Ron... Bill's comments below are all absolutely excellent and spot-on - particularly his mention about the UL1703 certification. That said .. if you decide to proceed with the repair, I'd like to add a several additional details to the process: 1. Ensure the j-box you purchase is certified by a NRTL as a "recognized" component for use on PV. Each lab has its own markings to indicate a recognized component. Cheap non-recognized parts may warp or fall apart in time. 2. Install the diode in the correct orientation relative to the PV polarity. The diode should be reverse-biased (not conducting) during unshaded operation of the PV module. 3. The diode current rating Bill mentions below is a *minimum*. If you have a choice between diodes that meet this minimum, or diodes that are rated [say] 25-50% more current than the minimum, opt for the higher-current part. I've seen diodes in j-boxes that were hot enough to boil water (literally) after conducting for a period of time. J-boxes are not conducive to heat dissipation. 4. Make all connections to the diode as solid as possible to minimize the contact resistance. Oxidation in poor connections will cause the contact points to overheat, leading to eventual failure of first the connection .. and then the diode and possibly the other components, including the j-box. 5. Suggestion #5 has two parts: a) Use silicone *adhesive* to attach the junction box to the module. Silicone "adhesive" is NOT silicone caulk nor silicone "sealant". b) Only use a silicon adhesive that's approved for use on PV. Anything less will not stay adhered to the PV backsheet for the life of the PV. Dow-Corning part numbers 737 or 804 are suitable, as are others. The primary difference between the 737 and 804 is the cure time. 804 is faster (~8 hrs vs. 24 hrs), but cost a bit more $ than the 737 last time I bought some. 6. Ensure PV backsheet and the mating surface of the j-box are clean and free of any oil (i.e. from your skin, etc.). Denatured 90%+ alcohol and Kim-wipes (or similar) can be used to prep both surfaces. Dow and others also sell a primer that can be used for this purpose. 7. Apply two long pieces of tape to the box lid in a "plus" pattern *before* you affix the j-box to the PV. This tape will be used later. Next, apply adhesive to the j-box flange evenly around the entire perimeter. No gaps or thin spots. Press the j-box down evenly, so you get equal amounts of adhesive squeezed out around the entire perimeter of the box. Feed the PV connection tabs up through the opening in the j-box in the process. Finally, use the tape to secure the box in place while the adhesive cures. Do not make any internal connections at this time. 8. After the adhesive has cured .. make all of the connections. Soldered connections (done properly) are superior to crimped or compressive connections. Some j-boxes use compressive connections only. Do your best with what you have. Test and make sure everything is working properly. If so .. congratulations. Dan -------------------------------------------- On Sat, 3/1/14, Bill Hoffer <suneng...@gmail.com> wrote: Subject: Re: [RE-wrenches] Solarworld diodes To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Saturday, March 1, 2014, 2:20 PM Ron Technically removing the junction box has voided the warranty and the UL listing of the module,field modification is not covered by the manual. Solarworld probably will not accept a warranty claim after the customer has done that. Considering that diode failure is relatively common ( Schottkey diodes are susceptible to surge damage from lightning and near strikes among others), I am disappointing that Solarworld would encapsulate diodes that cannot be field repairable, unless they are using the newer surge resistant switching diodes that have a better chance of a 30 year life ( and cost 10X cheap schottkey didoes).
That being said and assuming this is an off grid application that is under the AHJ's radar, there are replacement junction boxes available to salavage the situation, just make sure you check the diode specs and that they exceed the Solarworld diode specs ( I could not find it for that module) . Should be UL listed for the module Max Voltage rating , beware Chinese knockoffs, buy from a reliable source! Rough rule of Thumb, Diode needs to be rated at the max breaker size current + 25 - 50% to account for temperature and current derate. ST has a great application note AN3432 if you want to geek out on the details.... Look for a solderless clamping terminals or at least one that is spaced off the back of the module to make sure that you do not damage the back sheet when soldering, this connection is critical and a source of future failures in modules from over-heated poor solders. A Larger Junction box is better for heat dissipation with the diode away from the back of the module and to cover any damage that the removal of the existing JB may have done to the backsheet. You will want to get a 2 part potting compound like Dow Corning PV7010 to insure that penetrations and any damage to the backsheet is sealed from moisture, a source of future delamination and corrosion issues. If you are lucky you can get a dual syringe sample that should be good for several modules. IMHO junction boxes should be as large as possible and have access to the didoes that are above the penetration potting material. Even at sun $1/watt pricing it is stupid to let a module to have an early demise when replacing $.75 worth of diodes would get it up and running again! Good Luck! Bill On Fri, Feb 28, 2014 at 2:34 PM, RM You <solarea...@solareagle.com> wrote: Hi wrenches, I sold some 175w Solarworld panels a few years ago and the diodes have blown on one. Customer isn’t clear on why it happened and is taking the 5th but what I’m trying to find out is how to help him get the panel working again. He removed the Jbox off the panel, which is a low profile model with diodes moulded right into the casing. Would it be possible to replace this Jbox? Anyone have experience with Solarworld supplying replacement boxes? I have a couple of pics and will post them but not sure if the list allows pics. Thanks! Ron Young _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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
