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,
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.
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.
"This alternating current stuff is just a fad. It is much too dangerous
the straightest answer can only come from your licensed electrician who
knows your code and how it applies to your home/construction
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?:
regarding the rod and bonding and ground loop and more, please read
i was going to quote the parts about grounding and bonding but they are
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. :)
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
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