Gas line bonding


I've read a number of newsgroup postings and there is so much disagreement it is hard to get a straight answer. So don't give me the 'asked&answered' response - just save your breath. I might be flogging a dead horse but here we go....
My house was build in the 50's and all of the original outlets were two prong with no grounds. At some point in the last 50 years, before I moved in, someone upgraded the service with a 100 amp panel and added some more outlets which are grounded. I believe there are no grounding rods, only the cold water pipe is being used as the grounding electrode. This is one part that has lots of disagreement but I'm guessing this was up to code when the work was done. Also, this is not really where my question lies. The gas line is also bonded to the cold water pipe and sewer stack in the basement and there is a jumper over the water meter.
I'm thinking of adding a subpanel in the detached garage. It would be a fed through #10 THWN (4 wires) from a 30 amp breaker through existing 1/2" EMT. Can is use RW90 in Canada? Since it's a seperate building I would need to drive a grounding rod at the subpanel to comply with the code. Can you explain why this is necessary? If it's the same building then it is not necessary, right? The neutral and ground at the subpanel would not be bonded. That part makes sense to me. Also, would the gas line in the garage need to be bonded to the ground there? This would seem appropriate to me, but maybe not necessary. For now the ooooold heater chassis is not grounded.
Thanks for your time,
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J wrote:

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J wrote:

I'm an old telephone installer. we were told that a cold water pipe is a far better (reliable) ground than a ground rod.
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I believe this is mostly true assuming the cold water pipe is buried sufficiently deep and has a long run that result in earth contact area greater than a standard 3/4" x 10' ground rod. If I remember correctly, horizontally placed conductors like the cold water pipe has lower resistance to ground and the ground rod has better ground stability (that is, resistance to ground does no fluctuate as much due to changes in soil conditions). Anyway, by connecting the cold water pipe to the ground rod, you have the best of both worlds.
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J wrote:

J The answers I'm about to give are based on what I believe to be good practice but I have no knowledge of the Canadian Electric Code. The bonding arrangement you describe in your home would be perfectly normal under the US National Electric Code.
In general the Equipment Grounding Conductor of the circuit that is the likely source of the power to energize the gas line is considered sufficient bonding of the gas line under US codes. There is no harm in installing a separate bonding conductor to the gas line and that may be required if there is no electric circuit, which includes an Equipment Grounding Conductor, to the gas heater.
The reason that you should construct a Grounding Electrode System at the separate building is to reduce the likelihood of damage from lightning or a power cross to the supply wiring.
You said you would be using an existing EMT raceway to run your wiring so you won't be doing new trenching. That means that to build a better Grounding Electrode System than the minimum two driven rods you would have to excavate for that purpose. If your just using the garage to store and service vehicles that would not be warranted. If you have other uses in mind for the garage please say so.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
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the straightest answer can only come from your licensed electrician who knows your code and how it applies to your home/construction type/soil/climate. buffalo ny, from a non-electrician: your local electrician must be asked because some soil and climate conditions at your home address do not offer to you the otherwise good grounding practices we might suggest to you. gas: in some repiped areas like here the new underground gas lines are plastic, and connect to metal to meters outside the home. the ground rod idea may not necessarily apply, would you be creating an unwanted ground loop at the garage?: http://en.wikipedia.org/wiki/Ground_loop regarding the rod and bonding and ground loop and more, please read thoroughly: http://www.faqs.org/faqs/electrical-wiring/part1 / i was going to quote the parts about grounding and bonding but they are lengthy; you will find canada is included throughout the faq. as electrical codes evolve over the years to make life safer, we scratch our heads and wish the electrons were more visible as they run around in our main panel connections. :)
J wrote:

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Note, while internal gas lines should be bonded to a ground connection, it is not legal nor safe to use a gas line as a ground. Many areas now use plastic gas mains and service connections and will not have a ground available. Areas with steel or cast iron mains and service lines will have an insulated connection at the meter to prevent the internal ground from connecting to the underground mains and disrupting the anode corrosion protection that the gas utility uses to prevent the steel mains from rusting out.

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