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It is also normal to hear a quiet hum coming from the unit whenever it is powered on. You shouldn’t be able to hear this hum if you are 20 feet away. Sometimes humming can get louder or quieter over time. Turning the break on/off a few times can often help the contactor’s contacts re-seat, and get quieter.
Both of these noises are generated from the contactor within, and are normal.
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