Tuesday, January 31, 2012


One of the joys of Mexican electricity is the opportunity to meet it up close and personal.

I am not talking about the usual Gordian knot of power lines seen on many Mexican electrical poles -- even though they would make an interesting post.

What I am talking about is the almost universal lack of grounding in Mexican electrical systems.  Now, I know that sentence is not scientifically accurate.  After all, electrical current is always grounded at one point.  And that point, in an Mexican home, is likely to be you.

It certainly has been me recently.

I have a computer station in my living room where all of my computer gear is hooked up to one extension cord that runs through both a surge protector, and a combined voltage regulator and battery backup.

It looks quite impressive.  Maybe a bit too many bare cords for the feminine eye.  But it appeals to my testosterone-driven sense of technology

But like most apparently impressive systems, it is an illusion.  Because the electrical system to my house has no built-in grounding, touching any metal part on my computer table will give me a bigger jolt than Newt Gingrich endorsing Barak Obama.

And I have discovered the same problem with my new notebook computer.  Having taken to my sick bed, I brought it along for a bit of diversion.   A few moments ago, I stood up while holding it.  A radio falling into a bath tub could not have given me a larger jolt.

Well, I suppose it could have.  But the distinction was academic while it was happening.  Apparently, my bed was not a very good electrical conductor. But the moment my foot hit the tile floor, resistance was no longer futile.

The problem is hardly exclusive to Mexico.  I remember when I was growing up, there was at least one table or floor lamp that offered a shocking experience when turning it off and on.

But I am certain that the random electricity running through my computer systems cannot be good for them.  And my constant nomination to be the next Reddy Kilowatt is probably doing nothing for me, either.

There are some things about Mexico I am happy to keep impersonal.


sparks said...

I lived in a house in Seattle (computer age) that was still knob and tube wiring ... which means 2 wires.  I had to spilt out the ground wire from a multi-plug outlet and attach it to a metal drain pipe.  If all your water pipes are plastic here then I guess it's up to you to install a ground rod and connect to it.  Better than the shocks and possible loss of computer parts

Kim G said...

In all a/c electrical systems (wall outlet power), there's one "hot" wire and one "netural" or grounded wire. In the USA, we have a third prong which is also grounded, but if you go back to the circuit box, you'll find that it's connected to the same spot as the neutral wire. And you are probably old enough to realize that three-prong plugs are a lot more common than they were in your youth.

The reason for this third prong is a form of double-safety. First, any three-prong plug is impossible to insert incorrectly. But it's also much harder for an electrician to wire incorrectly, so it's a double-safe system. And that third prong is also wired to the chassis of newer electrical devices so even if something goes wrong upstream, if there's a short in the device, the electricity goes back to ground and not through your body.

However, you'll also notice that in the USA almost all outlets have different sized slots for two-prong plugs. The wider slot is the neutral/ground and the narrower slot is the hot wire. This is also a relatively newer invention, and is also a safety feature as it keeps the hot side of the outlet away from the metal surfaces of devices with only two prong plugs.

In Mexico, most outlets, particularly residential ones, are only two-prong, and I'm not sure if they are polarized, with one wider slot. If both slots are the same size, you need to unplug the offending appliance, rotate the plug 180 degrees, and reinsert it. This should solve the problem. If you can't do this, then your outlet has been wired incorrectly. If you are feeling bold, TURN OFF THE CIRCUIT BREAKER and then pull out the outlet, and reverse the wires inside. Otherwise call an electrician to do this. You can also buy a small device called a receptacle or outlet tester for less than $10USD to test your outlets (only works in 3-prong, but with an adaptor would at least tell you whether the polarity is correct.)

If you don't do any of the above, you could be in some real danger of a shock, so I wouldn't delay.

Here's an article with more detail if you are curious: http://amasci.com/amateur/whygnd.html


Kim G
Boston, MA
Where we've done a lot of wiring in our own house, so are fairly up on these things.

Kwallelno said...

The common is a ground. In the US the white wire is common, the black wire is hot. The ground wire and the common wire hook up to the same place in the fuse box.
The reason we have an extra ground is for extra protection in case the hot wire comes in contact with the common. If it is a good contact, the fuse will blow or trip. You may have a case of a little bit of contact with the ground/common, maybe a bad switch or plug. I would be willing to bet that you have braided wire instead of solid wire, one little bit of one of those connections has gone a little rouge on you. I had a plug go bad on my dishwasher last week. The thing quit. I pulled it out from under the counter, went to unplug the dishwasher and got drilled. I took the plug apart and there was a wee bit of stray wire from the hot side visiting the common side. A guy with a meter should be able to track down the leak. It is not good to have one's wires crossed.
 Another problem could be the ground at the fuse box. People who live on sand have problems with grounding. The sand dries out and you lose some of that common ground. I live on sand. I have my system grounded, with copper rod in three different locations.
 Good luck with this Steve, it is not the kind of problem that you have to live with, it can be fixed.
 And using a water pipe for a ground can get you killed.    

Steve Cotton said...

Thanks, Kim. No polarized outlets here. The offending outlet in the bedroom pretends to be a three-prong, but a quick look shows it is just a masquerade, I will get a 3-2 adapter to try your theory. Right now, of course, I can't reverse the plugs.

Steve Cotton said...

I will start my experiments when I return from China.

Kim G said...

If you have a three-prong plug and are plugging it into a three-prong  outlet and having this problem, I am 99% sure that your outlet is wired incorrectly. You really should get this fixed ASAP as any shock could be fatal.  At the very least, please be sure you are wearing shoes or sandals before using anything plugged into that outlet.

Kim G

Steve Cotton said...

My house in Salem had similar problems.  But I never had any shocks through my appliances.

Steve Cotton said...

Or stay in bed to reduce my own grounding effect. And, if worse comes to worse, I will be bed-ready for the coroner.

John Calypso said...

Timely post for me as I am doing some house wiring improvements in Puerto (some just yesterday ;-)  I will tie my next Blog entry to this - so Stay Tuned!

Felipe Zapata said...

One of the many excellent reasons to build one's own home in Mexico. Do it right.

sparks said...

I had one of those $300 peso voltage regulators (small metal box) that are suggested for general appliances.  It became corroded in our famous Melaque humidity and developed an inside short.  Touch the box and it would knock you soxs off

Steve Cotton said...

I never thought about the obvious culprit of humidity.

Steve Cotton said...

You wrote about this point, I think, in one of your home construction posts.

Steve Cotton said...

Shock terapy reduces memory.  So th say. :}