wires.
4. ALL receptacles and plugs have earth pin.
5. 3 prong design means a better fit (they don't waggle about at all)
6. much thicker pins - handle more current, do not bend, and seem to resist arcing damage better.
7. switched sockets .....etc.

The US /japan one only has the advantage of compact size, personally I can live with a bigger plug if it means better performance. I couldn't care less about cosmetic aspects!

just my tuppence' worth. -B.

Ok, I'll conceed that one, but only 50%, after all, how many people put a 16amp fuse on a .5mm cord?

You can get them in the U.S. I occasionaly use them here for 120 volt equipment (I brought a few items with me) and had a friend bring me some LEVITON (high quality plugs) from the U.S. They ave execelent grips on them.

The Leviton plugs have them too. I'm not sure they are an advantage, the gripping area is the area of the screw shaft,not the circumfrence times the area of the wire surface, a lot smaller.

Cut me a break. Since around 1960 all of the outlets in the U.S. have grounds. In the U.K. you can buy appliances with 2 condoctor cords with two plug pins that can usually be forced into U.K. outlets. They are supposed to be for export to the E.U. but they are sold.

Many of the appliances sold here come that way too, but I must be the only person who cuts them off and puts three pin plugs with large grips on them. I also write the name of the appliance on its plug.

It does not make an difference electricaly, the appliances come with two conductor cords and I don't replace them.

See above.

That's a big problem here. Many appliances use 15-16 amps (at 230 volts) and come with the smaller round plugs which are rated at 16 amps, but not for continuous duty. When we moved into this appartment, all of the outlets had burnt "hot" pins because the previous tenants plugged high current heaters into them.

I replaced the outlet for our oven with an airconditioner plug, which except for the round pins looks like a U.K. plug. It's no longer used we replaced it with a gas oven.

1. switched sockets

Maybe. only good if they are not at floor level.

One advantage we have here in Israel is that all new construction requires a GFI on all outlets. Usually it's BEFORE the main circuit breaker.

As someone said earlier, it depends upon how much you pay. If you buy cheap junk, you get cheap junk. :-)

Geoff.

You've no choice in the UK - all plugs must conform to the BS standard. One without a cord grip wouldn't.

No you can't - legally. With the exception of shavers or toothbrushes etc designed to fit a transformer isolated bathroom outlet, everything must be fitted with a '13 amp' plug with a suitable fuse.

Well if you reach down to plug/unplug you can operate a switch at the same time. Most do as it's sort of bred into them through habit - most outlets have always been switched in the UK.

The usual modern way here is to have a split load consumer unit. One set of MCBs protected by an RCD and one set not. The non protected used for fixed loads like cookers and water heaters where slight leakage might cause an RCD to trip. But we seem to be moving to one RCBO (RCD and MCB combined) per circuit.

In general it's not possible to buy poor quality plugs and sockets in the UK.

This is one example of the bottom end price wise, but will give good service for years.

Of course you can pay several times that much for chrome etc finish accessories.

Electric clothes dryer, stoves/ovens, and permanently installed air conditioners are only available in 240 V versions. Also, larger sizes of electric space heaters. The first three are probably more likely to be wired in directly to a junction box than to use a plug/socket. There are several incompatible types of 240 V plugs. All are huge, bigger than the UK plug, and expensive. Tam