Not an electrician... Dimmer to fan?

icurbyou

icurbyou

Well-Known Member
Still working on the grow box.. Finalizing some things and trying to make sure I know what im doing before I burn down my house.

I want to a fan, in my exhaust line to pull hot air out...

But, I also want it on a dimmer switch, so on hot days I can turn up the speed (if need be) and on cooler days I can slow it down...

My question is this... How would I hook this fan, to this dimmer switch and then have it plug in able?
Is it SAFELY doable?

FAN:
b398a826-e4b1-48c0-be1c-afb96204c513_300.jpg


Inductor 4 In. In-line Duct Fan - DB204 at The Home Depot

Dimmer:
ebfaa324-d3c8-40b9-862f-e6a678c273e4_300.jpg

Product Information Error Page


All the while keeping the ability to:
plugged-in.jpg


Plug or unplug.
 
haha... Anyone with maybe some more tips or insight.. "try it and see" sounds like a stoned response to playing with high voltage.
 
all the dimmer is is a shut off switch ,, splice it into the line , the dimmer part just adds more or less power to it .. if the fan is 110 there should be no problem
 
Yes it can be safely done. The dimmer is what is called an "adjustable rheostat", meaning that it can control the variable speed of of the fan by applying resistance to the fan motor in terms of voltage.

For safety's sake, make sure you cover exposed wire ends with at least electrical tape and make sure you wire it correctly.
 
Use a fan speed control switch instead of a light dimmer. Safer- fan will last longer. Same place (Lowes or HD), couple bucks more. Buy an ext cord and junction box at the same time. Wiring instructions will be on the control switch directions.
 
justcurious said:
Use a fan speed control switch instead of a light dimmer. Safer- fan will last longer.
Click to expand...

Yep, a motor speed controller is the thing to have, but not because it's safer or will last longer- a dimmer for incandescent lights simply will not control a motor's speed. Dimmers are intended for a resistive load, that being the filament in a light bulb; motors are inductive loads.

If you try to run a fan motor on a dimmer, it will spin the fan when the dimmer control is fully on but the motor will stall at anything lower.
 
Polish Guy said:
The dimmer is what is called an "adjustable rheostat"
Click to expand...

I've heard of these kind of dimmers, but I've never really seen one. most of them are actually pwm (Pulse Width Modulation) made with cheap parts. a tinny rheostat, triac, and noise filters mostly.. as the ac voltage goes up and down (60 times per second) it adjusts how long it applies that power. easier to show then explain. How do light dimmers works? bottom picture shows a dimmer's output at about 50%. the sharp spike in voltage in the middle of the wave is what causes noise.

the only foreseeable problems I can think of is noise or the dimmer overheating. like someone said earlier, try it and see. if it works, great. if something overheats or causes noise in a tv or radio, then you might have to find a better way. best of luck
 
Al B. Fuct said:
Yep, a motor speed controller is the thing to have, but not because it's safer or will last longer- a dimmer for incandescent lights simply will not control a motor's speed. Dimmers are intended for a resistive load, that being the filament in a light bulb; motors are inductive loads.

If you try to run a fan motor on a dimmer, it will spin the fan when the dimmer control is fully on but the motor will stall at anything lower.
Click to expand...


it can be a cheap simple solution if it does work, but yes, the motor being inductive can cause the dimmer or motor to overheat. failing to spin shouldn't be to much of a problem if you notice it right away. heat would be a concern here also.
 
lorenzo08 said:
it can be a cheap simple solution if it does work, but yes, the motor being inductive can cause the dimmer or motor to overheat.
Click to expand...

Problem is, dimmers DON'T work as speed controllers.

failing to spin shouldn't be to much of a problem if you notice it right away. heat would be a concern here also.
Click to expand...

If the motor stalls but there's still a current running through it, the sort of overheating that may occur is a handy excuse to have the fellers from the local fire brigade over for milk & cookies.

The nut is that a dimmer isn't suitable as a motor speed controller. Not only will it not control speed, it is most definitely a fire hazard. The right device is sold in hdwe stores on a shelf literally right next to the wrong one, so why invite disaster to save a few bucks?
 
and just what is wrong with milk and cookies? go for it, use the light dimmer, just make sure you have marshmallows and sticks ready too! :)

I've been looking into solutions for this too.. I've seen circuits similar to light dimmers that are made for motors. they just have sorta a minimum adjustment added to it and an active monitor to keep the motor turning. another option is a ceiling fan wall switch, with high medium and low. that would probably work great, and be safe. they use capacitors to limit the current going to the fan. only down side is it's not as adjustable.
 
I really don't know how well made those inline fans are made, but I know for a fact that ceiling fans are tested by ceasing the shaft and monitoring the temperature for a number of days.

safety sucks, but must come first
 
lorenzo08 said:
and just what is wrong with milk and cookies? go for it, use the light dimmer, just make sure you have marshmallows and sticks ready too! :)
Click to expand...

...and have an explanation ready for the fire chief about those parsley plants in that snazzy basement greenhouse you've built.

I've been looking into solutions for this too.. I've seen circuits similar to light dimmers that are made for motors. they just have sorta [...]
Click to expand...

Yes, modern dimmers are PWM devices as are motor speed controllers but that won't make them properly control a motor. The SCR/triac devices used in a MSC are not of the same current capacity as those used in dimmers.

In the end, there's more than one BSEE around here, but what does that matter? Even this old techo wouldn't attempt to re-engineer a dimmer to make it spin a fan when I can get the right device, which has been through UL/CE safety testing before it ever got on to the shop's shelf. There's not that much difference between the cost of a dimmer and a MSC to justify trying to fudge it, certainly not at risk of fire.

Nothing spoils a good night's sleep like having to chat with the FB chief about this-n-that at 4am with 3 fire trucks in the street in front of your place!
 
al b fuct is right ... the fans speed will vary with a change of frequency ... not resistance.... i should have known better ... but i smoke too mmuch.
 
lorenzo08 said:
I really don't know how well made those inline fans are made, but I know for a fact that ceiling fans are tested by ceasing [don't you mean 'seizing'? -Al] the shaft and monitoring the temperature for a number of days.
Click to expand...

With all due respect... who cares? A seized motor shaft is not a normal condition and end-users are not in the business of testing seized motors.
 
ceased shaft is worst case scenario testing. it's similar to a stalled motor, but at a higher powered wattage.

I would be more worried about the dimmer overheating then the motor. I'm not suggesting to rewire a light dimmer, but a ceiling fan controller is a cheaper alternative and is meant for controlling fan motors.

how much is a fan speed controller at a grow shop? jw
 
I'm not sure how much counsel on tech issues I want to take from someone who doesn't know the difference between 'ceased' and 'seized.'

Of course, everything's more expensive at a grow shop than at your local hdwe. No surprises there. An MSC is about $30 at the hdwe.
 
Al B. Fuct said:
I'm not sure how much counsel on tech issues I want to take from someone who doesn't know the difference between 'ceased' and 'seized.'

Of course, everything's more expensive at a grow shop than at your local hdwe. No surprises there. An MSC is about $30 at the hdwe.
Click to expand...


you sound like you're enjoying picking on me. lol. I'm not a great speller, and that's the spelling google suggested for me.

do they sell adjustable fan speed controllers at lowes or home depot?
 
i think questons like this would be better to ask in IT forums, i mean.. you talking to stoned people here lol
 
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