Horner APG XLt OCS - Manual (Page 21)

MAN0878-04-EN CH. 4
August 12, 2009 Page 21 of 100 ECN # 979
CHAPTER 4: ELECTRICAL INSTALLATION
Note: Each XLe/XLt unit is sent with a datasheet in the box. The datasheet is the first document you
need to refer to for model-specific information related to XLe/XLt models such as pin-outs, jumper
settings, and other key installation information. The web version of this manual has all of the XLe/XLt
datasheets attached to it. Visit our website (see page 96) 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).
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 25
ohms. Horner APG recommends less than 15 ohms resistance from our equipment to ground.
Resistance greater than 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 shows a two-point ground
connection 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