A number of AC power cords on Ebay seem to be miswired - Page 1
Forum section: electronics / general

author: kff
author_rank: Contributor
timestamp: January 17, 2015, 10:51:08 pm
content: A couple of weeks ago I bought a cheap SMD rework station from ebay and noticed that the fuse was on the neutral line. After a bit of digging, I isolated the problem to the 3-prong power cord (US version), in which the live male pin was connected to the neutral female pin and vice versa. I just bought a replacement power cable on ebay, from another seller, and this new cable is exactly the same! It appears that a batch of defective cables was manufactured by some clueless company in China and has now made its way to the US market.If you recently bought a cheap 3-prong power cord, or an appliance of questionable quality that included such a cable, you may want to check that it is wired properly. The right pin (with plug facing away) should be connected to the female pin labeled L (for live).

author: Monkeh
author_rank: Super Contributor
timestamp: January 17, 2015, 10:56:18 pm
content: Mostly irrelevant.Far more concerning is the obscene impedance.

author: electr_peter
author_rank: Unknown
timestamp: January 17, 2015, 11:12:48 pm
content: Live and neutral reversal on a cord is one of the least things to worry if you are concerned with cable quality overall.However, this is an indication of sub-par quality. Cut and dissect these cords to be sure. And maybe you should not buy cheapest junk from eBay and expect it to be excellent quality, safe and not fake.Check this forum, there were multiple topics about fake power cords.

author: kff
author_rank: Contributor
timestamp: January 17, 2015, 11:20:27 pm
content: Why would the reversal be mostly irrelevant? Wouldn't it mean that:1) the fuse in the appliance is on the neutral line, meaning that it won't protect in case of a ground fault2) the appliance is always energized even when the switch is in the off position?

author: Monkeh
author_rank: Super Contributor
timestamp: January 17, 2015, 11:22:39 pm
content: Quote from: kff on January 17, 2015, 11:20:27 pmPolarity is not assured, especially with detachable cables. Equipment should be double fused or be capable of surviving until an upstream OPD opens.QuoteIrrelevant, it will be functionally disabled if you open either conductor.Ponder supplies with no neutral. Yes, they exist.

author: electr_peter
author_rank: Unknown
timestamp: January 17, 2015, 11:30:58 pm
content: Quote from: kff on January 17, 2015, 11:20:27 pmBecause if polarity is relevant, your device is a POS (or that device is very specialised and you MUST know what you are doing - which is not in this case).QuoteFuse functions as a gross overload protection. Ground/neutral/etc. fault is not covered by fuse. Fault may not have enough current to trigger the fuse.QuoteNo, device is not powered*. With live and neutral switches (DPDT) type device both lines are cut. But it is enough to cut one line - device is not energised. If it is energised, something is faulty.*Very small leakage currents may flow.

author: dannyf
author_rank: Super Contributor
timestamp: January 18, 2015, 12:01:04 am
content: QuoteNo surprise. Simply part of the reason for the amazingly low prices the ebay sellers can offer.Most people don't realize the high cost of low prices until it is too late.

author: kff
author_rank: Contributor
timestamp: January 18, 2015, 12:39:00 am
content: Thank you for your comments electr_peter and Monkeh.Can it be that you feel this way about reverse polarity because you live in countries with 220V outlets where both wires are energized?Here in the US most outlets are 110V. There are three wires in a typical circuit -- hot wire (110V AC), ground wire, and neutral wire. The neutral wire is typically connected to ground in the electrical panel.Because neutral is connected to ground, most appliances here are fused and switched only on one side. A reverse polarity power cord is the same as a reverse polarity outlet, and those are definitely a safety violation in the US (e.g. your house would not pass an electrical inspection if your outlets were miswired). See for examplehttp://www.structuretech1.com/2009/04/reversed-polarity-outlets/The reasons are what I mentioned above:1) Appliance is energized (meaning it has live voltage inside) when the switch is off. So if you stick a fork in your toaster while standing on a wet carpet and touch the heating element, you could get electrocuted, even if the toaster is switched off.2) The fuse offers additional protection on the live wire in case of a ground fault. On the neutral wire it does absolutely nothing -- neutral is already connected to ground. Sure you could still get electrocuted, but blowing a 1A fuse is much better than tripping the typical 20A breaker in the distribution panel.

