When did polarized plugs come out?
Although polarized outlets and plugs were introduced in the 1880s, they were not popular at first and did not become standard until the mid-20th century. What is the point of a polarized plug? Most appliances would work if they were plugged in "upside down."
Why are electrical plugs polarized?
Polarized outlets and plugs are used primarily as a safety feature to help prevent the danger of electrical shock. On such a device, if the plug were non-polarized, electrical components would likely retain an electrical charge even if switched off, producing a severe risk of electrical shock.
Which leg is neutral in a polarized plug?
With a NEMA 1-15 polarized plug, there is no ground terminal, only line and neutral. The neutral blade is wider than the line (hot) blade is. In the socket, the slot is wider. “If all the wiring is done to the national code, the neutral polarity is connected in a known condition.
What is the purpose of polarized electrical plugs?
Why Do Some Electrical Plugs Have Polarity?
- Identification. Polarized plugs are designed to be used in only one orientation, meaning that each blade of the plug is supposed to be inserted into a specific hole in the ...
- Purpose. Polarized outlets and plugs are used primarily as a safety feature to help prevent the danger of electrical shock.
- Non-Polarized. ...
- Warning. ...
Are polarized plugs required?
Non-polarized outlets were common in older homes, changing any non-polarized outlets you may have in your home will keep your house current on safety codes. Every outlet should be replaced with a polarized outlet in an up-to-date home sale for safety.
When would we use polarized plugs?
Most appliances would work if they were plugged in "upside down." But it provides a measure of safety for the appliance and house wiring to be aligned in terms of polarity. This is the reason why most appliance plugs are polarized—so they can only be plugged in neutral-to-neutral, hot-to-hot.
When did three prong plugs become standard?
1969In 1969, Underwriters Laboratories mandated three-prong plugs on major appliances for safety. At that time, only half of the receptacles in US homes were three-prong. Wiring in most homes did not include a grounding wire. The screws and outlet boxes were either connected to the neutral, or connected to nothing.
Why are some plugs not polarized?
Plugs with the two of the same-sized prongs are considered non-polarized because there is no clear distinction as to which prong is for the “hot” side and the “neutral” side.
Can I replace a polarized plug with a non-polarized plug?
replacing a functioning non-polarized plug with a polarized plug will not make it safer. However, the opposite (replacing a polarized plug with a non-polarized plug) could make a device unsafe to operate.
Can you plug a polarized plug into a extension cord?
Identification. A polarized plug is easily distinguishable from other plugs because the blade on one side is wider than the other. Consequently, a polarized plug can only be inserted into an electrical outlet one way.
Are 2 prong outlets legal?
Are Two Prong Outlets Legal? According to the National Electric Code, two-prong outlets are allowed in homes as long as they are properly working. If you choose to replace your two prong outlet, you do not have to upgrade to a newer model.
Are old two prong outlets safe?
Why are Two-Prong Outlets Considered Dangerous? The main reason two-prong outlets are considered outdated and dangerous is due to their lack of grounding. Grounding is how electricity is safely transferred in the case of an unstable current.
What year did ground wires become standard?
In 1901 the NEC was changed to recommend -- but not require -- grounding of low-voltage distribution systems, and in 1913 it was changed to make grounding mandatory.
Why do plugs have two holes on the prongs?
These bumps fit into the holes so that the outlet can grip the plug's prongs more firmly. This detenting prevents the plug from slipping out of the socket due to the weight of the plug and cord. It also improves the contact between the plug and the outlet.
When did polarized outlets become standard?
Although polarized outlets and plugs were introduced in the 1880s, they were not popular at first and did not become standard until the mid-20th century.
Why are electrical outlets polarized?
Why are electrical outlets and plugs polarized? Wednesday, July 11, 2018. Polarized electrical cord plugs are designed so that they can only fit into a socket/outlet one way. One of the two vertical prongs is slightly taller than the other, with a corresponding tall and short slot in the outlet, which makes it impossible to insert ...
