Slashdot Mirror
Solving a Wiring Mess?
FueledByRamen asks: "While trying to run a new power line for a large Sun mass-storage cabinet (located nowhere near a 220 outlet of course), I had the misfortune of needing to pop the lid on my main power distribution panel (previously opened in the late 80s). The whole thing is a rats nest and probably a fire hazard - old-style wiring with broken-down cloth/plastic insulation strewn everywhere, and the utility's incoming power cables have some sort of junction in them that's the size of a 1-liter bottle (on each wire) and is covered in layers of electrical tape. Even (gently) putting the panel back on jiggled something important, and there was a nasty cracking noise and half the breakers blew (all breakers in one of the 2 columns). I've worked with mains voltage in the past (wiring new rooms, installing lighting), but nothing on this scale, both in terms of complexity and potential for death. How do you industrious Slashdot readers go about fixing a mess like this (on a tight budget, no less) without getting a mains-induced glimpse at the great beyond?"
Good god man, leave that mess alone and hire a professional that knows what they are doing. Don't ever put your life in the hands of Slashdot; are you utterly insane?
Maybe it's just me, but some things are worth paying for. I prefer juice in my stomach, not coursing through my entire body...
Stop by my site where I write about ERP systems & more
Hire an electrician.
pay someone who does it for a living, not a hobby. if they die, you dont have to worry. Its not something to do to save money... something are worth paying for.
sPh
Well, why not use wireless electicity distribution? There even is a RFC for it: 3252 :)
--
If code was hard to write, it should be hard to read
1. Let the thing catch fire
2. ??? (Collect insurance)
3. Profit!!
That's the kind of job they get to do.
Just go down to your friendly appliance store and get a can of "Cable-B-Gone" (tm)
Don't blame Durga. I voted for Centauri.
I'd use my tongue as a voltimeter. If i***BBBBZZZZZUUUHHHHHAAAAAAA!!!!!!!!***
Hire a professional electrition.
Does the name Pavlov ring a bell?
Are you sure YOU weren't the cause of the blackout of 2003?
You've got to be kidding right?
My god, I expected this to be signed "a recently unemployed power grid manager in Ohio"...
I might not speak for everybody but I'd imagine that the majority of people went "Hire an electrician" when they read that story. I really don't think you want to be mucking around in there with "some sort of junction in them that's the size of a 1-liter bottle" as you don't appear to know what that is (neither do I).
I know you want to save money but you're likely to fry the electric equipment in your establishment and might take yourself with it. Hiring a professional would likely be cheaper in the long run.
I've worked with mains voltage in the past (wiring new rooms, installing lighting), but nothing on this scale, both in terms of complexity and potential for death. How do you industrious Slashdot readers go about fixing a mess like this (on a tight budget, no less) without getting a mains-induced glimpse at the great beyond?"
I Am Not An Electrician, and from the sounds of it, neither are you.
I'd suggest hiring one.
// TODO: Insert Cool Sig
You Insensitive Clod.
Port 80, we dont need no stinckin port 80.
You have two options:
1) Hire a professional electician at a very high rate of pay to rewire the box and make it safe.
2) Hire a burn specialist at an extremely high rate of pay to patch your smoking body together after attempting to fix it yourself.
5) Mike Tyson sounds like a girl.
4) Honey, that's just the PMS talking.
3) [Redneck accent]Hey y'all, watch this...
2) Betcha can't...
1) We'll save a lot of money by not hiring an electrician...
'Nuff said.
-Looking for a job as a materials chemist or multivariat
No, you plug it in slowly and run away. Quickly.
'Sensible' is a curse word.
You have two options:
1. Read National Electrician's Code and the
Emerald book (IEEE guide). Then figure out
who installed the wiring and get a full layout
from them. Buy electrician's equipment as
necessary. Fix the problem.
2. Hire an electrician. You'll still need full
layout of your wiring.
There's also insurance reasons as well. Having someone other than a qualified electrician do the work can void your fire insurance.
send an email to your PHB that says things like "fire hazard" "risk to operations" "danger to employees and $$$$ equiment" "violation of code" and/or "insurance risk". That should get you the authorization you need to do whatever needs to be done - which, as others have pointed out, is HIRE A PROFESSIONAL.
Is the juice worth the sqeeze?
... then you shouldn't be doing it.
Sorry, but this is the kind of thing that only years of experience can help with. If you didn't look at it and already know how to approach the problem, you probably shouldn't be messing around in there, unless you have all the time in the world to experiment and learn your way through the mess.
First I was surprised that IANAL advice hasn't landed some "Ask Slashdotter" in prison. Now we're aiming for our first fatality?
Robots are everywhere, and they eat old people's medicine for fuel.
along the lines of "you fscking idot don't try that at home". Well, that's totally against the hacker spirit of learning how to do it yourself, hopefully without killing yourself.
I've wired up several additional circuits in my home and my office and it's not that hard. All I needed was a little common sense, a copy of the Ugly's book, and the local home depot. In your case though, if the main drop coming in from the pole is bad, you need to have the power company turn off your service drop so you can replace it.
If the main lines coming in are safely insulated and do not need to be replaced, then what you can do is shut off the main breaker, unscrew all the circuits coming in to the individual breakers, and replace all your house wiring and perhaps all the breakers as well. This is not a job for the faint of heart, but I wouldn't say it's incredibly skill-intensive. Just takes some patience to wire up all that stuff and not slip with your hand/screwdriver and hit the main lugs. If they're exposed where they connect to the main breaker, then you might want to cover them up with cardboard and tape while you're working.
Oh, and don't blame me if you kill yourself. I'm not an electrician - an electrician would tell you to hire an electrician. I'm just telling you where *I* would start.
Suck it up and hire an electrician. Seriously. Yes, those of us who have done lots of electrical work and know not to connect power to ground may feel that it's horribly wrong to pay someone for this, but you really should do it. Even if you know what you're doing, things can always go wrong, and if you're not a licensed electrician you could be opening yourself up to lawsuits by the power company, building code violations, you could lose insurance, etc.
Now, if you want to do your own work inside your house, I would recommend that you get the electrician to install a master lockout switch (different from a master breaker in the panel) between you and the mains supply. Then, play with anything behind that, and you probably won't get in trouble with the power company. You can go re-wire your whole panel yourself, and save some money (getting them to install the lockout switch will be quite cheap comparitively)
There is no sig, there is only Zuul.
