Exercising caution when dealing with mains - Page 1
Forum section: electronics / beginners

author: Daniel_Reyes
author_rank: Regular Contributor
timestamp: October 24, 2015, 11:54:57 pm
content: Just wanted to know why "super contributer's like this feel compelled to comment?Sent from my SM-G900P using Tapatalk

author: c4757p
author_rank: Super Contributor
timestamp: October 24, 2015, 11:56:55 pm
content: Without a link to the topic in question......probably because somebody said something stupid. That's usually the case with "electrical safety" threads, they're typically a massive idiot orgy.

author: Monkeh
author_rank: Super Contributor
timestamp: October 25, 2015, 12:02:55 am
content: Quote from: Daniel_Reyes on October 24, 2015, 11:54:57 pmBecause it really hurts to see people playing with mains voltages when they can't understand a three component diagram?

author: Daniel_Reyes
author_rank: Regular Contributor
timestamp: October 25, 2015, 12:05:38 am
content: Quote from: Monkeh on October 25, 2015, 12:02:55 amPlaying with mains? How am I playing with mains if I refuse to move forward before I have a clear understanding of what I am dealing with? The mains I understand. His comment didn't contribute at all and only served himself. That is not what forums are about and this forum seems to be full of people on high horses.Sent from my SM-G900P using Tapatalk

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 25, 2015, 12:20:14 am
content: Mr. Reyes. Please remember that this is a public forum. Just because YOU understand the risks and procedures when dealing with power mains doesn't mean that OTHERS who come after will have that same knowledge and experience. The reason this forum is archived is so that people who come along later with the same question can benefit from the previous discussion.I would much prefer being accused of posting from a "high horse" than discover that someone who read something I wrote injured or killed themselves because I wasn't explicitly clear about the dangers. No apologies.

author: Daniel_Reyes
author_rank: Regular Contributor
timestamp: October 25, 2015, 12:21:25 am
content: Quote from: Richard Crowley on October 25, 2015, 12:20:14 amI can understand that. I'll move on then.Sent from my SM-G900P using Tapatalk

author: tec5c
author_rank: Frequent Contributor
timestamp: October 25, 2015, 01:44:35 am
content: Link to the original thread?

author: Andy Watson
author_rank: Super Contributor
timestamp: October 25, 2015, 01:51:04 am
content: Quote from: tec5c on October 25, 2015, 01:44:35 amhttps://www.eevblog.com/forum/projects/wiring-radioshack-spst-neon-rocker-switch/msg785066/

author: tec5c
author_rank: Frequent Contributor
timestamp: October 25, 2015, 02:49:27 am
content: Thanks Andy.

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 25, 2015, 02:56:28 am
content: Quote from: Monkeh on October 25, 2015, 12:02:55 amYeah, personally I don't want any injuries on this forum...Anyway, if you're annoyed with what they're saying, just ignore them - it's all fair game.Quote from: tec5c on October 25, 2015, 02:49:27 am+1, thanks for providing context!

author: German_EE
author_rank: Super Contributor
timestamp: October 25, 2015, 08:19:03 pm
content: 1) If I see an EEVBlog user doing something stupid I'm going to let them know before they kill themselves.2) If an EEVBlog user needs instructions on something that's mains powered I'm going to make damn sure that I give correct advice and that advice is understood, this may mean dumbing down or it may mean supplying long and detailed step by step instructions.3) I would rather supply the same advice again and again than see a user account cancelled because they killed themselves due to lack of experience and/or a stupid mistake.4) American 110V mains supplies will hurt you if you do the wrong thing, European 230V mains supplies will kill you.5)

author: Daniel_Reyes
author_rank: Regular Contributor
timestamp: October 25, 2015, 08:29:56 pm
content: Quote from: German_EE on October 25, 2015, 08:19:03 pmI understand. My skin is much thicker on this topic now.Sent from my SM-G900P using Tapatalk

author: briselec
author_rank: Regular Contributor
timestamp: October 25, 2015, 09:37:27 pm
content: I'm a little bit concerned about people using videos of industrial accidents as some sort of demonstration of what can happen if you play with the mains at home.It concerns me because it is so misleading. The prospective fault current in a main switchboard in an industrial installation can be huge which is why a short can be so catastrophic. The prospective fault current in a domestic house is tiny in comparison. You won't be engulfed in a fireball if you stick active and neutral together in your home.I fully understand people are trying to educate others on the danger but at least keep it pertinent . Some people tend to ignore advice that is so obviously over the top.

