Carbon Filter killing negative pressure/exhaust...why ?

Hey all !!!

I purchased a fan/filter combo - http://www.ebay.com.au/itm/HYDROPONICS-4-INCH-INLINE-CENTRIFUGAL-DUCT-FAN-DUCTING-CARBON-FILTER-KIT-/331877069139?hash=item4d456a3153:g:o08AAOxyBjBTThNl -

Fan CFM - 170
Optimal Filter CFM - 300
Tent Size - 1x0.6x1m

The fan is great, it works well with my intake (don't know the CFM its just a duct booster to push cooler air in).
When I have the fan running the sides of the tent get sucked in and the temp is around 25-26 degrees which is good for me. When I attach the filter the sides of the tent begin to push out ( due to the intake I would guess). It's kind of like the filter is restricting air flow too much and stopping the air being effectively sucked from the tent.

Can I fix this ? Cheers all !

Pic?

Duct booster fans won't cut it. Get an inline fan.

Either buy the appropriate sized inline for your scrubber or just take out the intake booster completely & run it passive.

If you start having temp or humidity problems then you need a 300cfm inline for the scrubber.

whitebb2727 said:

Pic?

Duct booster fans won't cut it. Get an inline fan.

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Cheers for the reply The duct booster is simply to draw some cooler air through ducting and it works well at doing that, its just as soon as the inline fan connects to the carbon filter...the tent heats up :/. Thanks

SPLFreak808 said:

Either buy the appropriate sized inline for your scrubber or just take out the intake booster completely & run it passive.

If you start having temp or humidity problems then you need a 300cfm inline for the scrubber.

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Hmm damn, research I did led me to belive the CFM of a carbon scrubber was only a problem if it was lower than the fans CFM rating...and they came as part of a single kit which is annoying. Thanks

WinnyBoyBlue said:

Cheers for the reply The duct booster is simply to draw some cooler air through ducting and it works well at doing that, its just as soon as the inline fan connects to the carbon filter...the tent heats up :/. Thanks

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That filter looks way too small for that fan.

Not all brands of filters can be run blowing out them.

I have a 4 inch inline fan and run a 8 inch filter. The fan can never exceed the filter cfm. The filter can be way bigger in cfm than the fan.

You can see the reducer.

You may need a bigger filter.

Better view if the fan and variac.

whitebb2727 said:

Better view if the fan and variac.
View attachment 3945899

Click to expand...

Ogh shit aha, that's a huge filter. Nice DIY room By a comment I saw I'm now thinking that the filter is meant to draw in air, hence its smaller size and these dust filter things I got with it that just got covered in black dust...was weird. So maybe I'm a total newb and just did it the wrong way around aha. Can anyone help confirm this ? I wouldn't know how to know the difference :3

WinnyBoyBlue said:

Ogh shit aha, that's a huge filter. Nice DIY room By a comment I saw I'm now thinking that the filter is meant to draw in air, hence its smaller size and these dust filter things I got with it that just got covered in black dust...was weird. So maybe I'm a total newb and just did it the wrong way around aha. Can anyone help confirm this ? I wouldn't know how to know the difference :3

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Yeah they are ment to be the other way, sucking through the filter, the dust cover been the first line of cleaning before going through the filter. Some people run filters the other way.
Turn your duct booster off as SPL said. If temps stay in range your golden.

it doesn't look like you have room, but filters work WAY better if they're in your growroom, pulling air in. some of them are designed to work both ways, but a lot of them are not, they have baffles inside that screw up the air flow if its going the wrong way.

WinnyBoyBlue said:

Ogh shit aha, that's a huge filter. Nice DIY room By a comment I saw I'm now thinking that the filter is meant to draw in air, hence its smaller size and these dust filter things I got with it that just got covered in black dust...was weird. So maybe I'm a total newb and just did it the wrong way around aha. Can anyone help confirm this ? I wouldn't know how to know the difference :3

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Thank you.

Yea. Might run better the other way. I doubt it. That filter just looks way to small for that fan.

coreywebster said:

Yeah they are ment to be the other way, sucking through the filter, the dust cover been the first line of cleaning before going through the filter. Some people run filters the other way.
Turn your duct booster off as SPL said. If temps stay in range your golden.

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I've put the filter inside the tent now, very top left in a corner. The negative pressure is still in effect but only when the duct fan is turned off. My only problem is I think it will heat up since i doubt the fan can draw air through ducting 2m long as passive intake, but shall see. Cheers for the reply

i've got a 4x4 that i use passive intake on, just open the bottom flaps on each side and it gets plenty of air, i have to close one of them half way to get the sides to start pulling in

Food for thought --- if you ever plan to upgrade your space size, then buying anything less than an 8" inline fan// is a WASTE of your money. Did you know for around twenty bucks they make a variable fan speed controller? well they do. And the things are swag. KNow how that little fan you got is wide open/full blast sounding all loud and holy smokes man... yeah that doesn't happen when you have a fan bigger than you need and reduce its rpm while still getting the proper torque to move air through the CARBON packed filter.

___Always troubles me when "gardeners" have trouble creating environments___
---Without it, you have nothing---
That's worth something

Also it has to do with blade style... axial fans, the ones like in a houSe fan, duct booster etc, create the highest cfm per watt than any style, however they make the least pressure. A centifugal or squirel cage type takes more watts for same cfm but creates most pressure so can handle ductwork and filters and such. A true inline fan is in the middle i beleive. A duct booster may be "in line" but its not the same, its a basic axial fan in a tube.... this is why duct boosters are just that boosters. This is why your furnace doesnt use an axial fan.

If ur just looking to move lots of air cheap n fast w low heat addition and theres no or not much resistance axial rocks it.... for any air moving that requires work like ducts, filters, etc, gotta go true inline or centrifugal...

SwitchHitter said:

Food for thought --- if you ever plan to upgrade your space size, then buying anything less than an 8" inline fan// is a WASTE of your money. Did you know for around twenty bucks they make a variable fan speed controller? well they do. And the things are swag. KNow how that little fan you got is wide open/full blast sounding all loud and holy smokes man... yeah that doesn't happen when you have a fan bigger than you need and reduce its rpm while still getting the proper torque to move air through the CARBON packed filter.

___Always troubles me when "gardeners" have trouble creating environments___
---Without it, you have nothing---
That's worth something

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I'm only ever going to have maybe 1-2 flowering plants at once, still very illegal here. All I have to do if caught is admit I'm a ''drug addict'' with 1-2 plants...any more I might cop a large fine/jail. In the future though, cheers for reply, definately sounds like something worth investing in if I go bigger in the future !

How are your temps now with the intake tuned off?

Your carbon filter acts not only as a scrubber for fragrance molecules. But, it also decreases the over all airflow through your space. Unless you've got a really good fan to push through.

I'm having issues keeping temps and humidity down in my cab. I have two 100cfm axial fans running full speed and it just isn't enough to pull the heat out. I am pushing through the carbon filter if that makes any difference. Looking at getting a ~200cfm inline. Is there any real difference in performance or sound between the metal spade shaped ones and the plastic ones with clamp on end caps?

I'd say if you could afford it. Go get a Hyper fan. They've got fan speed controllers inbuilt. And are fairly beefy. Even on lower speed settings.

I think they do a 6". Might be wrong. 8"might be their smallest model.