Yesterday I passed SFS6002 electrical safety course and got SFS 6002 käytännössä book. SFS 6002 electrical safety training is for all electrical work in Finland engaged in compulsory education, which must be renewed every five years. Now I know somewhat more than before on electrical safety related to electrical installations.
SFS6002 is a Finnish standard how electrical work should be performed safely. It is based on European general standard EN 50110-1 (Operation of electrical installations – Part 1: General requirements) plus Finnish national additions to it.
If you want to get your hands on the original European EN 50110-1 standard, you need to buy it. There are also free information on standard available: British edition of the standard BS EN 50110-1:2004 can be found on-line.
760 Comments
Tomi Engdahl says:
Should You Wrap Outlets In Electrical Tape?
https://www.youtube.com/watch?v=mY45ZDdiPn4
Tomi Engdahl says:
Using a TT earth where a TN earth already exists
https://www.youtube.com/watch?v=S5OtLg6voZY
Problems associated with using a TT earth at a location that already has a TN-C-S or TN-S earthing system. This could be for things such as a hot tub, EV charge point or an outbuilding.
A TT system must be completely separate from any other earthing system, including connections via extraneous conductive parts shared with other buildings. Earth electrodes cannot be installed where fault currents from other installations could cause a voltage to appear on the TT system.
Tomi Engdahl says:
What’s inside a Transformer?
https://www.youtube.com/watch?v=ONOyvBx2bp8
Someone asked me the other day ; Is there really oil inside a transformer !? So Today we actually opened one up, so you can all see what’s inside !
Tomi Engdahl says:
Shaver Sockets for UK Bathrooms – With Isolating Transformer
https://www.youtube.com/watch?v=hyaaPt6UuEU
An older example of a shaver socket outlet as used in UK bathrooms. Normal socket outlets are only permitted where they are at least 3 metres from the edge of the bath, so in reality they are never installed.
These shaver sockets contain an isolating transformer and are limited to 20VA, so are only of use for very low power items like shavers and toothbrushes.
Modern examples are very similar, although usually riveted together so more difficult to take apart for demonstrations like this.
Tomi Engdahl says:
How to Wire Three-Phase, 400V Distribution Board IEC – UK & EU
Wiring Installation Guide: https://wp.me/p4O3ZJ-bW0
Tomi Engdahl says:
Wiring 3-Phase, 400V Load Circuits in 3-Φ Distribution Board
Wiring Tutorial: https://www.electricaltechnology.org/2021/03/wiring-three-phase-distribution-board.html
Tomi Engdahl says:
Types of Earthing System for Electricity Supplies (UK)
https://www.youtube.com/watch?v=AWxeb2MI37c
The three main types of earthing for mains electricity supplies to buildings in the UK. TT, TN-S and TN-C-S.
TN-C-S Danger – Broken PEN Conductor (Combined Earth & Neutral)
https://www.youtube.com/watch?v=JRHyqouJPzE
Tomi Engdahl says:
Cooker Circuits Diversity, 15kW load, 32A circuit breaker.
https://www.youtube.com/watch?v=QQduU8RkjD8
Cooker circuits for domestic properties. Protective device, cable size, and what can be connected to the end of it.
In virtually all cases, a 32A MCB and 4mm² cable is suitable for cooking devices up to 15kW.
For connecting to the appliance(s), either 4mm² or 2.5mm² H07RN-F flex depending on the connected load.
Tomi Engdahl says:
Killer Screwdriver
https://www.youtube.com/watch?v=AGXQNLq19FQ
Neon tester/ terminal driver gets tested on a few thousand volts.
Not a good prospect if you were on the end of it, and you had it in your hand and inadvertently made contact with a few thousand volts.
Strongly advise to use a proper insulated screwdriver for terminals.
Use a proper voltage tester like a fluke with 2 probes to get a definitive answer to weather there is voltage or not.
Always ensure that your test equipment is rated for the voltage you want to test or work on.
Where ever possible do not work on live equipment moving wires about.
Play safe !
Tomi Engdahl says:
Liesi on edelleen vaarallisin sähkölaite
https://etn.fi/index.php/13-news/11986-liesi-on-edelleen-vaarallisin-sahkolaite
Tukesin mukaan sähkölaitteesta tai -asennuksesta alkaneita tulipaloja oli viime vuonna vähemmän kuin aiempina vuosina. Pelastustoimen PRONTO-tietokannan mukaan pelastuslaitoksilla oli viime vuonna yhteensä noin 2200 palohälytystä, joissa syttymissyyksi oli kirjattu sähkö. Vaarallisin laite on edelleen sähköliesi.
2200 sähkölaitteista aiheutunutta palohälytystä on pienin määrä seitsemään vuoteen. Liesipaloon liittyviä hälytyksiä oli 834 kappaletta. Niidenkin määrä väheni noin sadalla edellisvuodesta. Palon syynä oli useimmiten virheellinen toiminta.
Lieden jälkeen toiseksi yleisimmäksi syttymissyyksi on kirjattu viime vuonna valaisimet (189). Viiden eniten paloja aiheuttaneiden laitteiden joukossa olivat myös muut koneet ja laitteet (187) sekä kiukaat (109). Pienelektroniikan akku tai laturi aiheutti palon tai palovaaran 48 tapauksessa. Pyykinpesukoneesta alkaneita paloja oli 50 ja astianpesukoneesta alkaneita 54. Palo sai alkunsa sähköjohdoista ja -kaapeloinneista 93 kertaa, sähkökeskuksista 83 ja muusta sähköverkon osasta 75 kertaa.
Tukesin ylitarkastaja Jukka Lepistön mukaan liesipalon syynä on hyvin harvoin itse liedestä johtuva vika. – Useimmiten syynä on ihmisen huolimattomuus, varomattomuus tai kiire. Yleisin palon aiheuttaja onkin lieden unohtuminen päälle, Lepistö sanoo.
Tomi Engdahl says:
ARE AMERICAN PLUG SOCKETS DANGEROUS? | BABY GETS ELECTRIC SHOCK | BRITISH ELECTRICIAN
https://www.youtube.com/watch?v=Ihau12C9uq8
some observations about the differences between the UK and US electrics and fire safety.
In this video I show the differences between the UK plug and the US plug. Are American plug sockets dangerous? Find out more.
Tomi Engdahl says:
How dangerous are electrical wall outlets in the United States? Is it necessary to child proof them? What if a child stuck a fork in the outlet?
https://www.quora.com/How-dangerous-are-electrical-wall-outlets-in-the-United-States-Is-it-necessary-to-child-proof-them-What-if-a-child-stuck-a-fork-in-the-outlet
US Electrical Outlets and Safety Data
Per the NFPA (National Fire Protection Association, from data I believe is from the US CSPC – Consumer Products Safety Commission):
“Statistics from 2005 indicated that approximately 89 percent of electrical burn and shock incidents occurred among children 6 years of age or less.”
and
“Each year, approximately 2,400 children suffer severe shock and burns when they stick items into the slots of electrical receptacles. It is estimated that there are six to 12 child fatalities a year related to this.”
I guess that data makes me wonder about those who say they are safe.
US NEC Requirements for Tamper-Proof Receptacles
Because of this, starting with the 2008 Edition of the NEC (National Electrical Code) the NEC has required tamper-resistant receptacles be used in certain locations. The NEC is revised every three years, and the NEC has been increasing the requirement for receptacles to be tamper-resistant with the revisions.
Tamper-resistant receptacles work by having a plastic shutter in front of where the plug gets inserted, which is only moved out of place if objects are placed into both slots of the receptacle – something that young children are unlikely to do accidentally.
The latest edition of the NEC is the 2018 edition, and it covers tamper-resistant receptacles in Section 406.12 “Tamper-Resistant Receptacles.”
Receptacle Safety Caps
It is really easy for a child to remove those “safety caps” – plus they are a nuisance and people often forget to put them back.
GFCI’s are also a good idea, and the NEC adds to the places they require GFCI’s be installed with event edition of the NEC.
You can read a lot more about it here:
https://www.nfpa.org/-/media/Files/Code-or-topic-fact-sheets/InjuriesElectricalOutletsFactSheet.pdf
Tomi Engdahl says:
Using extension cords properly is critical to your safety. With continuous use over time, an extension cord can rapidly deteriorate, creating a potentially dangerous electric shock or fire hazard.
