Fan Speed Control

[Guest]

I have a 3x4x6' closet with two uncooled 400W HPS lamps that I've run before, but I just upgraded the ventilation to a 6" inline EcoPlus (440 CFM) and a scrubber. I knew the fan would be overkill, but that's not the problem...

The problem is that my closet is in a dirt-floor basement and the increased exhaust output stirs up mad amounts of dust the way it is now.

I need to slow the bad boy down. What do you all use for a fan speed controller? I'm a cheap bastard.

Thanks!

 

[Xtbudda]

I am thinking of getting one of these.
http://www.bustan.ca/product_detail.asp?menuID=1&SID=13&PID=896
that is the cheapest i have found so far, if you find anything cheaper, pass it on.

 

[stonewall]

for your fan with a PSC (permanent split capacitor) motor or a fan with a shaded pole motor a dimmer style speed control will work. These can be found at any quality hardware store for 20 bucks or so. Be aware that the motor will hum more at slower speeds with this style speed control though.

 

[Xtbudda]

Hey Stonewall
I thought it had to be a special type, as I had wondered about those light switches.
In my fan instructions it says to use a solid state controller.

 

[stonewall]

the dimmer style fan speed controller is a solid state speed controler. It is the same thing as you linked, just not plug and play.

 

[Guest]

I think I'm going to find another way to divert/disperse the air. Or maybe just run 30' of tubing to the nearest exhaust to outside of the basement.

Found this:

Can I use a dimmer switch to control the speed of my fan?

Contributed by: FRIEDELECTRICIAN
Submitted: 07-10-2003

You cannot use a light dimmer to control a fan. There is a growing misconception that this is safe to do, but the logic behind it is flawed.

Let me explain:
A fan that has no speed control when manufactured has copper windings inside that determine speed and horsepower. These windings are fixed and unchangeable, and wired to be operated at a certain voltage, with a fixed amount of amp draw. I will explain how this works, but first I want to dispel the reasoning behind this misunderstanding.

1. Why do they sell fan controllers at hardware stores?

They are to replace the controllers that are already on a multi-speed fan.

2. I have heard of rheostat's being used to adjust the speed of a fan, why wont this work?

Rheostats, like potentiometers are glorified variable resistors. While they can be used to adjust the speed of a DC motor, its a big no-no on AC motors. AC motors need to run at preset voltage, motor speed, and current draw. It is a balanced system.

3. Can I use a thermostat to act as a rheostat?

NO. Thermostats are on/off switches that turn on/off at a desired temperature.

4. Can I use a rheostat if I also use some type of thermal protection device?

NO. Thermal devices fail too. Sometimes they trip for no reason, then your fan would be off when your on vacation and that can be disastrous for your crop.

5. What's the best way to run my fan at my desired speed?

There are 2 ways. First, buy a fan that runs at your desired speed. Second, you could purchase a variable frequency drive, but these usually cost more than the fan itself.

6. Why do ceiling fans have different speeds if you can't control speeds of an AC motor?

Multi speed motors have more than one set of windings. The speed knob on a fan is a switch that switches current to a different set of windings. Each set of windings are almost like a separate motor. They would each have their own parameters. Remember, the knob is a switch, not a speed controller.

Please do not invite disaster. Best case scenario, your replacing fans like they are going out of style. Worse case, burn your house down. It is not worth it.

# Now I will attempt to explain the science behind it all.

An electrical device operates when current runs thru it. When to much current goes thru it will burn up the device, wiring, etc... All devices have a resistance to current. The filament in a light bulb is a good example. A bulb has a fixed resistance. You can lower or raise the voltage but the resistance will stay the same. You would affect the current running thru it, which if you lower(as with dimming) there are no bad side effects. But increased current with shorten the life of the bulb, or burn it out immediately.

Wire has almost no resistance, which is why we use it to take our current to our devices. The inside of a motor is nothing but wire. But when you wind it in a series of coils (like inside a motor), you create a dense magnetic field when current is running thru it, casing the motor to spin, and do work. This is called inductive impedance, or sort of a magnetic resistance.

If you stopped a motor from spinning (like holding onto a fan blade), the motor would smoke, then burn up. Holding the fan blade eliminates the magnetic field and creates a rush of current. The same can be said of reducing the voltage across the fan with some sort of outside variable resistor. You are essentially weakening the magnetic resistance and allowing a current rush outside the operating parameters of the motor. This usually isn't as harsh as holding a fan blade, but it can be disastrous. At the very least, it would severely shorten the life of the motor.

There is currently only one way to control the speed of a single speed AC motor. Using a variable frequency drive. They do not change current, voltage, magnetic field, or any other factor other than frequency. U.S. power runs at 60Hz. Changing the Hz on the power supply to a motor will change the speed with little or no adverse effects. These drives, however, are not cost effective outside of an industrial environment. Fans are usually cheaper.

Do yourself a favor, buy the fan with the speed you want.

Contributed by: strong_plaid

Bleed-off excessive airflow, using a mechanical valve

Controlling the fan speed may not be necessary. The airflow can be diverted mechanically as an option, in effect reducing the airflow without changing the fan's speed.

On the "out" pipe, one could put a y-split, with a flapper inside that can direct a fraction of the air to one half of the split (connected to your actual air circuit), and the remainder to the other (the "waste" air outlet).

Then, by adjusting the flapper's position, you could control the flow to your circuit, and dump the excess airflow.

 

[stonewall]

Notice I said dimmer style, these are solid state (chopper circuit)fan speed controllers for PSC and shaded pole motors. they are not dimmers/rheastat/potentiometers. They just look like the common old school dimmers that were rheostats.

sorry for the confusion.

 

[Sauce]

I got one of these:

http://www.discount-hydro.com/ventilation.asp (scroll down)

Works great and no need to rewire Only works on inline fans though (you're good).

 

[stretchpuppy]

I don't think lowering the fan will solve your dust problems.

Take care of your dirty grow area first and you won't have this problem.


MMM, nothing like a bunch of dusty bud after 75 days waiting.

 

[MTF-Sandman]

^^Exactly...fix the problem, not the symptoms.

Some plastic sheeting will do fine for a floor...just seal it up to the sides with some good tape (foil backed tape works great) and you'll be good to go.

 

[Harry Gypsna]

i used a b and q fan speed controller(like a dimmer but with a fan printed on the knob), like the fazfan from the old ukc...... but im not using it as the buzzing completely detroys any pretence of stealth...and actually makes me scared that it will blow up lol-so its sat in the cupboard while im using a too powerful fan at full speed lol

 

[Guest]

Thanks, everybody.

I've grown in this space before with a smaller fan and the dust wasn't a problem. If you saw my "basement" (actually a partially walkable crawl) you'd see why black plastic isn't an option. I have laid down carpet remnants in every spot possible and the closet is completely sealed and filtered.

I'm only a partial, not complete, dummy. LOL

Additionally, we're moving to OR in a few months so I'm trying not to make any major modifications.

There is another cabinet next to this one, about 1x3x4'... I'm going to vent into one side of the second cabinet and then have several 2" outlets on the other end of that cabinet to dissipate the airflow.

Thanks again for all the info.

peace