Any form of energy, when not properly controlled or harnessed, can result in serious danger to those who use it. Electricity at any voltage can be dangerous and should always be approached with caution. Direct Dangers of Electricity include a variety of hazards that include Electric Shock, Physical Burns, Neurological Damage and Ventricular fibrillation resulting in death. The indirect dangers of electricity include for example fall due electric shock, an explosion, or a fire.
Electric Current affects the body when it flows through. Human can feel around about 1 milliampere (mA). The current may cause tissue damage or heart fibrillation if it is sufficiently high. 10-20 mA is beginning of sustained muscular contraction (“Can’t let go” current) and 30 mA can cause the onset of potentially fatal respiratory paralysis. A low-voltage (110 to 220 V), 50 or 60-Hz AC current travelling through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60mA.
Today’s U.S. electricity system is a complex network of power plants, transmission and distribution wires, and end-users of electricity.
Electrical safety is the leading subject in the North American power industry, but at home people in USA are stuck with a 100+ year old plug design that is far behind other countries in terms of safety features.
ARE AMERICAN PLUG SOCKETS DANGEROUS? video gives some observations about the differences between the UK and US electrics and fire safety:
“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.
Perhaps the weakest link in the US electrical system video gives on overview of dangers of electrical outlets and extension cords.
Most of North America (and Central America, and some of South America) use connectors standardized by the National Electrical Manufacturers Association. Those connectors are called NEMA connectors.
NEMA 1-15 ungrounded (Type A) plugs have two parallel blades and are rated 15 A at 125 volts. They provide no ground connection but will fit a grounding NEMA 5-15 receptacle. Ungrounded NEMA-1 outlets are not permitted in new construction in the United States and Canada, but can still be found in older buildings. You can shock yourself with many USA NEMA connectors if you just slipped around the end at the wrong moment. That is the original plug from the very early 20th century… It couldn’t be changed later because there were too many NEMA-1 outlets in service.
NEMA 5-15 grounded (Type B) plug has two flat parallel blades like NEMA 1-15, and a ground (earth) pin. It is rated 15 A at 125 volts. The National Electrical Contractors Association’s National Electrical Installation Standards (NECA 130-2010) recommends that sockets are mounted with the ground hole up so that a falling object makes first contact with the ground pin. This socket is recommended in IEC standard 60906-2 for 120-volt 60 Hz installations. NEMA 5-15 grounded (Type B) sockets accepts also NEMA 1-15 ungrounded (Type A) plugs. In stage lighting, this connector is sometimes known as PBG for Parallel Blade with Ground, Edison or Hubbell. “Typical” 120v receptacles are protected with 15A breaker. This protects the outlet against overload.
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 has been increasing the requirement for receptacles to be tamper-resistant with the revisions after that.
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 TR-rated outlets feature “TR” engraved into the outlet faceplate, typically between the two prongs. The shutters remain closed until the proper plug is inserted. This ensures that items like knives, forks, or loose jewelry are not able to access plugs, thus reducing electrical shock injury.
Nothing is safe. There are only degrees of safety. None of these designs can always prevent a determined or negligent person from electrocuting themselves.
There are some people that think that TR Tamper Resistant Outlets Suck
There are also higher current than 15A outputs in use in USA, but a general-use receptacle cannot be on any circuit larger than 20 amps. The NEMA 5-20 AP variant has blades perpendicular to each other. The receptacle has a T-slot for the neutral blade which accepts either 15 A parallel-blade plugs or 20 A plugs. The NEMA 5-20 AP wall socket can accept both 20A plug and 15A plug.
While normal electrical outlets in USA output 120V AC, that’s not the whole story and the voltage the power distribution to most houses work. The distribution voltage is normally the sum of the two 120V lines that are are at opposite phase (180 degree phase shift) plus neutral wire. But in some cases power can come from two 120V lines that have 120 degrees phase shift (some locations which use certain type of three phase power feed). Learn about the US electrical system in this The US electrical system is not 120V video:
US electrical system uses circuit breakers as wiring and fire protection. Circuit breakers are there to stop the cable in the walls of your house melting and possibly catching fire – circuit breakers and fuses perform the function of stopping a fire (which of course is also very dangerous to life). Standard circuit breakers shut off power when the current is too high, like 10, 15, or 20 amps, but a mere 0.030 amps through a body can cause paralysis of skeletal muscles and stop the human heart.
If you are at new house built according current code, you are likely to have also GFCI or AFCI designed trip before anything bad happens. GFCI can protect in many cases against human touching live wire and ground at the same time. But GFCI does not provide protection in all cases, for example if you have your finger between live and neutral contacts on mains plug. AFCI is designed trip if there is arching on the wiring like bad contact, loose wire or failing insulation on wire. AFCI can detect many problems, but not all.
Generally, when things get hot because of overloading, it’s at the connection point and not in the wire. For instance, a lot of electrical fires start at the plug/socket interface either because the connection is poor, there could be corrosion, etc. And sometimes they can happen when nothing is overloaded! This is one of the circumstances in which arc-fault circuit interrupters can save lives.
Overloading an electrical outlet is a common cause of electrical problems. Theoretically the breaker should protect the outlet against overloads, but it does not always do that especially if outlet or wiring is in bad condition. Do not use cords, plugs or outlets that appear damaged, replace them. Always ensure plugs are fully pushed in. Check all outlets to ensure they are cool to the touch, have protective faceplates and are in proper working order. Only grasp plugs by the plug body, keep fingers away from the front edge near the pins and do not pull plugs out by the cords.
There is a a recommendation that do not use extension cords or multi-outlet converters for appliances, because there are many problems related to US extension cords.
