Quiet Ceiling Fans: A buyers guide

Complaints about noisy ceiling fans are not uncommon.  Sadly once a fan has taken up grinding, whirring, ticking, humming or a host of other annoying noises it can be hard to silence.  Buying smart in the first place is the best option.  To help you do this Spinifex has outlined the key points to consider when looking for a quiet ceiling fan.

Note that there is no such thing as a silent ceiling fan.  Anyone saying otherwise has let their marketing team get too carried away.  Moving air, electric motors and mechanical systems all produce some noise.  The key is to limit the noise from the fan to a level that isn’t materially louder than the ambient background noise.

If you already have a noisy ceiling fan you want to fix, try reading the Spinifex article Noise: A Guide To Silencing A Noisy Ceiling Fan.

 

Mechanical Noise

Worn or low quality bearings, loose parts, imprecise manufacturing, bad design and fan wobble are the main causes of mechanical noise.

What to look for:

  • Precise motor housing tolerances (i.e. symmetric components with even gaps between them).  If compromises have been made on the components consumers can see, the internal workings are likely to be worse.
  • Sealed maintenance free high quality bearings.
  • Factory balanced rotor, blade irons and blades (i.e. all moving parts).
  • Blades that are firmly attached and are resistant to warping.  Loose or warped blades are a significant cause of wobble and noise.
  • Aerodynamic plastic blades are preferable and materials like MDF should be avoided.
  • Light kits that attached securely to prevent rattle.
  • Die cast aluminium motor housing because of its structural durability, or stainless steel or plastic when exposed to salt spray.
  • Padding on the hanging bracket where it attaches to the ceiling to prevent resonance.

There is no excuse for significant mechanical noise from a ceiling fan.  If you have recently purchased your fan and are unhappy with the noise you are hearing, contact your manufacturer for assistance.

 

Electrical Noise

All electric motors make some noise and every installation has its own idiosyncrasies making it impossible to determine how much noise a given fixture will make prior to it being hung, however some potential causes of noise can be eliminated.

What to look for:

  • Energy efficient motors that at least meet the CSIRO’s benchmark for efficient ceiling fans of 1.87m3 per minute per watt of electricity with the fan on high.  Generally if a manufacturer has gone to the effort of using an efficient motor, they are likely to be using quality components in the rest of the unit.
  • Motors with 16 or more poles, vacuum impregnated high-grade copper windings and laminated insulated cores to prevent eddy currents and subsequent motor hum.
  • Motors that are NOT over sized for your fan.  Put as a metaphor, a Ferrari motor in a Toyota isn’t going to make your Toyota a great car; it just costs more to run.
  • Controls designed to be compatible with the fan motor.  Generic controls and steady state controls often result in electrical noise.

Note on ripple control signal noise:  In some areas of Australia the power distributor sends high frequency signals down the power lines to communication with electrical appliances like off peak hot water systems and street lights.  These signals typically come on at particular times of the day or night and result in a high pitched whining noise.  This noise is independent of the quality of a ceiling fan’s design or construction.  Fortunately it can usually be fixed by installing a signal filter.  For a full description of this problem and its solution read the Spinifex article Noise: Ripple Control.

 

Air Turbulence Noise

As a blade moves through the air it generates turbulence along its upper surface and the tip of the blade.  For a detailed description of this phenomenon read the Spinifex article Noise: Air Turbulence.

What to look for:

  • Aerodynamically shaped blades with a curved profile similar to a bird’s wing, with a thicker leading edge and a thinner trailing edge.
  • Wooden blades rather than metal blades as they generally don’t ‘chop’ the air as much.
  • Blades with a smooth surface to prevent turbulence.  Avoid rattan and styled blades with raised sections or holes.

Note for larger rooms you get quieter and more even air movement from a couple of fans run at a lower speed than a single bigger fan.

A common myth is that more or bigger blades move a larger volume of air.  If a blade tracks through the turbulence of the blade in front it becomes less efficient.  This is exemplified by 3 bladed electricity generating wind turbines which are designed for both efficiency and quietness.

 

About the author

This article was prepared by Lachlan Torrance, a naval architect with 15 years experience working with fluid dynamics combined with mechanical and electric systems.  Lachlan has been part of the engineering teams responsible for some of the world’s most advanced sailing yachts including Wild Oats XI, Yendys, Alfa Romeo / Shockwave and Loki.

Image of Ball Ceiling Fan in Brushed Aluminium