Cross-mating solar PV connectors? Know that testing is not certification

Damage to photovoltaic systems caused by cross-mating of different PV connector brands is a recurring issue. Stäubli, home of the MC4 connector and one of the leading manufacturers in this space, issued a release this week noting that one reason cross-mating continues is often due to reports from individual testing from institutes regarding combinations of PV connectors from different manufacturers, which does not represent the higher compatibility standard of certification.

Basically, there is a distinction between design type certificates and individual testing. Here are those differences and the consequences of each from both a technical and legal perspective for installers.

Testing standards: minimum requirements for safety. The existing testing standards for PV connectors, such as IEC 62852:2014 + A1:2020 and UL6703, were created for the design and testing of connectors of the same type or type family from one manufacturer. These standards always refer to the connection of socket and plug within a type family and not to the respective individual parts of a connector.

“The testing standards above describe the minimum requirements for the safety of PV connectors, provided they have been developed and manufactured under the same quality management system, the same production processes, and manufacturing tolerances, and sufficient knowledge of the materials and technologies used,” says Guido Volberg, Senior Consultant Product Regulatory Affairs at Stäubli Renewable Energy. “Also, liability is considered if there is damage. Today’s standards are therefore not suitable for making a statement about the safety of combinations of PV connectors from different manufacturers.”

This fact also applies if two manufacturers designate their connectors as compatible on the condition that they inform each other of safety-relevant changes to the product. Even the smallest modifications can have a significant impact on the long-term function of the connection.

Damages and liability. Cross-connections can lead to burned connectors, arcing, and, in extreme cases, fires. There are various reasons for these common problems and damage when using combinations of different PV connectors.

Guido Volberg amends: “Among other things, a chemical incompatibility or also different thermal expansion parameters of the metal contact can lead to contact corrosion after some time. Under such circumstances, not only the project and the PV system are at risk, but also people and nature.”

The question then arises as to who is responsible for such damage.

“The manufacturers of connectors are not liable if they exclude the combination with third-party products. The PV system is implemented by the installer, which is why he can be held responsible in most cases.”

The type approval certificate. The internationally recognized design type certificate signals the tested and certified safety and quality of a series. It is issued by an accredited certification institute known as a notified body. To obtain such a certificate, a positive evaluation of the manufacturer and its production by the testing body are the first prerequisite. Not only is the production process, including handling of raw materials in incoming goods through to the dispatch of finished products, inspected, but also quality management in all its facets.

This comprehensive testing is repeated at regular intervals to be able to hold the certificate. These recurring tests, which also include the points of the initial test, ensure a consistent quality of the products, Stäubli says. These tests are performed on extensive sample quantities, usually taken from production by the expert.

A test report from individual testing is not a certificate.

In contrast to a design type certification, individual testing only describes the actual state of the existing sample, without taking into account the production processes or manufacturer’s quality management. This report may be commissioned by any party without agreement.

The one-time analysis is performed only on individual samples. The customer decides at the time of application what is to be tested and how. Volberg notes it is therefore also possible for the customer to establish the requirements whose fulfillment is supposed to be verified by testing the respective individual product sample. Based on these reports, no statement can ever be made about the long-term safety of a product combination, and much less a series.

Misleading statements can be made based on such a report, so any test institute should make mention of this fact with a clear statement in the test result, Volberg says.

Comparing the various procedures and basic principles behind design type certifications and individual testing makes clear that the respective results differ with regard to liability. No statements regarding the safety of products and product families can be made based on the test report from individual testing. Only the status of the existing sample at the time of the respective individual testing can be evaluated.

In the event of damage, product liability is not regulated, and responsibility usually lies with the installer. Both the manufacturer and the testing institute have noted a disclaimer.

The currently valid product safety standards and installation standards of the IEC prohibit cross-connection. Relying on individual testing reports to legitimize the cross-mating of PV connectors of different manufacturers can lead to significant risks and loss of safety for the environment, life and limb, but can also have critical consequences concerning the project and financial success.

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