booster fan vs inline exhaust fan

[budsofmadison]

so i got an ac infininity 6 inch booster fan blowing fresh air into my tent
i have a 6 inch spider farmer exhaust fan blowing air out
with both fans at full throttle, the 6 inch booster fan is blowing more air in my 3x3 tent then what the 6 inch spider farmer exhaust can take out does that make sense should the 6 inch exhaust fan be taking out more air then a 6 inch booster fan can blow in

 

[budsofmadison]

so i got a ac infinity 8 inch booster fan for my 4x4 tent and im gonna be using the 6 inch ac infinity fan in my 3x3 both are for intake

 

[Rootsruler]

Yes he did


Yes the less duct you have the more air you will get out of the same blower. Also turns make a difference. So the fan in the back on your picture if you just flip that around and get rid of the u-bend of duct would give you more airflow. A tight radius 90 degree turn adds the equivalent of 5 feet of duct in terms or air resistance. So that u bend is like adding 10 feet to your duct.

Do duct silencers work? I have my fan setup inside my tent mostly because outside of the tent it is noisy. I'd like to place the fan on the roof of the tent with just the filter inside. I'm exhausting out a window so I can't place the filter at the end of the duct run.

I saw a video from a fan company talking about filter placement. They demonstrated how attaching the filter to the incoming side messes up the air flow and doesn't utilize the entire filter. They're suggestion was to place the fan, open mouthed, inside the tent or, better yet, at one of the ports and the filter at the end of the duct run for better filter utilization.

I count five 90* turns in my ducting. If I reduce the amount of turns will this increase the CFM the fan is able to produce along with reducing back pressure?

Flexible ducting has ridges in it. Will smooth ducting help increase airflow and reduce back pressure?

I have a T6 fan in my 5 x 5 tent that is rated at 406 CFM. I'm assuming this number is at full bore. I've noticed it is in high to full mode a lot of the time. I'm wondering if my ducting is impeding the fans performance. I've been thinking about upgrading to an T8 so that the fan doesn't have to work so hard but if the problem is me impeding the performance through my duct install then I would rather try and optimize that first before moving up to a bigger fan.

Is it better to run an arc than a 90* turn if I have to make a turn? If 90* adds 10ft what does a 45* turn add?

 

[steamroller]

Do duct silencers work? I have my fan setup inside my tent mostly because outside of the tent it is noisy. I'd like to place the fan on the roof of the tent with just the filter inside. I'm exhausting out a window so I can't place the filter at the end of the duct run.

I saw a video from a fan company talking about filter placement. They demonstrated how attaching the filter to the incoming side messes up the air flow and doesn't utilize the entire filter. They're suggestion was to place the fan, open mouthed, inside the tent or, better yet, at one of the ports and the filter at the end of the duct run for better filter utilization.

I count five 90* turns in my ducting. If I reduce the amount of turns will this increase the CFM the fan is able to produce along with reducing back pressure?

Flexible ducting has ridges in it. Will smooth ducting help increase airflow and reduce back pressure?

I have a T6 fan in my 5 x 5 tent that is rated at 406 CFM. I'm assuming this number is at full bore. I've noticed it is in high to full mode a lot of the time. I'm wondering if my ducting is impeding the fans performance. I've been thinking about upgrading to an T8 so that the fan doesn't have to work so hard but if the problem is me impeding the performance through my duct install then I would rather try and optimize that first before moving up to a bigger fan.

Is it better to run an arc than a 90* turn if I have to make a turn? If 90* adds 10ft what does a 45* turn add?

Flexible hose as much as possible when not straight rigid will increase air flow.
I have no clue with air but in water a 90 is equal to 1 foot of head pressure.
That means the 90 is the same as pumping the water 1 foot above the pump nozzle.
5 90s could really reduce air flow IMO. Flex hose or even 45s as you mention will be better than 90s.

 

[smoke]

Flexible hose as much as possible when not straight rigid will increase air flow.
I have no clue with air but in water a 90 is equal to 1 foot of head pressure.
That means the 90 is the same as pumping the water 1 foot above the pump nozzle.
5 90s could really reduce air flow IMO. Flex hose or even 45s as you mention will be better than 90s.

