[RE-wrenches] PV panel backing

[Ray Walters]

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
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>
> 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 
> <mailto:solareagle at solareagle.com>> wrote:
>
> Subject: [RE-wrenches] PV panel backing
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org 
> <mailto: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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