Typical 15 Ampere 120VAC electrical service is supplied by circuit breakers that utilize magnetic trip mechanisms. High peak currents can trip these breakers although the RMS or average current is much lower.
The display of the LM15 meter family follows the peak load current to better indicate available service.
(Peak pulse durations of less than 1 millisecond will average to read lower values.)
EXAMPLES OF VARIOUS LOAD TYPES WITH SAME RMS CURRENT: