Non-Intrusive Electric Load Monitoring in Commercial Buildings

Abstract

Increased interest in optimal control, energy scorekeeping and fault detection for HVAC equipment in commercial buildings has focused attention on instrumentation required to obtain the desired data. In this paper we investigate what can be learned from measurements of electrical power at a single point, that of the electrical service for the entire HVAC system. This low-cost measurement has proved in field tests to be capable of detecting the power change when a piece of equipment turns on or off; detecting oscillating equipment power caused by poorly tuned controllers; and detecting suboptimal staging of multiple chillers. Detection of equipment start and stop transitions was strengthened by application of a nonlinear filter that determines the point of median power from a filtering window of user-selected width. A review of electric motor literature indicated that samples of electrical current taken at slightly faster than twice the 60 Hz fundamental can be used to detect several indicators of incipient motor failure. Tests were initiated to determine whether this technique can be applied to a number of motors on the same circuit.