Grounding the pump
ETAPUMP
requires a ground wire for safety. Connect the ground wire to any
ground connection in the junction box or to the controller enclosure.
Float switch cable
(This does not apply to swimming pool applications.) A long run of control cable to a
float switch can pick up damaging surges from nearby lightning. The best protection is to use shielded,
twisted-pair cable (Dankoff Solar Item #10326). Shielded cable has a metallic foil or braid surrounding
the two wires. Ground the cable shield as illustrated in Section 5.1.
CAUTION Ground the cable shield at the controller end only, not at the float switch.
Additional lightning protection
The
ETAPUMP
controller has built-in surge protection devices.
However, additional grounding measures or surge protection devices are recommended under any of the
following conditions:
1. Isolated location on high ground in a severe lightning area
2. Dry, rocky, or otherwise poorly conductive soil
3. Long wire run (more than 100 feet / 30m) from the controller to the wellhead, or to the float switch.
Additional lightning protection devices (surge arrestors) can be obtained from your
ETAPUMP
supplier.
The device(s) for the controller’s PV input, float switch and probe connections, must be rated for DC. The
device(s) for the controller’s AC output to the motor must be rated for 3-phase AC. In each case, the
clamping (bypass) voltage should be 90V or higher, but not much higher.
DO NOT GROUND the positive or the negative of the power circuit.
The best lightning protection
results from grounding the metallic structure only, and leaving the power system ungrounded. This is
called a “floating” system.
Explanation:
With a floating system and a good structural ground, lightning induced surges tend to
reach ground through the structure, instead of the power circuit. When high voltage is induced in the
power circuit, the voltage in negative and the positive sides tend to be nearly equal, thus the voltage
BETWEEN the two is not so high, and not usually destructive. This method has been favored for many
decades by most engineers in the remote power and telecommunications fields.
Exception for battery systems:
You can connect the pump to a battery-based home power system
that has a negative ground. If the wiring distance to the pump exceeds 100 feet (particularly in a high
lightning area), DC-rated surge protection devices are recommended.
Legal exception:
If the local electrical authority requires power circuit grounding, ground the PV
ARRAY NEGATIVE wire. This may increase the risk of lightning damage.
Solar array wiring
Bind the array wires close together, or use multi-wire cable. Avoid forming loops.
This helps induced voltages in each side of the circuit to equalize and cancel each other out.
Wire twisting for long runs
Twisting wires together tends to equalize the surge-induced voltage so the
voltage differential between the wires is small. This reduces the probability of damage. This method is
employed in telephone cable, for example. Some power cables are manufactured with twisted
conductors. To twist wires yourself, you can alternate the direction of the twist about every 30 feet (10
m). This makes the job much easier.
WARNING Keep solar pump wiring away from electric fence systems.
Do not connect the pump
system to the same ground rod as an electric fence system. Do not run a float switch cable close to an
electric fence.
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