A storage battery supplying emergency lighting and power shall maintain not less than 87½% of normal voltage at total load for a period of at least _____ hour(s).
See answer and applicable Code reference
The correct answer is: b) 1½
Article 700 focuses on the installation, operation and maintenance of emergency systems. As noted in the first sentence of Sec. 700.12(A), "Storage batteries used as a source of power for emergency systems shall be of suitable rating and capacity to supply and maintain the total load for a minimum of 1½ hours, without the voltage applied to the load falling below 87½% of normal."