Inline fan and can filter on push instead of pull?

[t33to]

I'd really love to not have my can filter in my grow space, it takes up a lot of room and I'd love to be have my ducting options a little more flexible.

So I was thinking, why not just put them outside the grow space and push air through them, instead of pulling it through. I could see this being an issue because there is always a chance the duct might come off and unfiltered air may leave the space.

So curious if anyone has experience with this?

 

[jocat]

yep

yep

i have a space i use that has no room for my scent scrubbing hulk of can, that's what i do and i think the only consideration besides fan size/airflow would be anew can that only saw use in the push configuration

 

[amanda88]

Sucking is good...sucking sucks air not just from the immediate stinky area but the Surrounds as well, so long as your nose don't smell the weed from the other side of your space ...all is well, but the consensus is to suck, leaving the blow to those that can! ..good luck

 

[Chunkypigs]

that is how I run all my tents.
filter on floor or hanging above, fan screwed and sealed to filter flange, hose into tent vacuuming out the hot stinky air.

I like to use a larger, quieter fan and filter to scrub multiple tents.

this type of setup is very good for finishing males safely and not getting the rest of your garden seeded.

 

[Jhhnn]

The only issue is maintaining a good seal on the pressure side of the fan. If you put the fan right on the filter, there's only one pressure joint to seal. If you stand the filter on end with the fan on top of it, gravity is on your side, never a bad thing.

 

[Twist]

I have been pushing air in my filter for 2 years now. With no problems.

 

[queequeg152]

fans dont care which side the static pressure is... as long as the filter is not super close to the fan.

must belike... 3 or 4 duct diameters away from the fan intake or exhaust.

 

[Jhhnn]

fans dont care which side the static pressure is... as long as the filter is not super close to the fan.

must belike... 3 or 4 duct diameters away from the fan intake or exhaust.

Why?

 

[mojave green]

Yes, why?

 

[queequeg152]

Why?

why the distance?

its called system effect. the air being chopped(humor me) by the blades becomes turbulent in the downstream flow... and this flow tends to stack up forming these gradients of pressure. on a centrifugal fan, the high pressure stacks up on the tangential size of the volute or fan housing, and takes a while to stabilize back into a steady state smooth flow.

anyway what ever. its called system effect, you can google it, but depending on the speed of the air, type of fan or blower...
4 cross sectional diameters is usually MORE than enough.

if you use a huge aspect ratio square duct, you take the circular or hydraulic equivelant diameter, not the corner to corner diagonal.

pressure losses increase with increasing Reynolds numbers in a duct flow. increasing pressure in the sytem reduces total flow capacity. how much? its hard to say without knowing the velocity, but generally a given system effects extract a larger and larger toll as the velocity or momentum of the fluid increases

so anyway, try and place bends and filters... enlargers, reducers etc. at least 3 duct diameters away form the fan. 4 diameters would be a more conservative number, but i wouldnt go out of your way to get 4 as opposed to three.

 

[Jhhnn]

why the distance?

its called system effect. the air being chopped(humor me) by the blades becomes turbulent in the downstream flow... and this flow tends to stack up forming these gradients of pressure. on a centrifugal fan, the high pressure stacks up on the tangential size of the volute or fan housing, and takes a while to stabilize back into a steady state smooth flow.

anyway what ever. its called system effect, you can google it, but depending on the speed of the air, type of fan or blower...
4 cross sectional diameters is usually MORE than enough.

if you use a huge aspect ratio square duct, you take the circular or hydraulic equivelant diameter, not the corner to corner diagonal.

pressure losses increase with increasing Reynolds numbers in a duct flow. increasing pressure in the sytem reduces total flow capacity. how much? its hard to say without knowing the velocity, but generally a given system effects extract a larger and larger toll as the velocity or momentum of the fluid increases

so anyway, try and place bends and filters... enlargers, reducers etc. at least 3 duct diameters away form the fan. 4 diameters would be a more conservative number, but i wouldnt go out of your way to get 4 as opposed to three.

Might help a little, I suppose, although I'm not sure that it really matters when system performance is radically reduced by the presence of a filter. I also think that the internal length of the filter would act much like a straight duct, maybe better because of air escaping through the sides.

It's not like figure 6, here-

http://www.greenheck.com/library/articles/11

I offered what I did as a simple, fairly stable & easy method that minimizes leakage possibilities. Sticking the end of the filter to a larger board with construction adhesive would make it even more stable.

 

[Midnight Tokar]

Sucking is good...sucking sucks air not just from the immediate stinky area but the Surrounds as well, so long as your nose don't smell the weed from the other side of your space ...all is well, but the consensus is to suck, leaving the blow to those that can! ..good luck

I forgot you were talking about fans there for a minute...........

 

[noyd666]

I did see an article years ago about distance from fan to filter, I have on top of mine or one of them a length of pvc pipe, sits on top of filter on floor upright and fan on top of that. have no idea whether it works any diff or not.

 

[queequeg152]

at velocities below 1000fpm or so we are most likely talking about single digit percent hits to total cfm here.

its not going radically effect performance if you jam the filter right onto the suctionside of the fan. its just something to consider next time you build something.

consider a length round metal duct. you can support the filter with a simple trapeze hanger if you need to.

 

[queequeg152]

Might help a little, I suppose, although I'm not sure that it really matters when system performance is radically reduced by the presence of a filter. I also think that the internal length of the filter would act much like a straight duct, maybe better because of air escaping through the sides.

It's not like figure 6, here-

http://www.greenheck.com/library/articles/11

I offered what I did as a simple, fairly stable & easy method that minimizes leakage possibilities. Sticking the end of the filter to a larger board with construction adhesive would make it even more stable.

i know system effects have a huge impact on induct FLAT filters... circular pleated ones? i do not think they will suffer as badly, or in the same manner provided they are on the suction side.

this is because the air being drawn in will be free of turbulence. there will still be the system effect around the fan intake though.

now if we are talking about putting these cirucular filters on the discharge side with the system effects? its my opinion that they will suffer especially badly, owing to the turbulence present immediately after the blower.

cant really defend any of that though as ive never seen papers regarding these sorts of filters, only inline types.

generally speaking
in order for filters in general to offer the lowest possible resistance to air flow the stream of air needs to be as smooth as possible. when you have stacked up air immediatly preceding a smooth bend, or turbulence from am obstruction, filters tend to have a more severe pressure drop across them.

someone get some static pressure probes and fool around with a manometer.