Damaged power cords are a serious residential electrical safety risk, and they are capable of causing both fires and electrocution. All power and extension cords should be checked regularly for signs of fraying and cracking. Power cords should not be stapled into place or run under rugs and furniture.
Besides making sure that the extension cord is in good shape, you need to be really careful that type of extension cord you use in USA. 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.
Equipment or in-wall wire heating 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 of the device. The size of wiring inside wall is rated based on the breaker size on the mains panel (typically 15A or 20A). The size of the wire on the extension cord can be condiderably thinner, and the mains panel breaker might not protect it against overheating due overload. Some better extension cords can have their own overload breaker built-in but not all.
I think allowing unfused 16 gauge (16AWG = 1.5 mm2) extension cords into the market is a potentially bad link in the chain that we could probably do with cutting out. That wire is still pretty OK up to 15A load current, will get warn. If you plug it to 20A outlet and load with 20A total load, it can get dangerously hot (around 1.8 times more power heating the cable at 20A than at 15A). Pulling 20 amps through that cord made it get very hot quite quickly.
In fairness, it used to be much worse. 18 gauge (maybe even 20 gauge) extension cords were available many years ago, but regulators had the sense to make 16 the minimum as time went on.
There are also small compact ungrounded extension cords that have such designs whete users can plug in plug so wrongly that they are halfway out leaving the live parts so that the live main voltage can be present on the exposed mains plug pins.
Most electrical fires aren’t the result of a single thing; they’re a cascade of individually not-great circumstances combining to make a bad situation. In order to reduce the risk of fires, we’ve continually been making the not-great things less bad.
256 Comments
Tomi Engdahl says:
Characteristics of the Neutral Conductor
https://www.ecmweb.com/national-electrical-code/code-basics/article/20890526/characteristics-of-the-neutral-conductor
Characteristics of the Neutral Conductor In any electrical system, the neutral is a grounded conductor that you must size and treat differently from ungrounded phase conductors. Do you know how to properly size a neutral conductor? Do you know the rules surrounding its proper application? If not, read on. This article discusses how to calculate the neutral current for various circuit configurations
Sizing the neutral: Sec. 220-22. You must size the neutral conductor to carry the maximum unbalanced current in the circuit (i.e. the largest load between the neutral and any one ungrounded phase conductor). You calculate the first 200A of neutral current at 100%. For all resistive loads on the neutral exceeding 200A, you must apply a demand factor of 70%. Then, you add this value to the first 200A, which we calculated at 100%.
You calculate all inductive neutral current at 100% with no demand factor applied. When working with cooking equipment or a dryer load, the feeder neutral load shall also be 70% of the demand load. You must use a multiplier of 140% when calculating the neutral current for a 3-wire, 2-phase or 5-wire, 2-phase system. The neutral conductors do not become overloaded because 120V loads switch in and out on the circuits at different intervals of time.
Part (a). The Code considers the neutral conductor a current-carrying conductor only when it carries the unbalanced current from other ungrounded phase conductors. When circuits are properly balanced, the neutral carries very little current. When sizing the load for a 2-wire circuit, the grounded neutral conductor carries the same amount of current as the ungrounded phase conductor. This type of installation has no unbalanced load; therefore, the neutral conductor carries full current.
When sizing the load for a 3-wire circuit, the grounded neutral conductor must carry the unbalanced load of the two ungrounded phase conductors. This type of installation has an unbalanced load – unless both ungrounded conductors pull the same amount of current on each ungrounded phase conductor.
You must use a specific formula to calculate the neutral current for 3-phase feeder-circuits. Where currents on Phases A, B, and C are of different values, you can compute the neutral current
Part (b). The Code requires the grounded neutral conductor of a 3-wire, 120/208V feeder-circuit to be the same size as the ungrounded phase conductors for a feeder-circuit derived from a 4-wire, 120/208V system.
This is because the grounded neutral of a 3-wire circuit (consisting of 2-phase conductors) carries approximately the same amount of current as the ungrounded phase conductor. Therefore, the Code does not allow a reduction in ampacity.
Part (c). The grounded neutral conductor of a 4-wire, 3-phase system supplying nonlinear loads must be the same size as the ungrounded phase conductors. The Code considers the grounded neutral conductor a current-carrying conductor due to the harmonic currents generated by these loads.
A demand factor of 70% applies to neutral loads exceeding 200A for nonlinear loads. You shall calculate nonlinear related loads at 100%.
The Code considers the grounded neutral conductor a current-carrying conductor because of the harmonic currents generated by these loads.
You must determine the size of the neutral conductor (based on its use with ungrounded circuit conductors) carefully. For example, the manner in which it shares loads between the other conductors determines if you can reduce its ampacity rating. Likewise, you must consider the number of current-carrying conductors to see if you must derate the neutral’s ampacity. The neutral conductor is special; therefore, you must size it accordingly.
Tomi Engdahl says:
The Differences Between Grounding and Bonding ― Part 5 of 12
https://www.ecmweb.com/national-electrical-code/code-basics/article/21162711/the-differences-between-grounding-and-bonding-part-5-of-12
To safely conduct any fault current likely to be imposed, electrical equipment must have bonding. This is often where the fun begins.
Tomi Engdahl says:
The Case of the Deadly Arc Flash
https://www.ecmweb.com/safety/arc-flash/article/20898038/the-case-of-the-deadly-arc-flash
How defective test equipment coupled with lack of training led to tragedy for electrical workers at a shopping mall.
For one electrician, the day began with a routine service call to troubleshoot electrical problems at a major department store in town. It ended with one person injured, two people dead, significant property damage to the facility, and serious lessons for anyone who works on electrical systems.
