Forums > Specific Focus > Home, Garden & Construction in Mexico

booboo9

Feb 25, 2007, 8:54 AM

Post #1 of 6 (2315 views)

Shortcut

how does "grounding" pole in the ground work?

Can't Post | Private Reply

what is the mechanism here? why is this necessary; and what is the best way?

raferguson

Mar 24, 2007, 5:28 PM

Post #2 of 6 (2256 views)

Shortcut

Re: [booboo9] how does "grounding" pole in the ground work?

Can't Post | Private Reply

Code in the USA is roughly as follows:

The wires coming from the utility to the house contain a "neutral" wire, and one or two "hot" wires (In a house that is wired for 220VAC, there will be two hot wires). Commercial power feeds often have three phase power and three hot wires. Note that the utility does not provide "ground".

The neutral wire is connected to the ground rod, and to the ground wires going through the house, at the main breaker box or where the power enters the house. Neutral and ground are connected at one, and only one, place in the home's electrical system. (The last code inspection we had done at our house, the inspector made the electrician take out the connection between ground and neutral in the old circuit breaker box, which had become a sub-panel in the new system, due to adding a new breaker box. In other words, we had neutral and ground connected at two spots, no one).

The three wires going to the outlet are hot (black), neutral (white), and ground (bare or green). All three wires go back to the breaker box.

There are a few purposes of the ground wire. First is to keep the voltage in the house tied to ground. Otherwise, a power surge could cause the neutral wire to have a significant voltage relative to ground. This could cause the hot wire to be higher in voltage than intended, relative to ground. Also, neutral, which is normally more or less at ground level, and relatively safe, could become "hot".

Another purpose is a form of lightning protection, again tending to keep the house wiring relatively close to ground during a lightning strike.

Grounding rods, then, are a safety item.

A typical ground rod would be 8 feet long, driven into the ground, made of copper coated steel, connected by a clamp to a heavy copper wire (8ga?) which goes to the breaker box. Note that in very dry sandy soil, a single ground rod may not be adequate, so more than one rod may be used, roughly 8 feet apart. (Dry sandy soil conducts electricity very poorly, so hard to get a good ground).

In some cases, copper water pipes are used instead of ground rods, or as a supplement to a ground rod.

I do not claim to know how or whether US electrical practices can or should be adopted with Mexican utilities. My guess is that these practices can be adopted, but that one would first need to identify which of the cables coming into the house is approximately at ground potential. That cable would be regarded as "neutral", and then tied to ground, and the ground rod, in the breaker box. Perhaps someone is more familiar with Mexican electrical practices, but given that this message has been unanswered for some weeks, it may be that no one here has much expertise in electricity.

I will say that a significant portion of the electrical work that I have seen in Mexico is very poor, so I believe that many of the Mexican electricians have no training, or very low personal standards, or both.

Richard

http://www.fergusonsculpture.com

Papirex

Mar 24, 2007, 7:29 PM

Post #3 of 6 (2245 views)

Shortcut

Re: [raferguson] how does "grounding" pole in the ground work?

Can't Post | Private Reply

Richard, your opinions of the competency and lack of training of the electricians in México coincide with my own observations of them. There are a very few exceptions, I have met a couple of very well qualified electricians here, but they are as rare as hens’ teeth.

The grounding rods I have seen used in México are only about one meter long, that is too short to be efficient, and would not be legal under the US National Electrical code. It is better than nothing though.

Grounding electrical systems in a building by clamping a ground wire to a water pipe used to be a common way to ground a system in The USA. Most plumbing codes now prohibit that practice. It can be dangerous to the occupants of the building under some circumstances.

I have had some heated discussions with electricians that wanted to use my piping systems for grounding their electrical systems in recent years. I often had to call the plumbing and electrical inspectors to convince them that it was no longer legal. Plumbing inspectors will not approve a piping system for use until all wires connected to it are disconnected, and electrical inspectors will not approve an electrical system until it is grounded.

It can be very harmful to the water piping system in a building to connect electrical ground wires to the pipes, particularly if the pipes are copper tubing, being connected to the electrical system may cause the pipes to deteriorate because of electrolysis.