Being zapped by A/C at any voltage, let alone 220/440 really is teh suck!
In all seriousness, a wire job as large as you describe will likely have to be permitted with your local government construction office. That means that the work has to be performed by a licensed electrician and it has to be inspected the appropriate government agency afterwards.
I figure it used to be white, but now it is covered in dried-on red stains.
Don't blame Durga. I voted for Centauri.
So, lick the terminals to find out which ones are hot (works with 9V batteries). Then, standing in a bucket of water, grab a big handful of cables and PULL.
Ignore the fizzing and the smell of burning hair. Douse any lingering flames with gasoline.
They say the first thing to go is your penis. Well, it's either that or your brain. I forget which...
It sounds like one of the main buses in the box got shorted out. You really need to get the thing rewired by a licensed electrician.
If the panel is at work, it's probably illegal for you to work on it. In the immortalized words of Beowulf Schaeffer, "Its Worth Yore Life And More To Go In There!" Seriously, as an uber-l337 633K, you probably have the ability to find the place where the short occurred -- but do you really want to (A) monkey around in a box with live current (it sounds like that is your main box, not a subpanel); (B) stick your neck out by breaking the law for your employer; and (C) possibly assume liability for burning down the building? No? I didn't think so.
If you're at home, you're probably allowed to work on it -- but most places require you to get an electrical inspector to look at it once you're done. Unfortunately, doing this requires getting the local electrical code, so that you know what you're doing -- and that's a whole separate rant. The National Electrical Code is adopted into most municipalities' building codes -- but it's copyrighted by the National Fire Prevention Association. Fortunately, the Supreme Court recently decided that it's unconstitutional to attempt to copyright the law of the land. Unfortuantely, you can't get the electrical code online yet -- you probably still have to buy it.
If you have that much current flowing in, there are bills to be paid for this.
If you have that much machines running, there's a budget for maintenance.
If your employer tells you to fix it yourself with new wire and duct tape, he either doesn't give a sh*t about you and your safety, or he's completely insane.
Hiring an electrician to install some lamp wiring is stupid and overkill if someone in-house can do it, but playing in an electric box isn't.
For the price it would cost you to have it done by a professional
1. you will cut the downtime,
2. have a fully secured panel (and certified)
3. If it catches on fire you won't have problem with insurance claims since it was certified (whereas if you mess around in this yourself without the credentials, you could run in a PILE and I do mean a PILE of problems). This point alone should make a perfect argumentation to any "managers".
4. Your paycheck isn't worth you life, especially if you have to turn around to slashdot for advice.
5. If you are so much on a tight budget, sell off one machine to pay for the contractor, or try to find someone that would do it for cheap, still, you'll have to pay for the material and it doesn't come cheap. I don't beleive in "tight budgets" for critical things like this, again, if you can afford having this many machines running, you can afford to support them, if they are all put to use, surely you are generating revenues, if they aren't , they can be sold.
6. See point #4 as a personnal advice.
I'd be really scared to work at some company that couldn't afford an electrician for a job like this, if they are so tight, chances are your paycheck will eventually bounce, so risking that much for that little...
--- Metamoderating abusive downgraders since my 300th post.
If you are not a certified electrician that has been trained to deal with that voltage range do not attempt to do so.
If you are going ahead anyway. Take another person with you at all times. Your buddy should be able to shut down the entire mains current within slit seconds. Your buddy should have a wood/rubber/plastic or otherwise insulating device that can be used to knock you away from the power source if necessary.
Never use both hands, current will flow through your heart and spine. Do not wear anything metallic such as chains, watches, rings etc.
Remember that even if you wear double or triple insulation that a high enough electrical potential can break through anyway. I work with 600+ Volt pulse LASER capacitors and I've seen arcs go through plastic.
To reiterate. If your not qualified do not attempt to do the job. Anything that you do based on any of the above is your responsibility only.
Good Luck.
If you outlaw the law, only criminals will have laws
Not only is it dangerous and lethal, not to mention analog... its ILLEGAL in most places for you to do the work unless you're a licensed electrician (some exceptions for certain 120vac work). Heck... a lot of places require you to have a Low Voltage certification to run cat5......
For home, who cares,,, for business: follow the rules.
Hire a professional. A real professional. It won't necessarily "be cheap" but it will be safe. When the powers that be balk, ask them which would be "cheaper", getting this fixed and staying operational, or having the whole thing go *POOF* and take the location out of service and still have to get it fixed.
If you are the unlucky person that has to fix it, then find the main that feeds that panel and TURN IT OFF.
Don't even think about trying to fix this problem while it is hot. Not unless you've got a deathwish and, if you have any family you care about, a great big life insurance policy that will still pay out after acts of stupidity.
I've worked around a few power systems, and the one thing above all else, give that electrical panel LOTS OF RESPECT. Always assume a circuit is hot, even if "you KNOW you turned it off earlier". Always leave a flag on the circuit that you turned off so that others know it is off on purpose, especially if you have to turn off a main to kill power to that panel. Always remember SAFETY FIRST, even when your working on a "dead" panel. If you have insulated tools, good -- use them. If you have heavy duty insulated gloves -- use them. Never work alone -- always have somebody around that is aware of what your doing and that can check on you from time to time, or better yet, keep you in sight. They don't have to help you work on the circuits, but if something goes horribly wrong and you get zapped, that person can call 911 and get you help.
. 62,400 repetitions make one truth -- Brave New World, Aldous Huxley
There is a reason that master electricians get paid the big bucks (and it's not all about just _surviving_, either).
;-) The situation you describe frankly sounds quite dangerous. Is burning the building down worth saving the cost of hiring a pro?
IANAE, but anyone can play anything on the web, right?
If you're *totally* determined to do it yourself, do the obvious. Turn off the upstream power (omit long-winded story of how to power a data center when the main is down - been there ). Make sure you understand what all the parts are, how to tell if they need replacing, and have replacements on hand before you start.
I would guess that there are innumerable sources of education and product sales in this area, so it shouldn't be *that* hard to figure out what everything is, why it is there and how to test it.
On the other hand, there *is* a learning curve involved, and I shouldn't need to point out the dangers of working on a *hot* box based soley on theoretical knowledge! How long do you have to learn how to fix it before you get more than just sparks?
