Greg's 75g

[WarDog]

Originally Posted by gregzz4

I'm going to run 2 independent ducts from the storage tote and connect them to 2 independent vents with the fans pulling.

Yeah buddy, thats the way to do it correctly. That wye you got set up is improper venting practice to the extreme. Too much back pressure causing an air flow bottleneck. Great diy project!

[gregzz4]

Ya I was hoping that wouldn't be the case but these fans just can't create enough pressure

[daplatapus]

Originally Posted by WarDog

Yeah buddy, thats the way to do it correctly. That wye you got set up is improper venting practice to the extreme. Too much back pressure causing an air flow bottleneck. Great diy project!

Looks great! I was expecting a lot worse from your description.
In the strictest of air flow practices, if those are 4" lines you'd need a 4"X 4"X 6" Y for it to work as you'd intended. Just use Pi R squared to figure out the square inch of 4" round (X2 for 2 pipes running into one) verses the size you want to run it into.
I highly doubt those fans are pushing the limit of a 4" pipe though. A 10' run (including friction loss for elbows) at .05 inches static pressure loss, a 4" pipe can flow 45.8 CFM. That's pretty low static pressure, but I'm not sure what pressure those fans can push without cavitating.

A thought to also consider... I have had some instances in a somewhat similar application of 2 fans feeding from a common plenum. One fan started a few seconds before the first and from the suction it created in the plenum it pulled air backwards through the second fan and the blades of the second started rotating backwards. Sometimes the motor's are not powerful enough to counteract that reverse spinning and they just sit there cavitating until they either burn up or shut down from overheating. What fixed it for me was just installing a baffle between them, making 2 separate plenums.

[gregzz4]

Thanks for all your thoughts and input guys
I finally have it working as I was hoping

2 independant fans, ducts and vents did the trick
I smoke tested it last night and everything goes outside now
"She ain't pretty, she just looks that way"

I think I hear them knocking on my door right now to check me for a Grow Op ....

[H2o2]

Well done but now I have to do mine when I get home as Kelowna is warming up

[gregzz4]

Thanks Harry. Hope it's inspired you to do something DIY too

I should have known better when I started this project;
I dealt with engine cooling systems for nearly 25 years and have always known that a puller fan is more efficient than a pusher
That and I shouldn't have trusted the flow #s I read on the web for 4" ducting

Anyway, 'tis all good now

[gregzz4]

For anyone curious about doing this themselves ...

Apparently duct tape can't support the weight of my ducting with the heat - one of the ducts was hanging when I got home Thursday afternoon

It won't happen again as I've screwed the pipes to the fans and used aluminum tape to seal everything up

[WarDog]

Duct tape is a pretty useless long term solution. Glad to see you upgraded to the aluminum tape!