We have someone here that does estimating in the hvac field can't remember who. If he doesn't mind maybe @Moe.Red can put a hvac below his name

 

[Rootsruler]

We have someone here that does estimating in the hvac field can't remember who. If he doesn't mind maybe @Moe.Red can put a hvac below his name

IIRC, Scotty is an HVAC pro.....

 

[Rootsruler]

Flexible hose as much as possible when not straight rigid will increase air flow.
I have no clue with air but in water a 90 is equal to 1 foot of head pressure.
That means the 90 is the same as pumping the water 1 foot above the pump nozzle.
5 90s could really reduce air flow IMO. Flex hose or even 45s as you mention will be better than 90s.

The ducting I have is all flex hose but I have 90* turns to get it to the window I use to exhaust. I can reduce some of the turns to 45* but next run I'll need to position the tent so that the exhaust port is nearest to the window so that I get a straight shot at it with the least amount of 90's and the shortest duct path.

 

[Scotty 420]

Do duct silencers work? I have my fan setup inside my tent mostly because outside of the tent it is noisy. I'd like to place the fan on the roof of the tent with just the filter inside. I'm exhausting out a window so I can't place the filter at the end of the duct run.

I saw a video from a fan company talking about filter placement. They demonstrated how attaching the filter to the incoming side messes up the air flow and doesn't utilize the entire filter. They're suggestion was to place the fan, open mouthed, inside the tent or, better yet, at one of the ports and the filter at the end of the duct run for better filter utilization.

I count five 90* turns in my ducting. If I reduce the amount of turns will this increase the CFM the fan is able to produce along with reducing back pressure?

Flexible ducting has ridges in it. Will smooth ducting help increase airflow and reduce back pressure?

I have a T6 fan in my 5 x 5 tent that is rated at 406 CFM. I'm assuming this number is at full bore. I've noticed it is in high to full mode a lot of the time. I'm wondering if my ducting is impeding the fans performance. I've been thinking about upgrading to an T8 so that the fan doesn't have to work so hard but if the problem is me impeding the performance through my duct install then I would rather try and optimize that first before moving up to a bigger fan.

Is it better to run an arc than a 90* turn if I have to make a turn? If 90* adds 10ft what does a 45* turn add?

I don't really have any experience with duct silencers so not sure how effective it would actually be.

As far as the filter being on outgoing vs. incoming generally speaking it's more effective to pull air through an object than push it. This is why the air blows out the top of an AC unit vs. pulling in through the fan & blowing out the coils. Trying to push the air out the coil can lead to a lot of turbulence & certain areas of the coil getting more airflow than others. By creating a negative pressure inside the coil space we get more even airflow over the coil & I would assume a filter would work the same.

Yes any 90's will add restriction, but it's the equivalent of 5 feet, the 10 foot example was for a u bend. A 45 would be 2.5 feet. Wider radius turns restrict less than tight turns. And yes smooth duct does restrict slightly less than flex duct. Although I don't have an exact number as far as how much restriction it actually adds, I don't think it's a huge thing. I know that for HVAC we use the same size pipe whether it's flex or rigid.

The rating on your fan I'm sure is wide open with no duct attached to it. So as you add filters, lengths of pipe, bends & any kind of baffles or backflow prevention all reduce that number. So a 400 cfm fan with all that stuff attached to it may only put out 300 cfm.

 

[Scotty 420]

We have someone here that does estimating in the hvac field can't remember who. If he doesn't mind maybe @Moe.Red can put a hvac below his name

IIRC, Scotty is an HVAC pro.....

Yep that's me. Worked as a service tech for about 8 years & I do sales/estimating now.

 

[steamroller]

I don't really have any experience with duct silencers so not sure how effective it would actually be.

