Is lead crystal safe to the touch

Connection plug for solar modules

(first discontinued 2019, last updated January 2021)

No - it's not that bad with solar modules. TODAY all solar modules basically have a visually and technically similar connection plug. Only the very small leisure modules, like the larger ones in the past, manage without a plug and with a junction box. All others have had touch-safe plug-in systems for over 15 years.

Stäubli Electrical Connectors (formerly Multi-Contact) is the pioneer and world market leader for PV connectors and invented, after the rubberized MC-3 we loved, the original MC-4! The others today look very similar to this part and in principle they mostly "fit" together.

As long as you connect the same solar modules to one another in series, to form a string, it doesn't matter which uniform system is used there. But then there is often the transfer to a module or generator junction box, a parallel or even three to four-way connector, or directly to a solar charge controller or an inverter. Then you need the right counterpart!

BUT neither from the manufacturer of the MC-4, nor from some (not all) module manufacturers, you get a release, same plugs from different manufacturers to be connected to each other. The TÜV advises against it across the board.

But is that really unsafe then? Or do you have a 100% guarantee through a TÜV approval?
Other test institutes have already confirmed the compatibility on behalf of module manufacturers, although the production process can ensure different tolerances.

The reasons for the rejection lie in the possibly different conductivity and resilience and that you want to protect yourself from possible liability. Furthermore, the inventor understandably wants to sell his product.
Only the successor EVO 2, also manufactured by Stäubli, receives this combination approval. And the Dutch connector manufacturer Solinq takes over the guarantee for cross connections with MC-4. 

At the same time, there are certainly hundreds of thousands of systems around the world with a wide variety of plugs and with most of them, nothing has ever happened. Sometimes it was not even possible to determine which connector system was used.
But there have also been cases, especially in large-scale systems, in which the combination of high load (current / voltage) and connections that do not exactly match one another 100%, in extreme cases (heat and dust, environmental influences) for different expansion, conduction or resistance and thereby caused arcing and consequent damage.

In small leisure facilities or a small mini-system with one or two solar modules that are attached to the balcony, facade or roof and have no contact with flammable parts, the risk of cable fire and the resulting major damage is certainly minimal. Therefore, many suppliers of module inverters or system sets, especially from China, do not give a thought. Sometimes they simply write "C4 connector" for their replicas and avoid the "M" - otherwise they can be issued with a warning. Some claim "compatible" because it works, but are not approved. In the bay or on Amazon there are regular replicas that are not marked as such. But you can usually tell from the price and the shipping location ...

The module inverters from APSystems and EVT have MC-4 connections. Aeconversion says in the brochure: DC connector: H4 (MC4 compatible).
Letrika also uses Amphenol LTW H4. Thanks to the adapter, Enphase is available with either MC 4 or AmphenoL H4 UTX.

Some assemblers now offer short or long adapter cable sets that respond to the most common MC4 replicas. Another alternative would be to connect the plug to the solar module (Not the inverter) and replace it with the original counterpart (requires the appropriate crimping tool) or use a simple MC connection set that is crimped. In some cases, the module guarantee is then nonsensically void. But even this can certainly be gotten over with small systems.
In 23 years we have had next to no module warranty claim, except for a defective batch of BP modules, which were still replaced after the time had expired. On the other hand, it is very bad if you try to attach the cheap original connector to the cable without the special tool. Only the Sunclix variant from Phönix-Contakt can be connected to the cable without tools.

A large overview of many different systems can be found at one of our cable / connector suppliers HIS (Image source). 

So if it is important to you to strictly adhere to the manufacturer's regulations, you should pay attention to identical plug-in systems when assembling the system. On the other hand, there is so much that is done outside of the norm every day and it still works. Even the plug, which can be found billions of times in German Schuko sockets, has umpteen variants that sometimes fit more and sometimes less well. These are also potential risks - especially when the load is higher. Even today you can find hundreds of thousands of solar modules connected with luster terminals. Occasionally not even protected ...


We ourselves prefer the MC3 as much as possible - because it is "rubber-tight" (if it gets wet) and can be separated easily.

For the MC4 connector you need a pair of MC4 keys to unlock ...