Words of wisdom Ray! One has to occasionally measure the impedance especially if you are in lightning country!
I wish the midnite spd's had another blue led that told you impedance was in a good range. Probably not easy, but a nice dream! Dave Angelini Offgrid Solar "we go where powerlines don't" http://members.sti.net/offgridsolar/ [1] e-mail offgridso...@sti.net [2] text 209 813 0060 On Fri, 25 Jun 2021 12:16:18 -0400, Ray wrote: Copper can get a pretty good oxide layer on it as well, but I'm not versed in the science enough to know how any of that effects the conductivity. Instead, I assume that the NEC has investigated corrosion, and so we just follow the code. For plate electrodes (250.52(A)(7)), it just specifies dimensions and thickness, and specifically mentions bare iron or steel. 250.52(A)(3)(_1_) for Concrete encased electrodes (UFER) also allows bare steel reinforcing rod, while section (_2_) allows your #4 copper UFER. Lacking further information, I just go with the code, and my own ground impedance measurements over the years. My small sampling of measurements has found steel rebar grounds and large steel pipe (4"D and larger) to be under 25 ohms, while I have measured copper coated rods as high as 700 ohms in dry soil. I haven't measure copper UFER or compared it to steel, so again, I don't know. It might be better than steel, but all are allowed by code. Ultimately it might come down to soil and weather conditions for different areas? Ray Walters Remote Solar 303 505-8760 On 6/25/21 10:35 AM, Dana Orzel wrote: That's why we use the Ufer, our AHJ assumes that once a layer of rust develops this is not valid........... Dana Orzel Great Solar Works, Inc. C - 208.721.7003 d...@solarwork.com [3] Idaho Contractor - # 028765 Idaho PV # 028374 NABCEP # 051112-136 www.greatsolarworks.com [4] "Responsible Technologies for Responsible People since 1988" Please consider the environment before printing this email. -----Original Message----- From: RE-wrenches [5] On Behalf Of Ray Sent: Thursday, June 24, 2021 4:51 PM To: re-wrenches@lists.re-wrenches.org [6] Subject: Re: [RE-wrenches] Grounding Top of Pole Mount Array with a Ufer We always put our assumption in our plan notes, based on our interpretation of 250.52(A)(7). AHJs have never questioned it, and we also tie the pole to any rebar, so its all one big happy grounding electrode. Ray Walters Remote Solar 303 505-8760 On 6/24/21 6:49 PM, frenergy wrote: Ray, I couldn't agree more, its been my experience over the years that using 20 feet of #4 rebar in a building's footing was kosher and accepted NEC 250.52(3). There's a heck of a lot more surface area in 8" pipe 5-6 feet into the earth than rebar in a foundation footing. The ground at the bottom of the pole footing is also more likely to be damper. Our AHJ has always accepted the steel pole as a ground rod....common sense prevails sometimes. Bill Feather River Solar Electric Bill Battagin, Owner 4291 Nelson St. Taylorsville, CA 95983 530.284.7849 CA Lic 874049 www.frenergy.net [7] On 6/24/2021 7:31 AM, Ray wrote: Usually a steel pole in concrete has enough surface area to qualify as a plate electrode under 250.52(A)(7). It needs to be at least 2 sq ft and 1/4" thick, and have an electrically conductive surface. So we just drill and tap our ground connection into the pole, near the combiner box. Ray Walters Remote Solar 303 505-8760 On 6/24/21 8:16 AM, Dana Orzel wrote: For all of our free standing arrays we now use a Ufer clamp to the rebar either cage or just anti spin rebar that is welded to the pole in the concrete, with #4 braided copper up to the pole combiner box, inverter, etc. for our ground. With a pole mount & a concrete base it is way easier & less expensive than a ground rod, & the inspector seems happier with this approach. Dana Orzel Great Solar Works, Inc. C - 208.721.7003 d...@solarwork.com [8] Idaho Contractor - # 028765 Idaho PV # 028374 NABCEP # 051112-136 www.greatsolarworks.com [9] "Responsible Technologies for Responsible People since 1988" Please consider the environment before printing this email. -----Original Message----- From: RE-wrenches [10] On Behalf Of palumbo1...