Failure of mc4 connectors

mcgivor · July 2017

Has anyone come across mc4 connectors which fail to conduct, during my daily system checks I noticed that the current from the array was noticeably lower, a pigtail of different manufacturer to the panel it was connected to, was the culprit, movement made it conduct intermittently, my fix was to remove and make a married soldered splice with heat shrink sleeving.
This left me wondering could this be a more common problem that goes unnoticed.

littleharbor2 · July 2017

The Amphenol MC-4 like connectors are definitely different, internally, than other MC-4 connectors. Any chance you have any of them in the mix?

mcgivor · July 2017

No idea to be honest, but they don't have the same markings, one would assume if they connect together they should be compatible, best not good to assume anything I suppose, if different they should not mate, there should be a detent or something to prevent this.

littleharbor2 · July 2017

Amphenol connectors will have "Amphenol" molded into the body of the connector. I only mention this because I have used them and they require a different crimping tool. Their contacts are much heavier than a typical MC-4. With the vast number of makers of MC-4 type connectors I can see some not being compatible with others.

mcgivor · July 2017

No Amphenol markings, perhaps they are Chinese made, think I'll remove the others and solder splice, never liked interference connectors of any type, too many dry connections including the crimp can lead to problems, besides how often do we need to disconnect once installed.

Photowhit · July 2017

I actually bought some MC4 connectors on eBay that were crimped only. That's not up to code by my understanding. You can crimp and solder, but not solder alone. I understand, or at least have heard the argument, that it makes a pivot point so connections that will move even slightly, will eventually fail. Not sure why this isn't true of crimped connections.

BB. · July 2017

Yes, crimped connections are generally the only accepted termination technique for long life/high reliably connectors.

Solder wicks up (stranded wire) when soldered. It is that point at which the solder stops where there is a "fulcrum created" and any bending of the copper wire work hardens at that point.

Crimped connections do not have that transition point where forces are focused.

Solder connections can be fine, but the wire needs to be supported beyond the soldered point to strain relief/move/prevent the bending forces from reaching the solder joint.

-Bill

mcgivor · July 2017

BB. said:

Yes, crimped connections are generally the only accepted termination technique for long life/high reliably connectors.

Solder wicks up (stranded wire) when soldered. It is that point at which the solder stops where there is a "fulcrum created" and any bending of the copper wire work hardens at that point.

Crimped connections do not have that transition point where forces are focused.

Solder connections can be fine, but the wire needs to be supported beyond the soldered point to strain relief/move/prevent the bending forces from reaching the solder joint.

-Bill

So if for example an inline married splice is made, without any connectors, mc 4 or otherwise, the wire should be supported on either side to prevent movement, this would make sense as copper, when heated to a certain temperature, can either harden or become anealed, or soft , since soldering is at a lower temperature, the transition point where the heat is disapated becomes the weak point because it is now effectively work hardened, thanks @BB. You are an invaluable resource of information. The link below is the method I employ to eliminate the mc4 connectors.

http://www.instructables.com/id/Soldering-Tutorial-Inline-Splicing/

Solray · July 2017

The link is incorrect. It says to add shrink tube after you are done. Shrink tube needs to be put on before step 1 and slid away to an area that stays cool while soldering then but in place and heated after step 7.

mcgivor · July 2017

Solray said:

The link is incorrect. It says to add shrink tube after you are done. Shrink tube needs to be put on before step 1 and slid away to an area that stays cool while soldering then but in place and heated after step 7.

Go back and read step 1, pay attention to the note, at the bottom.

BB. · July 2017

Not mentioned in the instructions, but well commented on below is to use electrically compatible flux, not plumbing fluxes. Electrical fluxes will not cause corrosion. Plumbing fluxes are generally acid and will make a real mess a year later--And are impossible to clean from stranded cables (flux simply wicks up the strands).

Other tip... Make sure that you do not move/jiggle the wire while the solder hardens. If moved, you will get a cold solder joint (instead of mirror smooth surface, you will get a mushy/fractured surface).

Picking a "eutectic solder". Lowest melting temperature and reduces the chances of cold solder joints (goes from liquid to solid without a "mushy state").

-Bill

Solray · July 2017

I use a Velleman soldering station with a digital temperature readout to avoid overheating tiny fine wires on circuit boards, It's also a good idea not to overheat any solder connection as it can compromise the insulation on the wires.

Photowhit · July 2017

...or just use a dang butt connector....

Aguarancher · July 2017

One of the toughest environments for a wire splice is in the submersible pump application. When you can’t have a failure this is what I’ve used. There are other suppliers and this link is for example only.

https://www.amazon.com/dp/B00E8O5ZPO

mcgivor · July 2017

Access to all products is not a luxury currently at my disposal, most things are available in Thailand, but not easy to locate, I do have rosen core solder, a butane soldering iron, heat shrink sleeving brought from Canada, so improvisation is needed, I'm not complaining,actually the challenges are somewhat interesting, just the mc4 connectors I did locate, proved to be incompatible.