According to the Consumer Product Safety Commission, misused or damaged extension cords cause about 3,300 residential fires each year, killing 50 people and injuring 270 others.
https://www.ius.edu/environmental-health-safety/files/power-cord-safety.pdf
Choosing a Safe Electrical Extension Cord
https://www.thespruce.com/select-proper-electrical-extension-cord-1824710
Why Extension Cords Are Dangerous
An extension cord essentially is a bundle of insulated electrical wires with a plug on each end. Electrical current flowing through wires generates heat, and when too much current flows through a wire, it can overheat and melt the plastic insulation of the wires, causing short circuits and fires.
This is normally not a problem when you plug an appliance directly into an outlet using its factory cord because the manufacturer has sized the cord appropriately for the electrical current demand, or load, that the appliance requires. But if you use an undersized extension cord to extend the reach of that appliance cord, you can exceed the safe load capacity of the extension cord, and the result can be disastrous.
Extension Cord Gauge and Length
Electrical extension cords come in different types, lengths, and sizes. Two important factors determine any cord’s load capacity, its ability to carry electrical current:
Wire gauge: The thickness or diameter of the wire affects how much current the wire can carry and how much the wire heats up.
Length: The length of the extension cord affects voltage drop, or how much voltage is lost through resistance in the cord wires.
For example, an 18 AWG cord may only be rated for 5 to 7 amperes (amps) of load at a length of up to 25 feet. To get the same load rating with a 50-foot cord, the cord must have larger, 16 AWG wire. Because of the voltage drop, it’s best to use the shortest extension cord possible for the job at hand.
Light-Duty Extension Cords
Cord length up to 25 feet: use 18 AWG wire
Cord length up to 50 feet: use 16 AWG wire
Cord length up to 100 feet: use 14 AWG wire
Medium-Duty Extension Cords
Medium-duty cords usually are grounded extension cords, which include the third wire and plug prong for grounding. They have plugs that accept three-prong grounded appliance cords.
Uses: televisions, computers, and other devices that draw up to 10 amps of power
Cord length up to 25 feet: use 16 AWG wire
Cord length up to 50 feet: use 14 AWG wire
Cord length up to 100 feet: use 12 AWG wire
Heavy-Duty Extension Cords
Heavy-duty extension cords are suitable for drawing 10 to 15 amps of power. These are always grounded extension cords that include a third wire and plug prong for grounding and have plugs with three slots for accepting grounded appliance cords.
Uses: tools and heating appliances drawing up to 15 amps of power
Cord length up to 25 feet: use 14 AWG wire
Cord length up to 50 feet: use 12 AWG wire
Cord length up to 100 feet: use 10 AWG wire
Note: Follow appliance manufacturer instructions regarding the use of extension cords. Some appliances never should be used with extension cords.
When using extension cords outdoors, below-grade (such as in a basement or crawlspace), or anywhere a cord might encounter moisture, the cord should be GFCI (ground-fault circuit-interrupter) type or should be plugged into a GFCI-protected outlet.
Tomi Engdahl says:
BykylewillisinNewsPostedJune 2, 2016 at 9:40 pm
5 Ways You’re Using Extension Cords Wrong
https://www.wirece.com/5-ways-using-extension-cords-wrong/
Tomi Engdahl says:
What will happen if a cord is plugged into a socket incorrectly?
https://www.quora.com/What-will-happen-if-a-cord-is-plugged-into-a-socket-incorrectly
Tomi Engdahl says:
Extension cords must not be used as a replacement for standard electrical wiring for a building. Never use an extension cord where it is put through a hole or opening in a wall, inside a dropped ceiling or under flooring.
Extension Cord Laws
https://legalbeagle.com/7325030-extension-cord-laws.html
When a power cord doesn’t reach to an outlet, the simple solution is to attach an extension to it. Extension cords were meant to be temporary power solutions or a means for bringing electricity to job sites where no power exists. More often than not, they become a permanent fixture, but the laws regarding safe use of electrical extension cords clearly state proper use, and OSHA, the Occupational Safety and Health Administration, places strict demands on workplace use of extension cords as well.
