Help me pick a fan

When I first started 3 grows ago I went and picked up a cheap 250cfm axial fan from home depot. It worked fine because I've only done winter grows. This time around I'm going to need something a little more.

Details:
I'm using a homebox (aprox 3'x3'x7') which is in a walk in closet. Exhaust is going about 20' with several bends in the duct. I'm using a 400w MH/HPS and a carbon scrubber. Ambient temp ranges from 70-75.

The fans I'm looking at are:
Sunleaves Windtunnel 409cfm
Seems good for price/power/noise

Fantech FG6 303cfm
A little less powerful and less expensive. I've heard good things about fantech.

So lastly I've read a few reviews on the Sunleaves Windtunnel that says they are quiet. but this is going to be exhausted into a bedroom. So is it THAT quiet? Also, how much CFM is too much CFM? Lastly, the Windtunnel appears to be a centrifugal fan but it doesn't say that anywhere, am I right?

I tested the Sunleave 4in fan.

https://www.rollitup.org/grow-room-design-setup/199168-line-fan-best.html

Thanks for the reply.

If the 200 CFM fan makes a good amount of air noise, would it be safe to assume the 409 CFM fan would make a LOT of noise? Even with proper mounting and insulated ducting, would that change the sound of the exhaust air?

I'm still curious if I need more CFMs than 250 due to the length of my ducting/ambient temps

The ambient temps aren't that bad if that's as high as it gets, but I'd be concerned about shifting it through 20 feet of ducting. I take it there's no way to make it shorter, like exhausting into the attic or anything?
I'd get the big fan and a fan speed controller, it's always better to have too much ventilation than not enough. You can't really have too many cfms unless it's lowering the humidity drastically.
As for the air noise, if it's not coming from a vibration but rather just the sound of air whooshing through the ducting, there's not a lot to be done. I've heard of duct mufflers but don't know anything about them, how they work or if they work so I'd hesitate to recommend one. Fitting larger ducting should reduce the noise somewhat, as the same volume of air could flow at a lower velocity, but unfortunately I can't help with specifics, sorry.

Bain said:

Thanks for the reply.

If the 200 CFM fan makes a good amount of air noise, would it be safe to assume the 409 CFM fan would make a LOT of noise? Even with proper mounting and insulated ducting, would that change the sound of the exhaust air?

I'm still curious if I need more CFMs than 250 due to the length of my ducting/ambient temps

Click to expand...

I would assume the 6in Sun leaves fan will have louder exhaust. It just because it is moving so much air.. The fan motor it self is not loud.

I would try one of the S&P fans, they are cheaper...

Hairy Bob said:

The ambient temps aren't that bad if that's as high as it gets, but I'd be concerned about shifting it through 20 feet of ducting. I take it there's no way to make it shorter, like exhausting into the attic or anything?
I'd get the big fan and a fan speed controller, it's always better to have too much ventilation than not enough. You can't really have too many cfms unless it's lowering the humidity drastically.

Click to expand...

There is no way of making it shorter. I don't own the property so I don't feel comfortable cutting any holes.

I thought about the fan/speed controller, but many people say they actually get louder when you put a controller on them. The air noise is less but the fan itself gets a humming sound.

I've read up on the S&P fans. I do like them but I can't tell if the CFM is too low. That's one of the things I'm trying to find out. The 6" model is 293/218. So is about 300 CFM plenty?