What the heck? Panels still making power even with canvas tarp over them

Hairfarm · April 2015

Greetings,

I covered my 6 kyocera panels with a heavy canvas painters tarp today to stop them from making voltage so I could wire them to my combiner box. After covering them then I took a voltage reading from each of the three strings and they're still showing a VOC of 39.0 VDC each pair. They are 6 Kyocera KD135GX's, each with a VOC of 22.2 VDC. More importantly, how could they still be creating any power with a canvas tarp over them?

I did this to prevent any accidental shorting while wiring them to the combiner box. With all six panels covered, shouldn't the VOC have been zero? All three strings (covered with canvas tarp) were showing me the same exact VOC that they were when uncovered. Is the sun shining through my tarp? It a heavy canvas painters tarp. Am I thinking about this wrong?

thanks.

SkiDoo55 · April 2015

Needs to be totally opaque to stop all light. Black plastic sheet etc. if you can see any light thru it so will the panels. it takes very little light to get voltage, just not much or any power.

Mountain Don · April 2015

You probably have voltage but very little amperage.

zoneblue · April 2015

Forget trying to cover them. Heres what i do.

- leave the mc4s between the first panel in each string disconnected.
- Wire everything up, combiners, disconnect circuit protection.
- Make sure you have breakers in teh combiner, that way in future you will be able to isolate the pv hot from teh disconnect should you need to do additional work on it (which you will).

Once everything is good to go, with the dv breaker in the disco off, clip the remaining mc4s. Engage the breaker, voilà.

If you have voided your warranty and cut off the mc4s, then well, so long as you only hold one of the array wires at once, you should be ok

Hairfarm · April 2015

Thanks for the suggestions. A Kyocera tech told me that VOC is even possible during a full moon and that if I had a tarp in daylight there would be still be a VOC reading on my multimeter but very little amperage, as Mountian Don said. The tech suggested using gloves and wire caps. I also like the idea of not connecting the mc4's too. Never thought of that.

thanks,

zoneblue · April 2015

Just only connect mc4s when you have no load on the line, else youll damage the silver plating.

solarix · April 2015

Industry SOP is supposed to be to cover panels when working on the wiring, but SEIA lab I think it was did some testing and found that even really good tarps leave enough illumination to cause lethal voltages on high-voltage arrays. We still have the "cover array" note on our drawings to satisfy the ignorant authorities, but we always leave a break in the chain like zoneblue says to prevent shocks.

Alaska Man · April 2015

Like others I wired the array, but left the MC4 from the positive + side disconnected and the breakers off in the combiner box. After it was all wired up, I connected the positive side MC4 of the array, went over to the combiner box and turned on the breakers one at a time.

zoneblue · April 2015

I suspect the cover the panels thing originated long ago when panels were expensive and hence small. Now, who the heck can lay there hands on a decent tarp the size of our arrays?

Photowhit · April 2015

I just wired my array and combiner box and flipped the breaker ahead of the charge controller the next morning... Though the breaker would handle the load.

What the heck? Panels still making power even with canvas tarp over them

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