National Electrical Code (NEC) Rules
Extension cords must not be used as a replacement for standard electrical wiring for a building. Never use an extension cord where it is put through a hole or opening in a wall, inside a dropped ceiling or under flooring. It is against the National Electrical Code to connect extension cord wiring through doorways or other structural openings like windows. Extension cords must not be hidden in any way behind structures, or covered with objects such as rugs. Extension cords must be clearly marked with a maximum amp to keep cords from overheating. Common amperage is 10, 15, 20, and 25 amps depending on the size and number of wires inside the cord.
Characteristics
Extension cords must have clearly marked characteristics to allow users to judge the compatibility of the cord to a project. There are two standard letters indicating type of service: S and SJ. S stands for hard service, and SJ stands for light service. Additional indications following the S and SJ marks include: T for more heat resistant thermoplastic insulation, E for elastomer insulation, a form of thermoplastic insulation with a more rubberlike composition, O for resistance to oil, and W for the ability to resist water and sunlight.
https://en.wikipedia.org/wiki/Extension_cord
Tomi Engdahl says:
I WAS TOLD THAT I COULD NOT PLUG ONE EXTENSION CORD INTO ANOTHER ON A CONSTRUCTION SITE. THE NEC DOES NOT SEEM TO PROHIBIT THIS PRACTICE. WHERE DO I FIND SUCH INFORMATION?
https://iaeimagazine.org/2007/july2007/i-was-told-that-i-could-not-plug-one-extension-cord-into-another-on-a-construction-site-the-nec-does-not-seem-to-prohibit-this-practice-where-do-i-find-such-information/
UL Lists what every one knows as “extension cords” as cord sets under the product category Cord Sets and Power Supply Cords (ELBZ), located on page 65 in the 2006 UL White Book or online at http://www.ul.com/database and enter ELBZ at the Category Code search.
Plugging one cord set into another is what many refer to as “daisy chaining.” Daisy chaining increases the likelihood of misuse, excessive voltage drop and overloading the extension cord and may create a fire or shock hazard, therefore, UL 817 requires that cord sets be provided with a tag label that identifies the dos and don’ts of using an extension cord to avoid dangerous hazards. One of the markings required on that tag states, “Do not plug one extension cord into another.” So that, if one extension cord is plugged into another it is a violation of NEC 110.3(B) because the cord set would not be installed in accordance with the Listing installation markings.
Tomi Engdahl says:
Safety Tips for Using Extension Cords
https://housetipster.com/housetips/1006/safety-tips-for-using-extension-cords
According to the Consumer Product Safety Commission (CPSC), extension cords cause over 4,000 injuries a year, and 13 percent of those injuries involve young children.
The CPSC claims the misuse of extension cords cause approximately 3,300 fires every year. These fires are caused by extension cords short-circuiting, being overloaded, being under a carpet or couch, or being old and/or damaged. You can reduce the risk of an extension cord causing a fire by making sure you’re using the cord correctly.
Avoid thin, bargain-priced extension cords which typically have a low wattage rating.
Never use a cord that’s cracked or cut. Throw it out.
Don’t use an interior extension cord for outside use. Buy an exterior extension cord.
Keep extension cords out of the reach of small children. Any outlet that’s not being used should be capped. This applies to wall outlets and extension cord ends.
Extension cords are meant for temporary use. Try not to make an extension cord a permanent part of a room. If the cords on your electric devices are too short, consider rearranging the room to place lamps and TVs closer to wall outlets. If this isn’t possible, ensure the extension cord is heavy enough to power the device or devices.
If building a house or adding an addition, don’t skimp on outlets. Think about where you will have lamps, TVs, computers, routers, printers, and anything that requires electricity.
Tomi Engdahl says:
https://www.allumiax.com/resources
Tomi Engdahl says:
How can NEMA electric plug be safe ?
https://diy.stackexchange.com/questions/93431/how-can-nema-electric-plug-be-safe
I’m quite scared every time I have to use NEMA plugs (I live in Japan).
Coming from europe, the bottom of the two connectors is insulated
This ensure that even if you touch them while plugging/unplugging, it will always be safe to touch.
