wire will have a specific voltage and amperage,
depending on the solar array configuration. While it’s
OK to have different amperage ratings on the input
strings (because the amps get added after leaving
the combiner box), you should not combine multiple strings of solar panels with different voltages.
I have two 10-amp breakers in my combiner box
for my 2 strings of solar panels.
The gray cylinder (circled in Figure C) is the DC
lightning arrestor. Its 3 wires go to the positive bus,
negative bus, and ground. It protects your equipment from lightning damage and is required by code.
3. GROUNDING EQUIPMENT
Proper equipment grounding is a must. It reduces
and prevents shock, trips a breaker if a ground fault B
occurs, and limits the potential for equipment
damage by lightning. Below the combiner box, I’ve
driven an 8' copper ground rod into the ground.
Underground, I connected a direct burial ground lug
to a 6-gauge copper wire connected to the combiner
box at the designated location. I screwed code-compliant ground lugs into each aluminum rail that
touches a solar panel. A copper wire extends from
these solar panel ground lugs to the ground rod
below the combiner box. Read John Wiles’ article, “To
Ground or Not to Ground: That Is Not the Question
(in the USA),” available at makezine.com/go/wiles.
4. DC DISCONNECT SWITCH C
How do I ground my power center inside my shop,
route DC cable into my workshop, and easily disconnect the DC power source for safety? With Square
Photography by Parker Jardine
D’s HU361RB 600V DC 30A unfusible disconnect
switch (Figure D). The cable entering the box from
the bottom right is the solar input from the OutBack
PSPV combiner. These wires connect to one side
of the disconnect junction and to the ground bus.
Three additional wires connect to the other side of
the disconnect junction and the ground bus, then
run into the building through the conduit. Check
with your local inspector to see if PVC conduit on
the DC side is allowed to enter the building.
Note the bare copper wire (Figure E) that’s connected to the ground bus bar, and then runs down the
side of the building to connect to another 8' ground
rod. The NEC requires a separate ground rod for the
AC side of the system, and these 2 grounds need
to be bonded together. Again, check with your local D
inspector for details.