The grounding requirements are one of the most confusing aspects of solar installation. Grounding is also what city inspectors tend to scrutinize the most. That is not a good combination unless you really like hanging out with your city inspector and want to fail the first inspection so you can see them a second time. But don’t stress, we’ve got some tips to help you avoid common grounding issues.
First, pay attention to what is shown on your permit plans. These plans have been approved by the city or county and if you follow those plans, the inspector should be happy with your work. There will be notes about the grounding that are very important. If you do not understand what those notes mean then you should ask the people who drew those plans for you.
Second, be aware of the grounding requirements for the equipment you are using. The NEC code says that all non-current-carrying metal parts must be grounded. This means any piece of metal that should not have electricity flowing through it has to be connected to the main grounding system at your house. This includes the solar panel metal frames, the racking for the solar panels, the metal conduit and all the metal enclosures of your inverter, AC disconnect and other components.
Fortunately, most of the racking companies have your back and designed their systems to do a lot of this work for you. The majority of racking systems are set up so that you only have to ground one rail in each row. From that grounding point, all the solar panel frames and all the rails in that row will be grounded through an integrated system that has been UL listed to provide a proper path to ground. In rail-less systems, you often only have to ground one piece of the racking and use a few jumpers to keep the ground continuous through the whole array. This integrated grounding will usually also include microinverters or DC optimizers if they are installed to the racking correctly. With that said, don’t make any assumptions. Read the installation manual for the racking system and follow the grounding instructions carefully using only parts that are specific to that racking system. Again, if you don’t understand the instructions ask the racking company or your distributor for clarification.
So now you have this grounding conductor (officially referred to as the Equipment Grounding Conductor (EGC) that will be on the roof, attached to the racking. You will run this EGC down through the conduit, through all equipment enclosures to the main service panel and your main grounding system. As that conductor goes through metal conduit, you will attach it to grounding lugs at both ends of every conduit. Sometimes you can get away with only grounding one end, but if you do that and the inspector isn’t happy, it will be a lot of work to fix so just do both ends and save yourself a headache.
You will also attach this EGC to lugs or grounding busbars in every piece of equipment. If it is a field installed lug or busbar (meaning it wasn’t installed by the factory), make sure scrape the paint off enclosure at that grounding lug to ensure you get a good path to ground.
Finally, when you get to the main service panel, you will land the EGC at the grounding busbar and it is also a good idea to continue it all the way to the actual ground rod or Ufer (a concrete-encased grounding electrode typically found inside your wall) if you can access it. If you can’t find that, then bond it to the grounding conductor that runs from the main service panel grounding busbar to that elusive ground rod.
Inspectors what to see that whole EGC run from the roof to the main ground rod to be continuous. That means no wire nuts. Any splices should be permanently crimped or welded. Busbars are allowed so you can use those if you need to have a break in the wire and you don’t have the fancy crimp tool or welding equipment.
If it is a long way from the solar array to the main ground, inspectors will often want to see an additional ground rod installed near the array. This is very common on ground mounted systems. The important thing to note is that this additional ground must be connected to the main ground for the property so you are still running that EGC all the way to the main service panel.
So good luck with your do it yourself solar installation and if you purchase your system from GoGreenSolar.com you will be very lucky because they will answer all your grounding questions so you can avoid extra visits from your city inspector.