What's the difference between these fans?

Track

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So, I'm getting a new carbon filter and with it I need a new fan.

However, there seem to be a bunch of kinds.

First off, there is this:


Then there is this:


And finally, there is this:


The pricing of all of them makes this even more confusing, because it's about the same per CFM.

Anyone?
 

Hackerman

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I like to stick with name brands.

Check Can, Hydrofarm (Active Air) and Vortex brands. All you need to decide is 6" or 8". Most go with 6" for a single light.

Make sure your fan CFM rating matches or exceeds your filter's CFM rating.
 

Track

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I like to stick with name brands.

Check Can, Hydrofarm (Active Air) and Vortex brands. All you need to decide is 6" or 8". Most go with 6" for a single light.

Make sure your fan CFM rating matches or exceeds your filter's CFM rating.
I thought it was the opposite.

I had a fan that exceeded my filter's CFM rating and it didn't work.

Ended up buying a fan that had the exact same CFM rating and it was perfect.

So, isn't it better to have a lower CFM fan than a higher CFM fan?

As for the brands, I have CATA, S&P and whatever is on this page:
http://www.hydrogrow.co.il/categories/32138/?page=3&sortby=price
 

Track

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I would go with a higher cfm and use a speed controller. Jmo.
A speed controller would mess with the voltage which would undoubtedly lower the life-span of the fan much like setting a ballast to 75% would lower the life-span of a bulb.

Also, my question was - which KIND of fan should I get, not which CFM rating.
 
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A speed controller would mess with the voltage which would undoubtedly lower the life-span of the fan much like setting a ballast to 75% would lower the life-span of a bulb.

Also, my question was - which KIND of fan should I get, not which CFM rating.

So, isn't it better to have a lower CFM fan than a higher CFM fan?
So that wasn't a question and you didn't ask right? Now I see why your pebbles are red.
Good luck. I am done trying to help you.
 

Hackerman

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The kind of fan you want is called an inline centrifugal fan.
 

Hushpuppy

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Of the three that you showed, I would get the middle one as that is the style that I have used with good results. However, it doesn't matter which off those you use as they all work the same way and do the same thing. The difference is one engineer says "ours has a special shape to improve air movement", while another engineer says "the shape of our fan allows for less drag on the air flow", and the third engineer says "our fan is shaped for a more efficient air flow". The true difference between the shapes is probably so small that only an engineer can measure it.

Track you are wrong about the change of voltage with a speed controller, my friend. It doesn't hurt the ffans because the speed controller digitizes the ac voltage and then uses pulse width modulation (also known as digital frequency)to control the speed of the fan by literally turning it off and on dozens of times per second. Where normal reduction in voltage through a given resistance would result in a rise in current (Ohm's Law), which would damage the components over time, the use of pulse width modulation simulates a reduction in voltage over time, while at the same time cutting off the current fflow as well so that "Ohm's Law" is tricked to prevent damage. :)
The same is true for the digital HID ballasts. The bulbs are driven by high frequency rather than high voltage, so the ability to reduce the percentage of power in a "dimmable" ballast doesn't hurt the bulb because there is no rise in current with the drop in voltage. :)
 

Track

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Of the three that you showed, I would get the middle one as that is the style that I have used with good results. However, it doesn't matter which off those you use as they all work the same way and do the same thing. The difference is one engineer says "ours has a special shape to improve air movement", while another engineer says "the shape of our fan allows for less drag on the air flow", and the third engineer says "our fan is shaped for a more efficient air flow". The true difference between the shapes is probably so small that only an engineer can measure it.

Track you are wrong about the change of voltage with a speed controller, my friend. It doesn't hurt the ffans because the speed controller digitizes the ac voltage and then uses pulse width modulation (also known as digital frequency)to control the speed of the fan by literally turning it off and on dozens of times per second. Where normal reduction in voltage through a given resistance would result in a rise in current (Ohm's Law), which would damage the components over time, the use of pulse width modulation simulates a reduction in voltage over time, while at the same time cutting off the current fflow as well so that "Ohm's Law" is tricked to prevent damage. :)
The same is true for the digital HID ballasts. The bulbs are driven by high frequency rather than high voltage, so the ability to reduce the percentage of power in a "dimmable" ballast doesn't hurt the bulb because there is no rise in current with the drop in voltage. :)
So, the only difference is in dBA? Some seem quieter than others but I haven't heard of all three just yet.

As for the speed controller.. I was always told (even on this forum) that dimming HPS bulbs drastically lowers their life-span. If this is not true, why does everyone keep saying it?

I actually thought that it was the opposite - that pulse width modulation was more damaging because it damages the capacitors which cause it to work, requiring frequent replacements.
 

Track

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So that wasn't a question and you didn't ask right? Now I see why your pebbles are red.
Good luck. I am done trying to help you.
No, you didn't understand my question.

I asked whether it's best to have a fan with a lower or higher CFM rating than the carbon filter you're attaching it to.

Telling me I could control the CFM with a speed adapter doesn't really answer my question. It's more like saying "Just buy whatever you want and figure it out later."

Also, no reason to get upset. If I made a mistake, I'm only human.
 

Hushpuppy

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There is a lot of mixed opinions and mixed information on dimming the lights being damaging. I am more extrapolating from the logic of using pulse width modulation in the lighting than from personal experience. But using PWM with capacitors shouldn't be harmful to them either because the PWM is more off an on/off than the full positive to negative swing of an AC sine wave (which passes through capacitors). The purpose of using capacitors in HID lighting is to load them with a higher charge that provides a "burst of power" to ignite the gases in the tubes. With electronic ballasts, you don't have the large caps as you don't need the burst of power. The gasses are lit using the higher frequency pulses. While caps are still used, they don't have to be as large.

The problem of reducing the voltage to the HID bulbs causing damage may be more about a degradation of the gasses due to them not getting as hot, but again I am more speculating with this as this is more in the chemical and electronic engineering area, while I am just a technician.
 

Track

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There is a lot of mixed opinions and mixed information on dimming the lights being damaging. I am more extrapolating from the logic of using pulse width modulation in the lighting than from personal experience. But using PWM with capacitors shouldn't be harmful to them either because the PWM is more off an on/off than the full positive to negative swing of an AC sine wave (which passes through capacitors). The purpose of using capacitors in HID lighting is to load them with a higher charge that provides a "burst of power" to ignite the gases in the tubes. With electronic ballasts, you don't have the large caps as you don't need the burst of power. The gasses are lit using the higher frequency pulses. While caps are still used, they don't have to be as large.

The problem of reducing the voltage to the HID bulbs causing damage may be more about a degradation of the gasses due to them not getting as hot, but again I am more speculating with this as this is more in the chemical and electronic engineering area, while I am just a technician.
Your input is always extremely appreciated.
 

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