Disclaimer: I've never done any hands-on on anything bigger than your average house feed. I do feel like I learned a lot from being a curious guy in general and having access to a Master Electrician for a couple years, including building out a new data center. And in your shoes, I would not undertake the task without hazard pay that would be higher than the cost of the electrician.
Another possibility is to call the power company, get them to take a look (say you smelled smoke, or saw sparks or something). I doubt they'll fix it, but they'll definitely escalate the problem for you.
If you're not living on the edge, you're just taking up space!
grep electrician yellowpages
What, you're scared of 220 Volts ? When we were growing up, we walked 200 miles through six feet of snow, wearing no shoes, and we repaired 2000 volt circuits with our bare hands. :-)
How do I perform brain surgery on myself?
What is the best way to travel about in a war zone?
What is the best way to tell my spouse that she needs to lose A LOT of weight?
How can I get close to the President while carrying a handgun?
How can I steal power from a high tension line?
It is by the juice of the coffee bean that thoughts acquire speed, the teeth acquire stains. The stains become a warning
Don't resign. A worker can notify his supervisor that due to what the worker believes that doing the task placed before them will put them in imminent danger, he can refuse to do that task. The worker then needs to fill out a form or two and contact the Occupational Safety & Health Administration. The worker cannot be disciplined for refusing to work in a dangerous situation.
Not to mention being able to slap you with lawsuits for damages, as well as building code violations if something goes wrong.
Electricity is not a toy (as I have heard, many times, because my father was trained as an electrician).
This is not a sig.
... at least through extremities. My old high school physics teacher used to stick his finger in light sockets for laughs. Then he would pull out the Variac and let you stick your own finger in a light socket with variable AC voltage. Up to about 30 VDC you couldn't feel a thing. When you control the voltage yourself, 110VAC is no big deal at all -- just a strong tingling in the finger (in the light socket).
"First thing to do is SHUT OFF THE POWER AND INSURE IT WILL NOT BE TURNED BACK ON UNTIL YOU ARE DONE!!!"
This is extremely good advice.* Professional electricians will put a little warning sign over any breakers, switches, etc. that are shut off that says essentially, "if you turn on power here, you'll kill someone." Make sure you have one.
That said, I too think this is a very good way to add yourself to the next Darwin Awards.
*Ignoring the goofup with "insure" used rather than "ensure", but that's not a *big* deal.
How 'bout putting up a picture of that mess for us to enjoy?
As a devoted employee trying to save your company money, the answer is obvious.
Step 1: Buy life insurance, lots of it. Name your employer sole beneficiary.
Step 2: Attempt to "fix" this yourself.
Step 3: PROFIT! The company can use the benefits (assuming the insurer doesn't use your actions as prima facie evidence of suicidal intent) to hire a professional to do the job right. You'll be dead, but that's a small price to pay, eh?
Seriously, what has our country come to where this is a legitimate question? Techies should be comfortable replacing wall switches and outlets, installing undercounter lighting, and other light work. But anything involving the main should go to the professionals without a second thought. If it's as bad as you said, it should also go to the lawyers - wasn't this building ever inspected? Who did this shoody work before, or allowed it to remain in such poor condition?
Think about it this way - imagine this was a manufacturing shop and people have routine cuts and burns and the like. No big deal, anyone with modest first aid skills can deal with it. But if somebody came in with a compound fracture and 4" of bone showing, would you patch them with the ace bandage and send them on their way? Or would you decide that this is one of those situations where you need to call in the professionals?
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
Turning the power off, even if you type about it in ALL CAPS, is not enough.
A big detail is that you must discharge any capacitors. THEY will kill you, even with the power off, and sometimes, they are not easy to find.
Don't do this, sheesh, it doesn't sound like a job worth dying from, now, does it.
If the answer to that is NO, then STOP WHAT YOU ARE DOING AND CALL THE BUILDING OWNER, inform him of the sub-standard wiring you found and ask him how you can 'work together' to get it fixed without any inconvienience, like reporting it :)
If your company owns the building, GET PROFESSIONAL HELP 220/440 is not for playing with, and any micro variations WILL cause problems in the future. Our MTF (money transfer faciclity) had a single strand not properly grounded in a secure vault, and everytime then bloody door was slammed it caused a parity error on a mulitprocessing enviroment and forced several hundred transactions to be re-run. Took 2 or 3 weeks and power monitors to locate the short and LOTS OF TIME to correct, minimize it by using people WHO KNOW WHAT THEY ARE DOING.
errr....umm...*whooosh* *whoosh* Is this thing on ?
Call your local IBEW and hire a guy that knows what he's doing. For my own home, I've quite often done barter work to help "pay" for any electrical work I couldn't handle myself.
Many of the electrical contractors out there are looking to have a website built. And frankly it's a good trade. Even if they have to "Buy parts" it becomes a business expence and then is deductable, as is any website "billing" I do for them.
It's a win-win situation, and everyone thinks they got the best deal.
But the bottom line is, hire a professional. Your main power line is nothing you want to screw-up.
-Goran
Carpe Scrotum - The only way to deal with your competition.
actually, black duct tape works best for wiring. grey is for ducts, and red/white/blue/green look good on your '88 accord as racing stripes.
I rewired my whole house from the power pole down (was 40s era ungrounded knob and tube with 30 amp service) so it can be done but some things will make it easier.
First, find an electrician friend or at least an electrician who is DIY friendly and get a professional opinion. If the insulation in the panel is bad it may be bad in the walls as well. You may not want to know.
While you can do the research and learning yourself, a pro will quickly spot certain gotchas like aluminum wiring without the proper anti-corrosion connectors or grease.
They will also likely spot other things you would probably miss such as certain Federal Pacific Electric panels and breakers (http://www.inspect-ny.com/fpe/sec1982.htm).
In my case I knew plenty about electricity in general but hiring a friend for a few hours to review the project and teach me the tricks really helped speed the job. He was also able to review the codes. Again, basic electricity wasn't the problem but my friend was intimate with all the issues like where GFCIs are required, required height of outlets, how many are required per wall, allowed location and hole sizes in floor joists, locations where conduit/BX is and is not required.
A lot of the codes sound arbitrary and to a certain extent they are but before dismissing them as silly remember that they represent the accumulated wisdom from the fires, electrocutions, etc. in the past. Building codes are all written in blood.
A pro can show you good tricks. For example, throw away the stupid paper template that comes with the retrofit junction boxes and simply hold a torpedo level against the box, use a tape to measure the proper height and pencil around the box then cut.
