Why the wide prong on a plug?

[marlboroman]

Has anyone ever figured out why they put one wide and one narrow on a plug that does not have a ground?

OK, I understand that on a lamp it's a good idea, or the socket shell and bulb threads will be live if the hot side of the power line is connected to that part of the socket.

But, lets say I have a all plastic cased electric power tool. (Like all of them made in the last decade or more). I'm holding plastic, which does not conduct electricity. It dont matter which side of the power line goes to which side of the motor on AC. What's the point of having that wide terminal? Is the only reason to piss off the user, particularly those of us who are older and dont have the best eyesight anymore. I cant see any other reason.....

My grinder does a quick job of narrowing that wide prong though !!! .

[metspitzer]

You don't have much to do. Do you? :)

[Donna Ohl]

Maybe they want the hot and neutral to be determinate just to protect against lawsuits?

Or, maybe it's a UL standard even for plastic-housed appliances?

[The Daring Dufas]

The wide blade is the neutral, the narrow blade is the hot. Some appliances may have the neutral attached to the metal chassis parts inside. Did I hear "shock hazard"? I used to work with an idiot who would cut the ground pin off plugs.

The hot wire is switched. If you grind down the neutral and plug it into the hot side, the item will be energized when the switch is off.

TDD

[mm]

What do they mean by double insulated?

One insulation is the plastic case. Maybe the other one is figurative, that they do the rest of the wiring as if it were a metal case?

[salty]

Or maybe the exposed metal chuck and drill bit are somehow connected to the motor within? Ya think?

Sheesh

[Bryce]

Here's a patent describing an insulated coupling that electrically isolates the chuck from the motor in a double insulated (class 2) power tool.

[salty]

How well does it work submerged?

You bet your life!

[Phil Again]

Short Answer: Lawyers and (product) Insurance.

Too Much Information (TMI) answer:

NEMA, National Electrical Manufacturing Association sets the standards for all US Electrical plugs and receptacles. Search for a Wikipedia write ups on NEMA standards. There are links at the bottom of the Wikipedia to NEMA configuration charts. Your plugs are NEMA 1-15 type plugs.

The National Fire Protection Association publishes the National Electrical Code. The NFPA has adapted the NEMA standard as part of its new building code for Electrical Safety. Many states adopt the NFPA electrical code standards in their building code and statutes for enforcement of such building codes.

Underwriters Laboratories, inc, the testing agency for Insurance companies that issue policies against product liability, adopts the National Electrical Code (which includes the NEMA standards) as part of its product safety testing and check list.

Thus, in order to purchase product liability insurance a maker of consumer products, like a homeowner's hand drill, needs to submit the product to UL for safety testing. UL will give its blessing only provided ...... (yada, yada, yada)

Thus the products you buy will have a narrow (hot or black wire) and a wide blade (neutral or White wire indicated by the "W" on the NEMA 1-15 standard.) Even if the general public safety intent and need for the narrow / wide blade makes no difference in a specific manufacturer's product.

[Stormin Mormon]

The "polarized" plug is for extra user safety. AC outlets have polarity-specific sockets because some devices can easily become dangerous if the polarized device is plugged in backwards. This happens when the switch or fuse inside the appliance is designed to disconnect only the "hot" and not the "neutral" wire when the device is switched off because it is cheaper than switches that disconnect both wires. The "neutral" wire is typically connected to ground at the main panel, so it is safer to use the switch to open the "hot" wire.

The device could still be "hot" even when the switch is off. Without a polarized plug, you can't tell which wire the switch will disconnect and may receive a shocking surprise!

In theory, safe devices are designed to keep a user from touching either the hot or the neutral. designers know which wires will be "hot" inside the device, they can take extra precautions to make sure they cannot break apart and electrify anything a user can touch. A broken "hot" wire can electrocute a user. Therefore, many appliances now have a polarized plug so the switch always disconnects the "hot" side.

A so-called "double-insulated" (IEC Class II) device may have a non-polarized plug because the same safe design has been made for BOTH conductors No single internal fault would be likely to cause an electrocution hazard.

