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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Jonathan Johnson on December 23, 2013, 03:28:22 pm

Title: Power Outlets Worldwide
Post by: Jonathan Johnson on December 23, 2013, 03:28:22 pm
We usually just turn up and have a choice of three industrial connectors to plug into with no problrms.  The US appears to have an ever increasing* inventory of outlets and wiring arrangements, grounding methods, etc.

It's partly due to the fact that we have multiple voltage standards: 120V single phase, 240V single phase, 120/240V single phase, 120/240/208 volt wild-leg single/three phase delta, 120/208V three-phase wye, 277/480V three-phase wye, etc.

Add to that the fact that there are several different amperages (15A, 20A, 30A, 50A, etc.) in common use, and the array of cord-and-plug configurations becomes bewildering.

Since previous standards allowed for bootleg ground (grounding through the neutral wire) in some appliances, typically kitchen ranges and clothes dryers, there are a few extras out there that are now considered obsolete.

About the only interchangeability is that 120V 20A receptacles allow you to connect a 120V 15A plug, and 240V 20A receptacles allow you to connect a 240V 15A plug. Common household wiring uses 14- and 12-gauge (American Wire Gauge) wiring, which means that both 15A and 20A circuits are available.

Could the United States switch to something more universal? Not easily. There is too much installed base to go changing things up. Look at how hard it's proving to switch the Internet from IPv4 to IPv6. Sure, we could decide to go to just 12-gauge wiring for household circuits and dump 15A circuits in new construction, but consumers would balk at the increased cost, and electricians would balk at the increased difficulty of handling heavier wire. It might also necessitate fused plugs on every cord, which so far only exist in holiday light strings.
Title: Re: Power Outlets Worldwide
Post by: Chris Hindle on December 23, 2013, 04:08:20 pm
It might also necessitate fused plugs on every cord, which so far only exist in holiday light strings.

And Air Conditioners.
Replaces one at the house last summer, and replaced one at the office 3-4 years ago. Both have plug mounted breakers.
I must say, it's not a bad idea, just makes for a bloody big 90ļ plug sticking out of the wall....

(edit: cunt spel)
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 23, 2013, 04:23:25 pm
Since previous standards allowed for bootleg ground

I was going to ask about that.  Is or was bootleg grounding ever an acceptable method of providing a ground?  Over here (UK) no one would ever think about connecting the ground pin to neutral in order to provide a ground.  I have seen neutral referred to as the 'ground conductor' here which I suppose would naturally lead you to think it was interchangeable with a proper ground.

It's partly due to the fact that we have multiple voltage standards: 120V single phase, 240V single phase, 120/240V single phase, 120/240/208 volt wild-leg single/three phase delta, 120/208V three-phase wye, 277/480V three-phase wye, etc.

We just have the one system.  415v three phase.  All three phases go to industrial and commercial premises and a single phase and neutral go to domestic properties to provide 240v.

About the only interchangeability is that 120V 20A receptacles allow you to connect a 120V 15A plug, and 240V 20A receptacles allow you to connect a 240V 15A plug. Common household wiring uses 14- and 12-gauge (American Wire Gauge) wiring, which means that both 15A and 20A circuits are available.

I was wondering how many domestic outlets the US have approved for use.  We just have one.  The 13 amp socket.  Before the 1960s, we had three sockets.  3 amp (not common) 5 amp and 15 amp.  These were fused at the fuse box.  Our current system uses a 13 amp rated plug and socket with a fuse in the plug selected according to the appliance.  Usually 3, 5 or 13 amps.

For industrial power we just have a handful of connectors in single and three phase options.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Tim McCulloch on December 23, 2013, 05:09:31 pm
The Code definition of what we call "neutral" is "Grounded, current-carrying conductor".  I suspect that the "ed" is left off in typographical error in some posts.
Title: Re: Power Outlets Worldwide
Post by: Jonathan Johnson on December 24, 2013, 12:20:51 am
The Code definition of what we call "neutral" is "Grounded, current-carrying conductor".  I suspect that the "ed" is left off in typographical error in some posts.

