Super Ceiling Fan Motor

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Little Bill

Little Bill

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Semi-Retired Electrician
I don't know what else to call a ceiling fan motor such as I found while swapping out the fan. The fan was not on a wall switch so I disconnected it hot, then put my breaker finder transmitter on the wires so I could find the breaker to turn it off.

The breaker finder sounded off so I turned off the breaker that was indicated. When I checked the fan the power was still on. So to avoid more false readings I just turned each SP breaker off, one at a time while having the HO watch my transmitter light.
None of the SP breakers controlled the fan, so I started with the 2-P breakers.
It was one of them.

I thought no big deal except it was a 30A 2-P on what I thought was #12 wire. Turns out the 12 was spliced onto #10 in the junction box. My "little voice" told me to check the voltage on the wires at the fan. Glad I did because I had 240V at the fan. The HO's husband (now deceased) took out a ceiling heater that was 240V and just used the wires and breaker for the fan.

My question is, how could the fan motor run on 240V for over 8 years? The motor was clearly marked 120V with nothing on the nameplate saying it could be wired for 240V.
It was "toast" when I took it down. The HO said she smelled something and her fan wouldn't come on so she called me to install a new one.
 
Maybe the fan speed control was always clicked to a lower speed adding life to that motor.
Of course low was still probably normal speed:p Imagine how fast it went on high! Probably a reason to set it on lower speed? Or maybe the widow just never used it.
 
Little Bill said:
I don't know what else to call a ceiling fan motor such as I found while swapping out the fan. The fan was not on a wall switch so I disconnected it hot, then put my breaker finder transmitter on the wires so I could find the breaker to turn it off.

The breaker finder sounded off so I turned off the breaker that was indicated. When I checked the fan the power was still on. So to avoid more false readings I just turned each SP breaker off, one at a time while having the HO watch my transmitter light.
None of the SP breakers controlled the fan, so I started with the 2-P breakers.
It was one of them.

I thought no big deal except it was a 30A 2-P on what I thought was #12 wire. Turns out the 12 was spliced onto #10 in the junction box. My "little voice" told me to check the voltage on the wires at the fan. Glad I did because I had 240V at the fan. The HO's husband (now deceased) took out a ceiling heater that was 240V and just used the wires and breaker for the fan.

My question is, how could the fan motor run on 240V for over 8 years? The motor was clearly marked 120V with nothing on the nameplate saying it could be wired for 240V.
It was "toast" when I took it down. The HO said she smelled something and her fan wouldn't come on so she called me to install a new one.
Click to expand...
Most likely is was an old shaded pole fan motor, they are very tolerant of things like this. You can control the speed of a shaded pole motor with a rheostat by changing the voltage. But in reality, you are changing the torque of the motor, and the FAN load is making it slow down. At double the voltage, the motor would have been theoretically capable of more torque, but because the frequency is the same, it turned the same speed it normally would, so the actual load on the motor did not increase. The motor was SATURATING, which was heating it up, but shaded pole motors are usually "impedance protected", which means they are designed to handle locked rotor current continuously (defined as no less than 15 days) without over heating to a point where it would start a fire. In this case, that extra heat handling capability was keeping it from burning up for 8 years. If it had gone locked-rotor AND double the voltage, it would not likely have been able to handle it, but one OR the other was OK.
 
Is this a rinky dink ceiling fan or a whole house fan which sucks like a jet turbine from the living space into the attic?
 
Jraef said:
Most likely is was an old shaded pole fan motor, they are very tolerant of things like this. You can control the speed of a shaded pole motor with a rheostat by changing the voltage. But in reality, you are changing the torque of the motor, and the FAN load is making it slow down. At double the voltage, the motor would have been theoretically capable of more torque, but because the frequency is the same, it turned the same speed it normally would, so the actual load on the motor did not increase. The motor was SATURATING, which was heating it up, but shaded pole motors are usually "impedance protected", which means they are designed to handle locked rotor current continuously (defined as no less than 15 days) without over heating to a point where it would start a fire. In this case, that extra heat handling capability was keeping it from burning up for 8 years. If it had gone locked-rotor AND double the voltage, it would not likely have been able to handle it, but one OR the other was OK.
Click to expand...