@gmail.com [11] Sent: Wednesday, June 23, 2021 9:33 PM To: RE-wrenches [12] Subject: Re: [RE-wrenches] Top of Pole Mount Array on Ledge Ben, There is a way if the ledge is solid and true. Twice I have done the following with ledge at 18" to 24" below grade. Excavate down to ledge, drill down into the ledge and you will determine the suitability of the following method. Drill for a pattern of many rebar penetrations in to the ledge. Drill to a reasonable depth (as deep into the ledge as you are able) in my case it was based on our drilling tool and bit length capabilities. We used a large sono tube. 42" as a recall, both of these jobs were over 12 years ago and my recall on the exact size may be off. Determine the best adhesive product to use in your drilled holes for the rebar, again my memory fails as to what we used based on recommendation from a local civil engineer. The sono tube height above grade was determined to be 2' for one TPM12 and 3.5' above grade for a TPM16. Depth down to the ledge determines how high above grade you need the concrete footing/base. Use rebar lengths that will end a few inches below the finished surface. For grounding you can coil up ground wire and lay it on the surface of the ledge before your concrete pour. I ran the ground wire through a short length of 1/2" or 3/4" PVC conduit, to protect the copper ground wire where it comes out of the concrete. Place the conduit coming out of the concrete with the ground wire just to the side of where the mounting plate base for the TPM will be and fill the PVC conduit with a good caulk sealer to keep air and water out of this hole as a nexus of concrete, and air will corrode the copper. The TPM's for those two jobs were made of 8" SCHD 80 steel, we had a large plate welded to the bottom with 4 vertical side supports on the pipe up about a foot. Place the appropriate sized anchor bolts in the concrete pour to match your TPM base. Both of these TPM's have worked out well over the years. Local conditions will determine the suitability of this method. Sent from my iPhone _______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org [13] List Address: RE-wrenches@lists.re-wrenches.org [14] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org [15] There are two list archives for searching. When one doesn't work, try the other: https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ [16] http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org [17] List rules & etiquette: http://www.re-wrenches.org/etiquette.htm [18] Check out or update participant bios: http://www.members.re-wrenches.org [19] _______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org [20] List Address: RE-wrenches@lists.re-wrenches.org [21] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org [22] There are two list archives for searching. When one doesn't work, try the other: https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ [23] http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org [24] List rules & etiquette: http://www.re-wrenches.org/etiquette.htm [25] Check out or update participant bios: http://www.members.re-wrenches.org [26] Links: ------ [1] http://members.sti.net/offgridsolar/ [2] mailto:offgridso...@sti.net [3] mailto:d...@solarwork.com [4] http://www.greatsolarworks.com [5] mailto:re-wrenches-boun...@lists.re-wrenches.org [6] mailto:re-wrenches@lists.re-wrenches.org [7] http://www.frenergy.net [8] mailto:d...@solarwork.com [9] http://www.greatsolarworks.com [10] mailto:re-wrenches-boun...@lists.re-wrenches.org [11] mailto:palumbo1...@gmail.com [12] mailto:re-wrenches@lists.re-wrenches.org [13] http://re-wrenches.org [14] mailto:RE-wrenches@lists.re-wrenches.org [15] http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org [16] https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ [17] http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org [18] http://www.re-wrenches.org/etiquette.htm [19] http://www.members.re-wrenches.org [20] http://re-wrenches.org [21] mailto:RE-wrenches@lists.re-wrenches.org [22] http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org [23] https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ [24] http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org [25] http://www.re-wrenches.org/etiquette.htm [26] http://www.members.re-wrenches.org
_______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org There are two list archives for searching. When one doesn't work, try the other: https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out or update participant bios: http://www.members.re-wrenches.org