And what we in the U.S. call the "ground wire" (or just "ground") -- what you in Europe call "earth" -- is really the "Equipment Grounding Conductor". When it comes to anything regarding codes, insurance, or any legal document, semantics are VERY important.

The term "neutral" is really a misnomer, as it's not truly neutral since it carries current. To use a single-word term, it should be referred to as "common" as it is a zero-voltage potential reference point for both poles of the 120/240V split, the grounding wire, and in a three-phase wye-connected system, to one leg of each of the phases (at the center of the wye).
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 24, 2013, 02:52:05 am
The Code definition of what we call "neutral" is "Grounded, current-carrying conductor".  I suspect that the "ed" is left off in typographical error in some posts.

Even with it's correct (in the US) title with the word grounded in it, there is a likelihood of people thinking it is ok to use it as a ground connection. Evidence of this is the common occurrence of bootleg grounding being mentioned here.  Something I had never heard of until I joined this forum.

With our terms of live, neutral and earth, no one confuses neutral with earth - in fact most people probably do not realise that they are connected together anywhere.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 24, 2013, 03:10:59 am
Even with it's correct (in the US) title with the word grounded in it, there is a likelihood of people thinking it is ok to use it as a ground connection. Evidence of this is the common occurrence of bootleg grounding being mentioned here.  Something I had never heard of until I joined this forum.

With our terms of live, neutral and earth, no one confuses neutral with earth - in fact most people probably do not realize that they are connected together anywhere.

Steve.

The only code-legal bootleg grounds were (and still are) for our split-phase 120/240-volt 30 and 50 amp services for electric dryers and stoves. While new installations require a 4-wire hookup (L1, L2, N, G) there were probably millions of installations with a 3-wire hookup that bonded the appliance chassis directly to the neutral conductor, and which are still code-legal since they're grandfathered in. When you purchase a new stove there will be a little "bonding" screw between the neutral terminal and chassis which you're supposed to remove if you buy the 4-wire power cord rather than the 3-wire "bootleg ground" power cord.

The US national electrical code (NFPA 70E) also allowed (and I think still allows in some industrial circumstances) for a metal conduit to function as the safety ground. For sound systems this is a mess since this conduit can be bonded to building steel in multiple places, almost assuring a ground loop differential voltage with the resultant ground loop current and speaker hum.

A receptacle "bootleg ground" was never officially allowed by the national code, but was sometimes (often?) done by inspectors and electricians in the 70's as a cheap way to convert old 2-wire power (hot and neutral) circuits to a 3-wire "grounded" receptacle (hot, neutral and ground). But combining a bootleg ground with a swapped neutral and hot creates what I've named a Reverse Polarity Bootleg Ground (RPBG) which can be really difficult to find as I've noted in other postings. Here's an article I wrote on the subject for Electrical Construction and Maintenance Magazine at http://ecmweb.com/contractor/failures-outlet-testing-exposed (http://ecmweb.com/contractor/failures-outlet-testing-exposed) where I go into detail about why standard outlet testing methods won't find an RPBG. As you can see from the sidebar in the article, this can also cause dangerous fault currents to flow between pro-sound gear components interconnected to multiple power outlets.
Title: Re: Power Outlets Worldwide
Post by: Stephen Swaffer on December 24, 2013, 09:43:26 am

I was wondering how many domestic outlets the US have approved for use.  We just have one.  The 13 amp socket.  Before the 1960s, we had three sockets.  3 amp (not common) 5 amp and 15 amp.  These were fused at the fuse box.  Our current system uses a 13 amp rated plug and socket with a fuse in the plug selected according to the appliance.  Usually 3, 5 or 13 amps.


Typically, we just use the 15A/20A receptacles which are interchangeable unless you have a 20 plug-pretty rare.  The other receptacles are for ranges (50A/240V) dryers (30 A/ 240V) and an occasional welder (50A/240V-ground no neutral) then we have 2 4 wire twistlocks for generators a 20A and a 30A.  But the load served by those extras would not be able to be served by the 13 A receptacle you use.