Also, before locating a box take a piece of straight coat-hanger wire, chuck it into a drill, and drill it through the baseboard or ceiling wherever you want to locate the box. Then crawl under the house or into the attic and the wire will give you the exact location so you can check for obstructions and you can drill the holes in the right place. Much better than trying to measure plus coathangers are free and the tiny hole is easily filled with a dab of spackle.
If you do get into major rewiring I recommend a few things:
1. Use 20 amp wiring - the material cost is very slightly higher but labor isn't. You have extra capacity and lower resistance losses.
2. More breakers - OK, I went a bit overboard with well over 20 breakers in a 1200 square foot house but running every kitchen outlet to its own breaker cost me very little in time or money and I have no problem running the microwave, coffee maker, waffle maker, toaster along with the fridge and dishwasher.
3. Outlets everywhere. I added outlets in every closet - they are great for powering chargers, adding a burglar alarm, etc. Add them where you might add appliances - I'm finally getting a garage door opener but the install will be easy since the outlet is already in place. While I was up in the attic I added an outlet under the eaves - handy every Christmas. I increased the number ouf outlets 3-4 fold and have used every one.
4. Run 240 to the garage - you will eventually want to run a small welder and even if not you might want to use it for an illegal backfeed from your generator in a blackout (just be sure to kill the main breaker first).
Upgrading to a solid over-engineered electrical system wasn't like getting a new computer or other toy - it was more like finally getting a pebble out of my shoe (no more blown fuses, no more sticking a three prong adapter on the extension cord then tossing it out the bathroom window to be able to mow the back lawn...) It's work but the result is nice.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
This is a definate case where you *MUST* hire an electrician. I emphasize *MUST* because you're probably going to kill yourself in the process.
Most states and communities have laws saying electrical work must be done by a licensed electrician.
I forewarn you though, he's going to want to kill the power to that box while he works. If it's as much of a mess as you're saying, it's more than just the box that needs rewiring. All those old cloth insulated wires go somewhere, probably to more fire hazards throughout your building.
Get a contractor to have a look at it. Where you caused a short just by putting the lid on, you're not far from starting a fire, and be glad those breakers are working, they may have just saved your life, and your equipment.
I'm not saying this because I think work should be farmed out. I'm a firm believer that I can do anything. But, even I have limits. Rewiring a building is a bit beyond what I'm willing to do. Even if I was willing, I know perfectly well it would take too long doing by myself, which will probably be unhealthy for your companies income, if the servers are all down for too long.
Serious? Seriousness is well above my pay grade.
What's the 4 things you have to know to be an electrician? 1) 240 will shock you 2) 480 will kill you 3) 4:30 is quitting time 4) The boss is a son of a bitch Will get you into any electrician's union. What's the one thing you have to know to be a plumber? 1) Shit don't run uphill
"Eve of Destruction", it's not just for old hippies anymore...
"Depression is merely anger without enthusiasm." - Anonymous
I am a lifelong blue collar guy, gardening, landscaping and construction. I have worked a fair amount part time with electricians. Do it yourself electrical work is ok for outlets, ceiling fans, etc, if you are smart with your hands.
But you need to stay FAR away from the Main Panel unless you are knowledgeable. That thing is dangerous, there ARE many non obvious mistakes you can make if you are not an experienced electrician. You can hurt yourself, burn down the building, damage stuff attached to the electrical system, and if you do something REAL IGNORANT, it is possible (unlikely) you can hurt someone working for the power company outside the house.
This is coming from a Gung Ho!!! Do It Yourselfer/ Shade Tree Mechanic
HenryJamesFeltus.com
Don't flag, lock it.
Get a keyed lock with one key.
Turn it off, lock it out, carry the key while you work.
That is the ONLY way to do it.
Don't have one of those? THAT'S BECAUSE YOU'RE NOT FARKIN' QUALIFIED TO DO THE WORK!
If you have not had the correct training, you CAN NOT safely lock out equipment. Sure. You locked it out. You stuck your wiggy in the wall socket to make sure you got a buzz. You tested each terminal and they were all dead. You started stripping wires. You reached way into the cabinet to unscrew some terminals in the back. It got dark and the building's outside lighting circuit turned on. Guess what? Someone ran the lighting circuit through the box.
oopsie.
You don't know what you're doing. Neither does the person who "told you how" to do this safely. Hire a professional.
"Reality is that which, when you stop believing in it, it doesn't go away." - Philip K. Dick
A electrical fire will put an even bigger dent in your "budget." You MUST hire a COMPENTENT electrican. (We had to replace gear went an incompotent wired out new 110 outlets 220. The Boss was "saving money") Comercial wiring is not where you cut corners. It's not a DIY thing. Not having it done by a certified professional may also void your insurance as well.
As you can see I don't care about my karma.
What, you're scared of 220 Volts ? When we were growing up, we walked 200 miles through six feet of snow, wearing no shoes, and we repaired 2000 volt circuits with our bare hands. :-)
You call that tough. When I was a kid, we didn't even have hands.
I used to write software at a high-energy physics lab. The technicians would put padlocks that only they had keys for on switches when they powered something down. Removing someone else's lock was grounds for immediate dismissal. If someone accidentally left a lock on something, they had to personally remove it or (you guessed it) face dismissal. They took these rules very seriously.
1. Buy/setup new power system
2. Move systems over one by one
3. Repeat as needed
4. Disconnect old system from power all at once
5. Trash bins out back
6. Proffitt??
#6495ED - cornflower blue
fixed a fuse with tinfoil
I've done that -- not a house fuse, but the "slow-blow" fuse protecting the motor in a (now ancient) Decwriter dot matrix terminal. (As I said, ancient technology). It was late, I was fixing some code, and a piece of paper jammed the print head and the fuse blew. No spare fuses. So I got a foil-wrapped chocolate bar out of the vending machine, wrapped some foil around the burnt-out fuse, replaced it and kept coding.
And yes, left a note to remind myself or whoever used the terminal next to replace it with a proper fuse.
-- Alastair
Hey, always nice to get the proper answer from the horse's mouth (i.e. the article author).
Seeing as how you ARE from the US, I'd simply call it "service". At least, that's what your local power company would call it:
Transmission = the 60kV and higher network that connects substations and switching stations.
Primary distribution = the 12kV to 25kV (sometimes up to 35kV, sometimes down 4kV) network leaving a substation.
