High-Voltage Fences For Zapping Would-Be Copper Thieves

coondoggie writes "It may be a gimmick or the ultimate answer, but a California city this week okay-ed a draft ordinance that would let businesses install 7,000-volt electric fences to protect sites from rampant copper thieves. As reported by the Sacramento CBS station, the reaction from one business owner to the ordinance says it all: 'It'll be a little fun to watch one of these guys get electrocuted holding my fence trying to rob me.'"

Re:If they want to stop the copper thieves...

[Hentes]

This. Most metal salesmen have a pretty good idea which piece of trash came from illegal sources they just turn a blind eye because it's more profit for them.

Re:Yikes...

[mcgrew]

When I was ten (half a century ago), by buddy actually did piss on an electric fence. Poor kid lay there screaming for ten minutes, but there was no permanent damage. I think this is an excellent idea; farmers and ranchers have been using electric fences to keep their animals in for decades, and I have yet to hear of anyone being harmed.

Re:7,000 volts?

[Baloroth]

I'm not a licensed electrician, but 7,000 volts sounds kinda' deadly.

Not really, as they say "current kills", not voltage. Static electric discharges frequently have a higher voltage than that. Lethality depends on a number of different factors. Of course, 7,000 volts of continuous DC current would most certainly be enough to kill most people, but electric fences usually use short pulses rather than continuous flow (at least, animal fences I've worked with, and been shocked by, do).

Re:Yikes...

[Anonymous Coward]

They tested pissing on an electric subway rail and that failed. They then tried the electric fence and it did work. Perhaps you should have watch the WHOLE episode before commenting here.

Re:Yikes...

[aevan]

The busted the third rail, but found electric fence plausible. http://en.wikipedia.org/wiki/MythBusters_(2004_season)#Peeing_on_the_Third_Rail [wikipedia.org]

Re:If they want to stop the copper thieves...

[gewalker]

They passed this in Indiana some years ago, the newspaper generally endorsed it, and the public mostly thought it was a good idea (after all they were not recycling copper frequently, nor were they in the salvage business). I think it is pretty much "sign here" and snap a picture. This did not stop copper theft either.

Electric fence detector

[godel_56]

BTW, if you ever need to determine if your electric fence is switched on or not, without putting your tongue across it, a portable AM radio tuned between stations and held close to the wires will enable the HV pulses to be heard.

Re:It's not the voltage, it's the current...

[viperidaenz]

Yeah, people keep saying that, but its not true. Have a read of ohms law. E=I*R and P=E*I (e=voltage, i=current, r=resistance, p=power) If you want to put 50ma through a person who has 2ko of body resistance, you need 100V. That'll pull 5 watts from the fence. If your electric fence is 10kv but can only deliver 1 watt, the voltage will drop to 45V and the current will be 22ma with a 2k load.

You're pretty safe with anything less than 30ma. Most RCD safety devices wont trip until there is a 30ma leak.

Note to copper thieves - gloves won't work

[raymorris]

I once touched an electric fence with a three foot stick. I got quite a jolt. It's current, amps, that are dangerous, but it's volts that jump through insulation, and these things have a lot of volts. If you're unsure whether gloves, say thick leather work gloves, will help, consider this - an electric fence is designed to drop a 2,000 bull. A bull covered in non-conductive hair, and under that, covered in leather. Hmm, I'm giving advice for THIEVES. Come to think of it, everything I just said is a lie. All you have to do is use your T shirt to cover the wire, so your hands don't touch it directly. It'll work, I promise.

Re:7,000 volts?

[John Hasler]

> I'm not a licensed electrician...

This is clear.

> ...but 7,000 volts sounds kinda' deadly.

Electric fence chargers such as the one I use to keep my horses in put out short high-voltage pulses with an energy per pulse of about 6 Joules. The peak voltage is 5,000 to 10,000 volts. The shock is quite painful but not deadly. It leaves no mark and does no damage. I know this from direct experience.

Re:If they want to stop the copper thieves...

[Runaway1956]

Forms? Not a lot is required. On the sales receipt that the junkyard keeps anyway, just record driver's license number and/or social security number of whoever sold the "scrap" to you.

We had a huge brass nut stolen from work. Damned thing weighed about 70 pounds. Special purpose item, it's made specially for the tie-bars on our machines. I don't know any other equipment that uses such a nut. The thing was shiny-brand-new, waiting to be installed the next morning, when it mysteriously walked out of the plant. $1,800 dollars, just gone, and the machine was going to be down for as long as it took the supplier to get another new nut, and ship it to us.

Several people spread out, and hit every junk yard within 75 miles, inquiring about that special purpose brass nut. It was located, and the proprietor did indeed have the driver's license number of the person who sold it to him.

At this point, the story gets really stupid: no charges were filed. The guilty party is still employed. I don't even know if that guy had to pay the junkyard owner back.

But, a simple driver's license number on the receipt got our nut back, and the machine in operation two days later, which was costing about $15,000 each day it was down.