author: Monkeh
author_rank: Super Contributor
timestamp: January 18, 2015, 12:43:47 am
content: Quote from: kff on January 18, 2015, 12:39:00 amNo. That'd be you, not me.QuoteNeutral is considered a live conductor just like the line conductor. Not only is it utterly moronic to stick a fork in a toaster, but the toaster should isolate both live conductors. If it does not, it is faulty by design.QuoteTo rely on correct polarity with a detachable cable you cannot control (NOT all plug/socket combinations are polarised) is faulty design.Yes, this cable is bad. But polarity should be irrelevant by design in normal equipment. Anything else is faulty by design.

author: codeboy2k
author_rank: Super Contributor
timestamp: January 18, 2015, 01:03:27 am
content: I live in Canada. Many devices here are only fused and switched on the hot side. The wall outlet is indeed polarized, and I can lick the neutral all day long if I was so inclined to gamble with the possibility of other faults. I won't.The point the OP was trying to make (which was met with harsh criticism) is that if the power cord polarity is reversed and the device has only a single switch in the hot side, this cheapo eBay power cord actually makes a continuous HOT side connection inside the device, even though the device is powered off (because the switch, being in the neutral, still breaks the circuit).The fact that the hot and neutral might be reversed in the external cable (that you can't control, as others have said) only exemplifies the need to service open AC devices using an isolation transformer, and (2) always unplug it from the wall if you don't need it powered on -- you should not rely on the power switch.* (3) never stick a fork in a toaster anyways

author: kff
author_rank: Contributor
timestamp: January 18, 2015, 03:18:55 am
content: Quote from: Monkeh on January 18, 2015, 12:43:47 amThis particular cable connector is covered by a standard (IEC 320 C13), has well-defined polarity, and can only be inserted one way.I didn't expect this thread to lead to controversy. An outlet with reversed polarity (which is the same as a normal outlet + the cable that I bought) is a code violation in the US. Clearly it can't hurt to warn other people to check their cables.

author: Monkeh
author_rank: Super Contributor
timestamp: January 18, 2015, 05:25:39 am
content: Quote from: kff on January 18, 2015, 03:18:55 am.. and that is on just one end of the cable.

author: codeboy2k
author_rank: Super Contributor
timestamp: January 18, 2015, 05:42:50 am
content: Makes me want to test my cables and throw out any that don't have it right.I wonder if that eBay cable you bought is a factory reject , like so many other things on eBay.The other point brought up is the resistance : 1.2 ohms ! it should be less than 100 milliohms or so. Maybe it's really bad or your own test leads are really bad. Did you zero your test leads, or at least use a relative mode?EDIT: I just measured one of mine, 1.2 meters, 14AWG @ 42 mOhm, 4-wire mode with a Keithley 197A

author: Monkeh
author_rank: Super Contributor
timestamp: January 18, 2015, 05:46:24 am
content: Quote from: codeboy2k on January 18, 2015, 05:42:50 amSeems high. Poor termination or bullshit conductor size.

author: kff
author_rank: Contributor
timestamp: January 18, 2015, 05:51:27 am
content: It is indeed 1.2 ohms! You need 35 awg wire to get this kind of resistance in a 4 foot (1.2 meter) cable.Edit: the resistance on the ground wire is actually over 2 ohms.

author: Monkeh
author_rank: Super Contributor
timestamp: January 18, 2015, 05:52:17 am
content: Quote from: kff on January 18, 2015, 05:51:27 amVastly more concerning than swapping two live conductors on a single phase load.

author: Towger
author_rank: Super Contributor
timestamp: January 18, 2015, 06:05:45 am
content: Cut it open and expose it's 4 strands of copper 'coloured' steel per core to the world.Sent from my GT-I8200N using Tapatalk

author: kff
author_rank: Contributor
timestamp: January 18, 2015, 06:26:53 am
content: I've cut the cable apart and the wires are microscopic as expected. Not sure if it is 28 awg but something in that vicinity. Resistance of a 50 cm length of wire was 0.5 ohm (with a zeroed out meter).The cable is marked asPVC YOUZHI DIANXIAN 227 53 (RVV) 300/500VEbay listing:http://www.ebay.com/itm/111424284330About $2.50 shipped, 448 already sold!