Secondary distribution = the 120V/240V (sometimes 480V) network on the "low" side of distribution transformers (which will look like the 10-gallon drums you see mounted on every N-th pole if you have overhead distribution in your neighborhood).
Service = the drop from a point on the secondary distribution network to the customer.
Slashdot is entertaining like pro wrestling is entertaining
it's not the volts it's the amps that getcha
God, I knew someone was going to say that. Ohm's law... I=V/R. If the voltage goes up, so does the current. They are not mutually exclusive.
Yoda of Borg am I! Assimilated shall you be! Futile resistance is, hmm?
I think that everyone here is pretty much saying the same thing: "IT IS STUPID TO TRY TO DO THIS YOURSELF!"
I have been on the recieving end of a 220v shock because someone flipped a breaker on a circuit after someone else did a home-brew wiring job. Had I picked up the wire with two hands rather than one, I would be dead and decomposing nicely by now.
I have done my fair share of homebrew jobs and after a number of lessons learned the hard way. I now have a lot of respect for electricity and use a great deal of caution with any wiring job.
Wiring something from scratch is one thing, what you describe is a DEATH TRAP!!! DON'T EVEN THINK ABOUT IT!!
I suspect that even an experienced professional would be a bit gun-shy with the setup that you have.
[And yes, I have replaced contact swtiches in my microwave, serviced the non user-servicable parts in my TV, swapped parts in my computer's power supply, re-wired my car, and a lot of other dumb things. I have some idea of what I am doing, but I wouldn't even consider doing that wiring job for a nano-second! Even I am not that deranged.]
Its been said already, but it cant be said too much.
I just wired a major remodel of our home, myself, and understand what I'm doing running a wirign circuit.. but I hired a pro to wire the main panel and subpanel and especially to hook it up to the feed, and to check my work. Doing this wrong can kill you. It can kill someone else. And "wrong" can be something simple and easy to overlook that you wouldn't think matters.
Hire a pro to come look at it, immediately. It aint worth the potential tragedy and legal issues if something goes wrong.
You can expect lots of sissy comments from posters afraid to improve themselves by learning something new. Ignore them.
Roll up your sleeves, don some rubber gloves, and start by straightening out that mess.
If you've ever made a really clean rackmount you know what to do. Make all the wires go in straight lines with nice ties keeping them together.
Now, I'm sure you've seen a movie where the protagonist has to defuse a bomb by cutting the correct colored wire, often in conditions that impair his color perception. This is very similar. You should use the same basic strategy, which is hover the wire cutters over each wire and drip sweat into that bubbling, crackling maze of death. Try not to flinch when each drop of sweat causes an electrical arc to sparc towards your face. At the last second when you think the entire box is about the explode (determined by sound) quickly cut the wire that seemed LEAST LIKELY. Note it is very important that you do NOT cut the wire that you were hovering over for a long time because it seemed right. That is the wrong wire and cutting it will kill you. Cut the one next to it.
Next add 'High Voltage Electrical work' to your resume and ask for a raise!
- For the complete works of Shakespeare: cat
a recently unemployed power grid manager in Ohio?
Some places require locks and tags to be sure the power doesn't accidently get turned back on while you're working.
:) Luckly, I didn't even work in a department that did physical repairs. We were just warned so some idiot wouldn't turn on a conveyor (or whatever) that was intentionally shut down.
I spent some time at a Walmart warehouse. Big facility, lots of cool conveyor belts. They made a *HUGE* point of tagging and locking anything you're working on. I guess it only makes it slightly more hazardous that all their racks are metal, so if you have a main wire disconnected, and it was touching the metal of the racks, you could make an electrical hazard out of a piece of metal 3 stories high and a couple hundred feet long.
Serious? Seriousness is well above my pay grade.
Big pansy! You call not having hands tough. When I was a kid we didn't even have bodies.
Geesh...
If its beyond your ablity, dont even think of doing it yourself.
you could easly die, or burn the place down since you obviously dont have a good enough clue to be doing that sort of electrical work.
YOu dont live near me i hope.. *shudder*
---- Booth was a patriot ----
You will save yourself a lot of headaches downstream. There's a time to DIY and there's a time when experience is essential.
Think of it this way: if the wiring had been done properly before, you would not be having this problem now.
--- Ban humanity.
Lots of comments here mostly ranging from the "you're an idiot" to "get a pro". No need to restate the obvious, so I'll just add my personal notes:
First, if you can, get a pro instead. That being said, there's a lot of good you can usually do without a pro's help. Playing with mains is not the thing to do if you're an armchair electrician like myself. Those sorts of things I usually leave to them. You can, however, do work on the non-mains wiring without seriously endangering yourself. I managed to wire my entire house to the box after the mains were properly installed and am quite living to talk about it.
Here's the problem with mains: They're either a) not breakered if you're past the mains breaker, or b) the mains breaker is too high to stop anything from frying you where you stand. One thing you definately want to avoid besides touching the mains is cutting them. If you cut it on the service side of the mains breakers, oftentimes they're not breakered back down the line. The line back to the transformer will glow very pretty red and probably catch on fire, depending on whether or not the transformer blows up right away or later. It can be impressive, I don't recommend it.
Work with one hand in the box when attaching wires to/from the breakers themselves. One hand behind the back will keep a path from going across your heart. Avoid standing in kiddie pools while working on the box. Strip the wires only right before you are going to hook them into the breakers, that way you don't accidentally make contact early. Shut off everything you can before playing in the box. If you can't shut off the mains, have a person near you to whack you away with a board or call 911. If you can shut of the mains, you're reasonably protected, just use a voltmeter to make sure.
Common sense prevails here. If it makes you shaky and nervous to get in the box, get a pro. Otherwise, watch yourself and keep your head on, and you can do some of the work without harm.
Blog,Twitter
Basically, don't fsck with the stuff unless you know what you're doing.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Yeah, I'm a little late for the party here. However, since I've seen electric utility safety films that make the worst drivers-ed film look tame, I've just got to say...
Sweet merciful crap, man! Please send Slashdot another note tomorrow that you hired somebody who fixed this - so we can see the report in a Slashback, and not be worrying that you're in our building somewhere.
Sweet merciful crap! I hope to goodness you're trolling.
In summary... Sweet merciful crap!
"Consider yourself a member of a virtual corporation with Mr. Torvalds as your Chief Executive Officer." - Linux Advocac
If you're talking about not having a 220-volt outlet nearby, you're probably American. But you're calling it "mains power", which is usually a Commonwealth thing. Are you by chance Canadian?
