National Electrical Code Tips: Article 690 -- Solar Photovoltaic Systems, Part
Only about 15% to 20% of the work of installing a Solar Photovoltaic (PV)
System is electrical. But that electrical portion can easily result in disaster
if not done correctly. Thus, Article 690 provides requirements for that portion.
- You can install a PV system to supply a structure, even if other systems
also supply it [690.4(A)].
- To put circuits of PV systems in the same raceway as circuits of a non-PV
system, separate the circuits with a partition [690.4(B)]. Identify and group
the PV conductors, making sure you identify them at all points of termination
not just the system end points.
- Arrange all modules and panels such that removing one doesn't interrupt a
grounded conductor to another PV source circuit [690.4(C)].
- Any inverters, motor generators, PV modules, PV panels, or charge
controllers you use in your PV system must be identified for, and listed for,
the application [690.4(D)].
- Only qualified persons can install and wire the PV system electrical
components [690.4(E)]. Keep in mind that the NEC uses the OSHA definition
of "qualified" and it has a specific legal meaning. See Article 100 for this
definition. In the case of PV systems, the most pertinent part is the installer
"has received safety training to recognize and avoid the hazards involved." That
means training specific to this type of installation.
Such training may be provided by the manufacturer or a manufacturer-approved
party. A firm that regularly installs PV systems and has a training program in
place can most likely be the source of such training for new installers under
- Route PV circuits along building structural members, wherever you can
visually determine where those members are. The NEC says "by observation," and
that's all you're technically required to do [690.4(F)]. But it's not much
of a stretch from there to using building drawings, stud finders, measurements,
and other means to locate these members. You want the conductors to be as secure
in their mounting as is reasonably possible.
- If you end up routing PV circuits in built-up, laminate, or membrane roofing
materials, make sure you clearly mark the location of these circuits [690.4(F)].
- If you install a bipolar PV system, calculate the sum of the two monopole
subarrays. If it exceeds the rating of the conductors and connected equipment,
physically separate the two subarrays. Install the wiring in separate raceway
all the way to the inverter [690.4(G)].
- A PV system can have multiple utility-interactive inverters in a single
structure. If they are remote from each other, list them all in a directory and
install the directory at each dc PV system disconnecting means and at the main
service disconnecting means [690.4(H)]. The idea here is to give First
Responders full information on how to shut down power inside the building so
they don't get electrocuted trying to fight a fire there.
- If you have multiple inverters but they are all grouped the inverters at the
service, a directory isn't required. The logic behind waiving this requirement
is the same logic for mandating the directory when these inverters aren't
grouped in one location. Generally, you want to make it safer and easier for
firefighters whenever possible. So the default should be to group the
disconnects at the service unless there's a compelling reason to do otherwise.