author: codeboy2k
author_rank: Super Contributor
timestamp: January 18, 2015, 06:27:35 am
content: Quote from: Monkeh on January 18, 2015, 05:46:24 amI thought it seemed high too. It's probably more than 1.2m. I just guessed, but it's longer than 1m and stretched from my fingertip to fingertip with my arms outstretched, and I am 180cm tall. so it might be 1.2 to 1.5m long. I also measured from the prongs, so it's likely plating and poor termination as you said. And finally, I really believe that it is 14AWG as printed on the side. It's from APC, not a cheap chinese one, and it's a thick and heavy cable.

author: codeboy2k
author_rank: Super Contributor
timestamp: January 18, 2015, 06:31:50 am
content: Quote from: kff on January 18, 2015, 06:26:53 amHoly sugar! that's a small wire. 448 fires waiting to happen

author: helius
author_rank: Super Contributor
timestamp: January 18, 2015, 06:51:17 am
content: Quote from: codeboy2k on January 18, 2015, 06:27:35 amPeople who are tall are also "wider", their armspan/height is greater than those who are short. This is because there are two arms. your cable is likely 2m

author: kff
author_rank: Contributor
timestamp: January 18, 2015, 07:00:45 am
content: Here is another picture with 22 awg wire for comparison. 22 awg is the thicker one!

author: codeboy2k
author_rank: Super Contributor
timestamp: January 18, 2015, 07:49:19 am
content: Quote from: helius on January 18, 2015, 06:51:17 amYou're right about my armspan being wider than my heightI decided to find a tape measure and measure the cable. It's 190cm.

author: mtdoc
author_rank: Super Contributor
timestamp: January 18, 2015, 08:01:50 am
content: Quote from: codeboy2k on January 18, 2015, 07:49:19 amIt's called having a positiveApe Index. It's considered to be a very good thing if you're a rock climber.

author: electr_peter
author_rank: Unknown
timestamp: January 18, 2015, 10:25:43 am
content: Quote from: kff on January 18, 2015, 12:39:00 amPlease read what we said above - there is no"feel"part about it. Maybe we"feel"this way because we are not stupid enough to have blind faith in wiring in unknown location.Later posts about crap quality cabling prove the point that there is more pressing matters than phase polarity.QuoteDo you have a blind faith about this? Typically != 100%QuoteThis is stupid, do not do it and and do not endorse it. It is dangerous with both phase polarities if only one of the conductors is switched. Use DPDT switches if you like.QuoteFuse function is not to protect against ground fault (which can be low current fault).Notion that neutral is safe is extremely stupid, do not do it and and do not endorse it. BOTH line and neutral are considered to belive conductors- you are asking for trouble if you neglect neutral.Yes, phase polarity should be correct. But if you equipment and cable is of crap quality, polarity is not the first thing to take care of.

author: SeanB
author_rank: Super Contributor
timestamp: January 18, 2015, 10:36:42 am
content: Miswired cords are pretty common, and here in S Africa the installation of a ground fault breaker is mandatory on all legal installations.http://mybroadband.co.za/news/energy/116854-this-is-how-people-steal-electricity-in-south-africa.htmlNot on these though.............. I have driven over the cables laid on the main road near an "informal settlement" on a few occasions, and even if I wound one around a wheel I would not stop until I was well away.

author: Tinkerer
author_rank: Frequent Contributor
timestamp: January 18, 2015, 07:08:25 pm
content: Quote from: kff on January 17, 2015, 10:51:08 pmNot just recently.Back in the middle of 2013 I bought a cheap power cord off ebay so I could have a spare to use with something. I ended up using it a couple times and thats it.(it wasnt connected for long either time)(I wasnt working at the time, couldnt spend tons of money)The cord says rated for 10A 250V, this is definitly wrong. The cord is thinner compared with a 10A 125V rated cord that I use for my computer. When I got the cord, I realized it was thinner but figured I didnt really care because I was going to be using it under an amp.As it turns out, the polarity is also reversed in this one. Upon measuring it(just a few minutes ago), it also has the increased resistance of something like 1.1?.(I did take into account my test leads) Also, upon double checking my measurements, the thing was so shoddy that one of the female terminals broke. Glad I didnt use this much.Guess I should buy a real one now.So, recently? Not so much, there must be at least 1000s of these cord floating around out there now in the US. And they have been out there for a couple years at least. So, I would avoid buying any cords from china/ebay unless you are certain they are made properly.