Thanks, that helps me understand more about this now. Just wondering how hot this thing got over the years. I didn't see any scorch/burnt spots anywhere. I did check the fan before taking it down by spinning the blades by hand. They would keep turning although would slow down. I was thinking maybe the capacitor was just burnt out. But after I noticed the burnt smell I didn't investigate any deeper.

mgookin said:
Is this a rinky dink ceiling fan or a whole house fan which sucks like a jet turbine from the living space into the attic?
Click to expand...

Rinky dinky ceiling fan:)!
 
I'm glad everything worked out for grandma. She has a good Sparky! :thumbsup:
 
A shaded pole motor would not have a capacitor.
The bearings may just have gotten sticky enough to keep the shaft from rotating. How did it feel to spin it with the power off?

Tapatalk!
 
Yeah, no cap. But with 8 years at elevated temperature, the insulation in the motor winding likely broke down. The smell was likely the final stage of that long term failure. The rule of thumb on insulation life is that for every 10deg. C over design temperature you take it, you decrease the insulation life by 50%. So assuming Class A insulation on a residential motor, that's 20,000 hours at 105deg. C, so 221deg. F (internal insulation temperature, not what you feel on the outside). There is however no rule of thumb on the effect of doubling the voltage has on insulation temperature, because you aren't supposed to do that ...:slaphead: Needless to say though, it was going to be well out of spec. Given that it lasted 8 years, and apparently there was no on-off switch (other than the breaker?) so it was likely running 24/7 (8,736 hours per year), 8 years is a testament to it's conservative design!

In the "impedance protected" concept, the motor cannot get hot enough to start itself or anything next to it on fire. How hot that actually is I don't know, but it would feel very hot to the touch. Normal motor surface temperature is allowed to be as much as 158 degrees F, and the human threshold for pain is 107deg. F, so once you touch something over that level, it's hard to tell how FAR over that level it is.
 
GoldDigger said:
A shaded pole motor would not have a capacitor.
The bearings may just have gotten sticky enough to keep the shaft from rotating. How did it feel to spin it with the power off?



Tapatalk!
Click to expand...

It didn't seem hard/rough spinning it by hand. As I said, I spun it with it on and it stayed spinning but not very fast.

Jraef said:
Yeah, no cap. But with 8 years at elevated temperature, the insulation in the motor winding likely broke down. The smell was likely the final stage of that long term failure. The rule of thumb on insulation life is that for every 10deg. C over design temperature you take it, you decrease the insulation life by 50%. So assuming Class A insulation on a residential motor, that's 20,000 hours at 105deg. C, so 221deg. F (internal insulation temperature, not what you feel on the outside). There is however no rule of thumb on the effect of doubling the voltage has on insulation temperature, because you aren't supposed to do that ...:slaphead: Needless to say though, it was going to be well out of spec. Given that it lasted 8 years, and apparently there was no on-off switch (other than the breaker?) so it was likely running 24/7 (8,736 hours per year), 8 years is a testament to it's conservative design!

In the "impedance protected" concept, the motor cannot get hot enough to start itself or anything next to it on fire. How hot that actually is I don't know, but it would feel very hot to the touch. Normal motor surface temperature is allowed to be as much as 158 degrees F, and the human threshold for pain is 107deg. F, so once you touch something over that level, it's hard to tell how FAR over that level it is.
Click to expand...

What I said was it didn't have a wall switch. It did have a pull chain switch. The fan did not run all the time.
 
Little Bill said:
It didn't seem hard/rough spinning it by hand. As I said, I spun it with it on and it stayed spinning but not very fast.



What I said was it didn't have a wall switch. It did have a pull chain switch. The fan did not run all the time.
Click to expand...
The pull chain switch may not have been rated for 240V either, but apparently at the low current the fan drew it survived just fine.
 
If I understand this correctly we had a 240 volt heater at one time that was removed, then same circuit was used to supply this fan. I also am understanding this fan is your typical "paddle fan". Those are usually PSC motors, and to change speed they switch different value capacitor into the circuit, which also essentially changes the torque of the motor and having more slip because of low torque results in lower speed. If this fan were to be run primarily on the low speed setting that would probably increase the life of it when operating at 240 volts, but you would see higher speed then if 120 were supplied to it, in many ways a lot of similarities to the shaded pole application earlier described.
 
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