The store was located in a large mall facility with an electrical system that was 480V, 4-wire with 277V from each phase to ground. Earlier in the day, the store had experienced several short power outages and erratic behavior of its HVAC system computer. After store personnel observed smoke coming from an emergency lighting box on the second floor, they called their maintenance department, who immediately disconnected the emergency circuit by shutting off the circuit breaker.
the store called a local electrical contractor to come out and troubleshoot the system.
The electrician from this firm had been to the shopping mall location several times in the past, so he was familiar with the facility.
The electrician arrived at the retail store only to find that the fire department was already there, due to the smoke and power outages. Borrowing a multimeter from the maintenance department, the electrician checked several routine things and then removed the cover from the emergency lighting circuit breaker in the main 480V switchboard.
For reasons we will never know, after checking all three phases, he made a comment to the effect that something was not right — and returned to the center lug a second time. As he made this measurement, a fireball erupted from the panel, severely burning all three individuals and causing significant damage to the electrical equipment and surrounding area. Although witnesses and medical professionals provided rapid response and assistance, the injuries proved fatal for the electrician and the fire official.
Tomi Engdahl says:
Pole tramsformer disaster
https://www.facebook.com/groups/2324569074469604/permalink/2891679884425184/
https://www.carscoops.com/2021/01/pickup-takes-out-lamp-post-while-trying-to-do-donuts/
Tomi Engdahl says:
How to avoid overloading your plug sockets at home It’s easy to plug too many devices into too few sockets at home. We speak to a fire safety officer to find out how to stay safe
Read more: https://www.which.co.uk/news/2020/03/how-to-avoid-overloading-your-plug-sockets-at-home/ – Which?
Tomi Engdahl says:
Coiled extensiom cord danger
https://youtu.be/DZvrIrAoA4g
Tomi Engdahl says:
5 Ways British and American Plugs Are Very Different
https://www.youtube.com/watch?v=lJ-JhChEy2I
In what is a highly charged issue, Laurence Brown looks at the surprisingly numerous differences between British and American plugs.
Tomi Engdahl says:
Plug Won’t Stay In Outlet
https://www.youtube.com/watch?v=0h_r2bD5bMs
This is a very common issue especially as the number of devices we are charging with 2 prong plugs seems to be increasing each year. I will show you why this happens by opening up an old outlet and also how to replace the old outlet with a new one. We will also discuss the recommended grade of outlet to use lowering the chance of failure in the future.
Tomi Engdahl says:
Hidden Tool in an Outlet Few Know
https://www.youtube.com/watch?v=NzyOLVoUpqA
Leah of See Jane Drill shows the two tools in an electrical outlet and demonstrates how the tools are used.
Tomi Engdahl says:
AC wiring tips for audio
https://www.youtube.com/watch?v=Ky7-m2s9dyI
What’s it take to properly wire AC power for high-end audio systems?
Tomi Engdahl says:
Main Panel Wiring for 120V & 240V
Step by Step Guide: https://bit.ly/MainPanel
Tomi Engdahl says:
10 Things You Didn’t Know About Outlets
https://www.youtube.com/watch?v=vUlvrX4R3jI
This video reviewing 10 things that have come up in comments from past videos to quickly review little-known design features, install best practices, and manufacturer details for common electrical outlets.
Tomi Engdahl says:
40 YEAR OLD 3-Way Switch NEVER Worked. Is It FIXABLE?
https://www.youtube.com/watch?v=7qMSm3HCEmk
Working 3 way switches! We know this is a very common issue in so many homes and we hope that this video can help a few of you out there! Thanks for watching and we’ll see ya in the next one!
Tomi Engdahl says:
I’m going to echo the note on the UL listing requirement. Using UL listed parts doesn’t count. It has to be listed as an assembly. If you build this yourself and use it, if anything at all happens, you will be personally liable, even if your wiring does not cause any problems directly. You are supposed to know that under the NFPA 70: National Electric Code, you are only supposed to use equipment listed by an accredited independent testing laboratory (UL, Intertek, ETL) and it must be listed for the purpose it is being used for. In this case, listed under the UL1640 Portable Power Distribution Equipment standard. If you connect this up, you are liable and whoever’s electrical source you connect to will be liable and the insurance companies will leave you on the hook. Canada will even confiscate it at the border because it is considered importing unsafe equipment.
Tomi Engdahl says:
Setting aside the UL listing issue, are you a qualified, licensed, electrical engineer, who can make all of the necessary safety calculations? What is the arc fault rating for the components being used here? Will the plastic enclosure components burn if there’s an arc fault condition inside this box? I’ve seen an electrical panel try to bend itself into a taco from the electromagnetic forces involved from a catastrophic dead short incident. I saw a blast of molten copper plasma shoot 50 feet straight out of the top of a padmount transformer enclosure when one of the windings overheated during a switching fault.
Tomi Engdahl says:
An early American electrical plug and socket was invented by Harvey Hubbell and patented in 1904. Hubbell’s first design was a socket which screwed into a lampholder (like the early lampholder plugs), but with a separable plug with pins (U.S. Patent 774,250) or blades (US patent 774251).
https://en.wikipedia.org/wiki/History_of_AC_power_plugs_and_sockets#:~:text=An%20early%20American%20electrical%20plug,blades%20(US%20patent%20774251).
On November 8, 1904, Harvey Hubbell II patented the first detachable electric plug in the United States. The Separable Attachment-Plug, US patent number 774,250, followed Hubbell’s electric switch design in 1891 and his patent for the pull-chain electrical light socket in 1896.
https://connecticuthistory.org/first-us-detachable-electric-plug-today-in-history-november-8/
Tomi Engdahl says:
https://www.epanorama.net/blog/2021/10/04/usb-c-vs-us-outlet/
Tomi Engdahl says:
Harvey Hubbell had patented the parallel blade plug in 1913
https://en.wikipedia.org/wiki/History_of_AC_power_plugs_and_sockets
Tomi Engdahl says:
TR (Tamper Resistant) outlets as they are called here are mandatory in all new construction in the US today.