author: jaxbird
author_rank: Frequent Contributor
timestamp: January 18, 2015, 07:24:57 pm
content: I recently had a cheap chinese power cable produce something like a 100mm flame just 300mm from my leg. Pretty scary.Not sure exactly what caused it (besides it obviously shorted inside), On closer inspection the cable looked pretty beefy on the outside, but cutting it up and looking closer I'm sure it was 99% plastic/rubber, the actual conductors were unbelievably thin.I believe the insulation of individual wires was random and close to near short at multiple points and probably the insulation made of a material melting at a low temperature.Life is already too short, no need to shorten it further using the cheapest and worst products coming out of China just to save a few $.

author: cosmicray
author_rank: Frequent Contributor
timestamp: January 18, 2015, 08:25:00 pm
content: Quote from: kff on January 18, 2015, 06:26:53 amThat eBay listing says the item is located in the US. How they can receive that minimal amount, pay the PP fee, the eBay final value fee, and still have anything left to pay USPS eludes me. Perhaps these were known defective, and someone dumped them into eBay to get rid of them ? CPSC might be interested in these test results.http://www.cpsc.gov/

author: ciccio
author_rank: Frequent Contributor
timestamp: January 18, 2015, 09:01:58 pm
content: Here in Italy (unfortunately) the standard plug is non polarized (there are two types, 10A similar to the two pin "Europlug CEE7/16" but with central earth pin and a larger 16 A type).So a reversed wire in a power cable will not be detected. Equipment design must take this into consideration.The problem with these cheap cables is the copper section: it's so small that you will run into problems.Once I bough a replacement PC power supply. The box contained a new power cable, that I did not use. It was clearly labeled 250V/10A 3x0.75 mm2.After some time I decided to use it (it was sitting in the lab shelves) to test a 1000 W audio amplifier.In less than one minute it started to smell, in two minutes it burst into flames. The bench surface has a charred area, where the cable was sitting.I looked at the copper: it was about 0.22 mm2.I contacted the supplier of the power supply: they answered that the cable was obviously only suitable for the 400 W supply with which it was sold, and it was not intended for other uses.... I responded saying that I was going to change supplier, and I did.Best regards

author: donmr
author_rank: Regular Contributor
timestamp: January 18, 2015, 09:51:35 pm
content: Quote from: mojo-chan on January 18, 2015, 04:16:17 pmIt still needs to handle at least as much current as the breaker or fuse on the supply system. Here in the US the minimum breaker for home wiring is 15A. Anything plugged into a 15A circuit must be safe up to that current.People often get this backwards, the breaker needs to be the weakest link in the chain so it will trip before anything else starts burning.Don

author: rickselectricalprojects
author_rank: Regular Contributor
timestamp: January 19, 2015, 12:54:44 am
content: ANOTHER WARNING!!!if you but anything of ebay that is prewired ALWAYS ALWAYS ALWAYS!!! check to see if it is wired properly. I had an experience once were I brought two led switch mode power supplies of ebay and the had the live wire screwed into the earth terminal on both the power supplies and I was lucky that I didn't shock myself.

author: amyk
author_rank: Super Contributor
timestamp: January 19, 2015, 02:14:21 am
content: Another reason to get anx-ray machine...?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: January 19, 2015, 02:53:13 am
content: Another reason to not buy bargain basement knockoff shit on eBay?I mean seriously, what do you expect? Do you honestly expect to pay 2 cents on the dollar for a power delivery product that'snotgoing to light your house on fire and burn you alive? Because if so, you're sadly mistaken. These people don't care about you, they don't care about your safety, they don't care about how many people their products kill. They're no different than the scam artists selling knockoff phone chargers on the street corner that will electrocute you if the humidity in the room gets too high.If you value your life or the lives of those near you, stop supporting these people and stop buying 10 cent shit on eBay.

