Most of the houses that I've owned have been built about 1957, and typically do not have grounded branch circuits.  When I've painted and worked on the houses, I've always installed new 2-prong outlets in the old wiring.  In cases where newer wiring has been installed for additional circuits and they include a ground wire, I install the grounded outlets.  The current house was built in 1976 and all branch circuits are grounded, which is nice; however, there is a fair amount of aluminum wiring in the house so I have to be sure how the device is wired before I buy a new outlet or switch.

I have been told previously that it's illegal to replace an ungrounded device with a grounded one if the wiring doesn't include a ground wire.  This would probably be applicable when the house is sold and if the buyer is misled into thinking the house has 3-wire service throughout, only to find out later that that isn't the case.

lawrence

The only grounded outlet was the 220V in the garage for the dryer.  The house was probably refitted to bring the outlets up to code after my parents passed away and we sold it.  It's a Levittown-inspired rancher (single story).

The house Cathy and I live in always had 3-prong outlets.  We added a 220V in the kitchen when we went from a gas stove to induction.  Both are in Rialto, CA.

It was a 4 prong receptacle? I doubt that unless it was upgraded later on.

My grandparents lived in a house built in '63 that had 2 prong outlets. Never problem in the 40 years they lived there.

A 240-Volt electric dryer outlet in the US is always grounded, otherwise the dryer wouldn't work.  

They used to have a shared neutral-ground wire and used a 3-prong plug.  This wire is required, otherwise the motor, timer, lights etc., wouldn't work as they need 120 V.  The frame of the appliance is supposed to be connected to this neutral-ground wire.

Since about 1998 they have used a 4-prong plug with a separate neutral and ground.

A 240-Volt electric dryer outlet in the US is always grounded, otherwise the dryer wouldn't work.

 

 

Correct, the outlet has a grounded conductor but not a grounding conductor. Its a technicality which results in NEMA 10-30 and NEMA 10-50 receptacles being classified as "none grounding" types. 3 pole, 3 wire:

i.pinimg.com/originals/11/80/d5/...

https://www.ebay.com/itm/363342688746QUE...

Where as 6-30r and 6-50r are grounding types despite not having a neutral (2 pole 3wire).  Modern NEMA 14-30r and NEMA 14-50r with a neutral and ground (3 pole 4 wire) classified as grounding types.

Code makes a distinction between a grounding and grounded conductors even though in that past it was an inadvertently common

error to treat them interchangeably. Ie, you could ground a dryer through a neutral wire but you could not use the bare grounding wire in NM-B cable as the neutral.

Yup! That was the big reason. Normally the the motor on a clothes dryer pulls roughly 5 amps.

10 gauge copper has a resistance of about 1.2 ohms per 1000 feet. So a reasonable worse case 100 foot home run would be 0.12 ohms. VD= IxR; would mean 5 amps  x 0.12 ohms = 0.6 volts on the frame of the dryer relative to other grounded objects like the cement floor or the washer. Typically 0.6 volts isn't even perceivable, so no harm in connecting the neutral to the frame.

That is until the neutral breaks, becomes loose underneath a screw, poor contacts in the receptacle, ect... then the frame of the dryers rises to 120 volts... One hand on the dryer, one on the washer, damp hands lowering skin resistivity... one does not have to imagine why the practice was deemed risky in modern times. 

For those over seas, here is the wiring diagram relevant to a US dryer-

3 wire:

i.stack.imgur.com/oYHa7.jpg...

4 wire:

i.stack.imgur.com/xB3g0.jpg...

True.  I knew I wasn't being very accurate when I said the wire was a combined neutral-ground, as it is technically a neutral wire (grounded conductor) that is also used to ground the dryer's frame.  

I think the reason it was changed is that just one single fault could cause the dryer's frame to become live, therefore able to deliver a fatal electric shock.  This would happen if the neutral wire broke at some point along the circuit. 

With the 4-prong design, I think you would need two simultaneous faults to cause this, i.e. first a break in the ground wire AND then another fault causing the live wire to contact the frame.

As for the ungrounded two-prong outlets of yesteryear, I think I may have seen these once or twice in older mid-century homes in Palm Springs, but even then it's only been the odd one or two.  I have certainly seen them for sale at Home Depot.  Yes they are kind of cool, if they are original to the house.  I like that!

