[RE-wrenches] ground

James Rudolph jamesrudolph99 at gmail.com
Sun Oct 2 08:20:02 PDT 2011


I agree with Ray. The best ground clamp I have found for the money ($1600)
is the Fluke 1630 ,its real easy to use and work well.

On Sat, Oct 1, 2011 at 1:41 AM, Ray Walters <ray at solarray.com> wrote:

> I'm a big fan of grounding at the array, and was sorry to lose 690.47D
> (which also clearly allowed the structure to be considered an electrode) .
> I think if you look at the sq ft. of metal in contact with the concrete,
> you can make a credible case for the frame fitting the definition of an
> electrode. IMHO, it's all about a low impedance path to ground.  Whether
> it's 20 ft of 1/2" rebar, or 4 ft of 6" diam pipe, or 4 ft of 2" x 2" angle
> iron, its all roughly the same required 2 sq ft of surface area in contact
> with the concrete.
>
> Actually if you want to be a real stickler and also enforce 250.53A2, a
> tough AHJ might demand 2 electrodes at the array in addition to the
> structural grounding all ready present.
> Me? I like the exception if the measured ground impedance is less than 25
> ohm. Most inspectors will be more than satisfied, if you just show them a
> quick reading with a clamp-on ground impedance tester.
> What If you're still over 25 ohms? If you're in lightning country, you
> really should sink another electrode anyway.
>
> Ray
>
>
>  On 9/30/2011 7:04 PM, Kent Osterberg wrote:
>
>> Ray,
>>
>> I believe that a pole-mounted or grounded-mounted PV array is considered a
>> structure and requires a ground electrode per 250.32.  Perhaps the exception
>> would cover the possibility a installing very small system without a ground
>> electrode.
>>
>> Kent Osterberg
>> Blue Mountain Solar, Inc.
>>
>>
>>
>> Ray Walters wrote:
>>
>>> I've also used 250.52A(7) defining plate electrodes. A 6" Sch 40 pipe 4
>>> ft in the ground has more than the required 2 sq ft of surface metal, and is
>>> at least the required 1/4" thickness.
>>> Also, the 2011 NEC dropped 690.47 D which required a grounding electrode
>>> at the array. Are you sure you still need this? I believe 2011 only requires
>>> you bond all the metal to the EGC, as always.
>>>
>>> Ray Walters
>>>
>>> On 9/30/2011 8:24 AM, Kent Osterberg wrote:
>>>
>>>> The requirements listed in 250.52(3) were changed in 2011. The rebar
>>>> used is allowed to be near the bottom of the footing or in vertical
>>>> foundation walls that are in direct contact with earth. If there was in
>>>> doubt in the past that the rebar in the concrete of a pole mount was a
>>>> suitable grounding electrode, the changes in 2011 should remove it.
>>>>
>>>> Kent Osterberg
>>>> Blue Mountain Solar, Inc.
>>>>
>>>> Richard L Ratico wrote:
>>>>
>>>>> As Dan points out, 250.52(A)(3) specifies several installation
>>>>> requirements in
>>>>> order for a concrete encased electode to qualify as a permitted
>>>>> Grounding
>>>>> Electrode. A pole mount foundation would certainly qualify if it met
>>>>> those
>>>>> requirements.
>>>>>
>>>>> Even if the requirements are not met, IMHO, any opportunity to
>>>>> inexpensively
>>>>> increase the grounding integrity of a system should not be overlooked,
>>>>> particularly in lightning country. Of course, a code compliant
>>>>> Grounding
>>>>> Electrode System is still required. Bonding a non compliant, but never
>>>>> the less,
>>>>> very substantial additional "electrode" to that system would not hurt
>>>>> anything
>>>>> and quite possibly help considerably.
>>>>> Dick Ratico
>>>>> Solarwind Electric
>>>>>
>>>>
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-- 
*James B Rudolph
NABCEP Certified PV Installer

*
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