MC4 connector
MC4 connectors are single-contact electrical connectors commonly used for connecting solar panels. MC4 stands for the manufacturer Multi-Contact and a Ø4 mm contact assembly pin. MC4s allow strings of panels to be easily constructed by pushing the connectors from adjacent panels together by hand, but require a tool to disconnect them to ensure they do not accidentally disconnect when the cables are pulled. The original MC4 connector has been installed over 1 billion times worldwide reaching an installed production capacity of over 100 GW.
Background
While small solar panels used for battery charging and similar tasks may not require special connectors, larger systems normally connect the panels together in series to form strings. In the past this was accomplished by opening a small electrical box on the back of the panel and connecting user-supplied wires to screw terminals within. However, bare terminals of this sort are limited to 50 V or less by the NEC code, above that only a licensed electrician can make the connections. Additionally, these sorts of connections were subject to problems caused by water leakage, electrical corrosion and mechanical stress on the wires.
In 2008 the US National Electrical Code was updated to require solar panel connectors to offer "positive locking", so that they were able to be plugged together by hand but only separated again using a tool.[1] So-called “MC4 compatible” connectors also pose risks. These do not only include counterfeits and imitations, but also connectors which do not look similar to the original, but can still be plugged together with the original.
General statement by Multi-Contact on mating connectors of different makes
Multi-Contact clearly dissociates itself from connections made with MC4 connectors and connectors from other manufacturers due to the high demands placed on safety and reliability of PV installations. Connectors that have not been produced by MC but appear mateable with MC components, and sometimes are being advertised as “compatible with MC4” by the manufacturers do not meet the requirements for safe, stable electrical connections and must not be mated with MC connectors for safety reasons. Multi-Contact does not take any responsibility for damages that result from such connections which have not been approved by Multi-Contact.
Loss of certification
The MC4 connectors made by Multi-Contact are UL, CSA and TÜV recognized only in combination with connectors from the MC4 product range. Any other connections are not UL and TÜV recognized. Per the UL standard used to certify PV connectors (UL6703): "This standard covers PV connectors whose dimensions are not defined in any national or international technical standard. Connectors are identified and tested with compatible mating part (or parts if multiple exist) and are to be of the same brand, unless multiple product manufacturers are submitting under the same evaluation for the purpose of proving intermatability." Multi-Contact does not have any such shared certifications with another company. When other manufacturers advertise a UL or TÜV certified connection of their connectors with MC products, this is incorrect and inspectors are requested to reject such combinations. Only partial tests have been made in such cases.
Violation of the National Electric Code (NEC)
Section 690 of the National Electric Code (which covers PV module installations) specifically states that (section 690.4) "... PV modules, PV panels, ac PV modules, dc combiners, dc-to-dc converters, and charge controllers intended for use in PV power systems shall be listed for the PV application." Since PV connectors are not "listed" by any certification agencies to be mated connectors from other manufactures, then doing so is violating the National Electric Code.
Technical risks and long-term performance
No long-term experience is available with cross-mating from the field. Experts question the forecast capability of short-term tests and accelerated aging tests with regard to the quality of a connection over a time span of 25 years or more. PV connectors are safety components which contribute to the operational safety (both personal and functional) of the installation. When connectors of different make are mated, this aspect is not guaranteed. Contact elements and insulation elements must be perfectly matched to the last detail. Over a long period of time this may only be ensured by continuous in-process tests which are run in- house by the manufacturer. Multi-Contact has been on the market with PV connector systems for over 18 years, looking back on according experience from both research and development as well as long-term performance of missions of connections. Simultaneously, characteristics of the connections are being recorded in test fields, proving a good long-term behaviour. For cross-mated connections this certainty is no longer given.
Description
MC4 connector systems are fully touch-protected and designed for high voltage and high current-carrying capacity. MC4 connectors are equipped with Multilam Technology for high energy-efficiency and long product life. Connector ratings include 1,500 V UL, 1,500 V TUV as well as CSA, JET and CQC.
Application and safety
Assembly instruction document for MC4 is MA231 and can be supplied by the manufacturer.