When it is quiet, especially at night, you may hear occasional small noises. Some “electrical” humming noises can occur in the evening or early morning. These small noises are often caused by the electrical pulses sent down power lines to activate off-peak hot water systems. These noises are often unavoidable and are not covered under the guarantee.
What are they and what causes them?
Ripple Control – Zellweger
Zellweger is the brand name of an electric switching device used for to control off-peak electrical loads such as water heaters. It is an example of carrier current signaling. Power stations transmit a ripple signal on the main transmission lines when off-peak rates start and stop. This ripple noise is picked up by the Zellweger, which after a random delay turns the hot water heater on or off. The noise is often picked up by other equipment, especially audio amplifiers and stereos and the noise can cause problems with other electrical devices. It is especially audible from ceiling fans running at low speed. Even some telephone lines can pick up the noise. The noise can be particularly obtrusive from some fluorescent light systems. [Wikipedia]
If you are hearing the tones at random times of the day, your electrical supply may be affected by harmonics; a power fluctuation that is not part of the normal electricity supply or ripple control signal output. Harmonics is caused by an interference created by other equipment on the network, such as inverter type air conditioners and switch mode power supplies for computers. The offending appliances may be in your home or other premises on the local power grid.
If you are being significantly affected by network harmonics, it may be of benefit to transfer the electricity supply to your premises to a different phase in the street. This is something you will need to discuss with your power supplier.
Not all ceiling fans are effected to the same extent by these harmonic noises. The design and material of the bell housing on the ceiling fan can sometimes amplify the electrical noise. Not every home is effected by these harmonic noises, but ripple control devices are used in NSW, Queensland and in New Zealand. These harmonic noises are not a fault of the ceiling fan, and therefore do not constitute a warranty or guarantee claim.