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Rich–
A grounding clamp for pipe can be made of either bronze or zinc. Visualize a figure-8 with a large loop at the bottom and a small one at the top. The bottom loop is a saddle-style clamp (that swings open) for the pipe and the upper loop is a set screw-type clamp for the wire. The grounding electrode conductor (GEC) should not be clamped directly to the pipe. Usually this is done because the installer is too lazy to manipulate the heavy wire into the proper part of the clamp, or because the clamp is too big for the pipe and the wire takes up the extra space.
There are grounding clamps of bronze for clamping the GEC to a Ufer (rebar) grounding electrode or to a driven ground rod. For these, you lay the wire against electrode and the clamp squeezes the two together. Ground rods are copper plated so no electrolytic action there. And I’ve never heard of any problem with the iron to copper contact between wire and rebar. I use a conductive, anticorrosive grease between Ufer electrode and EGC.
BTW, the gas pipe and the water pipe (if they are metallic) have to be connected to the ground at the service entrance. This is NOT to provide an alternative path to ground; it is to ensure that if a current-carrying conductor comes in contact with the pipe, the breaker will clear the fault. I knew of a plumber who was electrocuted because a gas pipe was hot and not grounded. He was grounded and when he grabbed the pipe, he was killed. Also, any exposed building steel has to be electrically connected to the ground at the service entrance.
Proper grounding is one of the least understood (or most misunderstood) of electrical basics–and I mean among electricians.
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Knowing that connecting copper pipe to galvanized pipe is a no-no, what about copper wire that is clamped onto galvanized water pipes to create an electrical ground? Will this connection remain strong?
*Your suspicions are right - copper & zinc are at opposite ends of the electrochemical scale, and will corrode quickly. I don't know whether there is some kind of special connector that gets around this - ask an electrical supply house or an electrical inspector. The other issue is that you can't trust pipes to be well grounded in the future - somebody is always coming along & splicing in something else.
*Clamped onto the pipe ? Or attached to a clamped that also clamps to the pipe ? I've even seen a supposedly qualified union electrician wrap the braided ground a couple of turns around a pipe and then used the approved clamp - go figure ? Better than seeing someone twisting aluminum and copper togeather in a wire nut.
*Here's a laugh for you - I messaged a friend who's an electrician down-town specializing in upgrading service panels and concersions to buried. I was hoping he could give me some info on the transition clamp. Anyway, he messaged back and said that the other week they found a 200amp service grounded by a 12by10 cabel to the gas pipe.
*Rich--A grounding clamp for pipe can be made of either bronze or zinc. Visualize a figure-8 with a large loop at the bottom and a small one at the top. The bottom loop is a saddle-style clamp (that swings open) for the pipe and the upper loop is a set screw-type clamp for the wire. The grounding electrode conductor (GEC) should not be clamped directly to the pipe. Usually this is done because the installer is too lazy to manipulate the heavy wire into the proper part of the clamp, or because the clamp is too big for the pipe and the wire takes up the extra space.There are grounding clamps of bronze for clamping the GEC to a Ufer (rebar) grounding electrode or to a driven ground rod. For these, you lay the wire against electrode and the clamp squeezes the two together. Ground rods are copper plated so no electrolytic action there. And I've never heard of any problem with the iron to copper contact between wire and rebar. I use a conductive, anticorrosive grease between Ufer electrode and EGC.BTW, the gas pipe and the water pipe (if they are metallic) have to be connected to the ground at the service entrance. This is NOT to provide an alternative path to ground; it is to ensure that if a current-carrying conductor comes in contact with the pipe, the breaker will clear the fault. I knew of a plumber who was electrocuted because a gas pipe was hot and not grounded. He was grounded and when he grabbed the pipe, he was killed. Also, any exposed building steel has to be electrically connected to the ground at the service entrance.Proper grounding is one of the least understood (or most misunderstood) of electrical basics--and I mean among electricians.