Horner APG XL7 OCS - Manual (Page 22)

XL7 User Manual
CHAPTER 4: ELECTRICAL INSTALLATION
Note: The datasheet is the first document to refer to for model-specific information related to XL7
OCS models such as pin-outs, jumper settings, and other key installation information. Visit the Horner
websites to obtain datasheets, user documentation, and updates.
4.1 Grounding Definition
Ground: The term ground is defined as a conductive connection between a circuit or piece of equipment
and the earth. Grounds are fundamentally used to protect an application from harmful interference causing
either physical damage such as by lightning or voltage transients or from circuit disruption often caused by
radio frequency interference (RFI). Grounding is also for the safety of the user.
4.2 Ground Specifications
Ideally, a ground resistance measurement from equipment to earth ground is 0 ohms. In reality it typically is
higher. The U.S. National Electrical Code (NEC) states the resistance to ground shall not exceed twenty-five
(25) ohms. Horner APG recommends less than fifteen (15) ohms resistance from our equipment to ground.
Resistance greater than twenty-five (25) ohms can cause undesirable or harmful interference to the device.
4.3 How to Test for Good Ground
In order to test ground resistance, a Ground Resistance Tester must be used. A typical Ground Resistance
Meter Kit contains a meter, two or three wire leads, and two ground rods. Instructions are supplied for
either a two-point or three-point ground test.
Figure 4.1 – Two-Point Ground Connection Test
METAL WATER PIPE OR
OTHER GOOD GROUND
GROUND ROD
GROUND
DISCONNECTED
FROM SERVICE
GROUND RESISTANCE METER
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