Can I use a dimmer with this fan?

Thread Starter

Bart Gojjer

Joined Apr 23, 2017
5
Hello,

I use electronics from time to time at work and am seeking advice for this problem. I want to dim the speed of a fan I have that is normally used to power an air dancer, like the ones used to advertise outside car dealerships. I am using my fan to inflate a prop for a video we are shooting. It's a similar design to the air dancer but I'm making a custom inflatable out of plastic bags. It is not quite as heavy as the air dancer and I want to be able to control (lower) the speed of the fan to find the sweet spot for how much power this inflatable needs to be inflated but still controlled and not destroyed. Question - can I use a dimmer to control the fan?

The fan is 1.0 HP, 115 voltage, 11/8 Amp, 60 Hz. My friend has a 1K dimmer that I can borrow and experiment with, but we both aren't sure if this will damage the motor. For my purposes, I want to turn the fan on in a dimmed state a few times for 2-5 minutes each time. Probably up to 8 times for us to rehearse with the prop, and then up to another 8 times to shoot the scene for the video. After that, I don't necessarily need the fan for anything else in a dimmed or undimmed state. I bought the fan for this project and may try to sell it when we're done with it.

This is a link to where I bought the fan: https://www.amazon.com/gp/product/B07FZ1PHZK/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

And here is a picture of some info on the side of the fan: fan pic.jpg

Any thoughts are much appreciated!

Thank you,

BenG
 

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Motor damage - not liklely. Dimmer damage likely. 1 HP is a lot and it's close to the limit of what might be used on a 120V outlet.

The best way to do what you want to accomplish is to buy a 240VAC 3 phase motor and to use a 120 V to 240 V, 3-phase VFD (or Variable Frequency drive) to drive the motor.

I didn't look at it closely, but https://www.driveswarehouse.com/ode-3-110042-1012 is an example.

I know that's not what you wanted to hear.
 

Thread Starter

Bart Gojjer

Joined Apr 23, 2017
5
D'oh! That's probably out of our price range. I may have to use my other hypothesized solution, which was to have a sort of "exhaust" hole between the fan and the inflatable to release a lot of the air before entering the inflatable. Or use a couple shop vacs in reverse to inflate this instead of my behemoth air dancer fan. I wouldn't want to damage my friend's dimmer.

Thank you for your thoughts!
 

djsfantasi

Joined Apr 11, 2010
7,842
D'oh! That's probably out of our price range. I may have to use my other hypothesized solution, which was to have a sort of "exhaust" hole between the fan and the inflatable to release a lot of the air before entering the inflatable. Or use a couple shop vacs in reverse to inflate this instead of my behemoth air dancer fan. I wouldn't want to damage my friend's dimmer.

Thank you for your thoughts!
How big is the hole into the inflatable? With water, I’ve fed the pump into a tee, with the straight leg into a valve. This adjusted the water flow over a waterfall.

The same concept could be used for air. Just an idea.
 

Thread Starter

Bart Gojjer

Joined Apr 23, 2017
5
oh this is a good point! I'm making the inflatable still so I can decide how big the hole is. I just have to get from the fan to the inflatable. The fan is 18" diameter. The inflatable is made out of .7 mil plastic. I was going to make a straight plastic "wind sock" at 18" diameter that attaches to the fan face and then attaches to a hole in the back of the inflatable. But maybe I should make some kind of adapter that can take me from the fan face to a tee (with a smaller diameter), then add a valve off the straight leg of the tee and then feed into a thinner plastic "wind sock" that then feeds directly into the back of the inflatable. And the perpendicular leg of the tee can be open to let off air pressure. I guess the challenge with all this is that narrowing the air flow from the 18" diameter fan face to a tee will mean sending a lot of air pressure into that tee?
 

MisterBill2

Joined Jan 23, 2018
9,304
Controlling the speed of the motor would be a bit of a challenge, and a variable speed drive for one HP will be expensive. A bypass scheme will be less efficient but for the time you wil be running it, still cheaper than a dimmer. The problem with a typical dimmer is that the chopping effect of the control distorts the line waveform, and induction motors do not like distorted power. A variable bleed bypass will be much simpler and a lot cheaper, and easier to control.
 

Dodgydave

Joined Jun 22, 2012
10,050
You can try Capacitors in series with the fan supply, try 1uF and if it's too slow add a capacitor (in parallel with the other) to make 2uF , that's how Ceiling fans work, make sure the capacitor is rated at 275V AC or higher.
 

crutschow

Joined Mar 14, 2008
27,751
You can try Capacitors in series with the fan supply, try 1uF and if it's too slow add a capacitor (in parallel with the other) to make 2uF ,
I've use that size capacitors to control the speed of a large table fan, but I think you will need a lot more capacitance for a 1HP motor, likely upwards of 10μF (film type).
A motor running capacitor may work.
 

