I have a spec on a job to ground all columns to a seperate ground rod outside of the building. Trying to understand why they would want that if all the building steel is connected. Also would you run an insulated ground so the bare ground would not bond the rebar in the deck?
grounding columns
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Buck Parrish
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Cavie
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Can you say DA (sorry,unknowing) Engineer?
petersonra
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I saw this once in a very old power plant. They did it because they got hit by lightning and it was part of the new lightning protection scheme.
It was a while ago but, IIRC, they used a bare copper wire (maybe #2) and strung it through the basement lengthwise, with radials out to each column. What I was working on was in the basement so I didn't really see much of what they did upstairs. It seemed to me they used something that looked a lot like a beam clamp to bond it to each column, and it looked like they used the same thing to hold it in place as it ran along the horizontal beams.
I don't know where the wire ended up going after it left the basement though.
It was a while ago but, IIRC, they used a bare copper wire (maybe #2) and strung it through the basement lengthwise, with radials out to each column. What I was working on was in the basement so I didn't really see much of what they did upstairs. It seemed to me they used something that looked a lot like a beam clamp to bond it to each column, and it looked like they used the same thing to hold it in place as it ran along the horizontal beams.
I don't know where the wire ended up going after it left the basement though.
petersonra
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- Northern illinois
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- engineer
I think the separate ground rod he is talking about is a single rod separate from the existing ground rod. Not one for each column.
I might argue this is code acceptable as the existing ground rod should already be bonded to the steel, and effectively what you are doing is bonding the new ground rod to the steel as well.
Seems like an expensive thing to do for no obvious reason.
It is being done because someone does NOT understand grounding and does not care how he spends OPM (other people's money)! I agree, that IF this is installed as an auxiliary ground rod and connected to the electrical grounding electrode system it does not violate the NEC, but I cannot see where it improves anything. The building steel probably is suitable as a grounding electrode itself, so you are effectively "grounding" a grounding electrode! Kind of like installing a ground rod to protect a ground rod....
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