How To Select The Perfect Ceiling Fan

Factors To Consider

A ceiling fan for your conservatory can be both a blessing and a curse.  When the sun comes out you suddenly realise just how hot it gets in your conservatory.  You can open the windows, put in blinds but it still gets so hot and by early afternoon too damn hot!  Some people even put air conditioning in but that is a huge waste of money.  When buying a ceiling fan you need to consider a number of important things in order to get the right fan to meet your needs and ensure that you spend your money wisely.  Here we will consider just what a ceiling fan can do for you and exactly what those considerations are.

How A Conservatory Heats Up

A conservatory works like a greenhouse trapping UV and infrared heat radiation even if outside is cool or overcast.  The floor and bricks inside also warm up and give off convection heat which then adds to the head from the incoming radiation to make it get hotter and hotter as the day goes on.   The hot air rises and gets trapped under the roof.  It is thus essential to have vents at the top to let this hot air out.  If you don’t then opening windows might let some of this heat out if there is a breeze outside otherwise it will tend to just sit there.

Three Ways A Ceiling Fan Cools A Conservatory

There are three significant ways that a ceiling fan can reduce and remove the unwanted heat from a conservatory:

1. Direct skin cooling – by virtue of the “wind chill effect” of air moving over the skin a cooling effect of 3-4°C is achieved.  For this smooth laminar airflow is required rather than turbulent buffeting flow which also feels more pleasant.  In humid conditions the effect of just having air moving over the skin is fantastic since hot humid still air is so unpleasant.
2. Removal of heat –  the hot air can be quickly moved away from the warm surfaces by a ceiling fan, thus cooling it down.  The problem is that unless a window is open then there is nowhere for this hot air to go which means you will simply get hotter and hotter, so it is important to open a window.  The ceiling fan will then draw in cooler air from outside due to the airflow around the room.  Note that it doesn’t have to be blowing directly out of a window like an extractor fan, the way the air moves creates zones of lower pressure near the windows that simply draws in air from outside.  Given that the greenhouse effect can easily cause temperatures inside to rise to 40°C or more this will make a big difference.  One tip is to open the windows and turn the fan on early in the day to prevent any build up of heat.
3. Night-time dissipation – this is where a real bonus can be achieved.  Since night-time air temperature can drop significantly even in hot climates the trick is to leave the windows open all night with the fan on slow speed in reverse.  The aim is to release all the of the absorbed heat in the solid materials of the floor and walls which if left warm overnight will get even hotter the next day.  These materials act as a store of heat energy and by circulating cool air over them through the night all this energy is dissipated leaving a store of “coolness” to operate the next day.  Solids heat and cool very slowly so this works very well and can be almost as effective as having air conditioning but without the cost.

Ceiling Fan Function

The function covers the operation and make-up of the fan.  This includes the technical specifications, performance, features, build quality and reliability of the ceiling fan.  Hear are the salient points to consider:

