Because the ground is not fuse protected. A short from the conduit to grounded frames and then to the "grounded" conductor passes through the comon "gronded conductor" bus to all of the modules in that string and all other strings that share that "grounded conductor bus" which is probibly all the modules in the array. Darryl
--- On Mon, 10/18/10, Nick Soleil <nicksoleilso...@yahoo.com> wrote: From: Nick Soleil <nicksoleilso...@yahoo.com> Subject: Re: [RE-wrenches] Target fire To: gilliga...@gmail.com, "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Monday, October 18, 2010, 4:08 PM Hi Matt: I saw you chimed in after I had sent my posting. It appears that the fire was caused by just the one fault at the loose 2" EMT connector. If one of the module strings was faulted, then the fuse protecting that one string should open, and thus eliminating that string from the array. Why do you think that the module level wiring contributed? Nick Soleil Project Manager Advanced Alternative Energy Solutions, LLC PO Box 657 Petaluma, CA 94953 Cell: 707-321-2937 Office: 707-789-9537 Fax: 707-769-9037 From: Matt Lafferty <gilliga...@gmail.com> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Sent: Mon, October 18, 2010 1:12:34 PM Subject: Re: [RE-wrenches] Target fire Andrew, The General/Prime Contractor on the job was SunPower vis a vis Powerlight. As per standard operating procedures there, the actual installation was subbed out. I don't recall which subs they used on this job, but there was more than one. Per their normal routine, one sub installs the racking, modules, and wiring from the modules to the combiners. This sub can have any one of several different license classifications. They use an electrical sub to install the combiners, homeruns, inverters, interconnection. The electrical sub is responsible for terminations. Although I wasn't onsite to inspect the charcoal, I believe there were multiple shorts, not just the separated coupling in the homerun. I suspect there was at least one ground-fault in the array prior to whatever happened at the coupling. If this was the case, then BOTH SUBCONTRACTORS FAILED. They are both at least partially responsible for what happened there. I have seen the racking system that was used on the Bakersfield project. The vintage used there had SEVERE problems with wire management. Absolute crap! Ground faults are common with that racking system. I have personally witnessed a system running with 8 amps of current on the ground using the same racking system. This was NOT on the Bakersfield site. Although I wasn't permitted to troubleshoot the problem, I was told that they had been chasing the ghost for several months. Ever since the initial installation. I have it from reliable sources that this condition is common and a known flaw in the design. At that time, their philosophy was that a ground fault is acceptable as long as there isn't enough current to trip the inverter offline. Central inverters commonly have up to a 10 amp GFP, so you can have one or more strings directly shorted and keep running. The concept that they kept installing systems with a known flaw like this is beyond acceptable. SunPower ultimately bears the greatest share of responsibility here. I do not know whether they have corrected the crappy wire management in that racking system since then or not. I certainly hope they have either corrected it or stopped using the system altogether. A comprehensive commissioning process would identify these problems and prevent the system from being placed into service. A visual inspection is the beginning of any commissioning process. As I said, I have seen these systems and they ain't pretty. Any schmuck can easily see numerous wires pulled across sharp-edges of sheet metal at various points throughout the array. Fail #1. Megger output jumpers... Fail #2. The concept that any building department has signed one of these systems off at all is mind-boggling. Another thing I find interesting... There was no mention of this condition in the fire investigation report. Only a recommendation to megger the remaining wires. What's up with that? How is it that so many of these systems have been installed and passed inspection? How many have caught fire that we haven't heard about? You know... Just a little fire. I would LOVE to know how much downtime has been logged because of this dangerous problem. And how much money has been spent troubleshooting and "fixing" faults caused by this problem. And how many "technicians" have been shocked during installation or service? One thing I can guarantee you... Unless you work inside the bowels of SunPower or this information comes out in a lawsuit somewhere, we will never know. Maybe WikiLeaks will have something on this someday. But I'm not holding my breath. For the record, I'm not a SunPower hater. I do hate crappy workmanship. I hate the practice of covering up crappy workmanship even more. You see, when you cover it up, it's just gonna keep happening. At least until somebody calls you on it. $0.02001 Solar Janitor From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Andrew Truitt Sent: Monday, October 18, 2010 12:04 PM To: RE-wrenches Subject: Re: [RE-wrenches] Target fire Thanks William. That is the first place I looked but I didn't see it in there. But I love all the resources on your website! - Andrew On Mon, Oct 18, 2010 at 12:47 PM, William Miller <will...@millersolar.com> wrote: Andrew: It may be in the report: http://mpandc.com/practices/Safety/safety_data.html William At 11:30 AM 10/18/2010, you wrote: Does anyone know who installed the infamous Bakersfield Target job? Andrew Truitt NABCEP Certified PV Installer™ (ID# 032407-66) Truitt Renewable Energy Consulting (202) 486-7507 http://www.linkedin.com/pub/andrew-truitt/8/622/713 "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!" ~William McDonough No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.448 / Virus Database: 271.1.1/3204 - Release Date: 10/18/10 06:34:00 Please note new e-mail address and domain: William Miller Miller Solar Voice :805-438-5600 email: will...@millersolar.com http://millersolar.com License No. C-10-773985 ____________________________________ Andrew Truitt NABCEP Certified PV Installer™ (ID# 032407-66) Truitt Renewable Energy Consulting (202) 486-7507 http://www.linkedin.com/pub/andrew-truitt/8/622/713 "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!" ~William McDonough -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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