How many times does a polarized receptacle change direction?
Since household electricity at wall receptacles is a 60-hertz alternating current, meaning that the electron flow changes direction back-and-forth 60 times per second, it might seem like polarization is a pointless waste of time.
Can polarity be defeated?
Correct polarity can be defeated if the outlet itself is wired backwards, which is a safety defect we check for at a random sampling of wall outlets during a home inspection. Some appliance manufacturers overcome this potential problem by using a double-pole switch that disconnects the circuit at both the hot and neutral wires.
When were separate plugs available?
Separable plugs had been available for more than a decade prior to Hubbell's 1904 design.
When did plugs come out with parallel flat pins?
Plugs per se with parallel flat pins, such as the "Fort Wayne" design were in common use by 1886, and flush receptacles, such as the "Bryant Electrical Company" design, by 1902. Hubbell had introduced its own parallel flat pin configuration in 1912.
What is the IEC 60884-1?
The international standard IEC 60884-1 defines the general requirements for plugs and sockets intended for household and similar purposes, IEC 60884-1 does not define specific plug and socket types , which are the subject of national standards in each country.
What is a patent for a plug?
In one patent, U.S. Patent 774,250 a plug was used with a socket which screwed into a lampholder (like the early lampholder plugs). In the other patent U.S. Patent 776,326 the same type of plug was used with various three-way adaptors that could be connected to lampholders or "a receptacle of any ordinary type".
How many round pins did Hubbell have?
Hubbell's first plug design had two round pins which differed from those already in use in Europe in that the tips of the pins had annular detents similar to those of present-day jack plugs to positively retain a plug in its socket.
What type of plugs did Hubbell use in 1906?
Hubbell's catalogue of 1906 includes various three-way adaptors similar to those shown in the US 776,326 patent, but modified for use with the coplanar flat pin plugs. The Chapman receptacle must have been in general use at the time, as it was the only type of non-lampholder receptacle for which adaptors were supplied.
When was the round pin invented?
Hubbell evidently soon found the round pin design unsatisfactory as a subsequent U.S. Patent 774,251 filed on May 27, 1904 shows lampholder adaptors similar to those of his first patent for use with plugs having coplanar (tandem) flat pins.
Why are most appliance plugs polarized?
But it provides a measure of safety for the appliance and house wiring to be aligned in terms of polarity. This is the reason why most appliance plugs are polarized—so they can only be plugged in neutral-to-neutral, hot-to-hot.
How many prongs does a grounded plug have?
Heavier appliances, such as those operating heating devices or motor-driven devices, usually have a grounded plug with three prongs. Light-duty appliances, such as lamps, are unlikely to have grounded three-prong plugs.
What does it mean when an outlet is unpolarized?
This too is sometimes seen in older homes. When you find an outlet that has vertical slots exactly the same width, it means you are probably looking at wiring that is quite old. These unpolarized outlets can be very inconvenient since polarized plugs will not even fit into them.
How to connect a plug to an outlet?
This is the neutral slot and the neutral plug blade. The configuration means that you can only insert the plug into the outlet slots in one direction— wide blade to wide slot, narrow blade to narrow slot. This ensures that the neutral wires in the appliance are connected to the neutral wires in the house circuitry and that the "hot" wires in the appliance and the hot wires in the house circuitry match up.
What is the plug on the end of an electrical cord called?
At the end of any appliance electrical cord, there is a plug with two or three prongs (blades) designed to fit into standard wall outlet receptacles. When there are three prongs, these are known as "grounded plugs," and they are designed to fit into wall outlets so the round bottom prong fits into the ground slot on the outlet ...
What is a grounded plug?
When there are three prongs, these are known as "grounded plugs," and they are designed ...
Can you plug an unpolarized plug into a polarized outlet?
It is generally not a problem to plug in an unpolarized plug to a polarized outlet in whatever way it will fit. But anytime you are replacing a plug on an older lamp or appliance, it's a good idea to install a new polarized plug.