Mike, have you considered using a non contact voltage detector for finding RPBGs?  I use a Fluke that gives me a blue light when some distance away then turns red when in close proximity to a "hot" wire to differentiate between hot and neutral on knob and tube systems when I have to deal with them.  Perhaps a plug with two individual wires coming out wire nutted/taped for safety along with a detector would be any easy way to ID a RPBG?
Title: Re: Power Outlets Worldwide
Post by: Geoff Doane on December 24, 2013, 10:22:18 am

I was wondering how many domestic outlets the US have approved for use.  We just have one.  The 13 amp socket. 


What do you do for electric stoves, ranges, or whatever they're called there?  Or does everybody use gas?  Or coal  :D ?

Until the NEMA 14-50 came into wide use in my part of Canada (sometime in the '80s?), kitchen stoves were tied into a pigtail coming out of the wall.  If you moved house, and were taking the stove with you, you disconnected and tied it in yourself.  It was good practice for a future career in Rock 'n' Roll.  ;)

GTD
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 24, 2013, 10:46:47 am
What do you do for electric stoves, ranges, or whatever they're called there?  Or does everybody use gas?  Or coal

Electric ovens are permanently wired in via isolating switches.  As are permanently installed room heaters and hot water heaters.

I think there is an equal divide between electric and gas for cooking in the UK.

Until the NEMA 14-50 came into wide use in my part of Canada (sometime in the '80s?), kitchen stoves were tied into a pigtail coming out of the wall.  If you moved house, and were taking the stove with you, you disconnected and tied it in yourself.

If you move house here and take your electric oven with you, a qualified electrician is supposed to do any dis-connecting and re-connecting... This hardly ever happens!


Steve,
Title: Re: Power Outlets Worldwide
Post by: Jonathan Johnson on December 24, 2013, 02:16:19 pm
What do you do for electric stoves, ranges, or whatever they're called there?  Or does everybody use gas?  Or coal  :D ?

Until the NEMA 14-50 came into wide use in my part of Canada (sometime in the '80s?), kitchen stoves were tied into a pigtail coming out of the wall.  If you moved house, and were taking the stove with you, you disconnected and tied it in yourself.  It was good practice for a future career in Rock 'n' Roll.  ;)

GTD

In the United States, wall-mounted ovens, inset cooktops, and mounted ranges are hard-wired. Slide-in (aka freestanding) ranges are cord-and-plug connected. As a general rule, any appliance that is not fastened to the structure is considered movable and may be connected via cord-and-plug.
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 24, 2013, 03:00:59 pm
Electric ovens are permanently wired in via isolating switches.

Actually, there is an exception to that rule.  When the hob and oven are separate units, they are often connected with our standard 13 amp plugs and sockets.

At my last house we had an electric oven and a gas hob.  Quite a common arrangement.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 24, 2013, 03:22:18 pm
At my last house we had an electric oven and a gas hob.  Quite a common arrangement.

What exactly is a "hob"? That's a new term for me.
Title: Re: Power Outlets Worldwide
Post by: Tim McCulloch on December 24, 2013, 03:42:12 pm
What exactly is a "hob"? That's a new term for me.

A gas cooktop, meant for permanent install without an attached oven.

(http://images.lowes.com/product/converted/825225/825225858416lg.jpg)
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 24, 2013, 04:15:27 pm
A gas cooktop, meant for permanent install without an attached oven.

(http://images.lowes.com/product/converted/825225/825225858416lg.jpg)

Very cool. I have exactly the same thing in my house with an electric oven that "required" a 4-wire 120/240-volt hard-wired connection (no plug allowed per the installation instructions) and a gas cooktop/hob with an 15-amp Edison plug to power its ignition spark gadget.   
Title: Re: Power Outlets Worldwide
Post by: Tim McCulloch on December 24, 2013, 04:39:48 pm
Do a google image search for "gas hob".  There are some really cool designs.
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 24, 2013, 05:30:46 pm
A gas cooktop, meant for permanent install without an attached oven.

