Inline Booster Fan - Worth a Try?

Howdy RIU! Ventilation question for you experienced heads out there: I’ve got 2 1000w air-cooled hoods (digital se HPS) running inline, being cooled by a single 6-inch 442-CFM centrifugal fan. The fan pulls cool air into my tent, pushes it through one light, then about 3.5’ or ducting, then the other light, then 3 more feet of ducting, then out. Like so:


->= |= X = O = O == |= ->


X is fan, O is reflector, = is ducting, | is tent wall


I also have an identical fan pulling through a carbon filter for smell and additional cooling. This just goes filter->fan->out.

My temps are ideal right now, but last summer I struggled to keep things cool. I was debating getting an 8-inch 720-CFM fan, but that would require a bunch of converters because my hoods have 6-inch ports.

My question is, would it be worth throwing in a 6-inch booster fan, like one of these?

TerraBloom Inline Duct Fan 240 CFM, 6 Inch, HVAC Metal Booster Blower For Exhaust and Intake Through 6" Ducting https://www.amazon.com/dp/B00WW4H8XY/ref=cm_sw_r_cp_api_aznLAbAQRN9HA

If I did get this thing, where would I put it? I was thinking either between the two hoods, or just after the second hood. That second bulb gets pretty hot, so I thought having a booster before it might help.

The two 6-inch fans are ALMOST cutting it, but not quite. What would YOU do? Switch to 8-inch? Get another 6-inch centrif fan? Or worth trying the inline duct booster fan? Thanks in advance for any suggestions.

I posted posted a similar thread, although not quite the same. I would try the most economical option first, and see how that works out. More air should move more heat. But I don't know what's going on inside those hoods circulation wise. It might be one of those instances where you get that pesky law of diminishing returns to rear its ugly head. But, you'd still have more air moving over those bulbs, and at a cost of a little extra power and a little more noise. C

The reason the second bulb gets hotter, is it's being cooled by already heated air from the first bulb. Have you thought about cooling them with separate ducting and fans? You could add that 240CFM inline to the loop, but it'd still be moving heated air, just more of it (which would give it less time to heat up, but it still wouldn't be as cool as your first bulb is) I do remember reading somewhere reputable that 200FM per 1000W is the MINIMUM you want, so you're right at the minimum with that single 440. The 440 is rated that way as it's the best it can possibly perform.

Velocity (volume) and pressure are related by Bernoulli's equation, so to get twice the air down a duct without increasing its size requires four times the pressure
Reference https://www.physicsforums.com/threads/2-fans-on-1-duct-work.196887/ I recommend reading that link as it talks about the physics of what it is you are wanting to do.

I'd try the inline duct booster fan furthest away from the centrifugal fan. Take temperature readings. Then try it in between the two lights and compare the readings. From what I've read, this will relieve some of the back pressure and allow the centrifugal fan to run closer to its rated CFM's. Gotta remember, got those ducting and hoods creating resistance and thus creating back pressure which puts your minimum of 200CFMS per 1000w light in jeopardy.

Hope I've helped some. if I have, feel free to check out my post on whether or not to keep my lamp cooling separate or to combine it all with the filtration and give your thoughts. Cheers!

vtguitar88 said:

Howdy RIU! Ventilation question for you experienced heads out there: I’ve got 2 1000w air-cooled hoods (digital se HPS) running inline, being cooled by a single 6-inch 442-CFM centrifugal fan. The fan pulls cool air into my tent, pushes it through one light, then about 3.5’ or ducting, then the other light, then 3 more feet of ducting, then out. Like so:


->= |= X = O = O == |= ->


X is fan, O is reflector, = is ducting, | is tent wall


I also have an identical fan pulling through a carbon filter for smell and additional cooling. This just goes filter->fan->out.

My temps are ideal right now, but last summer I struggled to keep things cool. I was debating getting an 8-inch 720-CFM fan, but that would require a bunch of converters because my hoods have 6-inch ports.

My question is, would it be worth throwing in a 6-inch booster fan, like one of these?

TerraBloom Inline Duct Fan 240 CFM, 6 Inch, HVAC Metal Booster Blower For Exhaust and Intake Through 6" Ducting https://www.amazon.com/dp/B00WW4H8XY/ref=cm_sw_r_cp_api_aznLAbAQRN9HA

If I did get this thing, where would I put it? I was thinking either between the two hoods, or just after the second hood. That second bulb gets pretty hot, so I thought having a booster before it might help.

