Ceiling fan

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A Ceiling Fan is a serious comfort booster on hot summer days. They can also be used to move down warmer air from very high ceilings in winter.



The cheapest & easiest way to install a ceiling fan is to put it where a light fitting pre-exists. Consequently most domestic ceiling fans include a combined light fitting. These light fittings are frequently not fully satisfactory.

Single glass bowl fittings have limited power rating, typically insufficient for room lighting. They are also of small size, making golfball filament bulbs the only usable bulb option.

Triple (or more) glass shade lights too often point straight at people in the room, which is an unpleasant form of lighting.


Imbalance causes shaking at high speed, and noise.

The first step to balancing is to ensure all blades are at the same height. Height differences can cause significant wobble. This is achieved if necessary by slightly bending the metal brackets the wood blades are attached to. Do not do this by pulling on the wood blades, as the wood is generally weaker than the metal.

Step 2 for an unbalanced fan is to remove the blades and weigh them, and group them into 2 pairs, the lighter pair and the heavier pair. Now reattach them with each pair of blades mounted opposing each other. This means that going round the fan in sequence the blades will be Heavier-Lighter-Heavier-Lighter.

If there is still unbalance after this, the imbalance position can be determined by holding a crayon very steadily very close to the hub as it rotates at max speed. The crayon will mark the hub on the lighter side, but not elsewhere. Be careful where your head is positioned when doing this!

Finally, any remaining unbalance can be corrected by trimming the outer edges of the wood blades on the heavy side, or by securely fixing very small weights on the light side. Care is needed when fixing weights, as the fixing will be subject to heavy vibration for years of use, and must remain totally secure. Flying metal weights are not recommended. For blades with a cane side where the cane is uppermost, woodglue & wood chips can be used on the cane to add weight.


Unbalance is the biggest source of noise.

Noise transmission may be reduced a little by using a penny washer and rubber tap washer on each mounting screw.

Where near silent operation is important, choose a large fan and operate it at a low speed.


The cooling effect of ceiling fans is often misunderstood. Ceiling fans cool people and other bodies that are above ambient air temperature, but they produce no cooling effect on the air or walls in the room whatsoever. Leaving a fan running when not in the room achieves zero cooling effect. In fact the energy used by the fan is converted to heat and warms the room by a tiny amount.

Speed Control

Most domestic fans have 3 speeds selected by a pull cord on the fan. Fans are also available with a wall mounted speed control. Fans are probably available with handheld remote controls by now.

Speed controls should always switch the fan on at full power first, then as the switch mvoes further reduce the power. This is to avoid the possibility of a fan failing to start on low power and burning out.

It is fairly easy to make one's own wall mounted fan speed control using a 2- or 3-gang lightswitch and some capacitors. Capacitors are used in series with the switched live to reduce fan power. Bleed resistors are fitted to the capacitors to discharge them when not energised. The capacitors should be rated to at least 400v. Polarised electrolytics must not be used.



Mount the fan high enough to avoid accidental impacts. The amount of force an impacting blade can produce is surprisingly high. Blades are rigidly fixed to the whole rotating mass.

Where headroom is insufficient, a ceiling hugging fan may be used. These don't blow air as effectively, but they do avoid loss of handy body parts. Fans can often be converted to ceiling huggers by replacing the suspension rod with a short one.

Where headroom is insufficient for even a ceiling hugging fan, designs exist that can be used safely within touching distance, but these are rarely seen on sale. The simplest solution here is to use a small enclosed fan. These are noisier and uglier, but when temperatures become unpleasant, such issues may become trivial.


IIRC falling ceiling fans kill 2 people per year on average in the US (need to check that). Ceiling fans need to be attached securely to ceiling joists, never fixed to plasterboard or laths, neither of which are capable of reliably handling the forces fans produce.

Custom Blades

It is possible to make your own custom blades if you are able to address the issues involved.

Blade sets can be made to any workable shape. Care is needed to avoid overloading the fan motor, blade sizing must be picked to give the same loading as the original design. With most fans loading margin is close to zero to minimise cost. Overload them and the motor fries. Probably the easiest way to measure loading is to measure fan speed on the lowest power setting. Lower speed means higher loading, and vice versa.

The blades must be robust enough to avoid any twisting in use, which would increase loading, leading to a positive feedback cycle and a flying ripped off blade section. This means no overly thin wooden sections.

If thin blade sections are wanted, metal backing can make this possible. However this approach should not be used on fans hung where there is any possibility of accidental touch, as it increases the blade injury potential. One of the injury limitation mechanisms is that the thin wood blades can snap off from the high momentum hub.

It is posible to use asymmetric blade systems if you're able to balance the forces effectively, but this is non-trivial.

Energy Efficiency

Ceiling fans produce a good deal of comfort for modest energy use. Comfort per energy use is very roughly an order of magnitude better than air conditioning, though naturally the degree of comfort improvement is more limited than ac.

Energy use and energy efficiency both fall at reduced speeds for nearly all fans. Reduced speed is achieved by reducing current, reducing torque and increasing motor slip, with consequent increase in rotor dissipation. Energy reduction at lower speed is significant, but not proportional.

Fans with a/c

When using a/c, simultaneous use of ceiling fans can reduce a/c run costs significantly by giving a lower cooling requirement for comfort.

Blade Types

There are 2 types of ceiling fan blades in use. The flat sheet blades most popular are not particularly efficient. Propellor blades are found on high efficiency fans, and roughly halve energy use for a given flow.

Fans Offgrid

For offgrid electricity systems, high efficiency fans should generally be chosen. These have propellor blades and energy efficient motors. With these, fans using as little as 6w can give a gentle breeze. The downside of high efficiency fans is cost. Where a whole house is to be equipped with such fans it may be tempting to make one's own using small efficient dc motors.

See Also