MisterBill2

Joined Jan 23, 2018
9,304
Several years ago I did install a variable speed control for one of those "whole house" fans that had been such a fad back in the 1950's. That was a 1/2 HP motor. That controller was rated for such a motor and it fit inside a regular single electrical box. It cost more than a dimmer at the time, about $30, and it came from the Grainger company. I am not sure if those are still available, but it would be worth investigating to find out. It did work fairly well, and so that is another option. The benefit would be not having to do any circuit designing or construction, and having a UL certified contrroller that would not start a fire.
The dimmer that you have might work, you would need to start out slowly and see what happens. If the blower did not start running then you would know to stop and switch it off. You would not want to try a full speed start, just a gentle one.
With a blower application the power required rises with the square of the speed increase. That part just came back to me. So if you get a slower speed start then you could be OK.

Another option would be to borrow a 20 or 25 amp variac and just start the motor with a reduced voltage. Some induction motors can start that way, although they do make much less power at the lower voltages. But since your aplication needs less power that may be OK.
 

Tonyr1084

Joined Sep 24, 2015
6,269
I'm looking at this from a different perspective: An 18" diameter opening has 254.3 square inches of surface area. Since we don't know the air velocity we can only guess at how it would react to choking down the surface area down to your "WindSock" adapter. We don't know what the final diameter is and it sounds like you haven't decided either. Nor do we know how fast you want the inflatable to inflate and deflate. All questions regarding the success of your goal.

Variable speed or variable intake - there's not enough information to decide whether your approach is a good one or not. And as @MisterBill2 was saying, changing the speed of the fan will result in the square (or square root) of the output. At full power your fan is putting out X cu. ft. of air. At 1/2 power your fan is going to put out 1/4 cu. ft. of air. Then there's the restriction funneling down from 18" dia. to whatever dia. your design is chasing. A larger inlet/outlet will mean a more rapid inflation and deflation of your inflatable than a smaller one.
 

MaxHeadRoom

Joined Jul 18, 2013
23,639
The problem with 1ph Triac control is poor control at low RPM, one alternative is to find a 2HP treadmill motor and a MC2100 version control boards, they control very smoothly down to zero RPM.
By using PWM control of the motor.
At least once a week, there is a free-for-take away T.M. where often the motor and or the controller is good.
Max.
 

MisterBill2

Joined Jan 23, 2018
9,304
I never mentioned reducing the intake side of the blower, only bleeding off some of the flow on the discharge side. The advantages are near instant response to changes and no loss of motor cooling airflow. And easily variable from almost zero to max. Since there is probably going to be a bit of ducting anyway, it would be simple to add, as well.
 

Reloadron

Joined Jan 15, 2015
6,065
I never mentioned reducing the intake side of the blower, only bleeding off some of the flow on the discharge side. The advantages are near instant response to changes and no loss of motor cooling airflow. And easily variable from almost zero to max. Since there is probably going to be a bit of ducting anyway, it would be simple to add, as well.
or bleed off some of the output side of the fan. Whatever works.

Ron
 

Tonyr1084

Joined Sep 24, 2015
6,269
Ducting is probably the most efficient way to go. But I still wonder how many CFM we're talking about. How much CFM going in and how much CFM coming out? If we're talking about ducting an 18 inch fan down to a 6 inch port - I'd think a re-engineering of the project would be in order.
 

MisterBill2

Joined Jan 23, 2018
9,304
There was never anu mention of a six inch port. There was a comment about "smaller" in post #3, but no size mentioned , and nothing about how much air the new inflatable will need. So here we are guessing again.
 

MisterBill2

Joined Jan 23, 2018
9,304
It is also important to understand the pressure and flow requirements of whaever the thing being inflated are, otherwise the thing will inflate rapidly and then the pressure will rise. At that point either the airflow will cease or something in the structure will fail, or the blower will either overload or underload. I have seen both, with different blowers. So the thing to do is to have a large enough vent capability that the vent can be slowly closed until the inflatable thing is acting the way it is intended to act.
 

Bernard

Joined Aug 7, 2008
5,788
On a much smaller scale a DC fan ran full speed lifting a ping pong ball in an open tube, control was with a servo controlled air valve to dump air on demand such that ball could dance or stand still. For larger operation might use a multi bladed shutter controlled with a linear actuator to dump air.
 
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