16
5.2
Grounding and Lightning Protection
Surges induced by lightning are one of the
most common causes of electronic controller
failures in solar water pumps. Damaging
surges can be induced from lightning that
strikes a long distance from the system, or
even between clouds. The risk of damage is
greatly reduced if these instructions are
followed.
Location of the pump controller
Place the
controller close to the solar array, not the
pump. This will reduce the risk of lightning
damage. Explanation: The controller’s input
circuitry is more sensitive to surges than its
output. It is safest to minimize the length of
the input wiring.
Construct a discharge path to ground
A
properly made discharge path to ground
(earth) will discharge static electricity that
accumulates in the above-ground structure.
This helps prevent the attraction of lightning. If
a lightning strike occurs at close proximity, a
well-grounded conductive structure can divert
the surge AROUND the electrical circuitry,
greatly reducing the potential for damage.
The controller has built-in surge protectors,
but they help ONLY if the system is effectively
grounded.
Earth connection – Create an effective
discharge path
It helps to picture this as a
“drain field” for electrons. Here are sugges-
tions for grounding, in order of their efficacy:
1. The best possible ground rod is a steel well
casing located near the array. Drill and tap a
hole to make a strong bolted connection to
the casing with good metallic contact. Bolt on
a brass terminal lug. After the connection is
made, seal the connection with silicone
sealant or other waterproof compound to
prevent corrosion. Protect the ground wire(s)
from physical damage so they aren’t stressed
by being stepped on, etc.
2. Install a copper plate or other specialized
grounding devices designed for the purpose.
Some systems use salts to improve the
conductivity of the surrounding soil.
3. Install one or more copper-plated ground
rods at least 8 feet (2.5m) long, preferably in
moist earth. Where the ground gets very dry
(poorly conductive), install more than one rod,
spaced at least 10 feet (3m) apart.
4. If the soil is rocky and doesn’t allow ground
rods to be driven, bury BARE copper wire in a
trench at least 100 feet (30m) long. If a trench
is to be dug for burial of water pipes, ground
wire can be run along the bottom of the
trench. The wire size must be minimum #6 (16
sq. mm) or double #8 (10 sq. mm). Connect
one end to the array structure and controller.
Or, cut the ground wire shorter and spread it
in more than one direction.
Dry or rocky locations
To achieve good
grounding at a dry or rocky site, consult a
local contractor who specializes in lightning
protection. It is best to plan the procedure in
advance, and to coordinate the effort with
other earth-excavating procedures that need
to be done. Reference: www.lightning.org
Bond (interconnect) all the metal structural
components and electrical enclosures
Interconnect the PV module (solar panel)
frames, the mounting rack, and the ground
terminals of the disconnect switch and the
controller, using wire of minimum size #8
(6mm2), and run the wire to an earth connec-
tion.
Ground connections at the controller
The
controller and junction box have redundant
ground terminals inside. They are all con-
nected in common with the metal enclosures
of both the controller and the junction box.
Ground connections can be made to any of
these points.
Ground connections to aluminum
This
applies to connections at the solar array
framework, and at the controller’s enclosure
box. Connections to aluminum must be made
using terminal lugs that have an aluminum-to-
copper rating (labeled “AL/CU”) and stainless
steel fasteners. This will reduce the potential
for corrosion.
WARNING
Failure to install
and connect an
effective ground-
ing system will
greatly increase
the risk of
lightning dam-
age and will void
your warranty.
We suggest you
wire the ground-
ing system FIRST
so it is not
overlooked. The
concrete footer of
a ground-
mounted array will
NOT provide
adequate electri-
cal grounding.
