4.2.4 Frame Ground Connection1. Loosen the screw.2. Insert a grounding wire (user-supplied).3. Tighten the screw.4. Connect the grounding wire to ground.ScrewGrounding wireTo groundWARNING• Proper grounding (connection to ground) is very important to reduce the risk to the user ofelectrocution or to protect the PBX from the bad effects of external noise in the case of alightning strike.• The grounding wire of the AC cable has an effect against external noise and lightning strikes,but it may not be enough to protect the PBX and to ensure electromagnetic compatibility. Apermanent connection between ground and the ground terminal of the PBX must be made.CAUTIONFor grounding wire, green-and-yellow insulation is required, and the cross-sectional area of the conductormust be more than 0.75 mm2 or 18 AWG.NoticeBe sure to comply with applicable local regulations (e.g., laws, guidelines).In most of the continental United States, the ground provided by the "Third wire ground" at the commercialpower outlet will be satisfactory. However, in a small percentage of cases this ground may be installedincorrectly. Therefore, the following test procedure should be performed.Test Procedure1. Obtain a suitable voltmeter and set it for a possible reading of up to 250 V AC.2. Connect the meter probes between the 2 main AC voltage points on the wall outlet. The reading obtainedshould be 108 V AC to 132 V AC.3. Move one of the meter probes to the 3rd prong terminal (GND). Either the same reading or a reading of 0volt should be obtained.4. If a reading of 0 volt at one terminal and a reading of 108 V AC to 132 V AC at the other terminal is notobtained, the outlet is not properly grounded. This condition should be corrected by a qualified electrician(per article 250 of the National Electrical Code).5. If a reading of 0 volt at one terminal and a reading of 108 V AC to 132 V AC at the other terminal is obtained,then set the meter to the "OHMS/RX1" scale, place one probe at the GND Terminal and the other probeat the terminal which gave a reading of 0 volt. A reading of less than 1 ohm should be obtained. If thereading is not obtained, the outlet is not adequately grounded. See qualified electrician.Document Version 2016-03 Installation Manual 1034.2.4 Frame Ground Connection
