Capacitor Selection for Salvaged Ceiling Fan - Page 1
Forum section: electronics / repair

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: March 09, 2020, 12:29:19 am
content: Hi all.I recently got this ceiling fan working satisfactorily, except for controlling its speed.The original unit, which may have been marketed as a Harbor Breeze SailStream, came with a remote that I do not have. The receiver/controller module inside the fan housing was badly damaged, so I gutted it. But before I snipped the wires I noted all pertinent connections, then Ohm'ed out the motor windings. In looking at the now redundant circuit board--a true marvel of 21st century Asian microengineering--I can see two fat 5uF @200VAC capacitors, what I believe are two 12V relays, and a whole host of other stuff I don't understand at all. But I don't care because I hate remotes and want this rig to be operated via wall switches anyway. So...In the admittedly lo-res photos attached are a couple of schematics I've drawn up which I hope somebody will scrutinize and help me correct if there are any errors. Here's what I think is going on: In the second photo (showing the fan's controller module disassembled) is a schematic I cribbed somewhere. Faintly visible down the middle of the paper is a dashed line. To the right of it lie a voltage source, a motor, and a start capacitor, labeled C1. This part of the circuit is now working, and the speed selection switch (on the left side) is yet to be wired up. But it doesn't include a way to reverse the direction of the fan's rotation, so I drew up another schematic, visible in the third pic. If I've got this right, the speed switch can add one or another capacitor in parallel with C1 which will somehow magically change the motor's speed. The Direction switch changes the way the main winding, labeled L1, connects to the secondary, which I have labeled L2. I may have this a bit confused, but I know the DC resistance of each winding, and I know the original onboard capacitors are both 5uF. Can I rely on these values for my own circuit build, and if so, how do I go about wiring them into a wall switch? Any help would be greatly appreciated.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 09, 2020, 02:12:30 am
content: One of the capacitors (probably the one with a higher voltage rating) will be for the "start" winding of the motor and the other two for speed control.http://repairfaq.org/sam/appfaq.htm#afceilf

author: Gyro
author_rank: Super Contributor
timestamp: March 09, 2020, 10:17:50 am
content: From your schematics, those are just motor-run capacitors - there is no 'start capacitor'. The switch / circuit is wired so that there is always at least one run capacitor in circuit (otherwise the motor would stall and overheat).The speed is just controlled by the amount of capacitance in series with the L2 winding. This varies the efficiency of the motor. The maximum capacitance setting is what would normally be regarded as the 'correct' motor run capacitor for efficient operation ( hence maximum speed). The lower capacitance settings simply reduce the L2 winding current and phase shift, reducing the efficiency of the motor and so making it run slower. C1 will be the lowest value capacitor that allows the motor to run reliably.P.S. You will probably find thatbothC2 and C3 are switched in parallel with C1 at full speed (especially if they are both the same value).

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: March 10, 2020, 06:07:44 pm
content: Quote from: Gyro on March 09, 2020, 10:17:50 am

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: March 10, 2020, 07:14:07 pm
content: Thanks, NiHaoMike and Gyro.I have gone ahead and ordered a dual 5uF capacitor but still am not sure how to wire them in. In considering your replies, I realized that errors have been introduced from the beginning in my presentation of the problem. First of all, the schematics may not tally with the circuit under test. Second, my observations and assumptions about how the circuit functions are imprecise. And I'm a dumbass.So let's have another look. I have a black box. I know that inside it are a receiver of some sort and a controller for a ceiling fan's light and motor. I never had the corresponding remote control, which contained a transmitter and some switches to allow the user to switch the light on and off and to change the direction and speed of the motor. Embossed on the housing of the box is a sort of wiring diagram, reproduced below. Exiting the box are a number of leads, some of which connect to the AC line (117 VAC/60Hz where I live) and some to a wiring harness which in turn feeds six wires into the skinny pipe that leads to the motor and light.Based on the wiring diagram found on the controller housing, I have identified the six leads in this way: White (1) connects to the neutral coming in from the AC wall current. Along with Blue, it connects to the light. White (2) is the neutral going in to the motor. It goes to one side of the secondary winding. Red passes through a wire labeled "Start Capacitor" to another wire labeled "Motor L" and thence to the other side of the secondary. Brown and Grey, both labeled "To Fan Reversing", go to opposite ends of the primary, or "Main" winding.The two capacitors inside the controller may or may not connect to the relays I noted earlier (incorrectly as 12VDC; actually they're rated 3A@125VAC), which respectively feed the Brown and Grey wires of the motor's primary. Does it matter whether I wire the new capacitors on to these wires as opposed to the pair which connect to the primary winding, where there is already a 4.5uF capacitor?I'm hoping that once I get the whole unit assembled and running smoothly I can present my findings in a way that may prove useful to future dumbass Dumpster-divers like myself.... Thanks again for your help.Update:Apologies are in order for the amazing level of stupidity I've shown in this thread.... I got good feedback that helped me interpret stuff I'd dug up elsewhere, but I just couldn't seem to make use of it. The problem was compounded by the fact that my salvaged fan had its glass globe frozen on, which kept me from accessing the motor's internal electrical connections. Hammer and chisel and some adhesive tape came in real handy here... The existing fan control switch I removed from the wall was a typical cheap Chinese unit, the kind which has a crappy plastic switch mounted on a PCB along with two capacitors and a couple of resistors. I believe it uses a multi-pole switch to provide various values of capacitance to the motor via series/parallel connections between the two capacitors, one 9uF and the other 4.5uF. Since the motor on the fan already had a 4.5uF capacitor of its own wired in, there seemed no way to use a wall switch to give me the series/parallel capacitor values I needed. And I wanted to run separate hot and neutral lines for both the fan and its built-in lamp circuit anyway to allow for two wall switches to control them independently, because I read that new electrical code in my area requires this.So here's what I did: I removed the motor's built-in capacitor and wired in the old four-way wall switch on a test jig. Cycling the switch through its positions, I got terrible results: the motor either didn't turn at all or turned at one of two different unacceptably slow speeds. Since all the other fans in this house are controlled by simple SPST wall switches that don't offer speed OR direction control, I decided to wire my new-old fan the same way. I tossed out the old switch, put the original 4.5uF cap back on the motor, wired in separate wall switches for the fan and light and called itdone.Ceiling fans like the one I've now dragged home, torn apart and successfully hooked up retail for $100 or more, so the $20 or so I spent on capacitors and switches was a bargain and a half. Now I've managed to replace a blown ceiling fan and lamp, and based on the research I've done, assisted by some sage advice picked up on this forum, I know how to salvage almost any ceiling fan that shows up in the waste stream. That might happen soon, andI'll be ready this time. Thanks again to all who responded.