A Hot Time at WalMart

Don’t Try This at Home

Did you hear about the solar panel fires on the roofs at various WalMarts?  Don’t let it happen to you!

Little bits and pieces of this story have been coming out in the solar trade press for a few weeks, now.  What I have gathered from this is that the rooftop solar power systems at 7 WalMarts have caught fire.  The roofs were steel and the stores were not extensively damaged, but the WalMart folks are miffed enough to sue Tesla over the affair.  Elon Musk’s Tesla did not install the systems, but they bought out Solar City, so it is a mess they inherited.  Since Solar City was started by some cousins of Musk, you can wonder if the next family reunion might be a little tense.

So what does this have to do with you and YOUR solar power system?  Maybe nothing and I bring it up so that we can make sure.  It is looking like the problem started with connectors.  Most of the panels I have came with MC3 or MC4 connectors and I have worked with Tyco connectors.  MC3 and MC4 won’t fit together.  Just a glance and you know that.  MC4 and Tyco connectors look just alike, but won’t fit together.  That’s good because the lookalike parts have just the opposite polarity.  You will have to use adapters to mate these up.

The WalMart problem seems to involve mixing MC4 and Amphenol H4 connectors.  They look alike and they fit.  Amphenol makes no claim that an H4 is an MC4-compatible connector and vice-versa.  The problem is, the Solar City installers used them interchangeably and the fit is a little sloppy.  Word is, Solar City knew of the problem and had begun a program of swapping out for truly matching connectors.  They just didn’t get to some in time and now the lawyers are swarming.

Something that can exacerbate the problem is not plugging them in tight, even when everybody is using the same connector.  Sometimes MC4s are really quite snug, getting that rubber seal seated.  When locked they can be a real pain to get unlocked, if you are experimenting and it would be really easy to forget and leave a connection half done.  Aside from a loose fit, that could be an invitation to water and corrosion.

In a low voltage system you might never have an issue with loose or mismatched connectors, but in grid tie, you can get into many hundreds of volts and a fair number of amps, resulting in conditions that will start and sustain an arc long enough to melt and then ignite connectors, which in turn can melt and ignite something else. Like a roof.

If your solar was installed by Solar City, have they come by to check and update your system?  Maybe YOU should.  Of course, it is a good idea to periodically check your system because STUFF HAPPENS, regardless of who installed it.  Are all the connectors snug and not charred or melted?  Does the insulation look good?  Any brown patches or cracks on the modules?  Battery cables tight?  You know what it is SUPPOSED to look like, so just look for anything that doesn’t look right.

Safety first!–Neal