To be fair, Under IEC / BS7671 standards the neutral conductor in the same Edison circuit if replicated outside the US would be classified as a PEN conductor, Protective Earth Neutral, and thus you would be correct in calling it a combined neutral-ground.

The NEC however requires it be treated it as a grounded conductor, that only by special exceptions given in the code, can ground the frame of the range or dryer.

In Eastern Europe it was common to have TN-C up to the sockets. You would only have two wires, Live and PEN, and the PEN conductor would land on the earth terminal and then jumper to the neutral terminal. Today this is forbidden, a hold over practice from the days of the soviet union.

www.asutpp.com/tn-c-earth...

You are correct, you'd need at least 2 failures, and with the recent code changes you'd need 3 failures. Code now requires most US dryers to be GFCI protected. The idea is that if you lost the equipment grounding conductor with a simultaneous insulation break down the GFCI would act as a last resort and trip.

www.electricallicenserene...

I think, that as time goes on all circuits in the US will require some form GFCI or GFP protection regardless of voltage, wiring method, rating, or equipment installed. Equipment grounding conductors can and do become compromised in a world where newer standards of safety dictate that multiple things must go wrong first before any danger becomes present. 

I guess I am lucky here because this 1941 house was remodeled sometime in the 1960's or 70's. At that time one of the bedrooms (2) was converted to a family room, with a washer dryer closet,  and another bedroom was added to the rear of the home, with its own bath. All the 120 outlets in the main house and other structures are three prong, grounded.

However, perhaps this was all done before four prong 240 volt plugs became the standard, because the plug for the original 240 volt dryer (which I soon replaced with a gas version), and all the rest of the 240 volt plugs, such as in the separate workshop (1,000  + sq ft) are all three prong. Never had a problem with any of those. I have seen four prong outlets and plugs at places like Home Depot, and always wondered what if anything they added. Now I know, so thanks.

I know what you mean about the replacements. Leviton and Eaton are no longer centered and I'm not sure about the others. Really makes me upset. Do you know about the other brands?

Code only requires upgrades if a device is replaced, or more commonly if the wiring is being extended/upgraded to a significant degree. The rest is considered grandfathered, so, it can legally remain for the rest of eternity. Fuse panels and knob and tube are nowhere near as bad as people make them out to be, provided they've not been illegally tampered with.

In some ways it would be kind of cool if everything in homes were double insulated- no way anything could ever become live. Two wires at the service head, 2 pole breakers, 230 volt appliances.  Here is such a main panel being made up in the Philippines: 

Like Japan they us two wire romex through out the home, and 3 wire romex for the 3 way switching. I think blue and yellow would make good vibrant contrasting colors here in the states- with blue, yellow and red for the 3 wire romex.

Some of those old sockets are only rates for 10 amps, gotta be carful plugging high amp draw appliances in them.

I think its 10 amps at 240 volts, 15 amps at 120 volts. This was the pre-NEMA days and the code at the time had a silly rule that some devices had to be rated less amps at higher voltages. 

I wish the US had settled on 240 volts instead of 120. We'd probably have 10 amp general use circuits wired in 16 AWG copper.

I love your pic btw! :)

Looks like a good book.

Just ordered a copy.

If feeling nostalgic,  here is the 1956 version of Wiring Simplified:

inspectapedia.com/electric/Wirin...

Well, that's a big outdated, no?

In any case, I placed the order, but still waiting for word from the store that the order is ready to be picked up. I suspect it won't be ready until Friday morning. We'll see!

Outdated bigly. As in most of the 1956 version is no longer code compliant. Still fun to read though.

What kind of appliance would require an outlet like this, with the horizontal slot?

20 amp socket

Sometimes used with high-power microwave ovens, heaters, large old A/C window units, and large power tools.

Much indeed. As long as said appliance can handle 60Hz, which most can, even if listed for only 50Hz, can't tell the difference. Schuko plugs aren't even polarised so the fact any leg could/is live is taken into account safety wise.

I do this in my own home. I refuse 120 volts when I can avoid using it. I find the added engineering effort of bootlegging an impractical half voltage out of a system so odd/dated/absurd/risky. Extra effort and material just stepping backwards.

Being honest even the new additions of the book come across as dated, but, at the same time, as long as the graphics are revised to follow the lasted addition of NFPA-70 it suites its job well in teaching people. 

There is one important thing that I want to clarify about that book and most other wiring books. When they use the term"ground" "going to ground" "traveling to the ground" or "grounded" in relation to clearing a fault they are referring to the path electricity takes back to the utility transformer and not the earth or soil itself. Very common misunderstanding. A typical ground rod comes in at 25 ohms and will not trip a breaker, where as a typical service neutral rarely exceeds 0.1 ohms. Fault current travels back to the main panel (or disconnect) via metal conduit or grounding conductors, to the grounding terminal in the enclosure, through the main bonding jumper, to the neutral bar and up through the service neutral going back to the transformer. It is one closed loop. The soil, earth or terra firma makes no difference in that regard.     

Our house is a mixture of grounded & ungrounded. The original part of our house was built in 1925, and the addition was built around 1962. Funny thing though, the man who owned the house before us was in the electric motor repair business for over 50 years. You would've thought that he would have updated the electrical over the years, but this was not the case. In fact, we upgraded to a 100-amp service with a breaker box vs the old 60-amp service with only 4 fuses for the entire house.

I have a few of these. This was one of several socket types I experimented with until I settled with schukos. Some models have a socket switch others do not. Some come with a parallel combo NEMA 1-15 / Euro plug.

I personally wish this was the dominant outlet in the US for many reasons, and it was supposed to be so, unfortunately someone must've traveled back in time screwing with critical events resulting in the after-thought NEMA 1-15/NEMA 5-15 we are stuck with today.

The modern AUS adapter fits perfectly in Chinese and old non NEMA US versions- 

This is a NEMA 10-50 range receptacle rated 50 amps and considered "ungrounded" in NEMA standards .

I personally wish the NEMA 10-20, 10-30 and 10-50 were re-classified as grounding types (as has been done in some parts of the world) plus reintroduction of the old US crow foot.

The Chinese are building these as grounding versions (technically incorrect by US standards) where the neutral pole is the grounding pole with a bonding strap to the yoke of the receptacle, pole Y as the hot and pole X is the second live or neutral when used in a 230/400Y system.

Very smart, and common sense. The round ground pins on other NEMA and NEMA-esque receptacles are essentially after thoughts, and do not make surface gripping contact the way flat contacts do.

https://www.amazon.com/Sintron-Straight-Receptacle-Suitability-Industrial/dp/B08HSYF96M/ref=sr_1_27?crid=L1XFT6TPREM2&keywords=nema%2B10-50&qid=1681089053&sprefix=nema%2B10-50%2Caps%2C119&sr=8-27&th=1

Amazon is the key. Try the US version, among others, that have on/off popups with Chinese sellers. Ebay for the old stuff.

In Japan they'll do that, where the cord has a separate ground wire and separate ground screw on the socket. Not something I approve of, but common there it seems.

This I came across on Amazon at a reduced price. When I saw it I had to get it.  

Technically speaking, the 10-50 and similar 240 volt receptacles are NOT fully grounded. This has been explained elsewhere in this thread (I think). For the safest ground, a separate path for the ground is needed; the 10-50 and similar outlets compromise this with the neutral wire. It's no safer (and perhaps less safe) than a 120 volt outlet with just two paths. One for hot, the other for neutral/ground.

That said, my laundry area in the main house, as well as the 240 volt outlets in the workshop, have only three prong outlets. Since I rarely use any of these (the dryer is gas), I'm in no hurry to change them to the latest and safest version. Some day!

Oh wait... there is a 240 volt air compressor in the workshop that I use whenever I need to fill tires. It also has a 3 prong plug. Oh well.

Under NEMA they are classified as non grounding H-N-H.

However, my line of thinking is have everything go straight 240 volts. No internal 120 volt components. Have everything be 3 wire, H-G-H, and just reclassify the 10-XXs and 18-XXs as grounding types. Have the crow foot become dominant. Ditch all the other NEMA types.

At least in my world...

The US residential system is split phase, a center tapped 240 volt winding. Each home receives two hots and one grounded neutral. The system is TN-C-S or rather technically PME.  Both hot legs are 180* out of phase, so between each hot and neutral (of ground) we get 120 volts, but between each hot wire we get full 240 volts. 

en.wikipedia.org/wiki/Split-phas...

I know

I'm saying ditch all 120 volt components and just reclassify the NEMA 10 and 18 as grounding types. Fewer receptacles moving forward.

Regarding the UK, I think they have on of the best systems in the world.