author: jbryan2
author_rank: Contributor
timestamp: January 19, 2015, 06:14:42 am
content: Quote from: kff on January 18, 2015, 06:26:53 amI can't remember where I read about these counterfeit "power" cables, it's been so long. Copper is expensive. Did the cord even match the picture, or did they skimp on the insulation too? Counterfeiting is a major industry in China, and they are taking every opportunity to pass off cheap materials for the real thing.Bargain hunters aren't exclusive to eBay. Counterfeit high-strength fasteners have already killed a lot of people because the fakes are almost impossible to identify without 100% testing. They're even being discovered in the aircraft and military supply chains. The defense industry is a particular target for counterfeit components not just because the potential profit is huge, but for other obvious reasons as well.You could be a good citizen and report it, give negative feedback on the seller (though they're probably spoofing their "99%" rating too), consider yourself educated, and buy from reputable suppliers from now on.It's bad enough when somebody cuts corners and burns their own house down. It's particularly tragic when your product burns somebody else's house down.

author: Corporate666
author_rank: Unknown
timestamp: January 19, 2015, 06:30:05 am
content: Quote from: suicidaleggroll on January 19, 2015, 02:53:13 amWell saidThere is a Youtube channel I came across of a guy (this one is in the UK but could be anywhere) that buys cheap shit on eBay and makes rant videos about how the parts he got are junk and he can't use them in his (commercial) projects because they will fail.He will buy 10 wall adapter power supplies for $5... or 500 1-watt LED's for $20... then go on an angry rant that such-and-such eBayer screwed him over because the LED's have a green tint and he can't use them as medical light replacements, or the wall adapters have tons of ripple or they fall out of the wall sockets and his customers are getting upset.And all I can think is... you dumb cheap bastard.... stop buying shit and thinking it should be top shelf stuff. And definitely don't keep doing it and blaming the sellers.No offense to the OP - I am not saying he's doing this, it just reminded me of the Youtube dope.

author: TMM
author_rank: Frequent Contributor
timestamp: January 19, 2015, 07:05:36 am
content: People buy IEC power cords? Every proper geek should have about 50 of them from PC monitors and powersupplies over the years. At least when they come with a reputable brand 400W+ powersupply you know it's wired properly and has appropriately sized wiring.

author: Artlav
author_rank: Frequent Contributor
timestamp: January 19, 2015, 08:46:41 am
content: Quote from: kff on January 18, 2015, 12:39:00 amNot exactly - in (most?) native 220V countries there is a live 220V wire and a neutral wire, not two different phase live wires like in USA.However, here you make no assumptions about which is live and which is neutral, so by all intents and purposes there are two live wires - apolarizedmains plug is kind of peculiar to look at.Not all equipment is designed with that in mind - on at least one occasion i had to flip a plug to stop a PC case from giving "static" shocks to people.But i never seen a fuse being present on both conductors.Quote from: rickselectricalprojects on January 19, 2015, 12:54:44 amDon't turn it on, take it apart!(and check everything)

author: tszaboo
author_rank: Super Contributor
timestamp: January 19, 2015, 10:05:48 am
content: Quote from: Artlav on January 19, 2015, 08:46:41 amExactly. The german schuko conenctor doesnt specify the polarity, plugs can be inserted either way. Coincidently, this is the best connector for mains. If any device relies on the IEC connector, the electrical designer has no clue about safety. So the cable polarity mostly does not matter, unless if you mix earth and neutral.This is no excuse of course for the tiny conductor inside.

author: coppice
author_rank: Super Contributor
timestamp: January 19, 2015, 10:22:47 am
content: Quote from: Artlav on January 19, 2015, 08:46:41 amThere is at least one country where the normal domestic and commercial delivery of power is 220V with the legs balanced about earth - the Philippines. This is like 220V power in the US, but in the US its a special case for high consumption appliances, while in the Philippines its what all appliances use. I think this comes from a historical position, where the country once used 110V power, but I am not sure.