<div dir="ltr">Gary - The tool is designed to measure the ground impedance for a grounding electrode by measuring the impedance through the earth and back through the service ground (which is assumed to have near zero impedance). I think it induces a current in the conductor and determines how much EMF it takes to push those electrons (R = V / I). For this to work it only measures a single connection to earth, and all other connections to earth are basically the return path. I was trying to use it on a system without a return path so it makes sense that I was getting a high reading.<div dir="ltr">
<div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><br><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><br><div><br></div><div><div><p class="MsoNormal"><span style="color:rgb(56,118,29)">For a brighter energy future,<br>
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</div></div></div></div></div></div></div></div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><p><span style="color:rgb(20,125,186)"></span><span style="color:rgb(20,125,186)"><img src="cid:image001.jpg@01CD17CF.85626660" alt="24 copy.jpg" border="0" height="133" width="200"></span><br>
<span style="color:rgb(20,125,186)"><br></span>"Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!"<br>
<br>~William McDonough</p><div><div><br></div></div></div>
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<div><br></div><div><br></div><div><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Jan 15, 2014 at 7:03 PM, Bill Brooks <span dir="ltr"><<a href="mailto:billbrooks7@yahoo.com" target="_blank">billbrooks7@yahoo.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Andy,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Larger cable tray systems have expansion joints (125 feet or more). If bonding jumpers are not placed around these joints, you will get a high reading.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">However, it may just be that your meter is flaking out with the long path to earth. I would try another meter before I would believe your high readings.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Bill.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a> [mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Andrew Truitt<br>
<b>Sent:</b> Tuesday, January 14, 2014 8:55 PM<br><b>To:</b> RE-wrenches</span></p><div class="im"><br><b>Subject:</b> Re: [RE-wrenches] EGC ground impedance<u></u><u></u></div><p></p><p class="MsoNormal"><u></u> <u></u></p>
<div><p class="MsoNormal">Bill - I'm using an Amprobe DGC-1000A. I let it self-calibrate and then simply clamp it on to a conductor, and it reads the impedance to ground (<a href="http://content.amprobe.com/manualsA/DGC1000.pdf" target="_blank">http://content.amprobe.com/manualsA/DGC1000.pdf</a>). I used it on a well grounded RBI system (driven piles) a few months ago and it measured ground impedances of less than 25 Ohms for all EGCs, as expected for a system with so much contact between the metal structure and earth.<u></u><u></u></p>
<div><div class="h5"><div><p class="MsoNormal"><u></u> <u></u></p></div><div><p class="MsoNormal">Ray - The tray does make a good conductor. I did some more testing and any point along the tray itself gives less than 10 Ohms; its only the #10 conductors between the array and the tray where the impedance spikes. The conductors are bonded to the tray with torqued, star-washered, copper/stainless lay-in lugs. There are no ground rods in the system due to the requirements of the capped landfill, but there is a UFER ground at the equipment pad that gives readings of < 1 Ohm for the GEC.<u></u><u></u></p>
</div><div><p class="MsoNormal"><u></u> <u></u></p></div><div><div><div><div><div><div><div><div><div><div><p class="MsoNormal"><u></u> <u></u></p><div><p class="MsoNormal"><u></u> <u></u></p></div><div><div><p class="MsoNormal">
<span style="color:#38761d">For a brighter energy future,<br><br><br>Andrew Truitt </span><u></u><u></u></p></div><div><p class="MsoNormal"><span style="color:#38761d">Principal<br>Truitt Renewable Energy Consulting, LLC</span><u></u><u></u></p>
</div><div><p class="MsoNormal"><span style="color:#38761d"><a href="tel:%28202%29%20486-7507" target="_blank">(202) 486-7507</a></span><u></u><u></u></p><p class="MsoNormal"><a href="http://www.linkedin.com/pub/andrew-truitt/8/622/713" target="_blank">LinkedIn Profile</a><u></u><u></u></p>
