ceiling-fanrecessed-lighting
A regular ceiling fan with wooden blades will cause a light strobe effect when mounted where the blades rotate under recessed/canned lights. I am wondering if I would have the same strobing problem if I got a ceiling fan with clear, acrylic blades like this one.
Anyone have any experience with this? I am thinking since the blades are clear they won't block the light when the circle under the canned light so maybe there is no strobing?
TL;DR: the dimmers aren't switching off completely: they're allowing some current to leak through, which is why you're seeing a voltage across the CFL. A different make of bulb may behave better with the leakage current that you're getting. Or perhaps a different brand of fan (if you haven't installed them all already).
I do know that operating CFLs in those sort of conditions will shorten their lives considerably, so you might actually be cheaper for you to use incandescents instead (a quick calculation says about 12 kWh per year for a 60 W bulb).
Read on for the technical explanation...
The voltage across the bulbs, Vb is determined by the formula:
Vb = Vin * Rbulb / (Rdimmer + Rbulb)
where:
The dimmer is a solid-state electronic circuit, so it has a very high effective resistance -- 10s of megohms is not unreasonable. Ditto for the control circuitry in the CFL. An incandescent bulb is a simple piece of resistive wire; a 60 W / 120 V bulb will have a resistance of 240 ohms.
Now, suppose the dimmer has a resistance of 50 MOhms and the CFL has a resistance of 10 MOhms; plugging the numbers into the equation above gives you 20 V across the bulb. OTOH, the voltage across a 60 W incandescent bulb will be about 600 microVolts, nowhere near enough to make the bulb glow.
If you have two bulbs in the light fixture, the resistance, R, of the two in parallel is given by:
R = R1*R2/(R1 + R2)
So if you have a CFL and an incandescent installed, the effective resistance is going to be very close to that of the incandescent alone:
R = 10,000,000 * 240 / (10,000,000 + 240) = 239.99 Ohms
Again, not enough to turn on either bulb.
With two incandescent bulbs, the effective resistance is half that of a single incandescent, so you have half the voltage across them.
The flickering you see with two CFLs is because the light you see is basically a high-voltage spark through the tube. The CFL contains circuitry to amplify the incoming voltage up to the point where the spark can occur. Under normal circumstances, the input voltage is enough to cause this spark 100 or 120 times per second (depending on mains frequency), which is far too frequent for the human eye to notice. With the reduced input voltage, it takes longer to reach the required voltage, so you notice the flicker. No two bulbs will be exactly identical, so they'll flicker at different rates and take different times to recover between discharges.
At first I would have said its just the noise of the motor Inducing the power into the windings. But since you hear the noise when the unit is off, It is obviously a noise near the bearing. Either your bearing has seized or the bearing housing assembly has been damaged.
The only thing to do is to try and gain better access of the bearing area and visually inspect. It could be the metal scraping near to the bearing assembly, but its so hard to tell.
Remediation action could involve - bending any contacting components - replacing the bearing (which will be difficult since its probably press-fit) - applying grease and lubricants to minimise scraping noise.
But once again, its hard to tell without looking.
Best Answer
"Clear" things do not pass 100% of light hitting them. A quick search indicates "up to 92%" for acrylic, generically (may be less depending on details of fan blades and how clean they are) - as such, you will still have at least some "strobing" effect if the light source is above the fan.