Fan Q

I always use US 110V 52" (54") fans in bedrooms. It is tricky getting the mounting right in order to keep the unit as silent as possible(no hum). A Maplin 110V Xfmr works well (about £17 IIRC). Running a 60Hz fan at 50Hz slows it down a bit and makes it quieter still. Big blades mean that there is no air noise on slower settings and they can run overnight without disturbing peoples sleep. Small ceiling fans IME are always much noisier.

We have ceiling fans in our bedrooms. More effective and quieter than any other option tried (oscillating, vertical, "standard",...). Wouldn't wish to use other than on slowest setting but the higher speeds can help to do a fast whoosh before going to bed if the temperature has been allowed to rise too high.

Most of those fans use shaded pole motors which will reduce speed with lower voltage as this allows the slip to increase. Use a variac to explore how low the voltage can be reduced and yet still allow the motor to start from stationary. Normally the oscillating mechanism imposes greater load at the end of each sweep so make sure there is enough torque to keep it working. You don't want the motor to stall as it will then cook.

It will cook long before it stalls. Been there, done that ;-) Power dissipation doesn't drop at anything like the rate that cooling drops off, as you slow it.

Stop buying crp and get a ceiling fan. Theyre vastly better. Sure they take a little time to fit, but are so worth it. Check the wiki page on ceiling fan noise reduction too.

NT

Also these fans that sit on the floor seem to send noise through the floor. A lump of foam can help as the fan itself is not noisy. I don't like the oscillation though, very offputting. Brian

What happens if you put a classical drill speed controller that modulates the proportion of a power cycle in the input lead?

The cooling will still fall off faster than the thermal heating but probably in a more forgiving way than with a variac or series resistor. I intend to investigate slowing my office fan down this summer if it ever gets hot enough to need it. Even on the slowest "quiet" fan setting it rearranges paper on my desk in most annoying way and on the hurricane setting it becomes hard to approach it to switch it off.

Luckily it has a remote. I don't understand why no-one makes one with a properly slow speed where the fan would be essentially silent. You only need to stir the air in a room up a bit to help make it feel cooler.

I dont see why it would

Cost. You need a large fan to have much effect when silent, you need a moto r able to run at lower rpm, you need more torque despite lower rpm, and a c ontroller thats smarter than a simple series cap to address stalling. Large fans are best put on the ceiling. Coincidentally its not hard to find near silent ceiling fans.

NT

Do you live in the UK? Whenever has it ever got too hot?

Philip

My first job was in a giant open-plan office with a high ceiling and rows of the suspended helicopter type fans. A game some of the YTS youths would play was to turn one up to max, and scarper. It took a while for them to speed up, by which time the miscreant had gone, and you then had the challenge of holding down all the papers on your desk, whilst being unable to reach the speed control, or leaving your desk to turn the fan off and watch your papers go flying, and it still took another few minutes to slow down.

Needs a more expensive motor to cover the wider range.

Large ceiling fans usually have something like a 36 pole motor, and a back-to-front arrangement where the rotor is outside of the field windings, but they can't go as fast.

Now imagine one of those, spinning at 30 times the speed, and generating similar air pressure and flow to a vacuum cleaner, at significantly less power consumption. Then you might be getting close.

I don't need to imagine one, there have been ones that run that fast for decades, they just don't get used in domestic equipment much.

Its like the vortex generators Dysoon invented, they had been used in industry for decades before he invented them.

to make money.

I listened to one of those today. I found it had very noisy airflow. Not a bedroom item IMO.

The digital motors are in the airblade hand dryers and the long thin pointy hoovers, not the fans - that said I haven't listened to an of their fans recently.

Which I suspect of being illegally loud. I keep meaning to measure the one in the bogs at work.

Probably only if you spend your entire working day there. ;-)

Chris

The bog standard "Madge armpit dryer" seems to be 82dBA, airblade 87dBA if run without actually using it or 90dBA with hands in the airstream.