Question: what is the maximum acceptable supply voltage tolerance for a 120v circuit?
Answer: Range A is for normal conditions and the required regulation is ± 5% on a 120 volt base at the service entrance (for services above 600 volts, the required regulation is -2.5% to +5%) Range B is for short durations or unusual conditions. The allowable range for these conditions is -8.3% to +5.8%.