Or electric.

(http://i.ebayimg.com/00/s/NjYzWDg4NA==/z/xO0AAOxynRRSQbWV/$T2eC16J,!y!FIdLe1!cBBSQbWUy4nQ~~60_35.JPG?set_id=8800005007)

What exactly is a "hob"? That's a new term for me.

You Americans should learn English!

Very cool. I have exactly the same thing in my house with an electric oven that "required" a 4-wire 120/240-volt hard-wired connection (no plug allowed per the installation instructions)

The smaller electric ovens we have here will operate as an oven or a grill but not both at the same time.  Therefore they can run at 3kW with a normal 240 volt 13 amp plug.  The larger ovens with separate grill or double ovens require a higher rated hard wired installation.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 24, 2013, 09:27:34 pm
Now here's something a little confusing from my side of the pond...

While the 3-wire 30-amp dryer outlet in the US is wired for 240-volts, we have a TT-30 (Travel Trailer) receptacle for our Recreational Vehicles that's very similar in size and form factor, but which is wired for 120-volts instead. What occasionally happens is that a homeowner pays an electrician to hook up a 30-amp/120-volt outlet on the side of the house to power his trailer in the driveway, and since a TT-30 looks a lot like a 30-amp/240-volt dryer receptacle that's what the electrician wires it for. Now plugging your $100,000 (or more) RV's 120-volt electrical system into a 240-volt power source generally destroys most of the electronics in seconds. See my article on this confusing problem at http://www.noshockzone.org/accidentally-plugging-into-240-volt-outlet/
 
Title: Re: Power Outlets Worldwide
Post by: Tom Bourke on December 25, 2013, 12:24:07 am
What occasionally happens is that a homeowner pays an electrician to hook up a 30-amp/120-volt outlet on the side of the house to power his trailer in the driveway, and since a TT-30 looks a lot like a 30-amp/240-volt dryer receptacle that's what the electrician wires it for.
That's just negligence at best, incompetence at worst.  Hell, the voltage is written on the face of many outlets. That is also why we measure, even if it was put in by an "electrician".
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 25, 2013, 03:33:32 am
You definitely have too many outlets and voltages!

How is the combined 120/240 dryer supply used?  120 for control circuits and 240 for heater elements?   If so, why not run it all on 240?


Steve.
Title: Re: Power Outlets Worldwide
Post by: Stephen Swaffer on December 25, 2013, 09:38:21 am
Not only is the voltage written on the face, but almost always (I want to say always, but....) screws for hot wires are brass colored and screws for neutrals are silver. Perhaps a small detail-but if you are working with stuff as potentially dangerous as electricity paying attention to details should be second nature-should at least make you stop and think about what you are doing.
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 25, 2013, 11:40:21 am
Having brass/silver screws to determine live and neutral seems strange to me as it's the sort of thing which most people are not going to notice.

We recently changed from red - live and black - neutral to brown - live and blue - neutral for fixed wiring as it is supposed to be less likely to be confused if the electrician is colour blind.

This colour scheme has been in use for at least forty years for flexible appliance cables but is a fairly recent change for house wiring.

Three phase too has changed.  It used to be red, yellow and blue for the phases and black for neutral but is now brown, black and grey for the phases and blue for neutral.

In my opinion, this seems to add confusion rather than make it more simple.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 25, 2013, 01:57:16 pm
You definitely have too many outlets and voltages! How is the combined 120/240 dryer supply used?  120 for control circuits and 240 for heater elements?   If so, why not run it all on 240?
Steve.

They do in fact use 120-volts for the drum motor and timer control, then save the 240-volts for the heater element. I think it's because the manufacturer can use the same 120-volt motor on its washers as well as dryers. Same for all power supply transformers to run the electronics. It's only when you get into pro-sound gear that is planned to be used in various countries that you'll see auto-switching suppliers rated from 90 to 250 volt at 50 or 60 Hz. I think that about covers all worldwide possibilities.

If memory serves, the original 3-wire bootleg grounded dryer outlet was originally a "temporary" exclusion sometime in the 60's to save money for home "electrification" which was becoming popular at the time. There was a lot of fighting between the electric and natural gas industries for the home power supplier. That's about the same time that aluminum wiring was allowed (and for the same reason). But that turned into a horrible cluster with lots of fires started in the walls of home due to aluminum oxide high resistance, as well as electricians using non-aluminum rated receptacles. Did the UK (or anywhere else) go through the crazy aluminum craze the USA did?   
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 25, 2013, 02:02:23 pm
Not only is the voltage written on the face, but almost always (I want to say always, but....) screws for hot wires are brass colored and screws for neutrals are silver. Perhaps a small detail-but if you are working with stuff as potentially dangerous as electricity paying attention to details should be second nature-should at least make you stop and think about what you are doing.

From "The Sound Guy is Always the Last to Know:

"No matter how idiot proof you build it, they keep making better idiots"
Title: Re: Power Outlets Worldwide
Post by: Kevin Graf on December 25, 2013, 02:06:05 pm
Today on a electrician's forum, I read about a electrician that got a contract to wire an industrial building of about 200 feet by 135 feet.
He needs to provide AC supply voltages to equipment consisting of;

120
208
229
236
380
400
470
480
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 25, 2013, 02:44:36 pm
Today on a electrician's forum, I read about a electrician that got a contract to wire an industrial building of about 200 feet by 135 feet.
He needs to provide AC supply voltages to equipment consisting of;

120
208
229
236
380
400
470
480

I used to add something called a buck & boost transformer to step voltage down or up a bit in industrial power. For instance, if you need to run a 240-volt heater on a 120/208 3-phase WYE circuit, a 208 to 32 volt transformer in "boost" mode will step up the 208-volts to 240-volts. And they're surprisingly small in size since in this instance its KW rating is only about 1/8 of the main load (32/208). Or flip the secondary windings and it's now in "buck" mode, allowing you to derive 208-volts from a 240-volt supply. And there are ones with several secondary taps for tweaking a voltage up or down a bit.

Of course TANSTAAFL (There Ain't No Such Thing As A Free Lunch), so the amperage draw on the circuit with a "boost" transformer will be increased proportionally. 
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 25, 2013, 03:17:55 pm
Did the UK (or anywhere else) go through the crazy aluminum craze the USA did?

There was certainly a shortage of copper here after WWII and for a while, stainless steel pipe was used instead of copper for plumbing.  My brother took some out of an old school he was converting to housing and I have used it in short lengths coming up from the floor to radiators.  It polishes up nicely and looks like chrome.

I am not aware of anything other than copper being used for domestic wiring but a lot of our high voltage transmission lines are aluminium.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 25, 2013, 03:22:44 pm
Today on a electrician's forum, I read about a electrician that got a contract to wire an industrial building of about 200 feet by 135 feet.
He needs to provide AC supply voltages to equipment consisting of;

120
208
229
236
380
400
470
480

My only thought on this is why?

Can't manufacturers standardise on voltage?  We managed to do that over fifty years ago.  It's either three phase 415 volts or one phase to neutral 240 volts.


Steve.
Title: Re: Power Outlets Worldwide
Post by: Malcolm Macgregor on December 25, 2013, 04:31:04 pm
Lucky us (Holland), you get to choose between 230 Vac L to N and 400 Vac L to L and standardized plugs.
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 25, 2013, 04:57:41 pm
Lucky us (Holland), you get to choose between 230 Vac L to N and 400 Vac L to L and standardized plugs.

And believe it or not, the USA still had parts of New York City electrified with DC until 1997. How would you like to tie into that for a sound gig?

