[RE-wrenches] PV panel backing

[Ron Young]

Thanks everyone for your insightful replies, have passed them on to the customer with comments. He only wants to try and get another 6 mo. out of the panel until he can afford to replace it; and as always there are circumstances to consider. Unfortunately his shop burned due to arson and no insurance coverage so money is tight.

Ron

On Sep 1, 2014, at 4:30 PM, Ray Walters <ray at solarray.com> wrote:

> I've done patch jobs on little 12 v systems, and had them hold up  for many years, but I concur,  I wouldn't try that at higher PV voltages.
> Silicon sealant actually is slightly conductive, at least according to other Wrenches when this subject came up several years back.
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer, 
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
> On 9/1/2014 2:43 PM, Martin Herzfeld wrote:
>> 
>> I concur with Dan.  Unless a controlled environment, a patch job on a module with a customer is wrong on so many levels.
>> 
>> Martin Herzfeld
>> California Solar Contractor License  #833782
>> Trenching Contractor, Pole Installation & Maintenance, Instrumentation
>> 
>> UL Certified PV Installer #17, OSHA 30
>> Principal Contract Solar Technical Inspector
>> OSHA-Authorized Construction Trainer
>> CompTIA Certified Technical Classroom Trainer (CTT+) #T3NSZCNBBKB4QTQG
>> Project Contractor & Consultant
>> 
>> Telephone & Text: 510-243-0190
>> 
>> Ron,
>> 
>> It's been my experience the only adhesives that work reliably on PV backsheets are those designed for the purpose, such as Dow 804 et. al..  Substances such as silicone sealant, tool polymerics, and others will appear to be suitable when first applied, but they eventually peel loose over a period of 1-5 years.
>> 
>> Issue #2: Heat of sufficient temperature to melt the backsheet may also have been hot enough to affect solder joints on and among the cells.  Crystallized solder connections will conduct current, but are more resistive, and eventually will degrade due to heating and cooling, leading to overheating and eventual failure.  Then too there's a possibility of micro-fractures created in the cells due to the heat, which take time to become apparent, but will also cause a PV module to quit working .. or at least quit working at its rated specifications.
>> 
>> Issue #3:  When PV are manufactured, the layers at a minimum are manufactured from tempered glass, EVA, cells and buss, EVA, then the backsheet (tedlar, kevlar, etc.), in that order.  The module is assembled under conditions of heat and vacuum.  With the backsheet melted, the environmental integrity of the laminate has been compromised, allowing ambient humidity into the PV.  While it may be functional now, long-term prospects for continued proper operation are questionable at best.
>> 
>> Unless there's a pressing reason to try to salvage the module, it's better to replace it.
>> 
>> Dan Lepinski
>> 
>> --------------------------------------------
>> On Sun, 8/31/14, Ron Young <solareagle at solareagle.com> wrote:
>> 
>> Subject: [RE-wrenches] PV panel backing
>> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>> Date: Sunday, August 31, 2014, 6:32 AM
>> 
>> Hello Wrenches,
>> 
>> I have an installation of 165w PV on a pole mount that was exposed to a fire from the rear when the customers shop burned. 6 of the 10 panels survived with only replacement of the MC4 plugs required but one of the panels that is still functioning had the rear coating melted off. The cells and electrical grid still function. Can anyone recommend a replacement coating that may salvage this panel for a few more years. I know if left exposed it will soon deteriorate but am wondering if some kind of commonly available non conductive rubberized or latex type of coating might do the job?
>> 
>> Ron Young
>> 
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