Tomi Engdahl says:
https://en.wikipedia.org/wiki/NEMA_connector
Tomi Engdahl says:
https://en.wikipedia.org/wiki/NEMA_connector
All NEMA 1 devices are two-wire non-grounding devices (hot-neutral) rated for 125 V maximum. 1-15P plugs have two parallel flat blades, 1⁄4 inch (6.4 mm) wide, 0.06 inches (1.5 mm) thick, 5⁄8–23⁄32 inch (15.9–18.3 mm) long, and spaced 1⁄2 inch (12.7 mm) apart.
In older plug designs both blades were the same width, so the plug could be inserted into the receptacle either way around. Many plugs manufactured since 1948 are polarized; the neutral blade is 5⁄16 in or 7.9 mm wide, 1⁄16 in or 1.6 mm wider than the line blade, so the plug can be inserted only one way. Polarized 1-15P plugs will not fit into unpolarized receptacles, which possess only narrow slots. Polarized 1-15P plugs will fit 5-15R grounded receptacles, which have the same wider slot for the neutral blade. Some devices that do not distinguish between neutral and line, such as internally isolated AC adapters, are still produced with unpolarized narrow blades
Tomi Engdahl says:
Holey Plugs, Batman! But… what are they for?
https://www.youtube.com/watch?v=udNXMAflbU8
The answer may surprise you.
Links ‘n stuff
I’ve made a playlist of my various electrical shenanigans. You can get to it here:
https://www.youtube.com/playlist?list=PLv0jwu7G_DFU62mIGZNag5vQ0a6tDGBpO
Tomi Engdahl says:
The GFCI/RCD: A Simple but Life-Saving Protector
https://www.youtube.com/watch?v=ILBjnZq0n8s&list=PLv0jwu7G_DFU62mIGZNag5vQ0a6tDGBpO&index=2
Tomi Engdahl says:
Asked in a recent interview with Parade if any of the KISS members have ever gotten injured during a concert, Simmons said: “Not seriously. [Original guitarist] Ace [Frehley] was semi-electrocuted in Lakeland, Florida, before the days of grounding. Back then, all the guitars were connected with long wires to the amplifiers, and if not grounded properly, if you touched a metal railing on the side, which he did, you got knocked on your ass.”
https://www.blabbermouth.net/news/gene-simmons-narrowly-avoids-fall-during-opening-song-of-kisss-concert-in-tampa-video/
Tomi Engdahl says:
Issues with Old Electric Wiring | Knob and Tube
https://www.youtube.com/watch?v=GknejVmb_tA
I recently purchased an investment property that originally had old knob and tube wiring but now has a hybrid of an updated electrical panel, romex, and the rest of the wiring is the original knob and tube. I will show you an example of a switch failure that could have very easily led to a fire and what you need to be aware of if purchasing or investing in old homes with corresponding old electrical systems.
Viewer comments:
You nailed it when you said “that has been tampered with”. Knob and tube- even 100 years old- is perfectly serviceable if undamaged and not tampered with. It used insulated wire, but was designed to largely not depend on it by use of the porcelain insulators and tubes. A grounding conductor can be easily added where it makes sense to have one. And the quality of those old devices is stunning compared to new ones. Any that are in good condition are fine. My dream would be to find an old house with an all original, unmolested electrical system. Probably pretty rare now. 100 years of people that can’t keep their hands off of it lol.
I believe that switch – 40s era – is arcing across that dust accretion.
Knob and tube is not dangerous in and of itself, even though it is not a grounded system. Classically, they ran single wires with one side of the house being neutral and one side of the house being hot. Connections were made in the wall with a hot or neutral only connected at one place, INSIDE the circuit box. Those separate wires passed through separate holes on opposite sides. Thus any contact was not possible apart from the fixture itself.
The problem comes when a new system is grafted onto knob and tube. Often the hot and neutral are taped together and run though the same hole. Now there is an element of heat and friction. The old insulation is dry, friable and subject to breakage due to heat. NOW the conductors are in close proximity to each other and undersized for the new load. Plus, if a rated connector is not used, they suffer wear from friction on the raw edge of the box and will short out on metal.
If you have knob and tube, don’t graft it to Romex. Run a new lead to the point of use. Use your existing fuse block as a sub panel connected to a modern panel box. Or, you could open all the walls and rewire the whole house. Your choice.
I mean, if it was *fundamentally* unsafe, you wouldn’t even have a house to worry about. It would have burned down decades ago.
Go ahead, guys. Start ripping me.
That basement needs a serious upgrade, BTW. *shudder* Too many generations of amateur work.
I had a switch that was probably original to the house, and it didn’t smoke like that, but the light flickered AND I could hear it arcing in the switch. Fixed that in a hurry!
The old federal pacific panels are far more dangerous than the knob and tube wiring.
Old age isn’t the only issue. A lot of houses around here were built with aluminum wiring in the 1970′s. Now the house flipper you bought from last year swapped in those flatter squarish light switches (so he could say “updated electrical”). But if those fancy decora replacement switches and outlets he found at the dollar store don’t specify aluminum and copper compatible, that nice ABC fire extinguisher in the video won’t be enough to save the place.
