NMC-64 Irrigation
• Rod installation
Drive the rod into the earth until about 10 cm (4 inches) is left above grade. If it is
impossible to drive the rod to the proper depth, it is acceptable to lay the rod
horizontally, 80 cm (2.5 feet) below grade.
In case the rod is exposed to damage, for example by lawnmowers or tractors it
can be installed in a hole, about 20 cm (8 inches) deep so that the rod is about 10
cm under grade and 10 cm above hole level.
The National Electric Code (NEC) mandates two ground rods unless you
can show less than 10 ohms resistance with one rod.
Ground Wire
The ground wire is a large copper wire that connects the main circuit breaker panel to
the ground rod.
• Material:
Ground rods should be copper clad or galvanized steel.
• Diameter:
Typically, 16 mm (6-gauge) copper wire is sufficient. If the wire run is greater than
20 feet, 20 mm (4-gauge) wire should be used.
• Length:
Minimum 2.5 meters (8 feet), preferably 3-meter (10-foot). A longer ground rod will
reach a soil with higher moisture content. Moist soil carries current much better
than drier soil.
The ground wire should be protected from damage by lawnmowers, tractors, etc’. It
should be buried minimum 15 cm (6 inches) under grade for protection and enter the
house as soon as possible. It is important that the wire not be cut; it should remain
continuous.
Ground Clamps
Ground wires should not be merely wrapped around a ground rod. Ground clamps are
used to attach a ground wire to a ground rod. The most common clamp is known as
an acorn clamp.
Make sure the ground clamps you select are rated for outdoor use. Do not use pipe
clamps rated for inside water lines or hose clamps to attach the ground wire.
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