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,