How to run a 104 volt fan without a Variac

[Dave Hoatson]

Many fans and motors in the early 1900’s and maybe late 1800’s were designed to run on 104 volts.

Running a 104 volt fan on modern 120 v will work, but stresses the motor. 

The increased voltage also increases the current.  104 -> 120 is a 15% increase.  But, this also causes a 15% increase in current.  Power = voltage x current.  1.15 x 1.15 = 1.32.  So, the higher voltage causes the fan to use 32% greater power (and heat).  Not good for a 115 year old rare fan.

Sometimes, I simply plug the fan into the 120 v wall outlet, but only run the fan on Low. This uses the fan’s internal speed coil to drop the voltage down to around 108-112 v, depending on the fan. Relatively safe, but not optimum. 

Most collectors say to use a Variac. This is an autotransformer with a knob to set the output voltage. These are big, heavy, and can output voltage that is higher than the input, so accidentally turning the knob up can really stress or damage your fan. 

I have a small Variac, made by Superior Electric. It is designed for 115 v input. My house is 122 v. When you set the knob to 104 v, it actually outputs 111 v. Turned fully up, it outputs 143 v. So, to use this on a 104 v fan, you need to set it using a meter and ignore the dial. And, don’t ever turn the knob all the way up.
 

I tested a KB Dial-a-Temp. $37.  It can control the speed, but it is not regulated. With the fan off, it always puts out 120 volts. You can turn the fan on High and adjust it for 104 volts, but when you switch the fan to Low, the load is reduced, the voltage increases, and the fan speed dies not change. And, if the fan has a centrifugal start switch, the extra load during start causes the voltage to drop down into the 80’s, making starting unreliable. It’s a good way to slow down a 1920’s desk fan, but it cannot provide a steady 104 v. 

Next up is a UmiPower LX-500C. $63. It is designed to operate Japanese appliances in the US, so it outputs a regulated 100 v, close enough to 104 v to do the job.

This works super well, with no issues, so that is what I’m going to use.

 

 

Edited November 27, 2022 by Dave Hoatson

[Bill Dunlap]

Nice option. With electricity prices going up (it's 35 cents per KWH here) using less has manifold benefits. First of all, it's cheaper, but the fans usually run cooler, quieter  with less vibration. In addition to that, your fans will last longer and need less maintenance. So, what's not to love?

Cheers,

Bill

PS, I have battery operated fans as well, that I can charge with cheap solar chargers. We have routine power outages here, but I flatly refuse to live without a breeze readily available.

[Russ Huber]

Typically, a 104-volt fan with a speed coil will show little to no speed change running through the gears on 120 VAC.  As far as stress on the windings is concerned put the fan on high-speed bypassing the switch coil and after it runs for 15 minutes + put your hand on the motor housing. If the 104 VAC old girl can't hack the 120 VAC stress your hand will tell you the story. 🙂 Same with the speed coil if you're using the lower speeds.

Amazon.com: VCT VT-200J Japanese Step Up / Down Voltage Transformer Converts Japan 100 Volts To 110V OR 110V to 100 Volt - 200 Watt,Black : Electronics

[Russ Huber]

These little variac buggers are great if you can pick one up for peanuts.  Compact and you can mount them in a decorative box. 

[Trevor Andersen]

I have 3 of these I use for fans best run below 120v. It doesnt work for DC but AC never an issue. I put them on a kill-a-watt and marked the dial for various volts so I can be sure its close to the right number. The dial is fully variable and not just 3 speeds as it might appear. 

https://a.co/d/5P5T7fy

 

[Russ Huber]

21 minutes ago, Trevor Andersen said:

I have 3 of these I use for fans best run below 120v. It doesnt work for DC but AC never an issue. I put them on a kill-a-watt and marked the dial for various volts so I can be sure its close to the right number. The dial is fully variable and not just 3 speeds as it might appear. 

https://a.co/d/5P5T7fy

 

• ✓ NOTE: This controller does NOT adjust below 50% to avoid burning out the motor. Not suitable for Shaded Pole Motor and Brushless Motor

Exhaust Variable Speed Fan Speed Adjuster 4.8A / 600W BN-LINK

Edited November 28, 2022 by Russ Huber

[Russ Huber]

1 hour ago, Russ Huber said:

• ✓ NOTE: This controller does NOT adjust below 50% to avoid burning out the motor. Not suitable for Shaded Pole Motor and Brushless Motor

Exhaust Variable Speed Fan Speed Adjuster 4.8A / 600W BN-LINK

I don't know why it would not be suitable for shaded and brushless motor?  McComas would probably know. 

