Safety

The MC4 connector format is a design originated by and belonging to Multi-Contact, and is not a standard configuration such as a NEMA type connector would be. Multi-Contact does not release to their completion any of the vital information concerning our product, especially the materials used, mechanical/dimensional data, or product characteristic controls used to maintain product quality and proper function. So any company that makes an MC4 compatible connector is quite simply guessing what all of these characteristics are. The seemingly simple and unimportant PV module connector has some very rigorous and extreme demands on it: survive outside in temperatures swinging from below freezing to near boiling, in direct sun or driven snow, arid dry or soaking wet, for 20+ years. This is while conducting and protecting upwards of 20-30kW DC of energy without failing. All facets of a connector product degrade over time, especially in these conditions, so the key is to have it always stay in a safe region for its expected life. The smallest inconsistencies or defects, can over a long period of time, easily push certain key properties out of the safe region and into a run-away failure. Such inconsistencies may at first be largely unnoticeable from a macro level: connectors mate together, keep water out and pass current without showing any noticeable signs of excessive contact resistance/heat. But over time (could be on the scale of months or years), the effects of these issues or mismatches can feed into exponential growth in resistive heat, seal integrity loss, or material reactions. All of which can easily become a shock or fire hazard. If you consider how unlikely (and by that we mean impossible) it is for someone to guess right all the dimensional schemes, tolerances, materials and control features of such a product, you can see how such inconsistencies can easily find their way into a compatible product.

Certification

None of the major 3rd party testing agencies (TUV, UL, CSA, ETL) will allow for the certification of PV connectors from different manufacturers without the written consent of all companies involved and the proven comingling and sharing of vital design and material information. Such a situation, at least from what we have been able to find, does not exist between any of the popular PV connector manufacturers. Certainly, no such agreement exists between Multi-Contact and another company. This is explicitly mentioned in the standards that are used to certify PV connectors.

For example:

UL6703 (Connectors for use in photovoltaic systems), section 1.5: This standard covers PV connectors whose dimensions are not defined in any national or international technical standards. 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.

So even though a module manufacturer may have a module certified with connector company s product and the same product also certified with connector company Bs product on it, this does not mean that the interconnecting of the 2 different modules is also certified. Since the NEC code as well explicitly states that a PV connector used in a PV system must be of a latching or locking type and be listed (certified) for the intended use, then mixing the mentioned pair of modules in a PV system as well is considered not to code.

National Electric Code (NEC)

The NEC specifically states the following:
690.4 General Requirements.
(B) Equipment. Inverters, motor generators, 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 certified by any agency for cross-mating with another companyÂÂÂ’s product, doing so in a PV installation is using it in a way that is not listed by the certification agency that evaluated the module product and thereby is violating the NEC code in doing so.

Warranty and Liability

With all of the above in mind, I think it is easy to see why Multi-Contact does not and cannot warranty the connecting of our PV connectors to those from other companies (and the same statement/situation is true from most other competitors’ point of view). We consider this a very serious issue and have seen in several real-world situations that cross-mating does cause problems and has resulted in fires and electric shock.

How do I determine what is a male or female connector?

The pictures below illustrate the differences. Roll your mouse over a thumbnail for a closer view.