I’m aware in some places (like where I live) those “hybrid” updates are illegal, once one thing gets touched the whole thing has to be redone. this leads to a situation where a professional electrician will quote a crazy high price for even something simple, and leads to people that do their own DIY fixes that either become ticking timebombs or burns the whole place down
Knob and tube systems are installed originally quite well in my experience, when someone modifies it (usually poorly) that seems to be when safety issues arise.
If an electrician walked in it would be his obligated duty to rip out all the old knob and tube and install a probably bonded and grounded electrical system starting with the service.
While I prefer to minimize costs in certain areas, but not the electrical system would have to be upgraded at least all the boxes plastic versions and latest outlets and switches to make sure that contact problems won’t happen. And a full electrical system rebuild might be necessary if the customer plans upgrading the house to alternative energy solar and battery.
Does “F” on the switch stand for Federal Pacific? Because if so then the saying stands true. It’s not federal pacific, it’s fire pacific
As a licensed electrician, I have seen so many instances of a well meaning homeowner attempting to “improve” the electrical system, and compromising the integrity to the point where I would not sleep in the house. They take a basically safe but inadequate electric system and “improve it” to the point where it is now dangerous. They don’t do it on purpose, but through lack of knowledge and or experience they cannot comply with all of the particulars of the NEC. There may be a dozen requirements of the NEC for the installation of just one outlet. I highly recommend that before someone attempts to do their own wiring to buy a GOOD book and follow the instructions completely. Then have someone competent check out their work, and I don’t mean uncle Fred. who drove a milk truck.
I can’t recommend a good do-it-yourself book because I have been taking CE classes for 40 years, and we use the NEC. This book will not be understood by laymen, because it uses terms which are particular to the trade.
I would probably not feel comfortable spending time in your residence, if you try to do your own electrical work based on what you learned on the internet. Do you know what size wire to use in all circumstances. do you know how much wire must be left in junction boxes? How about how many wires of each size can go into each different box? I have spent hundreds of hours in classroom settings and I still have to look up things in the code book as does every other responsible electrician. I’m sure I could look at a house wired by a welder and find at least a hundred different violations!
While the basic principals can be learned pretty easily, doing things right is a different story.
Major electrical work like knob & tube conversion will require permits and inspections in most jurisdictions if a DIY’er thinks they are up for the job. There will always be some that will bypass the permit process since they can buy all the components at their big box store. I guess you could buy some books and watch some videos to learn to do your own surgery on yourself or a loved one, but I’ll trust my surgeries to a qualified doctor.
Tomi Engdahl says:
Incorrectly Wired Outlet Found In Newly Built Home
https://www.youtube.com/watch?v=_rRa_CedJ38
I changed out a failed outlet (properly called a receptacle) in a friend’s home where I found 3 different mistakes made by the home builder/electrician. These mistakes don’t go against NEC but are not following best practices. I will quickly review what these 3 mistakes are and how to correct each.
Chapters
0:00 Intro
1:00 Mistake 1
2:13 Mistake 2
4:03 Mistake 3
6:30 Closing
Tomi Engdahl says:
How to Upgrade an Electric Meter to 200-Amp Service (Part 1) | This Old House
https://www.youtube.com/watch?v=LuEAVdpny2U
How to Upgrade an Electrical Panel to 200-Amp Service (Part 2) | This Old House
https://www.youtube.com/watch?v=KbO-4k6IaUs
Tomi Engdahl says:
You CAN Get SHOCKED by a Neutral Wire! This is How…
https://www.youtube.com/watch?v=yhFJzQB6_NM
Hey Gang! In today’s video we tackle a serious problem in this bathroom and that is this shared neutral. In this video we do our best to explain what a shared neutral is, why it’s wrong and what can go bad. This was a critical step in the renovation and we’re glad to have it knocked out! Thanks for watching and we’ll see ya in the next one!
Tomi Engdahl says:
Should An Outlet Be Installed Ground Down Or Up
https://www.youtube.com/watch?v=kYXvcog9MxY
You might have noticed over the years some receptacles (outlets) are installed with the ground down and others with the ground up. Sometimes this changes from room-to-room or home-to-home. The question is what way is correct? Is there a code that gives guidance? Is one way safer than another? Are there any drawbacks I should be aware of when picking during install?
Viewer comments:
Anything that mounts directly on the outlet, such as a nightlight or similar device, is clearly made to prefer ground-down orientation. Same with appliance cords, such as refrigerators. The overwhelming majority of outlets I’ve seen in my life are installed that way.
I’ve read the comments and it would appear that most viewers prefer GROUND Down. I’m 70 yrs old and am a traditionalist, so I also prefer Ground Down. But I don’t believe it’s the ground pin that should be the issue but rather – Neutral (White) on the left and Hot (Black) on the right. The issue is polarized plugs on things like wall warts, night lights and right angle molded plugs. All are designed with the wider blade on the left when properly oriented. Don’t fight established convention.
Ground down is definitely the best bc it makes the outlet look like a surprised face.
When I was a new home sales person for a national builder, the ground up plug indicated it was controlled by a light switch in that particular room.
Helped you quickly identify where to plug in your lamps.
When I was taught – and this was within the past 10 years, the argument for ground down was that when someone plugs a device into an outlet, naturally their thumb is on top, and first finger at the bottom; that’s just nature of how we plug things in. And when we do so, the first finger is slightly forward and has more tendency to accidentally touch whatever piece(s) metal are exposed. In a ground down environment, that finger would then touch the ground and you’d be ok. In a ground-up, that finger would complete the circuit and you’d enjoy a nice little surprise. I accept this argument, as the ones I’ve seen about the weight/gravity pulling a cord out and therefore a reason why you’d install a device ground down. But I tend – and is my practice unless the inspector or homeowner requests otherwise, to install ground up – primarily for the reasons you explained in your video. I know someone who had a plug come loose, and a nickel dropped down the wall, hit the hot/neutral, and actually blew a piece of the nickel into their eye causing blindness in their left eye. From that point on, I have installed ground up. And I have found that if you invest (and that’s partially the key) in a well built electrical outlet, the arguments about weight and constant pulling become somewhat antiquated. A cheap outlet, yes, a cord will fall out day and night, but with the more expensive outlets and GFCI’s that I’ve come a custom to install, I’ve preferred ground up and in all instances they have passed the city inspector’s code. Just my 2 cents, however….
