Appendix A. Grounding
recommendations
A.1 Grounding system installation
To prevent lightning damage to your equipment, Rain Bird recommends installing a grounding
system for the equipment (including controllers, weather stations, and central control systems).
The grounding system discharges lightning-induced electrical current into the earth rather than
allow the surge to pass through power wires or field wires to your equipment’s electronic
components.
A.1.1 Ground resistance
Ground resistance occurs when grounding system components, or the soil itself, oppose the flow
of electricity into the earth. Ground resistance is measured in units called “ohms” (Ω). The higher
the ground resistance (higher ohm readings), the less chance the surge will be shunted to ground
rather than to the equipment’s electronic components.
(p. 81) shows points where grounding systems can develop resistance. To decrease
ground resistance, Rain Bird recommends irrigating the soil around the grounding system. Each
grounding system should have a dedicated irrigation zone with sprinkler heads and its own
watering program to maintain soil moisture around the grounding system.
A properly installed grounding system should maintain a maximum ground resistance of 10 ohms
or less. If you are unable to reach a resistance of 10 ohms or less, you can decrease resistance by
surrounding the grounding rods or plates with ground enhancement material, such as POWER
SET from Paige Electric Corporation (pn 1820058), or GEM from ERICO (pn GEM-25A).
If ground resistance still measures higher than 10 ohms, you can extend the ground rod length as
described in “Ground Rod Stacking,” or use additional grounding rods, as shown in grounding
system design “Y” (Alternate).
A.1.2 Installation requirement
The following requirements apply to all grounding system designs (design Y and the “Grounding
Plate” design). All grounding rods or plates must be connected together below grade with #6
AWG or larger solid bare copper wire.
Section Appendix A. Grounding recommendations
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Summary of Contents for WS-PRO2
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