author: SL4P
author_rank: Super Contributor
timestamp: October 25, 2015, 10:29:10 pm
content: OK, As the cause of this thread, I'll apologise to Daniel for being flippant in my original post. It happens a lot on discussion forums with a bunch of armchair engineers...!The point I was hoping to make has clearly been picked up - that wiring up a mains switch is not insignificant - if you don't know what, how or why you're making connections.The device may work fine 'now', but what about under unexpected fault conditions or crossed mains situations. Insulation clearances etc.No one is being mean or 'personal'. We're just trying to prompt each other to 'think' in the proper circumstances. Hopefully it worked. Thanks.--- if you're looking for invisible energy burns, try high-power RF injuries, like a TV transmitter etc...You don't even have to touch the gear - just be in the wrong place under the wrong circumstances. Sobering.

author: Daniel_Reyes
author_rank: Regular Contributor
timestamp: October 25, 2015, 10:40:15 pm
content: Quote from: SL4P on October 25, 2015, 10:29:10 pmNo worries. Appreciate the apology. I suffered a minor career setback this past week so I was a little sensitive but I've achieved success with part of my power supply so I'm doing better now. Hope this mess of two posts helps someone someday. Don't let the bad days keep you down!Sent from my SM-G900P using Tapatalk

author: German_EE
author_rank: Super Contributor
timestamp: October 26, 2015, 07:29:13 pm
content: "The prospective fault current in a domestic house is tiny in comparison. You won't be engulfed in a fireball if you stick active and neutral together in your home."This is incorrect. Every domestic installation has an incoming 240V feed from the street which normally terminates in a 100A fuse. Even with a direct short between the meter tails that 100A fuse will take some time to blow during which may have an arc flashover due to the thousands of amps that are flowing through the fault. This could involve lumps of molten copper flying around and intense heat, not something I would wish to experience.

author: briselec
author_rank: Regular Contributor
timestamp: October 26, 2015, 10:05:50 pm
content: And is that a domestic installation in the video? I bet it isn't .Ok I should have stated the active and neutral of an individual circuit. I certainly didn't mean shorting the mains.Here domestic installations are supplied from a fuse either on a pole or in a box on the footpath, usually 60A. It is solely an overload protection device. It is NOT a short circuit protection device which is why no one should even consider touching anything before the individual circuit protection devices unless they are a qualified electrician.But this thread originated from a question about wiring up a switch on a portable device.I don't see the relevance of posting videos involving much more dangerous situations that can have much more catastrophic results where one would have to be exceedingly stupid to try and do it without the proper qualifications and training.

author: Ian.M
author_rank: Super Contributor
timestamp: October 26, 2015, 10:24:42 pm
content: I think its an Americanism to use a plug-in electricity meter. Apparently, if work needs to be performed on the feed side of the fuse box/CB panel, its usual to pull the whole meter to isolate it from the supply. There is obviously some risk if the user tries to pull the meter to isolate the installation while there is a load on it, and if the meter base is contaminated with anything conductive, one could easily get a phase to phase or phase to neutral arc.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 27, 2015, 01:50:09 am
content: Quote from: SL4P on October 25, 2015, 10:29:10 pmYou would really have to work hard at it to get a decent RF burn off a TV transmitter.All the high power RF connections are made via very large Coaxial Cables.Even climbing around on the tower won't have any discernible effect---I've done it!Also,remember that the transmitter's real power is only a fraction of the quoted EIRP,so a "100kW" station only produces around 10kW or so if you measure it into a Test Load.You are much more likely to get an RF burn from a high power MF Broadcast site,where the Mast is actually the antenna---the whole thing sits on a huge insulator.MF transmitter sites are rated at the actual power the transmitter can feed into a Test Load,so a 55kW MF Broadcast station produces just that --not EIRP!.Even so,you have to be quite close to a "hot" antenna structure (& the ground at the same time) to get a life threatening injury.People commonly cimbed on,& worked on "hot" antennas in the past.The reason it is not done anymore is because of concerns about the possible effects of working in strong RF fields,not because of a plethora of burns among station personnel.OK,various artifacts around such sites can give you a nasty burn due to RF pickup,but you do have to touch them.