Meanwhile with NEMA ones, there is no such insulation and I often see my appliance partially disconnected (but power still flowing) because of either the weight of the AC/DC or the cable has been pulled accidentally.
Well, you’re not supposed to touch the metal parts while plugging and unplugging, that’s what the ridged plastic area is for on the pictured plug — to give you better grip.
Nothing is safe. There are only degrees of safety.
European plugs incorporate more safety features, which makes them safer. But they also work with higher voltages, which are slightly more dangerous (230 instead of 120 in US or 100 in Japan).
I think it is better to regard them as less safe rather than unsafe, Just take extra care.
Do not use cords, plugs or outlets that appear damaged, replace them.
Always ensure plugs are fully pushed in.
Only grasp plugs by the plug body.
Keep fingers away from the front edge near the pins.
Do not pull plugs out by the cords
Do not let cords trail where they may be tripped over (causing plugs to be pulled partly out)
If you can do so, replace ordinary breakers and outlets with GFCI equivalents.
Tomi Engdahl says:
https://www.iqsdirectory.com/articles/power-cord/nema-connector.html
Tomi Engdahl says:
Domestic Plugs and Sockets
Notes on Diversity and Safety
https://www.plugsocketmuseum.nl/Plug-diversity.html
Tomi Engdahl says:
Power outlets in America are unsafe, dangerous and poorly designed! (NEMA Standard Sockets & Plugs)
https://www.youtube.com/watch?v=2cS6wWXQsHY
Un-sleathed pins, exposed terminals, shock hazard! Plugged in half way with exposed contacts and the power strip still works…
Extension Cords cause FIRES. USE POWER STRIPS
https://www.youtube.com/watch?v=jIxU9IsKK8I
Please do not use extension cords within your home.
As Firefighters we go to many fires involving extension cords -
Roughly 3,300 home fires originate in extension cords each year, killing 50 people and injuring 270 more. Extension cords can overheat and cause fires when used improperly, so keep these important tips in mind to protect your home and workplace.
Remember also not to overload your power strip and don’t plug space heaters into them.
Electrical fires, extension cord fires, power strips, fire safety, Firefighter,
Tomi Engdahl says:
What Happens If You Use Multiple Coiled Extension Cords?
https://www.youtube.com/watch?v=MGqNKEIQGWQ
Tomi Engdahl says:
https://www.quora.com/Is-it-safe-to-touch-the-AC-power-plug-prongs-of-a-recently-unplugged-device
If you accidentally plug one prong in the receptacle of an extension cord and the other is exposed, what would happen if you touched the exposed prong?
According to your picture below, the hot wire is plugged into the hot electrical wire by turning the plug upside down and using this cheap multi tap plug. Each prong is sized so that the hot is the small prong preventing the ground or neutral from plugging into it.
If a load such as a light or power tool was plugged into the extension cord, it would not have a completed circuit and operate.
However, if the load plugged in was switched on and you touched the exposed neutral pin while also being grounded by touching a grounded metal object, like a plumbing pipe, then you would complete the circuit and be shocked. This is an unlikely situation to have happen
Electrical outlets are designed to be as safe as possible but it has been my experience that people will always end up finding some way to hurt themselves.
Tomi Engdahl says:
Will 120v To Ground Trip a Circuit Breaker?
https://www.youtube.com/watch?v=gHQE5L6hbgs
Will a ground fault to a copper ground rod trip a breaker? Does a ground rod get rid of voltage? What is the purpose of a ground rod? How sensitive are GFCI breakers? What happens when you short out 120v to the panel frame? These are some of the questions that this video may cause you to ponder. While we don’t answer every question I do shed some light on what happens when you connect 120v directly to a ground rod and I demonstrate the voltage gradient that occurs in the soil around the grounding electrode.
Tomi Engdahl says:
Funny meme
Do not do this!
https://me.me/i/guide-to-fuse-replacement-guide-to-fuse-replacement-350-amp-3014307
Tomi Engdahl says:
Generator Earthing Types – TN-S or IT?
https://www.youtube.com/watch?v=mzCGE5wnWos
Earthing systems for generators.
Although an earth electrode may be present, it’s not likely to be a TT arrangement.
Tomi Engdahl says:
ELECTRICIANS’ Q&A :Do you need a fuse if connecting from a large to a smaller cable? – BS7671
https://www.youtube.com/watch?v=BAtCAAUpXsg
Can you connect a smaller cable to a busbar cable system without including a fuse to protect the cable?
Joe Robinson explores electricians questions related to the Woertz flat cable connector system we used for our Easee commercial EV charger installation.
Tomi Engdahl says:
ELECTRICIANS’ Q&A :Do you need a fuse if connecting from a large to a smaller cable? – BS7671
https://www.youtube.com/watch?v=BAtCAAUpXsg
Tomi Engdahl says:
Appliance Protection Classes 0, I, II, III
https://www.youtube.com/watch?v=eWHQRcO071E
Protection classes as defined in BS EN 61140, with Class I and Class II (double insulated) being the most common.
Covers all four classes, the protection methods for each one, and considerations when connecting equipment to a fixed wiring installation.
Tomi Engdahl says:
Test Lead Adaptors for various types of Socket Outlet
https://www.youtube.com/watch?v=0HqZ0bSInvA
Tomi Engdahl says:
https://www.electricaltechnology.org/2021/05/wiring-a-garage-consumer-unit.html
Tomi Engdahl says:
EVERY plug in the UK has a fuse.
Most circuits in the UK RCD protection.
Schuko isn’t fused. But then most of the equipment is instead.
in UK every plug has a fuse (maximum 13A) and set of outlets are protected with ~30A fuse/breaker.
In most of Europe the outlets are protected typically with 10A or 16A fuse/breaker. Devices have overload fuses and cable from outlet to equipment is thick enough to handle equipment normal load (if more than normal load then equipment fuse burns) current and trip mains panel fuse/breaker quickly if there is short circuit.
RCD is used in modern installations but not found on many older.
Extensions cords are built with thick enough wire that can handle the maximum load that can be connected to it (typically 1.5 mm2 wire than can handle 16A on free air, can be thinner on some special cases)
I don’t know a lot about the US…
But my internal alarm went off when stage techs would hand me a device to remove the earth on an amp when we had any sort of hum/buzz on a stage in the US…
That simply doesn’t exist in the UK, and would be banned if it did
Tomi Engdahl says:
Extension Cord Safety
Household Extension Cords Can Cause Fires
https://allinelectricinc.com/extension-cord-safety/
Choose the right extension cord for the job, and use it as specified. Extension cords can overheat and cause fires when used improperly. Overheating is usually caused by overloading or connecting equipment that consume more watts than the cord can handle. Damaged extension cords can also cause fires. Extension cords should only be used temporarily. Unplugging the cords when not in use.
Household Extension Cords Can Cause Fires
https://cpsc.gov/s3fs-public/5032.pdf
Discard Older Extension Cords Discard cords that are old and/or are missing important safety features, including safety closures, polarized blades and a large plug face that covers the outlet’s slots and is easy to grasp to unplug. Extension cords should be at least 16 AWG, unless they are 18 AWG with fuse protection. AWG refers to the size of the wires in the cord. The wire size is imprinted on the cord’s surface.
Tomi Engdahl says:
Choosing the Correct Extension Cord Sizes
https://www.thespruce.com/extension-cord-choices-1152867
Extension cords offer a means of extending a home’s or workshop’s electrical circuits when a lamp, appliance, or tool has an attached cord that is too short to reach the needed location. Most people have several extension cords they keep on hand for this purpose. What is often not considered, though, is that these extension cords need to be of an appropriate size for the power load being placed on them.
Matching Extension Cord to Load
Extension cords should be rated for loads that are at least equal to, and preferably greater than, the requirements needed to run a tool effectively. Extension cord lengths of 50 feet or less can be used based upon the chart shown below, but runs over 50 feet should implement the next heavier-sized cord to accommodate voltage drop due to the natural resistance of the wire.
