Ground Rod Tricks ?

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flashlight

Senior Member
Location
NY, NY
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Electrician, semi-retired
We did a new meter pan/disco for a small store in a 40-apartment building. We tapped the 500mcm feeders from a 400A disconnect which is fed from the street. The POCO has asked for an additional driven ground rod for our meter pan. We hit something hard about 2 feet down, maybe a stone footer for bsmt walls ? No luck getting through it, changing locations, etc. (3/8 bit goes through it past 3 ft. and it gets easier.)However, can't drive rod. Any tricks ? Or are we stuck the 200 + bucks for a 3-foot 5/8 sds bit to get past the rubble ?
 
raider1 said:
Can you dig a trench 30" deep and lay the rod in the trench?

Take a look at 250.53(G).

Chris
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Like Chris stated, either lay the rod down or use a plate electrode which also requires only 30" of depth.
 
480sparky said:
If it's only 2' down, dig it up and see what it is.
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Yeah... sometimes it's hard for a reason!

Last year I was working at a power plant that was adding on some pollution control. They were drilling to pour concrete pilings. In one spot they hit something hard. The position was marked by the surveyors, so the drillers kept drilling right through the hard stuff until they saw a bunch of wire come up out of the whole. They had drilled through a duct bank, cutting the feeds for the water cooling tower pumps. The surveyors mark was six feet off. Fortunately, the top duct was for the control wiring. The motor feeders were 13.8kV. Also fortunate was that there were spare ducts. Took two 8-man crews 72 hours to get the pumps back up and runnning.
 
flashlight said:
Any tricks ? Or are we stuck the 200 + bucks for a 3-foot 5/8 sds bit to get past the rubble ?
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Can you move farther away from the wall?

I noticed a 66" long (yes, 5.5 feet) 5/8" SDS-Max on the Bay right now for about $300. Now, that's a bit!

(I used ... sds 5/8 ... as search words.)
 
Smart $ said:
Yeah... sometimes it's hard for a reason!

... Took two 8-man crews 72 hours to get the pumps back up and runnning.
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Yow ! I wonder who paid for that ? Probably we did somehow ...

Thanks for suggestions. The area in bsmt. we are working is small and
tight, trenching would be a problem.

Will rent a 36 in SDS bit today (the longest they have) and see how that
works. Will also try to get rod pounding attachment, did not know about those.
 
flashlight said:
The area in bsmt. we are working is small and tight, trenching would be a problem.
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RICK NAPIER said:
I you are in a basement you are already under 30" from ground level if you go out the wall. Use a ten foot rod to assure 8" of earth contact.
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I was gonna make the same suggestion as soon as I saw basement:

If the basement floor is deep enough, you could drill through the wall and drive the rod horizontally (or at a downward angle.)
 
LarryFine said:
If the basement floor is deep enough, you could drill through the wall and drive the rod horizontally (or at a downward angle.)
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This is in NYC so I would rather take my chances with what is under the building rather than punching out under the sidewalk and into what unknown utilities ! (Call for a paint-up, sure, how much time do you have ?)

We did use the longer SDS bit and got through the rubble into soft/wet stuff.
(Wish I had the $$ for that five foot bit on the bay!) ;)
 
I drove ground rods with a pneumatic jackhammer one time. It thumped them right in. Had about 20 rods to drive. Carried the jackhammer around with a fork lift and slung it on the ground rods. Was pretty slick.

Roto hammer attachment is probably your best bet.
 
we dont have much for basements around here, so guys that have drilled the wall and shot the rod out horizontal, do you seal the hole around the rod when you are done or just leave it?

~Matt
 
nyhockey said:
Flashlight, In stead of the ground rod can't you just go to building steal? NYC is all rock .
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NYhockey, yeah it sure is all rock, except around the edges where it's filled in marshland. (Filled in with rock sometimes !) A lot of older buildings only have a water ground so for new services on old systems they're requiring driven grounds. Worked on a building today with NO ground, it was only a water ground and a plumber had disconnected it. If you tested for ground you still got it probably due to various pipe runs connected to building's structure. But maybe more precise testing meter would show high resistance.

Solved last one with long drill bit, but need to get driving attachment for SDS
hammer drill.
 
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