<p class="MsoNormal"><a href="http://truittreconsulting.weebly.com/" target="_blank">Company Website</a><u></u><u></u></p><p class="MsoNormal"><span style="color:#38761d">NABCEP Certified PV Installation Professional ID: 032407-66</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#38761d">Colorado Journeyman Electrician License No.: 600132</span><u></u><u></u></p></div></div></div></div></div></div></div></div><div><div><div><div><div><p><span style="color:#147dba"><img border="0" width="200" height="133" src="cid:image003.jpg@01CF11E1.65C92AB0" alt="24 copy.jpg"></span><br>
<span style="color:#147dba"><br></span>"Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!"<br>
<br>~William McDonough<u></u><u></u></p><div><div><p class="MsoNormal"><u></u> <u></u></p></div></div></div><p class="MsoNormal" style="margin-bottom:12.0pt"><u></u> <u></u></p></div></div></div></div></div><p class="MsoNormal">
<u></u> <u></u></p></div><p class="MsoNormal"><u></u> <u></u></p></div><div><p class="MsoNormal" style="margin-bottom:12.0pt"><u></u> <u></u></p><div><p class="MsoNormal">On Tue, Jan 14, 2014 at 10:47 PM, Bill Brooks <<a href="mailto:billbrooks7@yahoo.com" target="_blank">billbrooks7@yahoo.com</a>> wrote:<u></u><u></u></p>
<blockquote style="border:none;border-left:solid #cccccc 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in"><div><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Andy,</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">How are you testing the ground impedance of the EGC?</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Bill.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p><p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a> [mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Andrew Truitt<br>
<b>Sent:</b> Tuesday, January 14, 2014 7:25 AM<br><b>To:</b> RE-wrenches<br><b>Subject:</b> [RE-wrenches] EGC ground impedance</span><u></u><u></u></p><div><div><p class="MsoNormal"> <u></u><u></u></p><div><p class="MsoNormal">
Wrenches - What do you consider to be a safe ground impedance for a PV array equipment grounding conductor? NEC2011 250.53(A) says that if the impedance between the grounding <i>electrode</i> and earth is less than 25 ohms then no supplementary grounding electrode is needed, but I'm not clear on what that means for the ground impedance measurement within the array. For example, I am inspecting a ballasted landfill system (i.e. no penetrating the earth allowed - just a UFER at the equipment pad) where the ground impedance at the GEC is very low (<1 Ohm), but the array EGCs are showing ground impedances of between 500 and 1000 Ohms. The EGCs (#4) are connected to Cope cable trays, which are in turn connected to the inverter grounding bar via #4 bonding jumpers. The cable tray is grounded per manufacturer specs (large bonding jumpers at each joint), but the runs can be quite long (300'+) with many connections, though nothing appears to be loose. I intend to recommend that continuous conductors be installed to reduce array ground impedance, but any input on the issue would be very much appreciated.<u></u><u></u></p>
<div><div><div><div><div><p class="MsoNormal"> <u></u><u></u></p><div><div><div><div><p class="MsoNormal"> <u></u><u></u></p><div><p class="MsoNormal"> <u></u><u></u></p></div><div><div><p class="MsoNormal"><span style="color:#38761d">For a brighter energy future,<br>
<br><br>Andrew Truitt </span><u></u><u></u></p></div><div><p class="MsoNormal"><span style="color:#38761d">Principal<br>Truitt Renewable Energy Consulting, LLC</span><u></u><u></u></p></div><div><p class="MsoNormal"><span style="color:#38761d"><a href="tel:%28202%29%20486-7507" target="_blank">(202) 486-7507</a></span><u></u><u></u></p>
<p class="MsoNormal"><a href="http://www.linkedin.com/pub/andrew-truitt/8/622/713" target="_blank">LinkedIn Profile</a><u></u><u></u></p><p class="MsoNormal"><a href="http://truittreconsulting.weebly.com/" target="_blank">Company Website</a><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#38761d">NABCEP Certified PV Installation Professional ID: 032407-66</span><u></u><u></u></p><p class="MsoNormal"><span style="color:#38761d">Colorado Journeyman Electrician License No.: 600132</span><u></u><u></u></p>
</div></div></div></div></div></div></div></div><div><div><div><div><div><p><span style="color:#147dba"><img border="0" width="200" height="133" src="cid:image004.jpg@01CF11E1.65C92AB0" alt="24 copy.jpg"></span><br><span style="color:#147dba"><br>
</span>"Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!"<br>
<br>~William McDonough<u></u><u></u></p><div><div><p class="MsoNormal"> <u></u><u></u></p></div></div></div><p class="MsoNormal" style="margin-bottom:12.0pt"> <u></u><u></u></p></div></div></div></div></div><p class="MsoNormal">
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