[Trevor Andersen]

16 minutes ago, Russ Huber said:

I don't know why it would not be suitable for shaded and brushless motor?  McComas would probably know. 

Not sure why. Maybe just never tested for it during design and production. It runs everything AC Ive tried within specs but I haven't tried it on any centrifugal fans. 

[Russ Huber]

15 minutes ago, Trevor Andersen said:

Not sure why. Maybe just never tested for it during design and production. It runs everything AC Ive tried within specs but I haven't tried it on any centrifugal fans. 

McComas knows more about that stuff than I do. If it cuts off at 50% that would benefit a centrifugal switch start motor that the motor should not slow down to the point of engaging the start mechanism and cooking the start winding. At least that would be logical to me. I wonder if there is something about these solid-state speed controls that mess with certain AC motor function in an unhealthy way? 

[Roger Borg]

1 hour ago, Russ Huber said:

McComas knows more about that stuff than I do. If it cuts off at 50% that would benefit a centrifugal switch start motor that the motor should not slow down to the point of engaging the start mechanism and cooking the start winding. At least that would be logical to me. I wonder if there is something about these solid-state speed controls that mess with certain AC motor function in an unhealthy way? 

John and I corresponded over the summer about this very thing. Hope it's ok to share his words.

At the time I had a question of whether a router control could be used as a poor man's variac. He responded it chopped up the sine wave.

When the conversation shifted to the BN controller, he replied below:

Search: Google images for "Triac AC waveform" for examples of what a Triac does to the AC sine wave...

Your message peaked my interest of the BN-LINK Exhaust Fan Speed Controller.  I bought one, took it apart, and tested it with several different fans.  It has a VERY BASIC circuit and does not have the sophistication of the KB Electronics control.  It made the lamination's buzz in two of the fans.  The fixed minimum speed allows the motor to stall, (Which is not good).  Please use a Variac, or a KB Electronics KBWC-15K fan control for your best results.

[Paul Carmody]

I use the KB unit mentioned above on AC/DC fans.They work perfect.I have not tried on an AC fan yet because I integrated the controller to the line cord and gave them away to relatives.I plan on putting another together.Don’t take any of this as if I know anything as I am throwing this out only as a source of conversation.My understanding the reason a fan controller is not good for AC,is slowing it below recommended voltage will cause the motor to try and compensate and build heat.So with that thinking since these motors,fans,are designed to run on lower voltage all should be good??I’m speaking only on the KB unit since it’s the only unit I have used because the minimum speed can be adjusted so there is no chance to stall.Fans are different too than a motor that has a load other than spinning freely in the wind as far as reducing voltage.Like a saw or belt driver etc which makes it seem more plausible?
I will try soon on one of my AC fans and see anyway.

Edited November 28, 2022 by Paul Carmody

[David Kilnapp]

Terrific thread with excellent information. Thanks to all contributors.

[Paul Carmody]

Follow up on discussion.

I put this unit together.I know Variacs are the cats meow,but I run fans in 5 rooms +the garage.I also give away my restored fans, so it’s not realistic to buy Variacs by the case.Thanks to John McComas article on fan speed!

This is a KB unit, 6amp, solid state with built in noise suppressor .The last Westinghouse I restored is running on it now.For a week,15 hours a day.I locked it out at 110v and it runs smooth and quiet,no hint of vibration.First is pleasant and starts fine.Second is the speed that first was,and third is like second was.It’s dropped .12 amps across the board ,dropped 10 degrees in high,First time I have run one on a non AC/DC.Can’t say how it would work on a centrifugal??John?

On the ones made before,I incorporated the knob.On this one ,the  knob stem was  cut off and superglued at 110v .Which was the goal ,and less complicated as a gift

If you haven’t tried Wirefy heat shrink tubing,it’s great stuff.It is dual wall,has a glue inside that seals and sticks to the wire when heated.

Edited April 28, 2023 by Paul Carmody
Quiet.

[Doug Wendel]

"When you set the knob to 104 v, it actually outputs 111 v. Turned fully up, it outputs 143 v. So, to use this on a 104 v fan, you need to set it using a meter and ignore the dial."

I think on your Variac you should be able to loosen a set screw and adjust the dial so that it points to 104v when it is putting out 104v on the meter.