Switching DC Power on in New York, 120 Years After Thomas Edison

On November 14, 2007, Con Edison, New York Cityís electric utility, ceremonially disconnected its last direct current (DC) cable, on 40 Street east of 5th Avenue in Manhattan. Most of Manhattanís DC service had long before been replaced by the utilityís alternating current (AC) system, pioneered by Nikola Tesla, promoted by Thomas Edisonís rival George Westinghouse, and now standard throughout the world. Con Edisonís ceremony ended a service to New York City customers dating back to Edisonís first DC generating station on Pearl Street inaugurated in 1882.
Title: Re: Power Outlets Worldwide
Post by: Jonathan Johnson on December 25, 2013, 10:32:59 pm
How is the combined 120/240 dryer supply used?  120 for control circuits and 240 for heater elements?   If so, why not run it all on 240?

My understanding -- which may be wrong -- of the history of power in the United States is that Edison's DC power distribution system generated 110V (at the generator) and due to resistance losses in the transmission, the voltage was around 100V at the point of use. Light bulbs -- the primary product of Edison's company -- were designed for 100-120V. At the time, many homes weren't even wired with 240V service; only a single hot leg (110V) was installed to the home. In order to reduce the size of the copper wires necessary, both +110 and -110 service was available, with a "neutral" 0V third line. This 110V legacy of Edison's light bulbs eventually carried over into the AC distribution system, which was spec'd to provide between 110 and 125V at the point of use, with a nominal 117V.

Since both +110V and -110V were available, manufacturers took advantage of this and made 220V heating appliances that provided greater wattage than 110V could provide without the need to increase the wire size in the home. In the United States, the installed base of 110-125V devices is so large that it could be an economic disaster to force reconfiguration of wiring in homes and businesses plus replacement of billions of appliances to meet a single, 240V standard.

It's interesting to note that the voltage specifications have gradually increased, as the distribution system has increased its capacity. Where originally the expectation was to deliver 100V to the point of use, that specification gradually increased to 110V then 115V then 120V. Though the nominal voltage is currently 120V, it is not uncommon to measure voltages in excess of that, up to 125V. Likewise, the "high-voltage" service specification increased from 200V to 220V to 230V to 240V with a "maximum" now of 250V. If you look at very old receptacles and switchgear, you'll see some rated for "110/220V" or "115/230V," some "120/240V." It now is all rated "125/250V."

Most current appliances and motors without universal-voltage switching power supplies now are designed to safely accept up to 125V.
Title: Re: Power Outlets Worldwide
Post by: Jonathan Johnson on December 25, 2013, 10:41:20 pm
Having brass/silver screws to determine live and neutral seems strange to me as it's the sort of thing which most people are not going to notice.

I never trust the color of the screws; instead I go by position. I've actually held in my hands a 120V duplex receptacle in which the brass and silver screws were reversed by the factory. Of course, I wired it correctly, hot to the narrow slot and neutral to the wide slot.

When I wire a plug onto the end of a cord, I still go by position, not by color.

Anymore, I don't even pay attention to the color of the screws. If there is any doubt which screw goes to which contact, I meter it.
Title: Re: Power Outlets Worldwide
Post by: Kevin Graf on December 25, 2013, 10:51:17 pm
And in a parallel universe.

"Anyone know why voltage 120/240 is referred to as 110/220"

http://forums.mikeholt.com/showthread.php?t=158461
Title: Re: Power Outlets Worldwide
Post by: Steve M Smith on December 26, 2013, 02:06:23 am
Most of Manhattanís DC service had long before been replaced by the utilityís alternating current (AC) system, pioneered by Nikola Tesla

http://theoatmeal.com/comics/tesla


Steve.
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 26, 2013, 07:23:03 am
http://theoatmeal.com/comics/tesla

Steve.

Cool... Tesla was my favorite mad scientist.  8)

Title: Re: Power Outlets Worldwide
Post by: Cailen Waddell on December 26, 2013, 09:15:52 am

They do in fact use 120-volts for the drum motor and timer control, then save the 240-volts for the heater element. I think it's because the manufacturer can use the same 120-volt motor on its washers as well as dryers. Same for all power supply transformers to run the electronics. It's only when you get into pro-sound gear that is planned to be used in various countries that you'll see auto-switching suppliers rated from 90 to 250 volt at 50 or 60 Hz. I think that about covers all worldwide possibilities.