The wiring in the wall is already protected via MCB. The fuse protects to cord itself and also reduces the amount incident energy released at the point of short circuit, if the cord became shorted. With a 32 amp MCB the cord may melt before the MCB trips (adiabatic limit of the cord's conductor exceeded), or just arc/sputter at the point the cord is damaged, but with the fuse (in the plug) a fault in the cord instantly blows said plug fuse before anything bad can happen. The fuse responds faster, at a lower current, than the 32 amp MCB can. 

Ring circuits, at least back in the day, allowed much more power to be supplied to a building level via less copper. The load diversity also helped maximize the savings as it is not likely everything would be on at once. A whole residential lower level could be fed from a single 32 amp circuit, a second 32 amp ring socket  circuit for the upstairs, then one or two 6 or 10 amp radial lighting circuits. A 40 amp for the cooker, maybe another circuit for the boiler. 

There has to be a ground pin on the plug even if the appliance is double insulated as the safety shutters in the plug will not open. Ingenious idea as the shutters provide both child protection and rejection of a plug missing its ground pin. In the US missing equipment ground pins on metal tools like drills made for the bulk of electrocutions. 

 Attached Image courtesy of "Fatally Flawed"

 electrical.theiet.org/wiring-mat...

UK homes typically have at least one 6 or 10 amp radial lighting circuit in that should the ring MCB blow, hardwired ceiling and wall mounted fixtures are still functional.

A 32 amp ring and one 10 amp lighting circuit in the UK can supply more power than 4 120 volt circuits- two rated at 20 amps and two at 15 amps in a typical US home. Hence there are no code requirements restricting a circuit to any particular area as you find in the NEC. 

Well, went to Home Depot and picked up my copy of  "Wiring Simplified". It looks good.

If I have a complaint, though, it would be that the type is a bit small. Not so small that I need a magnifier, but sort of on the edge.

Anyway, I'm wondering if the original edition was in a larger format (2017 version or earlier, that is). Maybe not, since the added size might adversely affect sticking it in a tool box. LOL.

Anyway, I'll be roaming through Wiring Simplified over the next few days/weeks/months.

PS- About 40 years ago, I had a temp job with an electrical contractor who had helped wire a new building for the lab I was working. Wiring Simplified would have been a good read back then, too.

Have a look at the pictures in reply #46.

There is no strap between the neutral terminal and the receptacles yoke.

This is correct for a listed NEMA 10-30r and 10-50r.

I encourage you to look at any NEMA 10-30 or 10-50 made by a reputable brand like Leviton, Hubbell, Eaton, Legrand, ect.

the white ones were sold out, but I did manage to get some brown ones-

I like space space heaters though. 120/230 has its place.

I spotted this yesterday in Koffi, Palm Springs.  This place was built in 2008, so I don't know how this ungrounded outlet has found its way in here!  I find the cockeyed installation more objectionable than the fact that it won't accept a 3-prong plug 😂

Mark

Now thats way cool!

However I'd have to agree with the last two replies, that is either a hack job or the building is 70+ years old.

Came across these on Amazon. I'd really like the look of these in a US home.

The socket:

The plug:

And maybe even the wire, but in solid copper:

One can dream. Then again I could just buy and try lol. But I have to limit myself here, again, lol.

The nice thing about the swiss plug is that you can't touch the pins while energized and neither can something like a coin. The plug is small and compact, easy to insert and remove. 

Good eyes!

Maybe its just me, but now that I look at it the top holes seem bigger than the bottom holes which would indicate a dual 10/20 amp Inmetro socket. I think its silly though, just stick with a 16 amp type N. That would be ideal.

The plug is probably Italian, ungrounded type Cs usually have the skirt around them. 

Inmetro sockets come in two ratings- 10 amp and 20 amp. The 10 amp has smaller holes that the 20 amp:

See 3/6 and 4/7 figures and notes: https://www.plugsocketmuseum.nl/IEC60906-1.html

My guess is the seller is trying to cover both plug sizes in one device. Such practicality would definitely get it listed on Amazon.

Is the version of the NEMA 1-15 without the holes and slightly beefier solid blades. Typically reserved for 220-240 volts and used in China, Thailand and other Asian countries.

Because Asian countries end up with Euro plug appliances from Europe and NEMA 1-15 imitations from China, outlets both grounding and non grounding are designed to take the Type A and C plug and can technically take others like the type F even though type F will be left without its earth connection.