In most of the US, at least if you're in a city or a medium-heavily-populated county, there's probably a building code electrical code that says who's allowed to work on what kind of electricity. Usually in a home, you're allowed to work on sockets and switches inside existing electrical boxes, and almost everywhere you're not allowed to touch the main power feed yourself, and in some jurisdictions you can install new electrical boxes and plug-in circuit breakers yourself and in some you can't. (In New Jersey, you can negotiate with the building inspectors about not noticing things, but Darwin usually wants bigger bribes than they do...) In commercial buildings, you're more likely to need a license.
If you're required to use a licensed electrician for something, and you do it yourself, various Bad Things can happen, and if you do it your self and something goes wrong, more Bad Things _will_ happen. You do not want this... And you said that it looked ugly in there - this significantly increases the chances that if you do work on it yourself, something will go wrong, or perhaps Terribly Wrong, either because it really is an ugly mess or because it's beyond your skill level or both. And if you're renting your building instead of owning it yourself, your lease probably mentions some of the requirements. If you have fire insurance or liability insurance, those contracts probably also require licensed electricians for cases like this.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
This one is way more advanced. Just be careful where you point it.
Actually, I was shocked by 220 volts in an accident. When I say shocked, I mean I was held on to it for approximately 45 to 60 seconds. I don't know which was worse, the resulting heart attack symptoms or having to explain to very dumb doctors why I couldn't let go and that 220 is a lot to suck up. To the original poster, don't be such a moron, call a damn electrician already. Besides frying yourself, did you even consider the liability issues? Guess who'll be investigated if the building burns down.
Interesting, this is essentially how public key encryption works.
The problem they're trying to solve is that a message gets sent through a public channel (such as the postal service) without either party giving up their private key and without the data ever being unencrypted until it's safely in the hands of the recipient. The best explanation of it I've heard goes like this.
"Alice writes a message and locks it in a chest with her padlock. This chest has holes (hasps) for two separate padlocks. [Note: no reason it can't have n hasps, as in the wiring example.] She sends the locked box to Bob through the mail.
Bob places his own padlock through the remaining hasp, and mails it back to Alice.
Alice removes her own padlock and mails the box, with just Bob's padlock on it, back to Bob.
Bob removes his own padlock and reads the message."
Of course, this is all being done over TCP instead of the post, and with math instead of padlocks, but you get the idea.
None of this has anything to do with a wiring mess, but the similarities are striking.
It's rare that you're presented with a knob whose only two positions are Make History and Flee Your Glorious Destiny.
"Oh boss, I've just found some more work for those Indian outsource guys"...
What's that?
Oh OK, "the Indian qualified electrician guys who specialise in handling hazardous situations that will almost certainly kill a geek techo who would only consider tackling this kind of task as a way of getting the receptionist to throw a smile in his direction for once"
Happy now?
Seriously though, there is life outside whatever burnt out dot com shell you are currently living in, with only the roaches keeping you company. You need to get out and get your bare feet on the grass for a while. Smoke something. Lie in the sun with your eyes closed. Try and forget there was ever a place and time when you thought it would be smart to do your own high voltage wiring.
[x] auto-moderate all posts by this user as insightful
>> Don't you have any interns at your place?
> No, no... temps.
No, no, no... redshirts.
if the answer isn't violence, neither is your silence / freedom of expression doesn't make it alright
I lived in a rented house in college that had what turned out to be dangerous wiring.
LESSON 1: Polarity
Here's a cool tip for you. When wiring up electrical outlets, if you reverse the hot and the neutral lines, you actually create a voltage potential between the outlets. I discovered this because I touched the stove and the refridgerator at the same time accidentally. I got a huge jolt, shook a bit, and called the land lord.
LESSON 2: Breakers and Wiring Guages
If you should ever run wiring in your house, you need to make sure that the breaker that you use matches the capabilities of the wiring. If you should decide to run wiring into an attic using 15 amp capable wiring, it is a bad idea to put a 30 amp breaker on it. It's an even worse idea to hook up approximately 27 amps worth of electrical heaters to this circuit because it will cause the wiring in the wall to catch fire. Of course if one assumes that the person wiring the house isn't insane, you may not know to avoid plugging in said heaters.
LESSON 3: DOCTORS ARE NOT ELECTRICIANS
Eletricity isn't brain surgery, and just as you don't want an electrician siticking sharp metal objects into your brain, you don't want a doctor futzing with wiring. Actually I suppose if you are a doctor who does know how to work with electricity it would be okay, but the one who had previously owned our house had no clue on the subject. Worse, he had no clue and he mistakenly thought that he knew everything.
So, if you look in the electrical box and it instills fear in you, call a professional. Don't even think of doing it yourself.
This sig has been temporarily disconnected or is no longer in service
Coming next on Ask Slashdot:
I've been getting bad headaches for weeks now - they're getting worser and I'm seeing flashing lights. Can the slashdot community give me any advice on do-it-yourself brain surgery with a dessert spoon and a screwdriver ?
This question has to be the dumbest thing I have ever heard on Slashdot. The man must be a complete cretin to even consider asking for advice.
To start off, I am an electrician.
.5 of an amp can kill you and anything higher than about 3 amps will allow the mortuary to not have to charge your widow for your cremation. Just supply the urn, ma'am.
Hire a professional, period. It may very well save your life.
Anything higher than about
I'm pretty sure that the budget will get modified to accommodate your needs when you tell your boss that the new system cannot be installed due to the shoddy condition of the mains box.
If you are forced to work on the box yourself, immediately contact OSHA, your local Fire Marshal and your local State or County Building Inspector.
They should be able to convince your employer that it would be in their best interest to have the electrical system repaired by a Licensed-Bonded commercial electrician.
I worked at a medium sized amusement park while in college. The park was over 35 years old and much of the wiring and junction boxes were equally as old.
Late one summer night, with the park full of people, all the lights on 'main street' went off.
I was nearby the park's main junction box and helped one of the engineers, an unassuming guy who had worked at the park for years, by holding a flashlight while he started work on the box.
The box was ancient. Cloth wrapped wires. Giant fuses. Old rusty exposed mechanical switches. The works. For whatever reason, one of the main switches had popped open. The engineer first tries popping it back in place. The lights flicker and it just pops back out.
