AC ceiling fan

Check the rubber vibration isolation joint(s).

If there are none, it would likely have been humming from day one.

RL

Check the capacitor.

Rubber mounts are good to the ceiling...

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Check it in what way ? would it cause a 'beat frequency' of ~5Hz ? ( UK is 50Hz)

If it's not spinning it could be a bad capacitor on the motor especially if it responds to a push start.

Could be the bearings need a lube

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  Jasen.

is it still a capacitor?

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  Jasen.

It all works fine, apart from the fact that it 'hums'....

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Remove the new hearing aides you just recently got?

Not dried out or cut through?

RL

No- your original description made it sound like it was stalled. Now it sounds like it's not coming up to speed. Unless you have a motor repair shop, give it to a metals recycler.

Yes, it could. If the cap has lost some of its value, it will give the wrong phase shift, and the motor would vibrate at twice mains frequency. As the rotor slips, the shorting bars in the squirrel cage occasionally line up with the stator poles and give different current and torque. So, the slow throbbing humm you hear is the slip of the rotor.

Jon

Is the fan a variable-speed model? Motors differ in their characteristics, and a ceiling-fan motor is often an oddball low-torque type.

Thanks, that makes sense to me with my limited AC theory of nearly 50 years ago...

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Yes, three speeds, with reverse facility...Low speed it's quiet. Med speed it's irritating. High speed , forget it. ( night time sleeping, that is). Daytime in a lounge with TV on, it's probably unnoticible...

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Possible but sounds far fetched. Simplest explanation is usually best, and that would be worn out of round sleeve bearing for shaft.

That would be consistent with torque causing the hum, and perhaps just a clean/lube will lessen the required torque. For some motors, bearing wear can cause the rotor to move off-center in the stator windings, which is worth checking. Minor bearing wear is OK if you relube with a solids-in-suspension oil (I kinda like Tri-Flow, with PTFE (?)microbeads).

Wow, I haven't seen a sleeve bearing in a ceiling fan made later than the

1930's. I suppose that could be, but the low speed and weight of the rotor and fan would really BEG for a ball bearing. All the ones in my house are definitely ball bearing.

Jon

A few shorted turns?

The standard old-time design was a bronze (or babbit) sleeve (or cone) bearing in a pool of oil. These last essentiallly forever, so long as there is still liquid oil wetting the bearing. One cleans them out and replaces the oil every 25 years or so.

In the 1970s, I lived in Sweden and rescued an old cast-iron table fan with variable speed, needed to blow rosin fumes away from soldering. The fan had been in the basement longer than anyone recalled. I took it apart, cleaned and oiled it. It was in perfect mechanical condition. It was all sleve and thrust bearings of bronze, in cast-iron housings.

When I first plugged it in, it sat there and hummed, turning lazily. Huh? Then it hit me - that fan was very old. Just what kind of electricity did it need, AC or DC?? Turned out to be DC, and Sweden converted to AC in something like 1920, whereupon the fan become inoperable. But it was too well made (and expensive) to just throw away, so it lived in the basement. In the 1970s, silicon rectifier diodes were common and suitable, and so that fan got a full-wave rectifier bridge upgrade. That did the trick. When I visited Sewden in 2010 or so, my business partner still had that fan, and it still worked.

Joe Gwinn