Extension Cord Wire Gauges, Amperage Rating, and Wattage
Wire Gauge Amperage Rating Wattage Rating Power Tool Used
#18 5 Amps 600 Watts Detail Sander, Drill, Jig Saw
#16 7 Amps 840 Watts Belt Sander, Reciprocating Saw
#14 12 Amps 1,440 Watts Circular Saw, Miter Saw, Router
#12 16 Amps 1,920 Watts Table Saw, Radial Arm Saw
Special caution should be taken with electric space heaters. You should never use an extension cord to plug one of these heaters into a power source. Numerous house fires have occurred when heaters are plugged into extension cords, due to their high wattage and amperage demands. Instead, space heaters should be plugged directly into electrical outlets, but even there you must be careful not to exceed the amperage rating of that circuit.
Choosing a Safe Electrical Extension Cord
https://www.thespruce.com/select-proper-electrical-extension-cord-1824710
Unless you are always lucky enough to have an electrical outlet positioned exactly where you need it, you almost certainly use electrical extension cords around your home. However, most people don’t understand just how dangerous it can be to use the wrong kind of cord. The U.S. Consumer Product Safety Commission has found that extension cords are among the most dangerous electrical devices in our homes, due to improper cord sizing and use. Each year, accidents from extension cords kill around 50 people, result in 4,000 injuries requiring hospital treatment, and cause more than 3,000 residential fires. Most extension cord failures can be prevented simply by using the right type of cord for the job.
Why Extension Cords Are Dangerous
An extension cord essentially is a bundle of insulated electrical wires with a plug on each end. Electrical current flowing through wires generates heat, and when too much current flows through a wire, it can overheat and melt the plastic insulation of the wires, causing short circuits and fires.
This is normally not a problem when you plug an appliance directly into an outlet using its factory cord because the manufacturer has sized the cord appropriately for the electrical current demand, or load, that the appliance requires. But if you use an undersized extension cord to extend the reach of that appliance cord, you can exceed the safe load capacity of the extension cord, and the result can be disastrous.
Extension Cord Gauge and Length
Electrical extension cords come in different types, lengths, and sizes. Two important factors determine any cord’s load capacity, its ability to carry electrical current:
Wire gauge: The thickness or diameter of the wire affects how much current the wire can carry and how much the wire heats up.
Length: The length of the extension cord affects voltage drop, or how much voltage is lost through resistance in the cord wires.
Gauge is a numerical rating of copper wire diameter and is identified by an American Wire Gauge (AWG) number. For example, a 12 AWG, 120-volt cord contains 12-gauge wires and is intended for use with standard 120-volt outlets. In the AWG rating system, the smaller the number the thicker the wire.
For example, an 18 AWG cord may only be rated for 5 to 7 amperes (amps) of load at a length of up to 25 feet. To get the same load rating with a 50-foot cord, the cord must have larger, 16 AWG wire. Because of the voltage drop, it’s best to use the shortest extension cord possible for the job at hand.
Light-Duty Extension Cords
Light-duty extension cords are those that resemble lamp wire cord. These cords should never be used with anything other than very light-duty devices. They are especially dangerous to use with space heaters and other heat-generating appliances, such as toasters or clothes irons, which draw heavy electrical loads. Light-duty cords often are not grounded: They have only two plug prongs and do not include a third wire and prong for grounding, so you should never be used with appliances that have a three-prong grounded cord.
Uses: lamps, clocks, and other light-duty electrical devices drawing up to 7 amps
Cord length up to 25 feet: use 18 AWG wire
Cord length up to 50 feet: use 16 AWG wire
Cord length up to 100 feet: use 14 AWG wire
Medium-Duty Extension Cords
Medium-duty cords usually are grounded extension cords, which include the third wire and plug prong for grounding. They have plugs that accept three-prong grounded appliance cords.
Uses: televisions, computers, and other devices that draw up to 10 amps of power
Cord length up to 25 feet: use 16 AWG wire
Cord length up to 50 feet: use 14 AWG wire
Cord length up to 100 feet: use 12 AWG wire
Heavy-Duty Extension Cords
Heavy-duty extension cords are suitable for drawing 10 to 15 amps of power. These are always grounded extension cords that include a third wire and plug prong for grounding and have plugs with three slots for accepting grounded appliance cords.
Uses: tools and heating appliances drawing up to 15 amps of power
Cord length up to 25 feet: use 14 AWG wire
Cord length up to 50 feet: use 12 AWG wire
Cord length up to 100 feet: use 10 AWG wire
Note: Follow appliance manufacturer instructions regarding the use of extension cords. Some appliances never should be used with extension cords.
