I received this in an email from a friend while we were discussing some house wiring issues.
This friend lives "I was assuming (rightly or wrongly) that in the states, like us, some devices which are double insulated have a 3 prong plug moulded onto the cable but the ground prong is not actually wired up. Here, all of our plugs and wall sockests are 3 pin."
Do they (the UK) really use 3 pronged plugs without a ground wire connected to the ground pin on double insulated devices?
Can't speak about 3 prong but I have some single pole switches not grounded. In fact they don't have a ground connection on them. I do see the newer single pole switches with a ground screw that I just purchased this week at homedepot. My house has a grounding rod but I wonder why the couple of switches I saw were not grounded even tho I saw the ground wire inside the box twisted together but not connected to the switches I observed. I was tempted to jump wire them to the switch to ground it but I'm not sure if I would be doing more harm than good??? I'm a newbie in electrical wiring.
It would seem very dumb to have a plug with a ground prong and not have it connected to anything. I've never heard of it in the USA. What would be the point? To make people go find a 3 prong to 2 prong adapter when none is needed?
But as far as it being an NEC violation or safety issue, if it's only on appliances that are double insulated, it's misleading but not really a safety issue. Double insulated doesn't require a ground.
A key point in the comment from my UK friend was "Here, all of our plugs and wall sockests are 3 pin."
That would eliminate the need for a 2 prong adaptor regardless of whether the ground pin was wired or not.
I've never heard of it in the US either, but who has ever checked?
I've opened a few appliances over the years and as far as I recall, anything with a 3 pronged plug had a ground wire from the cord connected to the case.
Did I ever ohm it out to see if the ground pin itself was wired? No.
Have I checked every device with a 3 prong plug to see if the ground pin was wired? No again.
I'd be shocked (no pun intended) to learn that we (and even the UK) use three prong plugs with no ground wire to the pin, but I'm wondering if anyone knows for sure.
All (modern) UK AC outlets have built-in shutters which close off the holes for the AC feed when not in use; the ground (earth) pin on a plug is slightly longer than the two AC pins and its insertion into the outlet is what moves the shutter out of the way so that the plug's AC pins will go in.
For that reason you always see ground pins on UK plugs (and wall-wart type devices), even if the ground isn't actually required by the device.
Newer electrical outlets in the U.S. are showing up with safety shutters but I don't believe a ground pin is required to open them, just both flat prongs pushing against the shutters simultaneously. A toddler usually sticks a fork/paperclip into only one opening in an electrical outlet. Of course, I been told that when I was a crawling rug rat, I pulled the power cord from the bottom of my mother's Singer Sewing Machine and stuck it in my mouth. I've had a taste for electricity ever since. I was told that I turned blue(explains the brain damage) and my extremely full diaper(shocked the crap out of me) had to be changed. ^_^
That's right, the big UK plugs have identical pins for hot and neutral, so a plug without the ground pin would have no way to indicate polarization. Thus I can believe that even double-insulated appliances have a ground pin for that reason alone.
I have no idea if it's contrary to any standards in the US and Canada to have a ground pin where it's not needed, but I've never *noticed* a ground pin on anything marked with the double-insulated symbol.
What I always wondered in a double insulated drill with no ground, if the operator accidently hits a power line say buried in a wall they could be electrocuted.
if the drill were grounded it would trip the breaker
It's been more than ten years since I was in the UK, but yes, I have seen devices with a two-conductor cord and a plug with a *plastic* "ground pin" that serves only to open the shutters and to ensure the correct polarity.
I don't recall what fuses -- and where -- are in devices that come with a preattached plug in the UK, but devices often came without a plug, probably because a variety of outlets were still in use: two small round pins (5A, I think), and three larger round pins (13A, I think) -- perhaps others as well, but those are the two I recall. The more recent system is to have an appropriately rated fuse in the plug: "spare" plugs typically came with a 13A fuse installed, but fuses were available in several different ratings, even as low as 1A, IIRC.
I could not find any last time I was there, but they used to have switched plugs (with slide switches on the edge of the plug opposite the cord entry), so that one didn't have to keep pulling the plugs out to disconnect the device altogether.
I'm curious but not enough to look it up but I wish one of our British friends could answer a question about their wall outlets. Here in the states a wall outlet installed for something like a large window AC unit that runs on 240VAC will not have a neutral if it's a 3 wire outlet. A ground and two hots which will measure 120VAC from the hot to ground or neutral because it's either phase A or B. On the U.K. outlets I'm wondering if there is only one 220VAC hot, one neutral and one ground/earth connection?
Yes, that's all there is to be; they run 240V (or whatever their actual specific level is) just like we run 120V. There's no such thing as 120V as they don't derive it as done in US from the center-tap xfer.
Then that would explain the necessity of making sure the plug is inserted correctly. Of course, Europe uses 50 cycle power so their hum on the radio speaker is a lower tone. ^_^
If the cord *has* a ground wire, my expectation is that it would legally have to be, to avoid the situation where someone electrocuted themselves after re-using the plug/cord combo (assuming it had some form of plug/ socket at the far end rather than being hard-wired to the device) with a different (faulty) device where the ground was needed.
However, it used to be quite common for devices where there was no ground requirement (e.g. radios) to have only two wires (live and neutral) in the supply cord - no ground. In that situation, the earth (ground) pin would still be present in the plug, but obviously not connected to anything. Back then, all plugs could be taken apart by the end-user to get at the integral fuse though; at some point molded plugs started appearing (the fuse accessible via a trapdoor on the plug's underside) on new devices, and that's where I can't be 100% certain of the answer - I don't know for sure if two-core cords were outlawed at that stage or not.
The only UK-style molded plug I have with me in the US uses a three-core cord even though the device it powered has no ground requirement), but that's not really enough of a sample to deduce anything ;-)
Oh, the UK plug standard is BS13
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by the way, but I don't think the article says one way or the other about molded plugs on devices with no ground requirement.
there's always a fuse[1] in the plug on anything modern; internal on older or user-replaced plugs, and accessed via a door on the underside of the plug on molded plugs. There may or may not be additional fuses in the device itself. The only exception I know of are for electric razors, which use a 2-pin unfused plug (suitable outlets are available for bathrooms with a built-in isolating transformer in the wall plate).
[1] From memory internal plug fuses on domestic AC could be 13A, 10A, 5A,
3A or 2A. Users typically weren't smart enough to use the right fuse for the device - if the original blew, they'd just toss a 13A fuse in there and call it good...
Very old installations do use all sorts of oddball AC plugs and sockets, but those haven't been seen in houses in a *long* time - by the time I was born in '74 the plugs with 3 rectangular pins were in normal use, and as far as I know had been for years.
You know, I think I remember that too - manufacturers would ship a product with bare wires to save costs and expect you to buy and fit your own plug. All kids were taught how to wire a plug at school...
I don't think I've ever seen one of those! Modern UK outlets all have to have an integral switch as part of the wall plate, but that wasn't always the case with older ones, so I could see how a switch in the plug could be useful. I expect they became illegal (to sell as new) when switched wall outlets became mandatory in new work.
Don't know about the UK and NOW, but in Zambia years back they used the UK style outlets - the switched type and the shuttered type - and there were plugs with plastic pins to open the shutter from what I remember. - If my recollection is correct they would definitely not have been grounded. The pin also establishes polarity (not +/- but line or "neutral")
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