Evolution of/improvements to the K55?

[JW]

Just wondering if there have been any significant improvements to Emerson's K55 over the years. I stripped my plastic '81 Emerson for a good cleaning/"tune-up" last night and saw where "170/120 RPM" is actually stamped on the motor (even though the fan has 3 speeds.) Obviously, it has 4 blades. Many of the new models advertise speeds of 200 RPM and over on high, even with 5 blades and a 14 or 15 degree pitch. How could they do this, and is it possible to do something to my K55 to speed it up, aside from doing anything to the blades?

[Deleted]

The reason your Emerson goes slower is because it's the same motor assembly that the Emersons with the plastic blades use, and those plastic blades are HEAVY, so they used a smaller-value capacitor to make the motor go slower and with more torque.

Casablancas, on the other hand, have extremely light blades, and use high-value capacitors, 10uf, the highest I've seen in K55-motor type fans. So they go much faster. 6 is more standard.

[JW]

So could I basically switch out the capacitor (I assume that yellow thing in the switch housing) and make it go faster without frying the fan?

[Andrew G.]

JW said:

So could I basically switch out the capacitor (I assume that yellow thing in the switch housing) and make it go faster without frying the fan?

If you did that, the fan wouldn't move at all. Try putting a higher value capacitor in your fan. It will give the motor more speed.

[Deleted]

JW said:

So could I basically switch out the capacitor (I assume that yellow thing in the switch housing) and make it go faster without frying the fan?

Well you'd want to be very careful, raise the value too high and the motor will overheat. I wouldnt bump it all the way up to the 10 of Casablanca, assuming it's 5uf I would maybe go up to 7.5 safely, but that's only a guess. Experiment. If the motor gets hotter faster than it currently does, you've gone too far.

[Deleted]

Dan said:

The reason your Emerson goes slower is because it's the same motor assembly that the Emersons with the plastic blades use, and those plastic blades are HEAVY, so they used a smaller-value capacitor to make the motor go slower and with more torque.

Correction: I over-simplified it a bit.

The higher value capacitor used in any given motor, the higher the speed will be, and the *higher* the torque. However it will draw increasing amount of current, and the more current, the more heat. Using a higher value of capacitor than is optimized for the motor could result in overheating.

A greater load (with the torque being constant) also results in greater current draw, and more heat. There's an optimal capacitor value for the motor windings that results in the greatest efficiency, but the load is also a factor. The capacitor value has to be optimized with both the windings and the load, lest the motor overheat.