Furthermore, even with a polarized plug, a single internal fault can be deadly in an ordinary appliance. The third prong (ground) can save your life if there is an internal fault of the hot touching exposed metal, and a GFCI can save your life if there is an internal fault of the neutral to exposed metal (where you could otherwise become the missing "neutral" connection to ground as you are electrocuted).

You are an ignorant fool to grind down the polarized plug.

[Stormin Mormon]

Some people learn by reading. Some people learn by being taught. Others just have to go piss on the electric fence themselves.

[Stormin Mormon]

The rest of the time, you can have the safety of having a three wire grounded device. I'm with you, I do carry the three to two "cheaters".

[The Daring Dufas]

A famous man once wrote something to the effect: "Experience is a fools best teacher." My father taught us how to do electrical wiring when we were kids on the farm. I have experienced shock therapy many times over the years. I would hope others could learn from my experience.

TDD

[Claude Hopper]

This is called bureaucratic bullshit.

[EXT]

While this is true, it also true that manufacturers need to make products as stupid proof as possible. The cost of the plug is minimal, and really causes no inconvenience to the users, as you will get it right 50% of the time without even looking. Don't sweat over such minor stuff, when there is some serious stuff out there you really need to worry about.

[TD]

The Daring Dufas wrote in news:ge3jis$dnc$ [e-mail]:

The companies use it in case you need an extension cord. Then you'll be forced to buy an extension cord with the wide blade.

[Dave Martindale]

I actually own an older Dremel tool that has a plastic coupling to isolate the output shaft. The motor has a pair of bearings, and the output shaft has another pair of bearings. The two shafts are in line but don't touch, and a splined plastic coupling connects them.

It works fine for transmitting rotation, but it makes the tool almost unusable for routing and some grinding and milling operations. The output shaft is just a short stub, and the bearings that hold it are only half an inch apart. So any side load on the cutting tool has plenty of leverage in applying force to those bearings, which are only held by the plastic housing. The result is lots of chatter.

I notice that all of the more recent Dremel tools I've looked inside have a single shaft from chuck all the way back to the rear end of the motor. So there are only 2 bearings, and the chuck is better at withstanding side loads.

But the newer Dremels are *still* double insulated. I think they do it with insulation between the steel stampings that make up the armature magnetics and the motor shaft. So if the insulation on the armature wire wears through and touches the steel, the armature could become "hot" but the shaft would still be isolated.

Dave

[The Daring Dufas]

I'm not going to call you names but that's the silliest thing I've seen posted in a while.

TDD

[bud--]

The NEC is written by panels that include many interests - manufacturers, engineers, contractors, labor, affected industries. UL and the NEC try to be compatible (but I can think of at least one place they conflict). As far as I know, the NEC has no standards for receptacle configurations except RVs and trailer parks. UL develops standards for products from different panels of knowledgeable people. It is independent from the NFPA and NEC, but people involved also want UL standards and the NEC to not conflict. UL does not adopt the NEC.

UL standards are for product manufacturing. The NEC is primarily an installation standard.

The NEC has limited product design requirements. Equipment installed must be "approved". Approval is strictly the decision of the "authority having jurisdiction" which is typically a state or municipality. The AHJ usually wants products to be "UL listed" (or maybe listed /labeled another reputable lab which probably tests to UL standards).

NEMA is a manufacturers group. It sets a number of standards. The question is how those standards become requirements for equipment. NEMA receptacle configurations may be included in some UL standards, I don't know. UL could also just have performance and design standards, for example plugs must be polarized, with specific configuration selected by manufacturers. (NEMA categories for enclosures have been adopted by the NEC.)

[Gary H]

[snip]

But it'll seem more like 10% because of selective memory.

No worrying, but a bit of arithmetic:

Can you turn a plug around in 2 seconds? That's an average of 1 second, since you have to turn it around half the time.

Now, how many times do you plug things in? It it's just 10 times a day, that's 36524 times a year (based on average 365.24 days per year). That's over 10 hours a year.

About 3 DAYS (and I mean REAL DAYS, 24 hours each) of your life wasted because of the unnecessary use of polarized plugs! Is that so minor now?