Thailand takes it a step further and has their own plug type "O" plug which is a hybrid of the US NEMA 5-15 but the the round pins and spacing of the Euro plug.

Lots of fun to be had!

I could write several dissertations on various EU practices; and IEC vs NEC practices. Fascinating stuff that is truly a world all on to its own. 

You've got the whole earthing system debate - TN-C-S vs TN-S vs TT vs IT vs PME...

230/400Y vs 3 x 230 sans neutral vs split phase.

Protecting the neutral via 2 or 4 pole MCB vs straight to the neutral bar. 

Radial vs ring wiring

Conduit vs twin and earth

Switches vs relays

Sockets vs hard wiring appliances

ect

Lots of those differences are covered in your vids. Thank you for posting them. 

120 volts is already to low, going lower would present more cons than pros. People forget that because we're clinging to an obsolete voltage we've got millions of transformers wasting energy throughout buildings and millions more on utility poles spending most of their time at less than 5% load.

416Y/240 would consolidate 600Y/347, 480Y/277, 208Y/120, 240Δ/120 and split phase 240/120 into a single system. 416 volts for heat strips, 3 phase motors, commercial cooking equipment, high bay lighting and roadway fixtures with 240 volts for all other equipment and homes.

Since doubling the voltage for the same current means you can go twice the distance for the same % voltage drop or 4 times the distance at double the voltage with half the current for the same % voltage drop not even factoring the advantage of 3 phase over split phase; a single pole mount or pad mounted transformer can serve many more customers while being in the desired voltage drop bandwidth. Serving more customers means greater loading diversity with a utility transformer being subjected to a relatively flat load curve vs one with sharp peaks and troughs as in the modern US distribution system. For example, as people wake up homes begin pulling more power that begins to sharply drop as people leave for work, as people arrive for work load picks up in offices. As people head out for lunch load drops somewhat in factories and offices as load picks up in restaurants serving the lunch rush hour. Load drops at these places and pickups at work. As people leave work, load drops off  at work but increases at homes as people make dinner, turn up the heat, ect. Defrost of food market refrigerators and freezers can take place at night. The combined 24 hour load of a community resembles a valley. Transformers are most efficient when driven continuously at around 80% load.  In stark contrast all the 10, 15, 25 and 50kva transformers serving homes that see about a few amps most hours of the day with 200-300% 90 minute overloads in the morning and evenings.

In Europe it is common for a single 3 phase transformer to serve an entire village or at least large chunks of it- many homes, restaurants, businesses, schools, institutions, government, pump houses, ect making for a very efficient distribution system.  

Lower voltages waste energy, take obscene amounts of resources, create unnecessary complexity, and are way less safe.

Ah, but they are not far off! Consider all the safety mechanisms UK plugs and sockets have that others don't.  Plugs are an art as much as they are a science. 

Well, if you've never experienced 2100-3000 watt grills, fryers, toaster ovens, hair dryers, microwaves, toasters, electric kettles, panini presses, space heaters, irons, vacuum cleaners, front load washers with heaters, insta hots, electric showers, ect I could understand the sentiment. 1500-1800 watts is simply not enough power to be thoroughly practical and has motivated a lot of the energy wasting practices in the US. 

I think you were referring to ungrounded outlets to which I agree in full but I just wanted to use the opportunity to encourage others to discover the joys of 240 volt living.  

Until you factor in heating cold water locally is much more efficient than idling a 50 gallon tank 24/7 or even a tank-less heater. At 120 volts it takes too long to heat cold water so you essentially have to do a hot fill. And because water cools in between runs things like DWs had to do several 2+ gallons prewashes to get the temperature hot enough for the wash before thermal holds. Front loads end up with lukewarm hot fills since the energy in the pipes simply dissipates in the walls and floors.

3000 watt appliances heat and cook faster, a big plus while using the same amount of energy. To raise 1 cup of water 100*F requires the same amount of energy regardless if the heater is 500 watts, 1,500 watts or 3000 watts.

But again, factor in the watts loss of the US distribution system and its clear were trying to heat the outdoors.

The code is trying to get 16 AWG copper and 10 amp circuits legal yes, however in any case 240 volts will always maximize the amount of copper used and reduce losses. There is also the addition of safety in that doubling the voltage doubles the current through a fault speeding up clearing time of fuses and circuit breakers. Earth/ground fault loop impedance of a circuit greatly improves at 230 volts to ground with any given length.