Where is Ground Clamps [RE-wrenches]

Jeff Clearwater clrwater at earthlink.net
Mon Apr 21 11:46:21 PDT 2003


<x-flowed>
Hey Jay,

That grounding screw and approved grounding hole from Sharp is a 
joke.   Good example of the disconnect between some designer in some 
office in Sharp, the Code,  and good common sense professional 
installation practices.  If I'm going to ground something to handle 
the 15 amps required and not have it corrode for the life of the 
system, then any electrician knows the difference between a 15 amp 
solid connection and a manufacturer's ground screw that's only use is 
for the miscellaneous bolts recycling container!

I use 1/4" SS button hex head screws - coarse thread -  on the block 
style Aluminum ground lugs with SS external star washers that dig 
into the sides of the oval mounting hole (not the "approved ground 
hole") on the Sharp panels really well.  Tourqed to 10 foot lbs they 
are a far superior ground to any silly 1/16" machined slotted head 
screw that you can barely get a driver on.  I run a continuous 8 
gauge solid CU to every panel down the one continuous line created by 
any unused mounting hole set.

If that voids my UL warranty well then it's the industry that has to 
change - not my practices.  I'm glad to stretch for Code compliance 
but not when it's ridiculous!

Jeff C.
Village Power Design

>Hi John and Bill,
>
>OK, so here is my question.
>
>I'm holding in my hand a "grounding screw" from Sharp/Schott.  This screw is
>SS, is machine thread, and is really really small.  It is so small that it
>will rattle around in the listed grounding hole.  Yes it has a star washer.
>
>How is using this any different than installing a star washer on the frame
>either under the mounting frame or a surface attachment for the top down
>style?
>
>And if the manufacture gives me a grounding screw, can I use anything else
>without voiding the UL warranty?  If so, can I install the ground anywhere,
>or do I have to use the approved grounding hole?
>
>Thanks
>
>jay.
>
>
>>  Jay:
>>
>>  The problem with grounding through the frame is that many of the frames
>>  are anodized aluminum (read as excellent insulator).  Unless the
>>  structure has been evaluated as a grounding member you can't rely on it
>>  to provide the equipment ground.  I think this could be solved with
>>  insulation piercing hardware, e.g. star washers, but so far none of the
>>  structure manufacturers has developed this concept to the point that it
>>  can be listed as a means of grounding.  In absence of Listed "systems"
>>  that provide equivalent grounding means, the Code says you have to run a
>>  ground wire to every module to make sure it stays grounded.  The UL
>>  requirement for a ground is 0.1 Ohms at 60 Hz.  Given that we are
>>  talking about dc I think UL would also want to see a dc impedance
>>  measurement as well.
>>
>>  Based on my own experience I have measured grounding impedances far
>>  above this level when using only the frames for grounding.  Others such
>>  as J. Wiles and B. Brooks have also confirmed high ground impedance on
>>  frames when only the structures are used. Until we have a grounding
>>  structure system I think you have to run a ground wire (even one long
>>  one daisy chanied) to every module.  Also, J. Wiles has convinced me
>>  that all splices in the equipment ground wires should made with "non
>>  removable" pressure connections, i.e. butt splices or ferrules. Just my
>>  $0.02.
>>
>>  If you have any questions or if I may be of any further assistance,
>>  please do not hesitate to contact me.
>>
>>  Best Regards,
>>
>>  John Berdner
>>
>>  SMA America, Inc.
>>  12438-C Loma Rica Road
>>  Grass Valley, CA  95945
>>  530.273.4595 - Tel
>>  530.274.7271 - Fax
>>
>>  -----Original Message-----
>>  From: Jay Peltz, Peltz Power [mailto:jay at asis.com]
>>  Sent: Monday, April 21, 2003 09:50 AM
>>  To: RE-wrenches at topica.com
>>  Subject: Re: Where is Ground Clamps [RE-wrenches]
>>
>>  Hi Dean,
>>
>>  Can you give me the code # that states all panels must be grounded in
>>  addition to the metal frame they are on?
>>
>>  One installer I know puts in the permit all grounding to be done in
>  > accordance with 250.136(a).  This allows for only a single ground wire
>>  from
>>  each seperate array.  Makes it much easier.
>>
>>  thanks,
>>
>>  jay
>>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village

877-SOLARVillage
PO Box 764
Boonville, CA 95415

61 Baker Rd
Shutesbury, MA 01072
413-256-6777, 413-825-0372 (Fax)
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