Aguarancher · July 2017

Find any submersible pump installer in your country and you will find all the components listed in my link. I am not aware of any other way to maintain a watertight connection 150' down a well..lol. First time you use the waterproof shrink tubing you will be sold. Ask the pump guy for DYI instructions on the install. I use a propane torch for setting the shrink tube, just keep the torch moving as to not over heat the tubing. You will see the sealant ooze out the ends..

Solray · July 2017

I used those on the connections to my Sprinkler system valves.

mcgivor · July 2017

The application is not submerged in water 150'down a well, it's just an alternative to mc4 connectors which are seemingly incompatible, in free air, protected for the most part by the panels themselves. Appreciate the suggestions none the less, my fix is to solder, then use 3M self vulcanizing tape to seal out the elements with a heat shrink cover for added protection , the crimp connectors would be great, if they were readily available, but they are not .

softdown · July 2017

mcgivor said:

Has anyone come across mc4 connectors which fail to conduct,

Yes.....a couple times in fact. Keep in mind that sometimes I macgivor stuff with leftover parts and an adventurous spirit.

Solray · July 2017

> @mcgivor said:
> The application is not submerged in water 150'down a well, it's just an alternative to mc4 connectors which are seemingly incompatible, in free air, protected for the most part by the panels themselves. Appreciate the suggestions none the less, my fix is to solder, then use 3M self vulcanizing tape to seal out the elements with a heat shrink cover for added protection , the crimp connectors would be great, if they were readily available, but they are not .

mc4 are also a crimp connection with a way to disconnect that does not involve cutting wires and if you buy good quality double contact type they virtually never fail barring abuse or misuse of the connector.

nickdearing88 · July 2017

I had one of my MC4 connectors fail but since my system is mostly used to experiment, I figured it was because my panels get disconnected and reconnected so frequently. Before joining the forum, I also didn't know they were not intended to be disconnected while under load.

mike_s · July 2017

Let's be clear - MC4 connectors are unique to Multi-Contact, the sole manufacturer. All the rest should be called MC4 compatible, at best. Especially the CCC (Cheap Chinese Crap) ones. No doubt, some are copies of copies of copies, hence the incompatible dimensions which cause problems.

mcgivor · July 2017

If the Multi Contact is the only true mc4, the ones used on most panels would in all likelihood would be copies, so short of replacing all of them, or at very least the end of strings to pigtails.with the genuine ones, there would be a possibility of incompatibility.

littleharbor2 · July 2017

If disconnected under load they arc and burn the contacts. Virtually all solar panels have a label attached to the leads, near the MC-4 connectors warning you to NOT disconnect under load.

Estragon · July 2017

MC4 is likely a set of specifications, which may be subject to patents and licencing of varying length and enforceabilty in various parts of the world. Like any such set of specifications, it can and will be used to produce goods which will meet those specs to varying degrees. The original specifyer will have an interest in producing to that spec and protecting a brand name.

Photowhit · July 2017

Since they connect, I don't think this is McGivor's problem, but their are also Tyco connectors which look very similar to MC4 connectors. Just wanted to put this here for those who are reading back looking for MC4 problems. We've seen people being confused about this in the past....

westbranch · July 2017

I have 3 brands of MC4 connectors on 3 brabnds of PV panels... all 3 brands work as they are supposed to, so long as they are mated with the same make! .
To clarify this discussion Solray's statement needs a small addition,
mc4 are also a crimp connection with a way to disconnect that does not involve cutting wires and if you buy good quality double contact type they virtually never fail barring abuse or misuse of the connector, when used with the same make

mike_s · July 2017

Estragon said:

MC4 is likely a set of specifications,

Nope. MC4 is a connector system made by one company, but widely copied. Whatever specs exist, they are not available for the copycats to work from.

Stäubli Electrical Connectors does not recognize a compatibility between Stäubli Electrical Connectors MC3/MC4 connectors and connectors from other manufacturers. -- Staubli/Multi-Contact

And, if you need to be concerned about compliance with code, you don't want to mix manufacturers:

In the UL File QIJQ2.E343181 belonging to the category “Connectors for Use in Photovoltaic Systems – Component” under the section Conditions of Acceptability you will find the following statement: “These devices have only been assessed for UL Recognition with specific types of mated connectors within their product family. They have not been assessed to operate with any other similar devices from any other manufacturer” -- ibid.

There's more info at the link.

mcgivor · July 2017

Nice comment, concise useful information, thank you @mike_s

mryimmers · July 2017

I seem to think I read somewhere cutting off the connectors on your solar panels will void your warranty.

softdown · July 2017

MC4 copies? I have not seen anything but MC4 connectors used for the past 1/2 dozen years or more.

Failure of mc4 connectors

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