Ducting the filter

[Snook]

Going to incorporate a filter into my next grow. Purchased a 6" Phresh filter, 16 inchs long that will filter a 160 cuft tent: it will mate up to an 8", 550cfm centrifugal fan via a 6"to8" transition piece and then 2 feet of 8" ducting from fan to attic. Filter requirement is 400cfm fan.

Maybe I'm over thinking this but Is there a down side to putting that 8" to 6" reduction between the 6" filter and the 8" fan?

EDIT: I know I will loose some of those cfms but too many?

 

[betshtick]

Going to incorporate a filter into my next grow. Purchased a 6" Phresh filter, 16 inchs long that will filter a 160 cuft tent: it will mate up to an 8", 550cfm centrifugal fan via a 6"to8" transition piece and then 2 feet of 8" ducting from fan to attic. Filter requirement is 400cfm fan.

Maybe I'm over thinking this but Is there a down side to putting that 8" to 6" reduction between the 6" filter and the 8" fan?

EDIT: I know I will loose some of those cfms but too many?

You can probably find a flow chart somewhere if you really want to know what your cfms will be... The fan is a bit oversized for the filter, so it will be restricted more than if you had an 8" filter with no reducer, but you will still flow plenty of cfm, way more than you need for that size tent so I wouldn't worry at all.

 

[queequeg152]

Going to incorporate a filter into my next grow. Purchased a 6" Phresh filter, 16 inchs long that will filter a 160 cuft tent: it will mate up to an 8", 550cfm centrifugal fan via a 6"to8" transition piece and then 2 feet of 8" ducting from fan to attic. Filter requirement is 400cfm fan.

Maybe I'm over thinking this but Is there a down side to putting that 8" to 6" reduction between the 6" filter and the 8" fan?

EDIT: I know I will loose some of those cfms but too many?

in such a simple setup as this, with such a small length of duct, it does not matter where you place the reducer so long as its a few cross sectional diameters away from the blower itself.

for an 8" blower, simply place a straight section of rigid duct at least 16 inches long before you reduce down to 6.

regarding your cfms.

its impossible to say without a few things.

static pressure/cfm charts from the blowers manufacturer. and static pressure drop across the carbon filter itself.

both of those things might be available, but i doubt it.


elbows, reducers etc. all have static pressure coefficients easily available from smacna and ashrae.

your 550cfm is probably at like 0 inches static pressure. with a filter you are probably at like .25 - .5 inches of static pressure.

you will probably be down to like 350-400. its a centrifugal fan though, which is good as they tend to generate more static pressure.

if you are so inclined, you can install static pressure pickups across your fan to measure the TESP(total external static pressure) across the fan and compare it to the fans documentation, or approximate cfms with some crude calculations.

the dwyer mark 2 inclined manometer is a great value. imho every one should have them standard on all house air handlers... only like 40 bucks.

a manometer will tell you when your filters are fouled... ducts crushed, leaking, blowers dirty etc.

 

[Boutique Manettino]

In my personal experience, I found a 6" Vortex fan (standard size - CFM may be higher or lower than your 8" fan) to be a lot of suction for a DR120 (Secret Jardin) tent.

I switched down to a 4" Vortex and I found that to be adequate. I had to place hard ducting (ABS pipe) into the inlet ports (passive intake) in order to maximize the air flow in and out of the tent and reduce the suction - the sides pulled in and the frame was flexing.

I would have no problem ducting up from a small filter to a larger fan... that was sucking in thru the filter. I would suspect it will be noisier than if match sized, or as I often do, over size the filter and then duct down to the fan.

I only use a tent for cloning, early veg and the odd mom.

 

[Fly by Night]

8in fan may render 6in filter ineffective. Too much suction, not enough contact time with carbon. Check for odor late into flower. Peace

 

[sdd420]

I think your fine just make sure you use a controller for the fan so you can use it at less than full speed and adjust the speed as needed . Peace sdd

P.s keep it simple look up kiss thread for simple nutes program

 

[mufinman]

in such a simple setup as this, with such a small length of duct, it does not matter where you place the reducer so long as its a few cross sectional diameters away from the blower itself.

for an 8" blower, simply place a straight section of rigid duct at least 16 inches long before you reduce down to 6.

regarding your cfms.

its impossible to say without a few things.

static pressure/cfm charts from the blowers manufacturer. and static pressure drop across the carbon filter itself.

both of those things might be available, but i doubt it.


elbows, reducers etc. all have static pressure coefficients easily available from smacna and ashrae.

your 550cfm is probably at like 0 inches static pressure. with a filter you are probably at like .25 - .5 inches of static pressure.

you will probably be down to like 350-400. its a centrifugal fan though, which is good as they tend to generate more static pressure.

if you are so inclined, you can install static pressure pickups across your fan to measure the TESP(total external static pressure) across the fan and compare it to the fans documentation, or approximate cfms with some crude calculations.

the dwyer mark 2 inclined manometer is a great value. imho every one should have them standard on all house air handlers... only like 40 bucks.

a manometer will tell you when your filters are fouled... ducts crushed, leaking, blowers dirty etc.

Manometer. Like high velocity grease??? you have a link... brother. really?

EDIT: Everything else sounds logical.

 

[mufinman]

I think your fine just make sure you use a controller for the fan so you can use it at less than full speed and adjust the speed as needed . Peace sdd

P.s keep it simple look up kiss thread for simple nutes program

Thanks sdd, I do have a controller. I'm good with the nutes.

EDIT: boy am I whacked! this isn't my thread.

 

[queequeg152]

Manometer. Like high velocity grease??? you have a link... brother. really?

EDIT: Everything else sounds logical.

you are confusing me too. wtf is a manometer used for with grease? must be a diff instrument.

here:

http://www.dwyer-inst.com/Product/Pressure/Manometers/Stationary/SeriesMarkII

you also need the static pressure probes too, and some 1/4" tubing. you can get the tips from anyone provided they have hose barbs that match the manometers.

you can even make your own from brake line tubing and solder or adhesives.