If memory serves, the original 3-wire bootleg grounded dryer outlet was originally a "temporary" exclusion sometime in the 60's to save money for home "electrification" which was becoming popular at the time. There was a lot of fighting between the electric and natural gas industries for the home power supplier. That's about the same time that aluminum wiring was allowed (and for the same reason). But that turned into a horrible cluster with lots of fires started in the walls of home due to aluminum oxide high resistance, as well as electricians using non-aluminum rated receptacles. Did the UK (or anywhere else) go through the crazy aluminum craze the USA did?

We are renovating our kitchen for Christmas (which is a whole 'nother thread) but I pulled out our dryer, which had an adapter I made to bootleg the ground as we have an old 3 prong dryer outlet....  Anyway, I decided to replace the cord and install a 3 prong dryer cord set, opened the dryer and discovered that when originally wired with the 4 conductor cord set, by the appliance deliver guys (my mistake to let them do that), they had never pulled the bootleg grounding wire out of the dryer, so it was destined to be bootleg grounded no matter where we plugged it in...  I could say I'm surprised they didn't know to pull it when the 4 conductor cord set was installed but I'm not....

I find it interesting that a house built in '84, with a good electrical panel and correct grounding on outlets still got a 3 conductor bootleg dryer outlet. It is only 10 feet from the panel....
Title: Re: Power Outlets Worldwide
Post by: Mike Sokol on December 26, 2013, 09:43:12 am
they had never pulled the bootleg grounding wire out of the dryer, so it was destined to be bootleg grounded no matter where we plugged it in...  I could say I'm surprised they didn't know to pull it when the 4 conductor cord set was installed but I'm not....

I'm not surprised either. And the same goes for double-bonding the Ground and Neutral bus in sub-panels. That causes neutral currents to flow in the safety ground wires which causes a voltage difference between two different outlet grounds. That voltage difference between the outlet grounds is what causes ground loop currents in sound systems which can result in ground-loop hum (the pin-1 problem).

I'm now working on a table top experiment that will show how these neutral contaminated grounds can allow bass transients (such as kick drum and bass) to modulate ground-loop-hum in sound systems, causing a distortion I call GLID (Ground Loop Intermodulation Distortion). I'm fairly certain that GLID is responsible for "fuzzy" or "loss of bass definition" in some (many?) live and studio sound systems.

But there's lots more testing and listening to be done. Once I get the experiment and demonstration designed and some empirical data gathered, I'll see if a few of you would like to do a peer review on my findings. Too much fun. ;)
Title: Re: Power Outlets Worldwide
Post by: Cailen Waddell on December 26, 2013, 09:48:43 am


I'm now working on a table top experiment that will show how these neutral contaminated grounds can allow bass transients (such as kick drum and bass) to modulate ground-loop-hum in sound systems, causing a distortion I call GLID (Ground Loop Intermodulation Distortion). I'm fairly certain that GLID is responsible for "fuzzy" or "loss of bass definition" in some (many?) live and studio sound systems.

Your holiday project sounds much better than mine....
Title: Re: Power Outlets Worldwide;
Post by: Stephen Swaffer on December 26, 2013, 02:52:38 pm
Having brass/silver screws to determine live and neutral seems strange to me as it's the sort of thing which most people are not going to notice.

I would argue that "most" people perhaps should refrain from wiring a plug.  :).  I do not use them to determine how a plug is wired; however, if I find myself wiring a hot wire to a silver screw and a neutral wire to a brass colored screw, you can bet I am going to stop and double check my work.  Maybe its just me, but the more clues I have to help me get it right the better. To quote another post in another place "I am paranoid-but am I paranoid enough."

The devil is in the details-it is usually little things that cause big headaches in sound setups-and dangerous situations in power wiring.