Grounding - Weathermatic SLFSI-T10 Design Manual

WEATHERMATIC SMARTWIRE™ GROUNDING REQUIREMENTS
Grounding all electrical connections of a two-wire system is a critical step to ensure the system is
protected from damage by electrical surges and nearby lighting strikes. Although every irrigation
controller (conventional wired or two-wire) should be grounded, this step is often overlooked during the
installation. System failures and even a fire can be easily avoided by following a few simple steps.
Lightning, in particular can do a lot of damage to an irrigation system because irrigation systems have a
lot of wires underground where lightning can access the entire valves and wire network. Although
grounding can prevent a lot of electrical damage to an irrigation system, a direct hit from lightning will
likely cause damage even if the system is properly grounded.
The critical measurement for determining whether a system is grounded properly is call "resistance-to-
ground" In other words, it is the measurement of how easily a surge of electricity or lightning can enter
to the earth once it is made its way on to an irrigation systems electrical circuits. The lower this
measurement is, the better. Typically, if the resistance to ground is lower than the resistance of an
irrigation systems electrical components, the electrical surge will find its way to earth and not through
the electrical components. This is called least path of resistance.
The objective of proper grounding techniques is to provide the least path of resistance for any potential
electrical surge or lightning strike.
The green wire on any irrigation equipment is the wire that needs to be connected directly to the
grounding circuit. For Weathermatic SmartWire™ equipment, any GREEN ground wire must be attached
to a #8* solid bare copper wire using the SLCONN splice kit. The bare ground wire must be connected to
a grounding circuit with 12 Ohms or less resistance to earth ground, measured with a ground resistance
meter or Megger. (see below)
*Ground wire must be one size larger than the largest wire in the system.
A grounding circuit is comprised of 4 major components:
•
Ground Rod(s) and/or Plate(s).
•
Ground Conductor - #8 bare copper wire
•
Exothermic or Cadmium Weld connections.
•
Soil and/or Ground Enhancement Materials.
8-foot bare copper
ground rod
8 | P a g e
Ground
resistance
Megger
clamp meter
Copper
ground plate
Cadmium weld
connector
Soil
enhancement
material