When ground is up, just the weight of the cord will, over time start to pull plug out. With ground down the ground actually provides a base for plug that keeps the cord from pulling out. Particularly with heavier cords.
I can’t stand ground up, trying to align plugs ground down is way easier because your thumb registers against the flat part of the plug rather than the more rounded part of the plug.
When I’m in Mass. many places have ground up and I was told it was a state or local code to install this way. I like the European Schuko plug where ground always makes contact first and the plongs are always shielded by the recessed face of the actual outlet. It is almost impossible to have shorts across the terminal as when the plug is pulled out far enough to reveal the prongs they are already disconnected from the power. US Codes are somewhat behind on outlet safety.
Most “wall warts” (power cubes)especially higher wattage ones have the wider blade (neutral) so that the best orientation is ground down. Ground up causes them to fall off or at least pull away from.
Ground down is easiest to insert. The ground prong is longer and can be visibly inserted, then your eyes can follow the flats into the plug.
In my opinion, if NEC isn’t making a recommendation after this many years, there must be a consensus among the rule makers that it truly doesn’t matter and there is no significant safety reason to pick one option over the other.
The real risk is with metal cover plates on duplex outlets. Old fashioned attachments used the center screw for the ground or support, resulting it being loose or missing. When the metal plate drops, excitement or disaster.
This problem doesn’t occur with Decora style receptacles or simply using a plastic cover plate.
Once you eliminate that risk, the very slight improvement in safety is overwhelmed by the significant decrease in safety from plugging equipment in upside-down. Every wall brick and GFCI plug expects a happy face orientation.
Which section of the NEC specifies the receptacle orientation? It’s not in 406, which only prohibits face-up orientation on a countertop or similar location.
The ground should be on top in case of kid drop something on it when it’s not plugged in all the way
I’ve been putting outlets in for decades, and I always did ground down, because I wanted the outlet to “smile”.
However, after seeing this, I will start putting the ground up.
I prefer ground-down for most outlets. I like the practice of reversing to ground-up for switched outlets. That’s how my builder did it. Sure beats walking around the room with a lamp to figure out which one is switched.
Tomi Engdahl says:
What Outlet Should You Buy | Leviton vs Eaton
https://www.youtube.com/watch?v=6jUa_HbUeoE
I am a fan of commercial-grade receptacles and think it is worth the extra money for the additional features, increased durability, and increased longevity. But which brand is best? This video dives into 2 of the 4 brands included in a survey we put out to our viewers asking “Which commercial-grade receptacle do you prefer?” Leviton and Eaton will be the focus of this video with additional videos comparing Leviton vs Legrand and Leviton vs Hubbell.
Chapters
0:00 Intro
1:50 General Feature Comparison
7:36 Internal Design Comparison
10:42 Price and Survey Results
12:42 My Pick
Tomi Engdahl says:
Why Do We BOND Neutral & Ground in ELECTRICAL SERVICE PANELS?
https://www.youtube.com/watch?v=_XM6rXjv0vc
This question has been asked by so many people over such a long time. Why on earth do we have to bond the system neutral and the equipment grounding conductors, and grounding electrode conductors in an electrical system?
Slight correction – objectionable current is current flowing on the EGC and metal surfaces (which are normally not current carrying) during normal conditions. The reason we don’t bond neutral to ground at subpanels is because that would connect the neutral and ground in parallel. Current “returning” from the load could take either path, depending upon the resistance in the circuit. Objectionable current is not about when all hell breaks loose and the pixies escape. It’s when the pixies are taking random paths home every day, all day.
Ground is grounded to earth only for lightning strikes. That’s the only reason. For 99.9% of lectures on residential wiring, you could leave out the fact there is a rod in the ground protecting against frying everything in the case of a lightning strike. It may be confusing, since transformers, and substations also are grounded, so someone may conclude that ground is a path back to source, when ground is only a path back to source in the case of lightning.
Tomi Engdahl says:
In many applications AC, so it does not matter too much which way oulet is connected with regards to the hot and cold – Unless you are going to connect it to ancient equipment like a very old TV set, their steel chassis was often connected to the neutral conductor but if the plug was wired the wrong way around then that chassis became live (hot), which meant there was a nasty surprise waiting on any outlet (antenna/ext. speaker etc) coming out of the TV.
Tomi Engdahl says:
it still matters for things, especially lamps, where the upper ring of the bulb’s base is often exposed – hot versus neutral is the difference between a shock or not. Similar for a toaster, and umpteen other devices that are polarized for safety.
Tomi Engdahl says:
Historically the US is a newer country and most buildings are wood. With that came a focus on fire prevention, In the US, the electrical codes are written by the NFPA National Electrical Code – NFPA.
Europe and the UK have much older buildings, usually made of stone and the focus on electrical codes tends more to electrical safety.
The U.S. Consumer Product Safety Commission (CPSC) reports that electrical receptacles are involved in 5,300 fires every year, causing forty deaths and more than 100 consumer injuries. (May 2015) Home Electrical Fires
Each year, 2,400 children in the U.S. are treated for injuries caused by electrical outlets.