The two 6-inch fans are ALMOST cutting it, but not quite. What would YOU do? Switch to 8-inch? Get another 6-inch centrif fan? Or worth trying the inline duct booster fan? Thanks in advance for any suggestions.

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I've gone through ventilation hell pal, what I've learned is to over power ND buy 15 dollar fan dimmer and get the speed exactly what works for you.

Trying to work it out on paper works in alot of commercial applications, but in a small hot room, that is affected by so many factors , even your house Temps, or if your not sealed than the outside Temps too.

https://www.growlights.ca/fans-filters-ventilation.html

I truly believe that booster fan link you posted will do absolutely nothing for you.

Your 6 inch fan way is way stronger and that will probably just slow it down.

I suggest a 6 inch fan per light, like this


https://www.growlights.ca/fans-filters-ventilation/6-inch-inline-fan.html


When you click on one of their fans. They have a checkbox option for fan controller.

Well there you go, two completely different ideas to make matters even worse. If it helps you any, I don't think projectinfo realizes how much the CFM from original fan, after the ducting and the two lights has actually diminished. It appears he thinks it's still 440CFM, which is not, I repeat not, the case. Sure, his theory "holds air" if you connect a booster directly to your centrifugal. It's called a booster fan for a reason. They boost slowed airflow.

Additionally, if you want to overpower and use a fan controller, you have to buy a whole new fan, and finding one that outputs at a higher CFM at 6 inches is going to be a lot more expensive (and louder) than finding one that outputs at 8 inches. If you go 8 inches, well then you gotta re-do all your duct work, too, and you wont even be getting the rated CFM for that fan because going from 8 inches to 6 inches creates A LOT of backpressure, which reduces the CFM of the fan straight out of the gate!

Go with the booster for now dude.

gjs4786 said:

Well there you go, two completely different ideas to make matters even worse. If it helps you any, I don't think projectinfo realizes how much the CFM from original fan, after the ducting and the two lights has actually diminished. It appears he thinks it's still 440CFM, which is not, I repeat not, the case. Sure, his theory "holds air" if you connect a booster directly to your centrifugal. It's called a booster fan for a reason. They boost slowed airflow.

Additionally, if you want to overpower and use a fan controller, you have to buy a whole new fan, and finding one that outputs at a higher CFM at 6 inches is going to be a lot more expensive (and louder) than finding one that outputs at 8 inches. If you go 8 inches, well then you gotta re-do all your duct work, too, and you wont even be getting the rated CFM for that fan because going from 8 inches to 6 inches creates A LOT of backpressure, which reduces the CFM of the fan straight out of the gate!

Go with the booster for now dude.

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Meh, go with the booster and report back

those booster fans are trash imo

GNOME GROWN said:

those booster fans are trash imo

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Well, it certainly doesn't have to be the booster fan we're all thinking of, and that he referenced. he can get a smaller, less powerful version fan of what he has now, and it will still do the same job of helping all that air get through. I wouldn't suggest it be any less than half the CFM of his current fan, though.

One 6" fan cooling two 1k lights in 6" ac hoods is the problem. That's a lot of heat for one 6" fan to handle, i'm surprised you don't have heat issues in the winter. You should 100% get another 6" inline fan so each hood has its own fan. The two 6" fans will pull pretty much the same watts as an 8" fan would and they will cool better with their own fan imo. Don't bother with those duct fans they wont do shit for 1k lights lol. Also check the seals on your glass, if they're leaky its going to be pushing hot air into your grow room.

Have yo

GNOME GROWN said:

One 6" fan cooling two 1k lights in 6" ac hoods is the problem. That's a lot of heat for one 6" fan to handle, i'm surprised you don't have heat issues in the winter. You should 100% get another 6" inline fan so each hood has its own fan. The two 6" fans will pull pretty much the same watts as an 8" fan would and they will cool better with their own fan imo. Don't bother with those duct fans they wont do shit for 1k lights lol. Also check the seals on your glass, if they're leaky its going to be pushing hot air into your grow room.

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I agree 100%! However, whether or not they are pushing out air into the room depends on how he's got the setup. Pulling = negative pressure, pushing = positive pressure (pushing out heat). Regardless, the seals should be checked, because even if the fans are pulling, you don't want unfiltered grow room air getting through the seals and exhausted, either.