As far as the filter being on outgoing vs. incoming generally speaking it's more effective to pull air through an object than push it. This is why the air blows out the top of an AC unit vs. pulling in through the fan & blowing out the coils. Trying to push the air out the coil can lead to a lot of turbulence & certain areas of the coil getting more airflow than others. By creating a negative pressure inside the coil space we get more even airflow over the coil & I would assume a filter would work the same.

Yes any (0's will add restriction, but it's the equivalent of 5 feet, the 10 foot example was for a u bend. A 45 would be 2.5 feet. Wider radius turns restrict less than tight turns. And yes smooth duct does restrict slightly less than flex duct. Although I don't have an exact number as far as how much restriction it actually adds, I don't think it's a huge thing. I know that for HVAC we use the same size pipe whether it's flex or rigid.

The rating on your fan I'm sure is wide open with no duct attached to it. So as you add filters, lengths of pipe, bends & any kind of baffles or backflow prevention all reduce that number. So a 400 cfm fan with all that stuff attached to it may only put out 300 cfm.

This is must know info for us all.
Thanks so much Scotty~!

 

[MDK]

Why do you need a booster fan? I run the T6 in my 5 x 5 and it exchanges plenty of air.

I have the exhaust fan mounted on the roof of the tent sucking air out while the bottom vents flow air into the tent and up through the canopy.

In case you don't know you want 3 air exchanges a minute minimum in your tent. Mine is a 5' x 5' x 6.5'. That gives me 162.5 cubic feet of space. I have the same ACI T6 you have. It maxes at 402 cfm. 162.5 x 3 = 487.5 cfm. I need a bigger fan. I'm looking at the T8 as a replacement. It puts out 807 cfm.

Is this 3x every 1 minute accurate? Everything I have looked up on it says 1 time every 5 mins is enough....

I'd like to know definitively for sure. Mine exchanges roughly once every 4 mins.....haven't seen any issue

 

[Rootsruler]

I don't really have any experience with duct silencers so not sure how effective it would actually be.

As far as the filter being on outgoing vs. incoming generally speaking it's more effective to pull air through an object than push it. This is why the air blows out the top of an AC unit vs. pulling in through the fan & blowing out the coils. Trying to push the air out the coil can lead to a lot of turbulence & certain areas of the coil getting more airflow than others. By creating a negative pressure inside the coil space we get more even airflow over the coil & I would assume a filter would work the same.

Yes any 90's will add restriction, but it's the equivalent of 5 feet, the 10 foot example was for a u bend. A 45 would be 2.5 feet. Wider radius turns restrict less than tight turns. And yes smooth duct does restrict slightly less than flex duct. Although I don't have an exact number as far as how much restriction it actually adds, I don't think it's a huge thing. I know that for HVAC we use the same size pipe whether it's flex or rigid.

The rating on your fan I'm sure is wide open with no duct attached to it. So as you add filters, lengths of pipe, bends & any kind of baffles or backflow prevention all reduce that number. So a 400 cfm fan with all that stuff attached to it may only put out 300 cfm.

In the video I saw they did a smoke test. They attached the filter to the intake side of the fan and added smoke to monitor air flow. You could see that most of the smoke entered the filter from the point closest to the mouth of the fan and utilized around 1/3 of the filter. Almost no smoke entered the other 2/3's of the filter. They then attached the filter to the exhaust side of the fan and added smoke and you could see the entire filter being utilized. They also mentioned something about airflow dynamics around the intake side of the fan being better without the filter attached as it somehow messed up the airflow pattern in a detrimental way.

I also read about how adding a rounded edge to the intake port in the fan housing evened out the airflow better than just a sharp edge.

 

[MDK]

i really think this exhaust fan is starting to go out , i wish i new a way to check it

Best I could say for checking it would be to see if it is drawing the amps/watts it should be

 

[Scotty 420]

In the video I saw they did a smoke test. They attached the filter to the intake side of the fan and added smoke to monitor air flow. You could see that most of the smoke entered the filter from the point closest to the mouth of the fan and utilized around 1/3 of the filter. Almost no smoke entered the other 2/3's of the filter. They then attached the filter to the exhaust side of the fan and added smoke and you could see the entire filter being utilized. They also mentioned something about airflow dynamics around the intake side of the fan being better without the filter attached as it somehow messed up the airflow pattern in a detrimental way.