Source
https://www.quora.com/Why-are-the-electrical-plugs-and-sockets-in-the-US-so-inferior-to-their-counterparts-in-the-UK
Tomi Engdahl says:
What Outlet Should You Buy For Your Home | Commercial vs Residential
https://www.youtube.com/watch?v=kX6xnOksQTc
Electrical Outlet Basics | How To Wire
https://www.youtube.com/watch?v=UwGoU3XVpnI
Tomi Engdahl says:
The US electrical system is not 120V
https://www.youtube.com/watch?v=jMmUoZh3Hq4
It’s more than 120V. It’s even more than the other 120V! It is the sum of the two (and sometimes a different two!) that makes us who we are. Learn about the US electrical system in this not-at-all snarky video!
Tomi Engdahl says:
How To Replace An Old 2 Prong Outlet Using 3 Prong GFCI
https://www.youtube.com/watch?v=qrtyUuL-eRw
Caution: Be safe and if you don’t feel comfortable with this install please call in a licensed electrician.
This video will demonstrate how to swap out an old 2 prong receptacle with a new 3 prong GFCI receptacle. This install follows NEC 406.4(D)(2) Non-Grounding-Type Receptacles code and we will go from start to finish. If you have any questions the best way to get help is to jump down in the comments or join our Facebook group “Everyday Home Repairs Community” where you can post your question.
Chapters
0:00 Intro
1:07 Turning Off Power
1:46 Removing Old 2 Prong Receptacle
2:29 Stripping Wires for New GFCI Receptacle
3:10 Wiring New GFCI Receptacle
3:53 Wrapping Receptacle with Electrical Tape
5:03 Testing New GFCI
5:31 How To Handle Multiple Receptacles On Same Circuit
One of the methods permitted in 406.4(D)(2) is to replace a non-grounding type receptacle with a GFCI type receptacle.
When doing this, the 2014 NEC required the “receptacle” to be marked “no equipment ground”.or their cover plates
When you replace a device in a house it must be protected with an arc fault circuit interrupter according to the National Electric Code. You can use either a Dual function breaker or dual function device. If you don’t care about the NEC you can just do whatever you want.
Tomi Engdahl says:
US vs German Pliers (WIRE CUTTERS)? Knipex vs Snap On, Irwin, Milwaukee, DeWalt, Craftsman, Wiha
https://www.youtube.com/watch?v=6bnqFwAf7HM
Tomi Engdahl says:
Holey Plugs, Batman! But… what are they for?
https://www.youtube.com/watch?v=udNXMAflbU8
Tomi Engdahl says:
Why are Outlets and Receptacles in Hospitals Upside Down?
https://www.electricaltechnology.org/2021/10/outlets-receptacles-hospitals-upside-down.html
Why Are Hospitals Outlets Upside Down as Compared to the Residential Receptacles
Most of you guys may have noticed the inverted electrical outlets installed in the hospitals while the same receptacles are fixed the right side up in the residential and home applications. General questions arise here: is it the best practice to do so or is it a code and finally, which direction should electrical receptacles be installed? Well, we will discuss one by one as follows.
Why are Hospital’s Electrical Outlets Upside Down Instead of Right Side Up?
As we know that in a three prong plug and outlet (also known as socket), the narrow blade is for Hot (live), the wide blade is for Neutral, and the longer Pin is for ground as a safety purpose. The newer 3-prong outlets are installed upside down in hospitals because a partially plugged-in right side up outlet may create chaos in case a fork or any other metallic tool falls down on the upper two terminals (Hot & Neutral) which leads to a short circuit and hazardous fire. This is the reason why they install the receptacles in hospitals in an upside down position instead of right side up.
In case of an upside down outlet, dropping something metallic on the exposed part of the plug, it will first touch the ground pin and may trip the circuit breaker which is supposed to do so for better protection.
Is it OK to Install the Outlet in Upside Down Position?
Well, It is not a code to install the outlet in a specific position e.g. you can install in any direction either the ground prong is top or bottom. The debate still continues between the trade and union electricians but the vote is for Upside down outlets in case of hospitals and patients. In addition, some commercial locations are required to install the receptions in opposite directions (upside down position) in case of metallic faceplate. Nowadays, plastic faceplates are common in home applications, so it does not make sense to install the inverted positioned outlets.
Tomi Engdahl says:
Many electricians will install one receptacle with the ground pin up to identify which outlet is tied to a wall switch. Common in prefab homes.
Tomi Engdahl says:
Some where in year 2002, I had same doubt. So, I checked in NEC and their was no specific requirements or recommendations. Hence ground slot position Up or Down, we consider as NO PROBLEM and accept it as it ees.
Tomi Engdahl says:
Ground down is usually in residential ground up I see mostly in commercial and they say they do that to prevent Sparks (grounding) if something should fall on the plug
Tomi Engdahl says:
Ground up as when the plug is pulled our the tendency is to get the index finger behind the plug which is safe to touch the earth terminal have way our of the socket, the other way around you could discover the life stud
Tomi Engdahl says:
What to Do When You Hit an Electric Wire Within a Wall
https://homeguides.sfgate.com/hit-electric-wire-within-wall-93166.html
Tomi Engdahl says:
https://www.dfliq.net/blog/electrical-wire-gauge/
Tomi Engdahl says:
Powering the Smart Revolution at 277 Vac
July 27, 2021 by Ron Stull – 4 Minute Read
https://www.cui.com/blog/powering-the-smart-revolution-at-277-vac
Introduction
Widespread deployments of smart systems in out-of-home locations, as well as high-power applications such as roadside vehicle chargers, is driving easier access to ac-dc power supplies capable of handling a 277 Vac input derived from the standard 480 V three-phase industrial supply.