The guy looks at me and says "Point the light at the ground. Help me find some old wire". He searches around with his hands for a minute and finds a snipping of some very heavy guage plastic insulated wire.
To my shock, the guy closes the switch shut with one hand while using the other to hold the insulated part of the wire and *arc-welds the switch shut* with the wire's exposed conductor! Sparks flew, the lights snapped back on, and I damn near shit my pants. This good old boy engineer didn't even blink. "That should hold it until we can get someone out tomorrow".
The only thing I can figure is that he was somehow electrically insulated, perhaps from his huge set of balls for even considering something like this.
I worked down at Kennedy Space Center, in the old Flight Crew Training building. It had a crawlspace that was used to run wires, which was accessible by pulling up one of the big, heavy floor tiles (there was a special tile-pulling tool). The crawlspace was maybe three feet deep -- with the bottom foot or so consisting of old cables, dating back to the Apollo days. Pulling up a floor tile always reminded me of the scene in Raiders of the Lost Ark -- all that was missing was a dropped torch and Indy saying "Snakes... Why did it have to be snakes?" Anyway, every time they tried to clean out these wires, they ended up knocking out something important, so eventually they just let them accumulate.
One time we had to run a network cable from one end of the building to the other -- nearly 100 meters -- and the only way we could figure out to do it was to send someone down there to crawl it through. I'm glad I didn't draw the short straw that day...
I object to that article, and to the next reply.
The key too handling high voltages safely, is to become a good resistor
So resistence...is not futile?
That's nothing
Where I work (warning ugly website ahead) one of our top salesmen was out on a startup on a 4160VAC starter. The customer asked him how wide the stacks were, so he took out his metal measuring tape and measured across the phases.
He was ok, by sheer luck, but the measuring tape has two very decent burn marks at each end where the voltage jumped out and grabbed it. He was thrown back quite a ways and didn't want to move for about twenty minutes, but he lived.
I'm not an electrician, but I've done a lot of my own electrical work, and I've put in a good bit of study to make sure I'm doing it right.
The problem you describe sounds like a major one, and you'll need to hire an electrician. It's what I would do, and I feel comfortable wiring anything in my house this side of the main breaker. Fact is, you may need to replace the whole panel, and that requires coordination with the utility company to pull your meter, and you'll probably need a new service entrance. That's just not a handyman job.
That said, the "old wiring" may not be as bad as it looks. Get a professional opinion, of course. There are a few kinds of old wire with paper/cloth insulation. The oldest Romex has a shellacked paper or cloth outer wrapper and rubber insulation on the wires. The rubber becomes brittle with age, and should probably be replaced to avoid shorts and arcs. Later Romex still had the shellacked paper, or asphalted paper, but the wires have modern thermoplastic insulation. The outer wrapping of the cable can get brittle and very messy, but the insulation holds up okay. As long as Romex of that era isn't totally disintegrating, it's not an issue to panic over, as the thermoplastic insulation is durable.
If you see any aluminum wires in your breaker panel other than the service entrance or a heavy-gauge subfeed, have your electrician rewire the house ASAP. Aluminum wire for branch circuits is a house fire waiting to happen, even with "aluminum rated" outlets.
If you're going to do any major electrical work, go down to Town Hall and talk with the building inspector. They're usually quite friendly and helpful. Their job is to help you do things right and follow the codes. The codes are there to keep you from making mistakes others have already made, and to keep you from doing something foolish and unsafe. If you're polite and friendly, your inspector will probably be glad to sit with you for a while and give you pointers on how to do the job right.
Of course, it helps if you already know how to do it right. The National Electrical Code can be hard to track down; a lot of libraries don't seem to carry it, and those that do classify it as a reference work, so you can't borrow it. Luckily, thanks to a recent Supreme Court decision, building codes which are enacted into law lose any copyright protection, so you can go ahead and photocopy away.
You may also find other helpful books. I'm particularly fond of Wiring Simplified, a book that covers most common household wiring tasks and includes Code references.
When sparks start shooting out of things, though... that's time to call the pros.
There are way, way too many variables at work here for you to even think about doing this yourself.
...but you will be the one on trial for manslaughter. Or criminal damage. You will plea bargain, successfully. You'll have a minor criminal record, and will only have a minimum of jail time - possibly only community service. If you're lucky, you'll only have to see the family of the dead fire victim once, at sentencing.... ...all because back in 2003 you decided that your employer would most likely be pissed with a $5000 bill for electrical work.
Here's a situation - quite likely, actually, happens all the time:
You "fix" it. Somehow. By some miracle. You don't even seem to break anything.
Two years from now, the "Super-Duper Electrical Bonding Compound Series A-723A-P" that you used cannot handle the heat surge. There is a fire. There are several hundred thousand dollars worth of damage, or worse, a person dies.
A full investigation ensues. It is found that some idiot used Super-Duper Electrical Bonding Compound Series A-723A-P to join two wires when, of course, any competent licensed electrician knows perfectly well that since there is a Purple Snoklefactor drawing 23.3 amps off of main bus B, the specs call for Compound A-723-A-PqA-7! You idiot!
The investigators realize that only a talented layman who doesn't do it for a living would have made such a simple mistake. Armed with supeanea power, they swoop in, asking anyone and everyone "Have you ever seen anyone in that box?" Your company, is a desperate attempt to avoid being sued for MILLIONS - I am not exaggerating - of dollars, decides to finger you as the person who made unauthorized repairs, in an attempt to shift at least part of the liability on you. It won't suceed, of course, they will still have to pay something...
Is it really worth it? This type of stuff happens all the time. Electricity is simple, at heart - but the complex interactions that go on in the heart of commercial power should only be tampered with by those who know EXACTLY what they are doing. Otherwise, buildings burn, property is lost, and people die.
Ok folks
I've wired power panels in residential situations. I have NO unreasonable fear of electricity. I used to work professionally in HEAVY duty power electronics (Multiple 10s of KW UPS systems). I've worked on 400Hz AC Power supplies (Hurts more than the 60Hz stuff). I've been zapped by 220 3phase more times than I care to remember, and even 400 volts DC. I used to have lockout tags. At one point I even used to do wiring that required an electrician to sign off on my work, and never had to change anything
You know what I would do in this situation?
CALL AN ELECTRCIAN
Does that sum it up?
