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Is your solar power system safe? How can you be sure?
We are receiving more and more inquiries about fixing solar power systems from folks whose system has stopped working and the original installer can no longer be found. Sometimes a violent act of nature prompts the need for our services, but all too often we are seeing shoddy work that has failed far too soon.
Case in point, we received a call from a true “rocket scientist” the other day who had a solar power system installed about seven years ago, but now he was having a problem. We learned that the system had been installed by an air conditioning company (you’ve seen their ads), and it had two SMA Sunny Boy 2800 inverters—now well out of warranty—and one of them was displaying the dreaded, ground fault error. Ground faults occur when a normally ungrounded, current-carrying conductor makes contact with something that is grounded, such as the frame of a solar module, the system racking or even the conduit itself. Ground faults can be dangerous and are often difficult to locate.
When the solar system owner contacted his installation company, they offered to replace his offline inverter—for $5,000! Of course, simply replacing the inverter was unlikely to do anything about the ground fault, and it was possible that there was nothing wrong with the inverter at all, apart from being out of warranty. But in any event, charging $5,000 to simply do a one-for-one inverter replacement was highway robbery, and the system owner was pretty annoyed by the time he got around to calling us. Since there was no way to properly diagnose the situation over the phone, we agreed to come out and take a look.
Sure enough, one of the inverters was working fine, but the other displayed a ground fault message. The system owner told us that there was a combiner box on the roof, so we headed there to try and figure out where the fault might be. Here’s what we found in that “combiner box":
This is so NOT a combiner box!
This is a junction box into which the folks who threw this system together crammed the wires coming from the strings, joined them together (without any fusing to protect the array, to say nothing of the house) and then routed them downstairs to the inverters.
Another problem—the wires coming into this non-combiner box are all THHN, which is fine for a conductor running in conduit, but is no good at all for conductors coming from solar modules in the array. The insulation here is simply not designed to hold up under years of exposure to sunlight.
This is simply ignorant, shoddy work that has no place in the solar industry. Sadly, this particular company has not gone out of business, though the world would be a better place if they had.
People can get hurt this way. Property can be destroyed this way.
And the solar industry can get a very bad reputation this way.
We broke the bad news to the system owner and explained that what was needed was to replace the box on the roof with a proper combiner box, replace the improper wiring with USE-2 wiring that is designed to last on a roof, and bring the system back online. We also suggested that given that his existing inverters were out of warranty, he might want to consider upgrading to a single, transformerless inverter that would provide a ten-year warranty, the possibility of online monitoring, and much greater efficiency. That was the path he decided to take.
We installed an Outback combiner and upgraded the wiring. In so doing we managed to bring some order out of the previous chaos, take a look:
Now each of the four strings is properly protected by a dedicated, touch-safe fuse, and there is proper stress relief on the USE-2 conductors entering the box from the array.
We also installed ground lugs on each of the rails—something the air conditioning guys hadn’t bothered to do—and we installed two end clamps that had somehow been overlooked when the install was done.
The cool, new SMA 5000TL inverter allowed us to add monitoring to the system, as well as SMA’s emergency power outlet that provides a nominal amount of power from the array, even if the grid fails. In the process we were able to clean up the wiring on the ground, get rid of those air conditioning disconnect switches and install a proper disconnect. Oh, and while we were at it, we even arranged to donate the old inverters to Habitat for Humanity, providing the system owner with a charitable tax deduction!
Most importantly, we were able to restore his confidence in the solar array on his home. And maybe, even a bit of confidence in the solar industry itself.
There are a number of take aways from this experience that we would like to stress: