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Fabricant : Generac Power Systems Taille : 4.19 mb Nom Fichier : Langue d'enseignement:

10018. • NEC HANDBOOK available from the National Fire Protection Association, 1 Batterymarch Park, PO Box 9146, Quincy, MA 02269-9959. 2.1 BASIC STANDBY ELECTRIC SYSTEM Figure 2.1 shows a schematic diagram of a basic standby electric system. Both the UTILITY power supply and the STANDBY (generator) output are connected to an approved transfer switch. The transfer switch is required by electrical code and serves the following functions: • Permits the LOAD circuits to be connected to only one power supply at a time. • Prevents electrical backfeed between STANDBY power and the UTILITY power circuits. Notice that both the STANDBY and the UTILITY power supplies to the transfer switch are protected against overload by a main line circuit breaker. NOTE: Generac recommends the use of a Generac Power Systems “pre-packaged” type transfer switch (Part No. 0D4406) in conjunction with this generator. 8 Generac® Power Systems, Inc. Section 2 — Installation Guardian Liquid-cooled 40 kW Generator Figure 2.1 – Basic Standby Electric System 2.2 EMERGENCY CIRCUIT ISOLATION METHOD This prevents overloading the generator by keeping electrical loads below the wattage/amperage capacity of the generator. If the generator is powering only critical loads, within its wattage/amperage capacity, during utility power outages, consider using the emergency circuit isolation method. Critical electrical loads are grouped together and wired into a separate “Emergency Distribution Panel.” Load circuits powered by that panel are within the wattage/amperage capacity of the generator set. When this method is used, it is difficult to overload the generator. The transfer switch must meet the following requirements: • It must have an ampere rating equal to or greater than the total amperage rating of the emergency distribution panel circuit. • It must be installed between the building’s main distribution panel and the emergency distribution panel. 2.3 TOTAL CIRCUIT ISOLATION METHOD When a generator capable of powering all electrical loads in the circuit is to be installed, use the “Total Circuit Isolation Method.” It is possible for the generator to be overloaded when this isolation method is employed. The following apply to the transfer switch in this type of system. • Ampere rating of the transfer switch must be equal to or greater than the ampere rating of the normal incoming utility service. • The transfer switch must be installed between the utility service entrance and the building distribution panel. 2.4 GROUNDING THE GENERATOR The National Electrical Code requires the frame and external electrically conductive parts of this equipment to be properly connected to an approved earth ground and/or grounding rods. For that purpose, a GROUND LUG (Figure 2.2) is provided on the generator mounting base. Consult a qualified electrician for grounding requirements in your area. Grounding procedures must meet local regulations. DANGER Do not connect the ground wire to any pipe that carries a flammable or explosive substance – FIRE or an EXPLOSION may result. Proper grounding helps protect personnel against electrical shock in the event of a ground fault condition in the generator or in connected electrical devices. In addition, grounding helps dissipate static electricity that often builds up in ungrounded devices. Figure 2.2 – Generator Grounding Lug (typical) 2.5 GENERATOR AC NEUTRAL CONNECTIONS Generac uses an UNGROUNDED AC neutral. Grounding is recommended only at the main service entrance. 2.6 TRANSFER SWITCH START SIGNAL CONNECTIONS • 2.6.1 PRE-PACKAGED TYPE SWITCH Connect the six signal wires from the automatic transfer switch to the engine generator control, which is located on the upper right side and inside the lower control panel. Match wires 23, 194, N1, N2, T1 and T2 in the transfer switch to the corresponding wires on the terminal strip in the lower panel. The conductors for these wires should be in a seperate conduit from the main AC output wires. If the control wires are run in the same conduit, the control wires must be a shielded cable. • 2.6.2 “GTS” Type Engineered Switch Connect the two-wire start signal from the automatic transfer switch to the automatic start connection, which is located in the right hand corner inside the lower panel. Match wires 178 and 183 in the transfer switch to 178 and 183 on the terminal strip in the control panel. The conductors for the two-wire start circuit must be in their own conduit. If the control wires are run in the same conduit, the control wires must be a shielded cable. Generac® Power Systems, Inc. 9 Section 2 — Installation Guardian Liquid-cooled 40 kW Generator NOTE: When using a GTS switch, it is necessary to connect a 240V AC supply to N1 and N2 terminals of the generator to provide for battery charging. Wires T1, T2, 23 and 194 should not be connected. 2.7 BATTERY INSTALLATION DANGER ! ! ! Standby generators installed with automatic transfer switches will crank and start automatically when...

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