As consumers we mostly use appliances that are designed to plug into the 120 V ac domestic line, whereas utilities provide services at several voltages for different types of users and applications. Houses and other premises can have access to a 240 V service for large loads, while a 480 V three-phase supply is available for industrial uses. The phases are often used together to supply large loads, typically high-power electric motors used in industrial machinery.
480 Vac Advantages
Distributing power at 480 V delivers several advantages. The current is lower, for a given power demand, resulting in lower I2R losses in the line. In addition, cabling can have a lower current rating, saving cost as well as bulk in the distribution infrastructure. At the same time, the higher voltage allows greater capacity to connect more loads on the same line.
Where Does 277 Vac Come From?
Single-phase power can be taken from this 480 V three-phase supply by connecting between one phase and neutral. In this case, the nominal supply voltage is 480 V ÷ √3, or 277 V.
277 Vac Applications
With the adoption of low-energy LED lighting in factories, warehouses, offices, shopping malls, and street lighting, demand grew for constant-current LED drivers (suitable for connection to the 277 Vac supply and for generating a constant-current output for driving the LEDs). Things are changing now that the smart revolution is driving intelligent “things” into out-of-home locations.
As with earlier fluorescent and LED lighting challenges, taking a 277 V single-phase supply from the 480 V three-phase service enables a convenient and cost-effective solution. What’s different with the smart revolution is that many of these loads contain electronics modules that need to be powered from a regulated dc voltage. As a result, demand is growing for ac-dc power supplies that can connect to a 277 Vac input and produce common dc output voltages.
10% Headroom and 305 Vac Rating
To be able to handle a nominal 277 Vac input voltage, with 10 percent safety headroom, the power supply must be capable of withstanding up to 305 V at the input. As a result, you will see a growing number of ac-dc power supplies in the market that offer a universal ac input voltage range from 85 V to 305 V. There is a broad choice of regulated output voltages and various options are available.
Conclusion
Having a versatile selection of 85 ~ 305 V ac-dc power supplies available is useful to designers of IoT and IIoT equipment, installers, maintenance managers and purchasers who can now benefit from changes in the market, allowing them to quickly discover a suitable unit, off the shelf, to meet their exact needs.
Tomi Engdahl says:
https://www.electricaltechnology.org/2021/10/different-colors-electrical-outlets.html
Tomi Engdahl says:
In most office environments, a typical reading of neutral-to-ground voltage is about 1.5V. If the reading is high (above 2V to 3V), then the branch circuit might be overloaded.
Diagnosing Power Problems at the Receptacle
Oct. 1, 2004
https://www.ecmweb.com/content/article/20900908/diagnosing-power-problems-at-the-receptacle
Three measurements taken at one outlet can provide you with a solid understanding of a building’s branch-circuit power supply.
When clients call you because operating problems on pieces of their 120V equipment cause them to suspect their facility’s power supply, you have to decide where to start your investigation. Don’t proceed directly to the distribution panelboard that feeds the circuit first. Instead, first look at the outlet nearest the problem equipment.
The next step is deciding what measurement to make, but you only have three options to choose from: phase-to-neutral voltage, neutral-to-ground voltage, and phase-to-ground voltage. With these measurements, you’re well on your way to answering the following questions:
Is the outlet wired wrong?
Is the branch circuit too heavily loaded?
Do sensitive electronic loads have the voltage they need?
Office Troubleshooting Scenario
You could make a visual inspection of each receptacle for correct wiring, but that would be time intensive. It’s much easier to make measurements with a digital multimeter (DMM) or clamp-on meter with voltage measurement capability.
Phase (hot)-to-neutral voltage. This measurement is the voltage the load will see. Typically on a 120V circuit, you should get a reading of between 115V and 125V. Let’s suppose you measure 118.5V.
Neutral-to-ground voltage. This is a measurement of voltage drop (also called IR drop). It’s caused by load current that flows through the impedance of the neutral wire. Let’s suppose you measure 1.5V.
Phase (hot)-to-ground voltage. You can think of this as the source voltage available at the receptacle. Let’s suppose you measure 120V here.
Now the analysis begins.
the most common miswiring conditions are reversed hot and neutral wires and reversed or shorted neutral and ground wires. So how do you spot these conditions?
Some neutral-to-ground voltage should be present under load conditions, typically 2V or less. If the voltage is zero with a load on the circuit, then check for a neutral-to-ground connection in the receptacle, whether accidental or intentional.
The hot-to-ground reading should be higher than the hot-to-neutral reading. The greater the load, the more difference you’ll see.
Testing for Voltage Drop
On an ideal circuit, there should be no voltage drop. The less the voltage drop, the more “stiff,” or reliable, the source. In reality, however, there is always some voltage drop through the wiring system that can be brought on by one of the following:
Wire gauge will affect voltage drop. The smaller the wire gauge, the higher its impedance.
The length of the run is also a determinant. The longer the wire run on the branch circuit, the greater the impedance and the greater the IR drop.
The amount of load also affects voltage drop. The more heavily loaded the circuit, the greater the voltage drop. (V= I×R, so the more current, the greater the voltage drop.)
Tomi Engdahl says:
Made In China Power Strip – EXTREME FIRE HAZARD!
https://www.youtube.com/watch?v=yqamvvLDcMg
Not a word printed on the SOB, not even up to code!!, or passed by the UL (under-writers laboratory) or the CSA, not even an amperage rating! It couldn’t handle maybe less than 60 watts of power on it! DO NOT TRUST CHINA MADE GOODS!
You can also see how poorly formed the plastic is around the hole-slots for the plug. Its also starting to shrink and crack in spots and curl up. that was the warping you see in the video.