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Inline fan math
- Thread starter Dirt Bag
- Start date
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I would put the bigger fan on the exit and you won't have to worry about the smaller one impeding it.
So the 420cfm fan on a filter, through the hoods into the 735 cfm to exhaust. Problem solved.
So the 420cfm fan on a filter, through the hoods into the 735 cfm to exhaust. Problem solved.
This isn't really feasible with the hardware on hand.
Since this air simply enters FAN A from within the room and exhausts within the room as well, the only filters in place are (believe it or not) multiple hairnets stretched and zip tied over the openings to catch any dust. This has worked perfectly for us for years. A bag of like 1000 was dirt cheap on Amazon.
FAN B would have to be reversed within its housing as it has male and female ends. Which is what we had done with the original FAN A that died and has been replaced with the much better Hydrofarm 735.
Our options here (due to space, access, and hardware configuration) are keep or remove FAN B.
Thanks for your replies yall!
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Fans in series should not be necessary. The benefit is minimal if it is not actually a performance penalty. Fans in parallel are the better option when trying to apply two fans.
I suspect that you are concerned with the static losses from the 8' of flex duct. Best bet is to run rigid duct or at a minimum, keep the flew well supported without turns (as few as possible and no tight turns). Fact is that you'r better with a slightly oversized mixed-flow fan if you are going to push through the duct. They handle head pressure well. Centrifugal in-lines handle suction static admirably if you are going to pull.
I suspect that you are concerned with the static losses from the 8' of flex duct. Best bet is to run rigid duct or at a minimum, keep the flew well supported without turns (as few as possible and no tight turns). Fact is that you'r better with a slightly oversized mixed-flow fan if you are going to push through the duct. They handle head pressure well. Centrifugal in-lines handle suction static admirably if you are going to pull.
There is 1 foot of duct from FAN A to the first hood and 6 inches between the hoods for a total of 2 feet of duct, and I'm being generous, it's probably more like 20 inches.
Originally we had two hoods and one 420cfm fan pulling air through. That was fine.
We added a third hood and found heat below the light furthest from the fan so we added another identical fan on the other end pushing. That was fine.
The push died. Replaced it with a centrifugal inline 735 cfm.
Should I remove the pulling 420 cfm? Is it a hindrance? If it helps at all I would rather leave it. It's in a difficult to reach location. I don't have a meter to gauge the output.
There are caveats or exceptions to every rule I guess you could say but I would not generally connect two different fans in series as you'll see airflow loss or wasted power. The placement of the fan (vortex style) might not matter too much, but the best scenario would be to have each hood with its own duct to splitters and reducers e.g. 1 or 2 Y fittings from 6" to 8". In series can be easier/cheaper but as you said the heat distribution is not even. Have all three ducts going to splitters into the 420 cfm fan so that the air is pulled through the hoods up to the 420 cfm fan. If your 735 cfm fan is an exhaust, you can mount the 420 cfm fan right next to it but leave a space, no ducting. This way you use all the cfm with no parasitic loss.
I was finally able to remove FAN B and airflow greatly improved. When I unplugged FAN B before removing it I wasn't sure that I had pulled the right plug as it continued to spin at the same speed. It was definitely a hindrance. Replaced it with an elbow pointed up because straight was practically blowing the silver off the mylar.