I also read about how adding a rounded edge to the intake port in the fan housing evened out the airflow better than just a sharp edge.

It may have to do with exact way the hepa filters are designed/shaped or possibly even just that we aren't pulling a low enough negative pressure to use the whole filter. I will say that mine is hooked to the negative side the fan & the pre filter seems to be getting dirty pretty evenly across

 

[steamroller]

With water pumps any throttling should be done after the pump.
One reason is better intake , the second is the pump may over heat or possibly have a shortened life with flow being restricted from intake.
IMO with air the filter has equal restriction at either end? I may not see this clear though?
The fact you only see 1/3 of the filter being used is more a statement on the fans CFM IMO.
As the filter clogs the fresher parts will have equal draw until complete cleaning is needed. The filter only uses what it needs to allow max flow.
I have never used a filter on my fans.
I have 2 AC 6 inch I run in series blowing in and one 8 inch with 6ft of metal duct and one 90 blowing out.
Intake and outtakes on their own control.

 

[smoke]

I also read about how adding a rounded edge to the intake port in the fan housing evened out the airflow better than just a sharp edge.

Question id like clarification on.

I've read that adding a 8" to 6" adapter to the intake side of the 6" fan will increase the fans capacity? True or false?

 

[Scotty 420]

Question id like clarification on.

I've read that adding a 8" to 6" adapter to the intake side of the 6" fan will increase the fans capacity? True or false?

Definitely false, there is a max cfm a certain size of pipe can carry at a given static pressure. A smaller duct will never give you more air. If you put a 8 to 6 reducer on the outgoing side the air will blow with more velocity but there's a difference between velocity & capacity (or volume)

OK I realized I read that wrong, I can't imagine an 8 to 6 on the end of a 6 inch fan would do anything, it would be interesting to see it tested with a cfm meter

 

[MDK]

@Scotty 420 can you say anything on the exchange rate necessary? Thanks

 

[Scotty 420]

@Scotty 420 can you say anything on the exchange rate necessary? Thanks

Honestly there's no reason in the normal ventilation world that you ever need that much air exchange. The reason you often hear that I think has more to do with the CO2 needs of the plants. Which quite frankly given our relative levels of experience I feel kinda out of my depth telling you about the needs of the plants as I'm still very much learning that myself.

However what I will say is I find it hard to believe plants use up carbon dioxide at a rate of anywhere close to depleting an entire tent three times in a minute. I will also say that most people I know of that have EC exhaust fans run them at 10% & only ramp up when the tent gets too hot or humid. So running their fans at 10% the vast majority of the time there's no way people are actually getting that exchange rate other than an overheat situation. Which means most of the times there plants are living with a much lower exchange rate. Up until a few days ago my exhaust hasn't been on constant at all, it only came on due to high humidity really. My plants seemed to grow fine with no ventilation most of the time.

 

[steamroller]

Take this for it is worth.
Sorry if already posted;

AC Infinity

Create smart growing systems with advanced components like grow tents, fans, LED lights, and UIS™ controllers.

acinfinity.com

 

[MDK]

Right on, I got a local buddy his grow is behind mine...my fan runs 4 mins on 2 mins off at the moment on a 24/7 schedule like that. His is set based on temperature which I was weary of but so far it seems to be fine.

Trying to learn where I can dial back to cut costs

 

[Scotty 420]

Right on, I got a local buddy his grow is behind mine...my fan runs 4 mins on 2 mins off at the moment on a 24/7 schedule like that. His is set based on temperature which I was weary of but so far it seems to be fine.

Trying to learn where I can dial back to cut costs

I actually just changed my setup because of this very issue. I couldn't come up with a reasonable way to have the fan run on a timed schedule for constant change over while also having a temp/humidity limit. So I bought a 6" duct booster fan with a variable speed controller & mounted it right before my main exhaust. Set the booster fan to a low speed & just plug it straight into the wall so it runs constant at a very low cfm. Main exhaust is left hooked to my controller to maintain heat/rh.

