Gnd rod in handhole

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chris kennedy

chris kennedy

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Miami Fla.
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60 yr old tool twisting electrician
I have 4 handholes between bldgs. The PE's detail shows a 3/4 x 10 foot Cu rod in each made up to the steel cover and the egc. I have a grounding electrode system at both bldgs. Is the rod in the handhole to keep the cover at the same potential as the surrounding soil?
 
chris kennedy said:
... Is the rod in the handhole to keep the cover at the same potential as the surrounding soil? ...
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That might be what the designer is thinking ... it's a far-too-common misconception that adding isolated ground rods somehow promotes safety.

What IS necessary for safety is a low-impedance fault-current path from the handhole back to the ungrounded conductor(s) power source capable of activating the OCPD.

(Which it sounds like you do have since you said that it's all tied-into your EGC)

The following diagrams deal w/ light poles, but the principle is the same.
Step%20Voltage%20I%20.PNG


Step%20Voltage%20II%20.PNG
 
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The engineer could also just be complying with the NEC.

250.32 Two or More Buildings or Structures Supplied from a Common Service.
(A) Grounding Electrode
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IMO the hand hole is a structure.

The only question I have is it 'supplied' by the feeder or is the feeder just passing by.
 
The handhole and a mechcanical connection to the rod are often specified to permit the individual ground rods to be tested for resistance.
Don
 
don_resqcapt19 said:
... The handhole and a mechcanical connection to the rod are often specified to permit the individual ground rods to be tested for resistance ...
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That is understandable for "required" ground rods which are often placed in handholes for that very reason.

But what would you see as the need -- other than the possible "structural requirement" pointed-out by iWire -- to have what appear to be supplemental ground rods connected to the EGC in handholes along a feeder?
 
I don't really think it is needed or useful for voltages under 600 volt.

That said in the scheme of things it will not add much cost and can not that I know of make it 'less safe'.

If its on the prints go ahead and provide it. :)
 
iwire said:
The only question I have is it 'supplied' by the feeder or is the feeder just passing by.
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The conductors pass unbroken through the handholes. The EGC sized as per 250.122(B) is unbroken but stripped enough for a split bolt for jumper to the rods and lids. These are basically pull points in a 700 foot run. And I did look at the NEC def. of structure. So I guess I need to test each rod for 25 or drive 2.:rolleyes:
 
chris kennedy said:
So I guess I need to test each rod for 25 or drive 2.:rolleyes:
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Officially yes if the AHJ feels 250.30(A) applies.

If the AHJ does not feel 250.30(A) applies then no as 'voluntarily added' ground rods do not have to meet the resistance requirements.

If they are on the prints they should have been included in the bid. If you do not provide them a credit needs to be issued to the customer.
 
iwire said:
If they are on the prints they should have been included in the bid. If you do not provide them a credit needs to be issued to the customer.
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Don't get me wrong Bob, they will be installed. I never would have considered a handhole a structure until you pointed that out. So my OP was one of curiosity.
 
mdshunk said:
Curious to know about how far apart these hand holes are? Are they some even interval that would permit future 3 or 4 point FOP tests easily?
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They are just under 200 feet. And what is FOP testing?
 
chris kennedy said:
... I never would have considered a handhole a structure until you [iWire] pointed that out ...
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Nor would have I.

This once again proves that it's always good to examine anything from as many possible "angles / perspectives" as possible.

Thanks iWire.
 
chris kennedy said:
I never would have considered a handhole a structure until you pointed that out.
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The NEC definition of structure is surprising.

It seems unless it grows on it's own it is a structure.
 
iwire said:
The NEC definition of structure is surprising.

It seems unless it grows on it's own it is a structure.
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Interesting, so if I had used PVC or fiberglass handholes I drive a Gnd. rod and terminate it to what? The EGC?
 
chris kennedy said:
Marc, your THE MAN!
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Not really. I'm just speculating, is all. Future FOP testing may be the furthest thing from the engineer's mind. It might just be an old-time hold-over, why he's specifying a ground rod in or near each hand hole. Won't hurt a darned thing, but may offer little extra benefit if an EGC is otherwise present. Bob's "structure" analysis is certainly technically correct, but I privately wonder how often this is recognized in the case of hand hole boxes?
 
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