How common is it to have connectors fail?

[harveyc]

Hello there, new to the forum. I had a 11 kwh system installed in December 2013 which worked without incident until November 2015. Then, my I began getting AFCI fault messages on my SMA inverter which required resets more and more often. My contractor initially said that he thought it was a fault caused my my utility's power source but he eventually figured out one string (14 Canadian 250w panels) was causing the problem. SMA told him to buy an infrared camera to locate the problem and he discovered that several of the Canadia Solar connectors and one of his connectors had gone bad, partially melted. Those were replaced last week and now it's operating fine.

I'm obviously am not happy about this, operating only part of my system for 3 months or so. But I'm also concerned about how likely it is that future issues will come up. Has anybody had experience with this sort of problem or have an idea why this happened?

[Mike90250]

PV connectors (MC4 style) are not rated to connect or disconnect with power flowing. So I can see ONE connector going bad, but not a bunch on a whole string. First I ever heard of something like that

[bcroe]

Hello there, new to the forum. I had a 11 kwh system installed in December 2013 which worked without incident until November 2015. Then, my I began getting AFCI fault messages on my SMA inverter which required resets more and more often. My contractor initially said that he thought it was a fault caused my my utility's power source but he eventually figured out one string (14 Canadian 250w panels) was causing the problem. SMA told him to buy an infrared camera to locate the problem and he discovered that several of the Canadia Solar connectors and one of his connectors had gone bad, partially melted. Those were replaced last week and now it's operating fine.

I'm obviously am not happy about this, operating only part of my system for 3 months or so. But I'm also concerned about how likely it is that future issues will come up. Has anybody had experience with this sort of problem or have an idea why this happened?

Those connectors don't use precious metal contacts, so they rely on being continuously sealed to survive. If left
open to the air a long time, or exposed to any moisture, they have 2 strikes against long life. In my first year, I
went out during peak current production, and checked for any warm MC4s (or any other connectivity). Find
one, its on the way to failure. I don't usually check MC4s anymore, but everything else still gets the temp test.

Guess this test is a lot easier on a ground mount, add it to my list of advantages. Bruce Roe

[harveyc]

Those connectors don't use precious metal contacts, so they rely on being continuously sealed to survive. If left
open to the air a long time, or exposed to any moisture, they have 2 strikes against long life. In my first year, I
went out during peak current production, and checked for any warm MC4s (or any other connectivity). Find
one, its on the way to failure. I don't usually check MC4s anymore, but everything else still gets the temp test.

Guess this test is a lot easier on a ground mount, add it to my list of advantages. Bruce Roe

Thanks for the replies.

Bruce, why don't you check MC4s anymore?

[solarix]

I've always been concerned about MC4 (type) connectors that they don't really have that much engagement area. Even though the contacts look long and robust, they don't engage as far as you think they would. If they don't get plugged in all the way (should hear a click), you can have problems. Also if they are ever disconnected while current is flowing, the resultant arc will damage the contact and lead to a fault later on. Thanks for the tip on using an infrared camera.

[bcroe]

Bruce, why don't you check MC4s anymore?

I figured if they run cool at max power after being sealed for a while, they are undamaged and good for the long
term. Any changes need rechecking; for example I had to add a couple extenders to allow gaps for snow to
drop through. Any panels in storage have the leads plugged together. Once the system is stable, MC4 failures
could be many years away or never. Its not much of a risk; I'd only lose one string (of 10) and standing in the air
in the middle of a field, its not a fire risk.

I am much more concerned with the wiring where the power is concentrated to just a few larger conductors. I
have already had a DC and an AC circuit failure, in parts that operated well within their rating. I am now checking
these something like twice a year, and considering ways to make connections a lot more conservative, so they
don't heat up as much each day.

And I never, NEVER open a DC connector or switch with current flowing. Bruce Roe

[SunEagle]

One concern would be who performed the cable termination in the field. Remember we had one member find a number of loose connections made by the installer that allowed him to pull the MC4 right off the cable.

Using a thermal camera is an inexpensive tool to find hot spots at terminations or on the panel array itself for potential over heating and failure issues.

[harveyc]

One concern would be who performed the cable termination in the field. Remember we had one member find a number of loose connections made by the installer that allowed him to pull the MC4 right off the cable.

Using a thermal camera is an inexpensive tool to find hot spots at terminations or on the panel array itself for potential over heating and failure issues.

I was told that most of the failed connectors were factory connections and one was a connector they had installed.

[SunEagle]

I was told that most of the failed connectors were factory connections and one was a connector they had installed.

I guess even a factory made connection can fail if it isn't done correctly or is abused in the field. Probably it is not a bad idea to check all the connections.

[peakbagger]

We had a fairly expensive remote level indicators specified and installed for boilers at two different facilities recently at about the same time. The device consists of lots of little switches stacked up in a column to record water level at the steam drum which is a very important reading. At both sites we had problems with intermittent readings. We got different techs to check them out. At one site the tech found out that someone who wired it at the factory didn't strip the wires and just crimped over the insulation. He had to re-terminate most of them. The other tech wasn't so forthcoming but he made a few trips and mumbled something about bad terminations. It does bring into question factory quality control

[SunEagle]

We had a fairly expensive remote level indicators specified and installed for boilers at two different facilities recently at about the same time. The device consists of lots of little switches stacked up in a column to record water level at the steam drum which is a very important reading. At both sites we had problems with intermittent readings. We got different techs to check them out. At one site the tech found out that someone who wired it at the factory didn't strip the wires and just crimped over the insulation. He had to re-terminate most of them. The other tech wasn't so forthcoming but he made a few trips and mumbled something about bad terminations. It does bring into question factory quality control

Either the manufacturer was a US company where the work was performed on a Monday / Friday or it came from overseas company with little to no quality control department.

[solarix]

Some industries use connector contacts that are made to crimp on through the insulation so the boiler wiring might not have been all bad. They can work but are hard to verify - only a cheapo manufacturer would use them imho. On the other hand - crimp contacts in general are problematical in my experience. I don't really trust an electrical connection unless it is soldered.