Tomi Engdahl says:
How to Size Your Extension Cords to Lengths of the Run
https://www.thespruce.com/extension-cord-chart-1152866
Electrical extension cords are a great way to extend circuits to areas that you are working, away from available outlets. Sometimes we only need a short extension cord to give us the ability to plug our tools in and complete the project. Then again, we’ve all had many times where we’ve had to tie many extension cords together to reach the area that we needed to reach. But how many extension cords can one tie together and still have the amount of power to power up those tools? Is it actually safe to keep adding extension cords to an existing circuit?
Tomi Engdahl says:
Extension Cords Business Guidance
https://www.cpsc.gov/Business–Manufacturing/Business-Education/Business-Guidance/Household-Electrical-Products/Extension-Cords
The Commission has determined that extension cords (for indoor and outdoor use) that do not contain one or more applicable readily observable safety characteristics (minimum wire size; sufficient strain relief; proper polarization; proper continuity; outlet covers (for indoor cords); and jacketed cords (for outdoor cords) present a risk of electrical shock or fire and constitute a substantial product hazard.
The Commission’s determination has certain consequences described below. Notably, a product on the “substantial product hazard” list is subject to the mandatory reporting requirements of section 15(b) of the CPSA. 15 U.S.C. 2064(b).
Tomi Engdahl says:
Can I use an Extension Cord with a Space Heater?
Here’s everything you need to know about whether you can use an extension cord with your space heater.
https://heatertips.com/can-i-use-an-extension-cord-with-a-space-heater/
You should treat space heaters with special caution when it comes to installing them in your house. If you need an extension cord, for example, you have to spend additional attention to some safety aspects.
Tomi Engdahl says:
Why is it dangerous use a coiled extension cord
https://electronics.stackexchange.com/questions/192923/why-is-it-dangerous-use-a-coiled-extension-cord
What aspect using a coiled extension cord makes it more dangerous than using an unrolled power cord.
Many fire safety websites reference that an extension cord should not be used while coiled.
Is this due to the cord acting as an air core inductor (I can’t really see why this should cause fires). If this is the case, if every second loop is in the opposite direction is it safe.
My theory is that if the cord is getting heated from high current draw, when coiled all of this heat is in a much more condensed location, causing a greater temperature rise than if the cable was unrolled.
Tomi Engdahl says:
CAUSES AND SOLUTIONS FOR OVERHEATING OF WIRES AND CABLES
CAUSE OF CABLE OVERHEATING
https://m.zmscable.com/new/Cause-of-cable-overheating
Tomi Engdahl says:
How do I calculate the temperature rise in a copper conductor?
https://electronics.stackexchange.com/questions/22334/how-do-i-calculate-the-temperature-rise-in-a-copper-conductor
Tomi Engdahl says:
https://electronics.stackexchange.com/questions/480890/does-coiling-and-straightening-a-wire-change-its-resistance
https://electronics.stackexchange.com/questions/192923/why-is-it-dangerous-use-a-coiled-extension-cord
Tomi Engdahl says:
https://www.homelectrical.com/which-wago-connector-should-i-use.6.html
Tomi Engdahl says:
https://physics.stackexchange.com/questions/18623/effects-of-a-coiled-cable
Tomi Engdahl says:
Why is it dangerous use a coiled extension cord
https://electronics.stackexchange.com/questions/192923/why-is-it-dangerous-use-a-coiled-extension-cord
Tomi Engdahl says:
https://memeguy.com/photo/155107/fuse-replacement-guide
Tomi Engdahl says:
https://www.quora.com/What-electrical-plug-is-better-the-North-American-one-or-the-European-one
Tomi Engdahl says:
How to make a voltage stabilizer? Learn in details
https://labprojectsbd.com/2021/04/11/how-to-make-a-voltage-stabilizer-learn-in-details/
Tomi Engdahl says:
Revealed: the terrifying smoke alarms that will fail when you need them They’re cheap and deadly, and all over eBay and Wish
Read more: https://www.which.co.uk/news/2019/05/revealed-the-terrifying-smoke-alarms-that-will-fail-when-you-need-them/ – Which?