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+-- Thread: Ground rods (/showthread.php?tid=7218772)
Ground rods - JTTHECLOCKMAN - 02-12-2016
What is the story behind using 2 ground rods on a service these days. Is this true and where are they to be located and how are they wired and what size wire??? What is actually the logic behind it??? Thanks.
Re: Ground rods - meackerman - 02-13-2016
dunno the whys and whatfors, but when I hooked up my shop's electrical panel the inspector made us drive two long grounding rods, IIRC 8' apart.
Re: Ground rods - Robert Adams - 02-13-2016
Some soils don't have good conductivity and instead of needing pricey test equipment they just require two rods. But often ground rods aren't even used anymore as many are requiring a ufer ground instead which is basically a piece of the rear in the slab instead of a ground rod.
Re: Ground rods - EdL - 02-13-2016
Not always required, best to ask the inspector beforehand.
I installed a 60 amp outdoor service last summer to run a portable office trailer, inspector said 1 rod was fine.
Robert pretty much nailed it, nobody has the equipment to test the conductivity, to cover their arse, you pound a bunch of ground rods in.
Ed
Re: Ground rods - Bob10 - 02-13-2016
Last time I did a new panel one was required at the panel and where the water entered the structure.
Re: Ground rods - meackerman - 02-13-2016
in my case the previous owner ran only 3 wires from the house to the shop, no ground wire. so the inspector made us sink two grounding rods. no water in my shop, that would have been another big can of worms to deal with them on.
Re: Ground rods - Robert Adams - 02-13-2016
meackerman said:
in my case the previous owner ran only 3 wires from the house to the shop, no ground wire. so the inspector made us sink two grounding rods. no water in my shop, that would have been another big can of worms to deal with them on.
I'm surprised you got off that easy. The ground rod is required for outbuildings and so is a 4 wire service. He was a really nice inspector.
I'm not sure why the holdover for grounding water services anymore as most are pex now. We aren't even required to bond the water service on commercial. Give it a few revisions and it'll be ammended.
Funny our hose was built in 1960 and there was no requirement for grounding anything at the time. Have a new panel installed and running it as a sub panel till I get around to swapping to it as the main service... Too much to do...
My shop built by the PO didn't have a ufer ground unfortunately so they drove a ground rod. But they didn't bury the connection so It often gets ripped apart by the weedeater. No such thing as a weedeater proof clamp unfortunately...
Re: Ground rods - meackerman - 02-13-2016
apparently it was grandfathered in because it was put in before 4 wires were required.
its a long run with a few 90s in it so I don't know how we'd pulled a new set of wires.
the electrical coming in was about the only thing that was closely inspected.
Re: Ground rods - Mandrake - 02-13-2016
The NFPA / NEC requires a structure to be grounded either a single point (rod) with less than 25 ohms resistance, or with two rods set far enough apart that they do not electrically interfere with one another.
The type of equipment and effort required to test for the 25 ohm requirement is almost always more expensive than driving a second $6 rod into the ground, so that is what everybody defaults to.
I installed a pair of new rods a few days ago. I epoxied a water hose fitting to a section of 1/2" conduit and made a poor man's water drill. That got the rods all but 2' in. A sledge quickly finished them off. It was muddy, but took about an hour and about $12 in parts and $12 for the rods.
Re: Ground rods - meackerman - 02-14-2016
we used a jack hammer to put my two in. brought the pickup over and started them by standing in the bed of the truck ...