Quality Roundtable: Rain in the box

In April 2013 a 5 MW solar power plant was commissioned in Germany. One of many, surely, but this one was not designed “on the cheap.” A respected German solar company was contracted to build the plant as an EPC. A subcontractor installed the 235 W modules of a Chinese quality manufacturer according to the company’s specifications. The manufacturer explicitly permitted upright, horizontal, and upside-down installation because the devices were protected against water ingress in accordance with IP 65. The uppermost of three rows of modules was therefore rotated 180° to save cabling.

Yet over the course of the next two years, one module after the other failed, and the junction boxes burned out. In every case, it was always the top row of modules that was affected. The operator reported the damage to its insurance company, which found 1,270 conspicuous junction boxes in its first evaluation. The EPC replaced the affected modules in the scope of its warranty. The manufacturer delivered new modules, now 255 Wp, and with a different plug connector than the MC4 connectors on the original modules. That increased the cost of the replacement because the new modules first had to be converted to MC4 plugs so that they worked in the existing installation. In the first expert assessment, junction boxes that did not appear conspicuous were also marked in order to determine whether the problems would spread.

The water finds the gap

Sure enough, a year later more junction boxes had burnt out. Just to check, the insurance company opened a junction box and found moisture inside. A non-standard test with a garden hose demonstrated that splashing water could penetrate the module junction boxes that were upside down.

“That, of course, was not a standardized test,” says Matthias Graf von Armansperg of Accelios Solar, who supervised the insurance case. However, opening one of the affected junction boxes revealed a gap in the silicone seal. Afterward, the insurance company denied the claim for damages because it was only liable for damage caused by one-time external causes, such as storms, rodents, or theft. Moisture ingress over a long period caused by a manufacturing error was not covered. Meanwhile, the question was raised as to whether a serial defect was present.

Another insurance adjuster came to the conclusion that it was highly likely that all of the modules in this series, which all came from one particular plant in China, contained this gap. The cause of the problem could have been an incorrectly adjusted robot that applied the silicon. On the modules that were installed right side up, the gap was on the bottom of the junction boxes, while the gap faced upward on the upside-down modules. Rainwater penetrated the boxes through the gap, the wires rusted, and finally burnt out. The adjuster said that it was highly likely that none of the affected modules would survive for 20 years. It was clear to the operator that this was a case of a serial fault and it demanded the that the EPC develop a solution to avoid having to file a claim with the manufacturer for every single defective module.

Piece-by-piece replacement instead of a recall action

The EPC refused to listen to reason, however, claiming that ultimately the performance of the modules was not diminished and that there was no reason to exchange them, at least not until the moment when they failed. After all, the EPC said, the operator did have the option of filing a complaint with the manufacturer for the faulty modules.

At 22,000 pieces, that would be a tedious and expensive task. And nobody would reimburse these expenses. The strategy was clear: the EPC would simply wait out warranty period of five years, module by module, because complete replacement would be extremely expensive. For the operator, this tactic poses an existential threat because even if the module manufacturer picked up where the warranty of the EPC left off, it would only deliver replacement modules without covering the cost of replacement.

Possibly, although this is currently just speculation, this is why the EPC does not recognize a serial fault. After all, if the manufacturer only replaces the module and not the expense of the new installation, the EPC is left holding the bag for the costs. For the operator, however, a piece-by-piece replacement is not only untenable due to the continuous expense, but also because the installed modules would always be changing. The attorney retained for the case, Andreas Kleefisch, responded by calling for an evidentiary hearing at the district court, and the court commissioned a new expert appraiser.

For the court, the central question is how large the sample size of the faulty modules has to be to determine whether a serial fault is present. After all, the operator is generally on the hook for the costs of testing and proving a fault. The operator’s goal, of course, is full reimbursement for the costs of exchanging the panels, including removal and disposal of the old panels, as well as mounting the new ones.

According to the attorney, there has been no contact with the Chinese manufacturer yet because the EPC, as the contractual partner, is responsible for handling any damages. As so often occurs in the solar industry, this case too suggests a possibly deliberate loophole in the warranty conditions, according to which a faulty product must be replaced. When in doubt, however, the presence of the fault has to be demonstrated in every single part – in this case 22,000 times. This is senseless and unnerving. Which is why the court’s ruling is eagerly awaited.

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