Energized/Power in my mount-post-entire array (sorry, new to solar)

Dmott · February 2013

I did a little searching before making this post and couldnt find any information. Hopefully this isn't something basic and I'm just looking over it. I've been helping my grandpa with his off the grid solar arrays, and everything has gone well until now. He has more than a basic knowledge, and I can usually pick up on this sort of thing pretty quick. We have changed actuators, 5W panels and charge controllers for the battery/batteries, simple stuff.

One of the actuators, which controls tilt, on the dual-axis(?) array quit working. The azimuth portion was still working. We are not experts, but we tried to isolate the problem. We were thinking it was either the solar controller, or the photo-eye/ light sensor. While re-hooking up the second actuator, which controls tilt (which was not working automatically, only if you put a battery directly to it), one of the wires was re-installed in the correct spot, and the other was kind of flopping around, since I thought there was no power. When the loose wire touched the metal casing of the actuator, there was quite a bright blue spark/glow. We used our multimeter and there appeared to be around 70 volts running through the post into the ground, and throughout the entire system as far as we could tell. At this point the azimuth portion was still working, but here is the mistake. When tightening the same actuator case down, one wire was pinched, which took the 70 volts that was running throughout the entire array and ran it through the system/circuit backwards, frying the rest of the controller (I believe), then popping two fuses simultaneously. Now the array has no movement, no actuators are working. At that point there appeared to be around 100 volts running through the post/array.

We have ordered a new controller and sensor package, but my question is why would there be that power running through the entire array? There appears to be a ground wire connected to all of the panels, and onto a copper rod driven into the ground. I believe the array has 6- 35W panels, 2 sets of 3 wired in series, wired to eachother in parallel.

Any help would be appreciated.

inetdog · February 2013

Re: Energized/Power in my mount-post-entire array (sorry, new to solar)

Dmott wrote: »

We have ordered a new controller and sensor package, but my question is why would there be that power running through the entire array? There appears to be a ground wire connected to all of the panels, and onto a copper rod driven into the ground. I believe the array has 6- 35W panels, 2 sets of 3 wired in series, wired to eachother in parallel.

Any help would be appreciated.

As to the ground wires to each panel, they are grounding the exposed metal parts of the panel and should have no electrical connection at all to either the + or 1 terminals of each panel.

But unless you have an ungrounded system, somewhere the common + or the common - of the series strings (most likely the -) will be connected to ground.

When you say there is 70 volts or 100 volts "running through the post into the ground", where are you measuring the voltage? If you measure from the array + to ground (in a negative ground system) you should see the full array voltage. But no current will normally be flowing through that connection. Instead the current flowing out the + wire will return to the array on the - wire.
If for some reason an intermediate wire in the array itself is also accidentally connected to ground, then you will have a short circuit.

If the array was wired up to be ungrounded, and an accidental ground connection was made, that should not, by itself, cause a problem. But two accidental grounds from different voltages will.

westbranch · February 2013

Re: Energized/Power in my mount-post-entire array (sorry, new to solar)

to fill in some gaps please add a signature line with all the equipment you have as well as brands, etc. It will help in not having to dig through all the previous posts.

Have to assume you have at least a 24 volt system and parallel banks of batteries??

niel · February 2013

Re: Energized/Power in my mount-post-entire array (sorry, new to solar)

i agree you need to explain what equipment there is more accurately, but if you have 3 pvs in series at 35w, assuming these are most likely 12v pvs this will have a voc of around 21v or so give or take. x3 is about 63v or so. if the pvs are somewhat cooler than stc ratings the voc can be much higher than this so i believe that is your 70v you are seeing as it couldn't come from anywhere else now could it??

this begets the question of why so small of an array to track? i doubt it's really worth it.

Dmott · February 2013

Re: Energized/Power in my mount-post-entire array (sorry, new to solar)

Thanks for the help. inetdog helped a lot. I was testing from the terminals of one of the actuators (tilt) and the ground, which I think would be the same as testing the + and the ground. I was thinking the fuses were out when I did this, but now that I think back the fuses may have been in. A problem is that the panels are one hour away from us in the mountains, so I cant just go run out and check them.

inetdog also helped clarify why there was a spark when the wire which was supposed to go to the actuator touched the casing. Since the entire unit is metal, and is connected into the ground, when the wire touches it is a 2nd wire touching the ground, casuing a short circuit like inetdog said.

Thanks, I guess its supposed to be this way.

Also, the panels are 225W at around 36V, which might help clarify why it is a tracking array.

Energized/Power in my mount-post-entire array (sorry, new to solar)

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