Installation Guidelines on System Grounding and Equipment Grounding

Abstract

Grounding is an important part in all electrical construction projects. Especially in a housing unit, grounding provides a safe pathway for electricity that could cause a shock hazard to residents. There are two basic purposes for the grounding pathway: system grounding and equipment grounding. The main function of the grounding system is to provide low fault impedance to the ground fault currents for prompt and consistent operation of protective devices during a ground fault and to limit potential rise of electrical equipment. It also stabilizes system neutral potential only for the system with neutral grounding. The purpose of grounding the electrical system is to provide means to carry electric currents into the ground under normal and fault condition without exceeding any operating and equipment limits or adversely continuity of services. Along with the above purposes, it should assure that a person in the vicinity of grounded facility is not exposed to the danger of critical electric shock. Low voltage distribution system shall be provided with a separate green insulated grounding conductor for each single or three-phase feeder. The required grounding conductors shall be installed in common conduit with the related phase to neutral conductors. Where there are parallel feeders installed in more than one raceway; each raceway shall have an installed equipment ground conductor. Single phase branch circuits required for 220 volts lighting, receptacle and motors shall be consist of phase neutral and ground conductors installed in common conduit. The system ground and equipment ground shall be connected to the common ground base. All equipment metal frames shall be adequately connected to the ground bus. Ground rods of copper 20mm diameter with required length long shall be installed as shown on the drawings. High electrical conductivity with soft-drawing bare-stranded copper wire ground cable should be used to form the ground grids. All grounding medium shall be bonded together. This shall include electric, telephone and satellite television system ground and other underground metallic piping systems where they enter into the building. The common ground connections shall be made by using main size conductors and connectors. If a total ground resistance of 5 Ohms or less is not obtained with the ground rod, a longer rods or additional rods shall be installed until a combined ground resistance of 5 Ohms or less is obtained. All the grounding conductors and grounding rods shall be tested at the factory in accordance with the latest approved manufacturing codes and standards.