I have run boosters fans and it does help. I would keep the big fan at the cool air intake and the booster at the exhaust end, giving them as much space apart.
the best idea, imo, is pull the fan off the carbon filter and put it on your second hood so each hood has its own cool air intake, and fan. put the booster on the carbon filter.
other option is use lower wattage lights in summer, I know its not ideal but neither is heat stressed plants.

stoned-monkey said:

I have run boosters fans and it does help. I would keep the big fan at the cool air intake and the booster at the exhaust end, giving them as much space apart.
the best idea, imo, is pull the fan off the carbon filter and put it on your second hood so each hood has its own cool air intake, and fan. put the booster on the carbon filter.
other option is use lower wattage lights in summer, I know its not ideal but neither is heat stressed plants.

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Yeah, I thought about that too. Combining filtration with hood cooling. Then though, he'd probably have to reroute his ducting to avoid recycling hot air from his lamps. Probably has lamp heat going outdoors and his filtration indoors. Would probably screw with the temps more so than just adding a new fan to pick up the slack. Who knows, could end up being better that way.

GNOME GROWN said:

those booster fans are trash imo

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Agree

Have almost the same setup (my fan pulls), 1 inline 6 inch fan handles it with no problem, but must use a window air conditioner for the summer, as room is not going to be cooler than summer temps no matter how much air I move -good luck

Many thanks for all the thoughts here guys! I’m inclined to agree with gjs, simply because adding the booster fan costs 20 bucks and minimal effort. Not much to lose. I did wonder if the different CFM ratings could create some kind of pressure relationship that would put additional strain on one or both fans, which Projectinfo alluded to....

Seems like people may have (understandably) missed a detail in my long initial post - I do technically have one 6-inch fan per light in my tent! It’s just one directly cools both sealed hoods with air that never touches the grow room, and the other scrubs the air from the tent through a carbon filter. I have variable speed controllers on both of these centrifugal fans. The room exhaust fan with the carbon filter definitely aids a lot in cooling, but I generally feel like I need less power there and more CFM directly cooling the hoods. I usually have the fan with the filter at half power and the one cooling the hoods at full blast. So if I added another 6-inch fan to this tent, that would make three 6-inch centrif fans for two 1k lights...

Another option would be to just direct-cool the first light (so pull cool air into the tent, push through that sealed hood and directly out), and connect the second fan with the filter to the second hood. In that case, I would need to run the first fan at a lower power than the fan with the filter, but I have two variable speed controllers so that would be easy. That solution would be free - do you guys think that would work better than the duct booster? Thanks again for helping out a fellow potanist.

GJS - I will certainly check out your thread when I get another quick break at work!

stoned-monkey said:

I have run boosters fans and it does help. I would keep the big fan at the cool air intake and the booster at the exhaust end, giving them as much space apart.
the best idea, imo, is pull the fan off the carbon filter and put it on your second hood so each hood has its own cool air intake, and fan. put the booster on the carbon filter.
other option is use lower wattage lights in summer, I know its not ideal but neither is heat stressed plants.

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I didn’t see this or a couple other replies before I posted just now. I had almost the same thought, but that’s an interesting idea you had, using the booster for the filter. On the product page it states that the booster doesn’t create enough pressure to pull through a filter .... do you think they’re assuming you’re also cooling a light? Maybe if I cool each light with a 6-inch fan/controller, the booster would be enough to scrub odor and bring some fresh air into the tent. Have you tried that before? If that’s worked for you, I’ll probably try that. If not, I’m narrowing it down to: a) adding the booster fan right before the final exhaust outlet, or b) re-configuring so it’s [fan1->light1->out] and [filter->fan2->light2->out].

forewarning: i read original post and like 3 replies but not the rest so i apologize if i say something thats already been suggested or ruled out,
anyway heres my two cents:

1- cheapest solution- you would probably have way better results simply using your current fan after the second light to pull air through both lights rather than push it.
2- expensive solution- invest in a water chiller and use it to run a couple of "ice boxes" on your hoods. google "hydro innovations ice box" if you aren't sure what im talking about.
3- a less ideal, but still viable solution- Get a Variac controller and plug your lights into it, use it to dim your lights ever so slightly to reduce heat output until desired tempature is met, the downside to this option is obviously that you wont have the full power of your lights, but even if 10% less light gets you your desired temps then it may be worth it.