Electrolysis in a piping system is extremely rare; I have seen it twice in my working career in the piping industry. Copper tubing is particularly susceptible to the effects of electrolysis; it will develop microscopic porosity, and begin leaking. If you look at some pipes that have been affected by electrolysis, they will be wet from end to end, and dripping water. If you wipe the pipe dry and watch it, it will slowly become wet and begin dripping again. You will not be able to see where the pipe is leaking; the holes are microscopic.

The only way to repair a system with electrolysis is to remove any and all connections to the electrical system (that can be daunting in a medical building), and replace the entire piping system in the building. I speak from experience on this one, if you only replace the pipes that you can see leaking, you will be back in a month or less to replace some more of them. They have all been damaged, and will continue to fail one by one. You might as well save the time, and re-pipe the entire building without waiting for the rest of the system to fail; it will fail.

Rex

"The supreme happiness of life is the conviction that we are loved" - Victor Hugo

sfmacaws

Mar 24, 2007, 9:28 PM

Post #4 of 6 (2233 views)

Shortcut

Re: [RexC] how does "grounding" pole in the ground work?

Can't Post | Private Reply

Rex, this brings to my mind a water softening thing that some are using in Merida to congeal the minerals out of the water. It's low voltage wires connected to the water pipe (I'm assuming copper) and it is said to create a magnetic field that causes the minerals to come out of solution. They are then easier to deal with or filter out and don't attach to the inside of the pipes. Here's the web site of a recommended model. http://www.waterking.co.uk/...tic_conditioners.htm

I'm not sure if the electricity used to produce the magnetic field is enough to also cause the problems you describe, but I'm interested in what you think.

Jonna - Mérida, Yucatán

Papirex

Mar 24, 2007, 10:45 PM

Post #5 of 6 (2224 views)

Shortcut

Re: [sfmacaws] how does "grounding" pole in the ground work?

Can't Post | Private Reply

Jonna, I can’t give an opinion on this device. The PDF file that I opened hoping to find the specs on the device, just touted its’ effectiveness in removing minerals to make the water softer. I was hoping to find some technical information, and maybe a schematic drawing of how the electrical circuits are connected, etc.

This device is probably safe to use for your piping system. There are many devices that do have electrical connections that are connected to a building’s piping system, water heaters, pumps, etc. What you want to avoid is anything that uses part of the piping system as an electrical conductor. I don’t have enough information to give an opinion one way or another for this one.

This device is manufactured in Great Brittan so I am not familiar with the testing laboratory that they used to certify the device. In The United States, a person should always look for the UL label. UL stands for The Underwriters Laboratory. It is a testing laboratory that is so well respected that many building codes will not approve anything without a UL label on it for use.

A device without a UL label doesn’t mean that it is not safe to use, it just indicates that they have not tested it. If I have a choice, in The States, I will always buy the device with the UL label.

Rex

"The supreme happiness of life is the conviction that we are loved" - Victor Hugo

marquitos

Mar 27, 2007, 9:42 PM

Post #6 of 6 (2183 views)

Shortcut

Re: [RexC] how does "grounding" pole in the ground work?

Can't Post | Private Reply

My experience in guadalaljara is that the utility does a pretty good job of getting grounded power to your meter but once it leaves the meter and enters the house all bets are off as everyone does what is right in his own eyes. Most equipment is readily available in the larger towns but at about twice the price of the same equipment ( hecho en Mexico ) in the states go figure! Most of my Mexican friends commment, " con menos Burros mas elotes." , when I tell them that most of the safety equipment I installed NOB was made in Mexico.

If you need a ground in new construction the best ground available ( and the one required by code in the US) is a # 4 copper wire clamped to a 10 foot piece of horizontal rebar cast into the footing of your wall. However, in the last revision of the code an accepatable substitue in existing systems without ground wires is the istallation of a ground fault circuit interruptor outlet in the circuit. This device costs $ 6 - 12 dollars in the states and 16 - 24 in Mexico. It senses leaks in the electrical circuit and shuts down the circuit before most people even realize they are beginning to be shocked.
No idea is dangerous unless it's the only one you have