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Ceiling Fan and Blade Sweep Size
When purchasing a fan it is important to know what size fan you will need. The fan size is actually the diameter of the blade sweep. Typically 52" fans are preferred, but in small rooms, aesthetically and efficiently, they are just too big. Keep in mind that a smaller motor is used in 30" to 42" fans. If a small room has a high ceiling, the larger motor in the 44" is recommended over the 42" fan. Inversely, a large room, will benefit from 56" blade sweep or even two fans.
The table below is a general guideline for deciding what size fan you need, based on an 8' ceiling. Consider stepping up a size for higher ceilings for better efficiency and/or large pieces of furniture, like queen sized beds, for aesthetic appeal.
| Room Size |
Fan Size/Blade Sweep |
| 30" |
36" |
42" |
44" |
52" |
56" |
| 8'x8' (64 sq. ft.) |
X |
X |
X |
|
|
|
| 10'x10' (100 sq. ft.) |
X |
X |
X |
X |
|
|
| 10'x12' (120 sq. ft.) |
x |
x |
X |
X |
x |
|
| 12'x12' (144 sq. ft.) |
|
x |
x |
X |
X |
x |
| 12'x14' (168 sq. ft.) |
|
|
x |
x |
X |
x |
| 14'x14' (196 sq. ft.) |
|
|
|
x |
X |
X |
| 14'x18' (224 sq. ft.) |
|
|
|
x |
2 |
X |
| 16'x16' (256 sq. ft.) |
|
|
|
|
X |
X |
| 16'x20' (320 sq. ft.) |
|
|
|
|
2 |
2 |
Downrod Length
The table below is a general guideline for choosing a downrod length. The 3" inch downrod is standard on most fans except for huggers. Based on the most efficient height of between 9 and 11 feet. But also take into consideration the scale of the room for aesthetic purposes.
| Ceiling Height |
Downrod Length |
| 3" |
12" |
18" |
24" |
36" |
72" |
| 8' or less |
(a) See note below |
| 8' to 10' |
X |
|
|
|
|
|
| 10' to 12' |
x |
X |
|
|
|
|
| 11' to 13' |
x |
x |
X |
x |
|
|
| 12' to 14' |
x |
x |
x |
X |
x |
|
| 13' to 15' |
x |
x |
x |
X |
X |
|
| 15' or more |
|
x |
x |
x |
x |
X |
(*) - Ceiling fan blades should be at least 7' from the floor for safety purposes.
A Hugger type fan or a flush mount kit may be necessary on low ceilings.
Wobbling Ceiling Fan
Wobbling is usually caused by misaligned blades. And usually the blade irons have been bent. They can bend due to the weight of the blades over time, as well as human intervention.
First, turn the fan off. Sight along the edges of each blade, checking for warping. If a blade is warped, you may need another set of blades.
Check for any loose screws connecting the blade to blade-iron and blade-iron to motor (if wobble is accompanied by a "tick-tick" sound).
Also wiggle the hanging bracket and canopy and make sure it is secure and not loose. A loose hanging system can can cause a wobble by itself.
How to fix a Wobbling Fan
Vertical Variance (most common, where fan did not wobble before)
Using measuring device (ruler, yardstick, or even a piece of stiff paper and pencil) measure the distance from the tip of one blade to the ceiling. Leaving the measuring device in place on the ceiling, carefully rotate the fan blades (if it is a ball mounted fan be sure not to change the angle at which it hangs) so you can measure the next blade. Repeat with the remaining blades. Most likely you will find one or two blades either too high or too low.
Check the blade irons for cracks, especially near where the blade iron widens to accept the blades. If you notice ANY cracks, do not proceed with the next step; REPLACE your blade irons!
To correct - hold the motor with one hand (the switch cup makes a fair handle for this) gently applying pressure to the end of the blade (either up or down) will straighten the blade iron. Don't overdo it though, too much will weaken the blade iron. Double-check measurements and then test fan under power. This usually takes care of it.
Pitch and Centerline
If it still does not spin right, the Pitch or Centerline Angle of one or more blade irons may be off. The way to test these involves removing the blade irons from the motor and blades. To check the Pitch, hold the bases of two blade irons to a flat surface. With the blade-ends facing each other, the opposite sides should line up. That is to say the upper side of one should match the upper side of the other, and the same with the lower sides. Check all irons this way. To check the Centerline Angle, stack the blade irons together. Holding the stack firmly together at the bases, align them to one of the holes in the bases. Look at the blade ends of the blade irons. They should all be evenly spaced (for pitch) and lined up in straight lines. Unfortunately insufficient leverage prevents a quick fix for these problems.
Excessive Blade Weight (wobbles upon installation)
Sometimes fan blades are not exactly matched by weight. If the weights of the blades vary more than 0.5 grams, the order in which they are attached to the fan can cause a wobble. This would be apparent upon installation. To adjust a 4-blade fan, swap two neighboring blades (1-2-4-3) and retest. Re-try (2-1-4-3) if necessary. For a 5-blade fan, swap opposing blades (1-2-5-4-3). It is a good idea to number the blades with post-it notes and record the combinations tried, as this takes a few tries (1-4-5-2-3, 5-4-1-2-3) in most cases. If this does not take care of it, Blade Balancing Kits are available, consisting of a few 0.5 gram weights, and a way of determining the placement of the weights (usually a sliding 0.5 gram clip).
Wobble-correction is time-consuming, and it takes longer than it looks. Very rarely is a wobble caused by an out-of-balance motor. To test, run the fan without blades, if it wobbles severely this may be the case. A slight wobble can be corrected with one of the above methods.
Winter and Summer Use
In the summer, ceiling fans are very effective at lowering the apparent temperature by making use of evaporation. Circulation of the air rapidly increases evaporation. The more evaporation, the cooler the apparent temperature. This means the thermostat on the A/C can be set higher - saving you money.
With the reverse switch set for a downward airflow, in almost all cases this is counter-clockwise (looking up), running your ceiling fan on high speed creates a turbulent column of air. This cone-shaped area of maximum airflow is relative to the area and pitch (angle) of the blades, as well as the RPMs of the motor, hence the three speeds.
Use of the ceiling fan in winter can save you money on your heating bills. A large amount of heated air can collect in a large room with high ceilings before it can even be felt. In cold climates, where possible, heater vents are put in the floor. This is the most effective way to heat a room, because the air will rise. In a room with a 16' cathedral ceiling and the thermostat set at 68 degrees F - the uppermost 3 feet can be 90 degrees or higher before the heater shuts off. An incredible waste of energy.
With the reverse switch set for an upward airflow (clockwise), running your fan on low speed will force the heat accumulated at the ceiling down along the walls where it must rise again. This mild circulation of air provides a more evenly heated room, shortening the time it takes the heater to work. (Low speed is highly recommended to avoid drafts.)
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