 

[Rootsruler]

Take this for it is worth.
Sorry if already posted;

AC Infinity

Create smart growing systems with advanced components like grow tents, fans, LED lights, and UIS™ controllers.

acinfinity.com

If you go by the calculation they posted it comes out to roughly 3 times your base CFM. I posted before that 3 air exchanges a minute is minimum.

 

[MDK]

I actually just changed my setup because of this very issue. I couldn't come up with a reasonable way to have the fan run on a timed schedule for constant change over while also having a temp/humidity limit. So I bought a 6" duct booster fan with a variable speed controller & mounted it right before my main exhaust. Set the booster fan to a low speed & just plug it straight into the wall so it runs constant at a very low cfm. Main exhaust is left hooked to my controller to maintain heat/rh.

I got both a 6 inch exhaust and booster fan as well, I got it hooked up like buds does, booster pushing in bottom and big exhaust fan mounted directly outside the tent up top.

I like your idea though I may have to switch it up and try that out see where I can improve

 

[Rootsruler]

I let the fan passively pull air through the bottom flaps so that it pulls the air through the canopy.

 

[Scotty 420]

If you go by the calculation they posted it comes out to roughly 3 times your base CFM. I posted before that 3 air exchanges a minute is minimum.

If you go by the calculation they posted it comes out to roughly 3 times your base CFM. I posted before that 3 air exchanges a minute is minimum.

Yeah but their calculations also include 20% for a muffler & 50% for lights. I don't need to account for heat from my lights at all I'm running a heater in the tent. So there's 70% off their calculations I personally (& probably a lot of people as well) don't need

 

[budsofmadison]

I got both a 6 inch exhaust and booster fan as well, I got it hooked up like buds does, booster pushing in bottom and big exhaust fan mounted directly outside the tent up top.

I like your idea though I may have to switch it up and try that out see where I can improve

what i realized is my 6 inch exhaust fan ''405cfm'' was taking out more air then my 6 inch booster''205cfm'' intake booster fan could bring in both ac infinity so tonight i switched to an 8 inch ac infinity booster405 cfm fan to bring in air

 

[MDK]

Yeah but their calculations also include 20% for a muffler & 50% for lights. I don't need to account for heat from my lights at all I'm running a heater in the tent. So theirs 70% off their calculations I personally (& probably a lot of people as well) don't need

Would there calculations be for hps lights? Something putting off high heat just to cover all bases? And perhaps people running low temp led would suffice with less?

 

[Scotty 420]

Would there calculations be for hps lights? Something putting off high heat just to cover all bases? And perhaps people running low temp led would suffice with less?

Or depending on where you're growing heat may be an issue, although I would think in most of those cases bringing in outside air via exhaust wouldn't be much help as the only reason I could see to need to be worried about temps would be if your tent was in a warm climate. Which would mean you're just going to exhaust in more warm air. Me personally I'm in a basement that never gets above the low 70's so heat isn't an issue for me. And really based on that article the biggest reason they're advocating for as many cfm's as they are seems to be climate control. Which to me means as long as what you're doing keeps your climate in check you shouldn't need to do more IMO.

 

[Max]

Imo you only need an exhaust fan with passive intake

Agree.my 8’ phresh 720cfm exhaust fan that has a speed controller is plugged into an wifi temp/cool inkbird and comes on when room temp is reached.which is every 1.10 -1m.20secs and extracts the heat and rh..i use heat to control room temps..by using heat with a finned heater which has multible settings I can have it extracting the heat before the rh gets to high and when it’s not extracting the dehuey is helping keeping it in check..it’s just a 5x5 room .while 720cfm is over kill for that room size my thinking was if I get a big ass fan I can have it on low to keep the noise down.I have 2 6’ square shutters for passive ventilation and a big square box on the outside with hepa filters to trap mold spores .I’m in an outside insulated shed so that was a must have..