vtguitar88 said:

I didn’t see this or a couple other replies before I posted just now. I had almost the same thought, but that’s an interesting idea you had, using the booster for the filter. On the product page it states that the booster doesn’t create enough pressure to pull through a filter .... do you think they’re assuming you’re also cooling a light? Maybe if I cool each light with a 6-inch fan/controller, the booster would be enough to scrub odor and bring some fresh air into the tent. Have you tried that before? If that’s worked for you, I’ll probably try that. If not, I’m narrowing it down to: a) adding the booster fan right before the final exhaust outlet, or b) re-configuring so it’s [fan1->light1->out] and [filter->fan2->light2->out].

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I have had a booster fan on a carbon filter and was able to suck the walls of the tent in so defiantly sucked air through the filter. but carbon filters vary so you may not have the same results. I think you are on the right track, it is uniquely your setup (environment, location, building, etc.) so you will have some trail and error.

PS avoid bends in duct work and do as short of runs as possible.

Booster fans definitely work. IMO--and this isn't confirmed by any means-- people think they are garbage because they don't use them properly. If you make a booster fan work twice as hard as it's supposed to, it's going to give out on you. It also happens to be the cheapest option. I feel that if you used it in addition with another fan, IE. as a booster fan, you'd see positive results. Someone else mentioned that it doesn't matter how much air you have, it's going to be the same temp. I referenced this in my first reply. Sometimes, your setup is already as good as it's going to get without cooler air in place. I understood what you meant when you mentioned the identical fan pulling through the filter. So essentially, you have passive air intake operating on that one fan, right? Well, if your lights are too hot, they are going to give out more heat in into your grow room, which, guess what? Gets sucked up by your exhaust, and probably cycled back in again (depending on your setup) resulting in warmer and warmer air. Another person mentioned putting the booster at the end, or the path of MOST resistance. That's what booster fans were designed for, and you don't have much to lose, and a lot to gain.

vtguitar88 said:

I have variable speed controllers on both of these centrifugal fans. The room exhaust fan with the carbon filter definitely aids a lot in cooling, but I generally feel like I need less power there and more CFM directly cooling the hoods. I usually have the fan with the filter at half power and the one cooling the hoods at full blast. So if I added another 6-inch fan to this tent, that would make three 6-inch centrif fans for two 1k lights...

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I feel like your intuition is correct. The lights are space heaters, the more hot air that's moved, the cooler. This is where you need to add that booster fan. So you have 440CFM from the start, but after all that ducting, and those lights, you don't have 200CFM per light anymore. Probably drops down to 80-100CFM by the end, where you need that booster.

vtguitar88 said:

Howdy RIU! Ventilation question for you experienced heads out there: I’ve got 2 1000w air-cooled hoods (digital se HPS) running inline, being cooled by a single 6-inch 442-CFM centrifugal fan. The fan pulls cool air into my tent, pushes it through one light, then about 3.5’ or ducting, then the other light, then 3 more feet of ducting, then out. Like so:


->= |= X = O = O == |= ->


X is fan, O is reflector, = is ducting, | is tent wall


I also have an identical fan pulling through a carbon filter for smell and additional cooling. This just goes filter->fan->out.

My temps are ideal right now, but last summer I struggled to keep things cool. I was debating getting an 8-inch 720-CFM fan, but that would require a bunch of converters because my hoods have 6-inch ports.

My question is, would it be worth throwing in a 6-inch booster fan, like one of these?

TerraBloom Inline Duct Fan 240 CFM, 6 Inch, HVAC Metal Booster Blower For Exhaust and Intake Through 6" Ducting https://www.amazon.com/dp/B00WW4H8XY/ref=cm_sw_r_cp_api_aznLAbAQRN9HA

If I did get this thing, where would I put it? I was thinking either between the two hoods, or just after the second hood. That second bulb gets pretty hot, so I thought having a booster before it might help.

The two 6-inch fans are ALMOST cutting it, but not quite. What would YOU do? Switch to 8-inch? Get another 6-inch centrif fan? Or worth trying the inline duct booster fan? Thanks in advance for any suggestions.

Click to expand...

A fan is not a way to control temperatures.