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Yunhua Li, Ph.D., Bes-Tech Inc.
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Mingsheng Liu, Ph.D., P.E., Bes-Tech, Inc.
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Josephine Lau, Ph.D., Univ of Nebraska-Lincoln
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Low evaporator airflow is one of the common faults for rooftop units, which can be caused by dirty filter, evaporator fouling, or loose belt. Low airflow could result in frozen evaporator coil, reduced cooling capacity and indoor comfort issues. Accordingly, more fan power is consumed as longer operating time is required. With the widespread use of variable frequency drives (VFDs) on rooftop units, low evaporator airflow can be potentially detected by monitoring the fan power variation. In the paper, the principle of fan-power based detection is introduced first. Then, the detection algorithm is proposed including development of baseline and comparison of operational data with baseline. At last, the field test was conducted to verify the proposed method. The test results indicated that fan power based method can effectively detect low evaporator airflow for rooftop units.