1. Reliability and Warranty – A conservatory ceiling fan is something you want to last for many years so look for a reputable reliable manufacturer who gives a minimum of 10 years guarantee.  Fantasia offer a 5-10 year guarantee on most of their fans.  However a Lifetime Warranty is obviously much better and worth paying a bit more for since a manufacturer isn’t going to offer that and than make a poor quality product.  On the market there are only 5 brands that offer a Lifetime Warranty – Hunter, Minka Aire, Matthews, Star and Henley Fan.  All of these brands are stocked by Henley Fan as well as selling their own product and have been around for decades so the warranty actually means something.  Anyone can offer a Lifetime Warranty but it is of no value unless they are still in business when you need it. Hunter Fan for example is the oldest and largest ceiling fan manufacturer who have been around 125 years. It is important to note that the warranty almost always applies to the motor only and not to the blades. Neither does it apply to the light kit or remote control which are usually just 1 year’s warranty nor to the finish.
2. Dampness –  Whilst in the spring and summer months your conservatory can get unbearably hot in the winter it can get cold and damp especially if there is no heating on. This will surprisingly quickly lead to corrosion setting in which will affect the motor laminations (which are steel), the finish and the blades.  Cheap metallic finishes are likely to start to pit, crack and flake off within 2 years.  Blades can start to warp if made from hardboard, MDF or other cheap materials due to the effects of moisture.  This warping will make the fan unbalanced causing it to wobble making an annoying noise.
3. Specifications – How many fans do I need to cover my room?  This depends on the size and how good the performance is.  How high are my ceilings as a fan that is more than 0.5m above head height is not going to be very effective so you will need a drop rod to bring it down to the correct height.  If your ceiling is low then you will need a flush mounted or low profile ceiling fan. Do I want to use a pull chain or have a hand or wall remote control?  How many speeds do I need?  Do I want to have a fan that reverses so that in the winter I can bring trapped heat down to floor level saving me money on heating bills? Do I want to have a light with my fan, and if so one that can be switched at the wall? – meaning you will require a 4-core wire to be run from the fan to the wall control.
4. Performance – How many blades should I have?  There is a lot of misunderstanding on this point.  Less blades actually more move air per watt of power since there is less overall drag and so are more efficient but for a given speed more blades will move more air which means less noise.  Looked at from the other perspective for a given airflow less blades need to move faster and so make more air noise, create more drag and are less efficient. The other important consideration here is that the airflow needs to be laminar and NOT turbulent which feels uncomfortable on the face.  Laminar airflow is where you get a gentle smooth airflow from a slow rotational speed (in engineering terms where the Reynolds number is less than 2,000).   In reality there is not much difference between 3, 4 or 5 blades so the choice should come down to appearance and style.
5. Blade Size – The bigger the blade size the more air is moved and the more energy is consumed. However a larger blade running at a lower speed is much quieter than a smaller blade running at a high speed.  Typical sizes are 42″ (107cm) and 52″ (132 cm) but for very small rooms you can get a 36″(92 cm) size and for very large rooms look for 56″, 60″ or even bigger.  Look at each manufacturer for the span of action of a fan so you can size up how many you need to cover a large rooms.  In small to medium sized rooms 1 properly sized fan should be sufficient.
6. Speed – Most fans operate at 3 different speeds.  Speed interacts with size and power (see previous point).  Speed is controlled by either a gearbox (in rare situations) or more usually by a thyristor/capacitor and microchip controller.  The latest low energy DC invertor controllers are more accurate and can give 6-speeds saving up to 70% of the energy over an equivalent AC ceiling fan.  The early models were susceptible to voltage variations and spikes leading to unreliable operation.  The second generation DC controllers are extremely robust so make sure when you buy a ceiling fan that it uses the second generation technology.  Here the use of cheap components can lead to annoying buzzes and premature failure of the fan motor.
7. Features – Better manufacturers such as Hunter have many patented and useful features such as wobble free canopy mounting systems, low energy motors, easy installation systems etc.  Preventing wobble is essential to reduce noise to a minimum which can be very annoying especially if the fan is going in a quiet room such as a bedroom.  DC motors are completely silent plus can be run at very low speeds (as they have a 6 speed control) and so ideal for bedrooms.
8. Build quality – Cheap manufacturers will use cheaper components that will fail much quicker often just outside the 1-year warranty period.  At the core of a ceiling fan is the motor – one moving part – so not much to go wrong?  Wrong!  A cheap speed control capacitor can easily fail after 18 months or sooner and can start buzzing long before it gives up.  Cheap motor laminates can buzz and fail and unless the copper windings are encased properly in resin can corrode and short leading to motor failure.  This is especially important in conservatories where the ambient temperature at night can fall below the dew point causing moisture to condense onto the motor which in turn will lead to corrosion and failure.  Blades need to be made not from cheap cardboard or hardboard but proper plywood, ABS or seasoned or compressed solid wood to avoid twisting.