-- 73 de KG2V For the Children - RKBA! "You are what you do when it counts" - the Masso
And while we're at it, you've got to also consider P=IV (although in this case the P is quite massive). If the voltage increases, the current must decrease in order to maintain the same power. This is the reason a stun gun won't kill you; it can only pump out X watts.
***
Radio Shack. You've got questions...we've got blank stares(TM).
First: This is important. You want to play with the main breaker box in a serious way, Call the power company, inform them that you need to work on the breaker box in your building. Ask them to come out and switch off the mains at the street! Verify that this was done using a simple volt meter. (you can get a $20 one at radio shack.) A simpler way of doing this is to check to see that a previously working light or outlet is now depowered. To be thorough however you should use the volt meter to check the output of each of the breakers.
Second: Inspect the wiring for Blue/White vs Black/white pairs. Blue and White is the old stuff, and is damn near garaunteed to fail if you try to reuse it. General advice is to give up on any Blue/White pairs if you have any reasonable chance of rewiring those circuits.
Third: Verify that all circuits are hanging off from the correct size breakers. 12 Gague wire can handle up to 20 Amps, 14 Gauge can handle 15 Amps, and 16 gague can handle 10 Amps. Anything wires smaller than that Should Not Be used at the breaker Box You can use a breaker that is rated for a lower amperage than the wire can handle, but not higher. I.E. You can use a 10 amp breaker with 12,14, or 16 gague wire, but a 20 amp breaker can only be used with 12 gauge wire.
Fourth: The mains from the street are 3 major cables. These are different than the wires that go to "normal" outlets and lights in your house. The normal outlets and lights in your house use 1 of the two mains from the street and ground. A 220 Outlet uses both of the mains from the street and ground. Thus a 220 outlet has 220 volts, or 2 110 volt circuits 180 dgrees out of phase for those amatuer electricians in the crowd. What you need in order to wire up 220 outlets are the usual gague wire, but the breaker is different. For a "normal" circuit, only one breaker is neaded because only one of the three wires is "hot" meaning that it sources power. In 220 outlets, two of the wires are "hot". This means that both hot wires need to be connected to a breaker. The same rules for cable sizes applies as before. When running 220, you must use a double breaker of the correct size for your wire. What this does is if one of the two circuits blows the breaker, the breaker will disconnect both "hot" wires, rendering the circuit completely dead.
Fifth: Although it may seem like a good idea, do not use a breaker with any wire that is not "hot" You do not ever want the circumstance where your "hot" wire is powered, but the ground wires are disconnected by a breaker.
Sixth: All of the wiring into the breaker box should be exactly the length needed. No excess wire should be stored in the box. All cables entering the box should be clamped securely in place. (a hardware store will have the clamps for use with just about any breaker box and cable.) The wires in the breaker box should all have their shielding completely intact. Replace any wires for which the shielding is missing or damaged. All wires should be mounted into the breakers such that no unshielded part of the wire is exposed. If it is, disconnect the wire, and trim it such that only shielded portions of the wire are exposed. As a general rule, the breakers should be wired to one and only one wire each. If you do not have enough breakers for all of your devices I strongly recommend buying a bigger breaker box. If you must wire more than one wire to any given breaker, that breakers size should be determined by the size of the smallest wire being connected to it. If you have a brekaer with a 12 gauge and a 16 gauge wire connected, then the breaker should be a 10 amp breaker.
Once you are done, use a standard issue voltmeter to verify that there is no conductivity between any circuits when the breakers are all in the off position. Then, switch the breakers one by one to the on position and make sure
I wish I had a good sig, but all the good ones are copyrighted
In most residential wiring the thing you use to turn the power off to the main circuit box is the meter. You remove the meter, which by the way has a seal on it stamped by the power company, and this removes power from the two phases coming into the house. This is the only safe way to work on a main circuit panel. I do know know what kind of regualations there are where you live but in some places you can remove your own meter but not put it back. In other places you can not remove your own meter.
The reasoning behind laws in regards to not removing your own meter would probably be economic since that would be how you would steal electricy.
One point of contention I have about home wiring is the type of electrical box used to house switches, outlets, and various other junctions of wires. I am curious if anyone else agrees or disagrees with my thoughts on this matter.
The contention I have is this. I think metal boxes are much safer than plastic boxes. My reasoning is as follows.
1. With a metal box which is properly attached to the safety ground you have a situation where a live wire coming loose inside the box and hitting the box will immediately trip a circuit breaker.
2. If the live wire does not come loose but only gets flakey and hot and starts to burn your metal box will not burn along with it. It will still trip the breaker when the wire has burned enough to break free and hit the side of the box.
3. It is obvious to me that plastic boxes will not trip a breaker if a wire gets loose inside them.
4. A plastic box with a hot wire will actually burn and help in the process of burning down your house.
5. I think the only reason electricians started using plastic boxes was because there were cheaper than metal boxes.
6 Saying a plastic box is better because it insulates you and the wires inside from grounding out against the box implies total ignorance of one of the the purposes of a safety ground. It also allows shoddy wiring to go unnoticed longer.
Those are my reasons, what do you think?
dzimmerm
Jumping to correct solutions slowly is better than jumping to incorrect solutions quickly.
Take a look at the BOFH articles: (http://bofh.ntk.net/Bastard.html)
You've got plenty of ideas there about what to do with the main power distribution panel.
And you know what? It could be fun.
- "They misunderestimated me."
Was that before or after you repaired the 2000 volt circuit?
This sig is a figment of your imagination.
With the latter solution, if it hasn't rained for a while, then the ground is too dry and it doesn't drain the power and so flip the MCB (or blow the fuse). With the former solution, bits of corrosion can reduce the conductivity between wire and pipe and they cease to work correctly too.
The modern way of doing it is to stick a diode-based system on the neutral wire (behind the meter) that returns to the power station and attach the ground/earth wires to that. This ensures that any electricity that floods through ground goes straight back to the power station, and that the returning circuit current cannot instead go to earth and flood through someone/something that is touching an earthed item.
Now, even the more modern method relies on a component that could break and you wouldn't know it had broken until too late. This is why plastic is good. The best defense against wires touching the plastic covering and so slowly melting it, is to have a fuse of appropriate size in your plug. Wires only melt when too much current is going through them. If you have a fuse rated lower than the maximum current for all the wires in the device then that will blow before a wire catches fire. All UK plugs have fuses in them (although lazy people often just stick 13 amp fuses in them - even if it is only a lamp). Do US plugs have the same?