NFPA 111-2019 Standard on Stored Electrical Energy Emergency and Standby Power Systems. 6.2 Transfer Switches. 6.2.1 General. Transfer switches shall be rated for transferring the connected loads between the energy converter and the building electrical service. 6.2.1.1 Transfer switches shall be permitted to be electrical electronic or a hybrid of both. 6.2.1.2 Any transfer switch shall be rated for transferring all connected electrical loads from one power source to another. 6.2.1.3 Transfer switch characteristics shall be sized for the connected electrical load. 6.2.1.4 Transfer switches shall provide rated isolation between the electrical load and the alternate source(s). 62t5 Transfer switches shall be permitted to be separate devices within their own enclosures or an integral part of the ECE. 6.2.1.6 The capacity and endurance rating of transfer switches shall be sized for all classes of loads to be served. 6.2.1.7 The method of operation of transfer switches shall ensure that the most likely causes of switch failure result in the loads being connected to the building service, 6.2.1.8 Means shall be provided to check the operation of the transfer switch. 6.2.2 Switch Capacity. 6.2.2.1 The capacity of the transfer switch, electronic or electromechanical, shall be rated for all classes of loads to be served. 6.2.2.2 The transfer switch, including all load current—carrying components. shall be rated to withstand the effects of available fault currents. 6.2.3 Transfer Switch Classification.NFPA 111 pdf download.
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