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Exhausting two fans through the same hole?


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#1 cypher79

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Posted 11 April 2012 - 06:04 PM

So im currently trying to get my extraction set-up figured out for my next growing project. I've got 2 fans for extraction, one is a 6" ruck high power temp control and the other is a 5" high power manual control. Now at my last place i had them both exhausting through the same 6" hole i cut in the wall via a y-piece. Now I'm starting to get the feeling that maybe that was a bad idea as it used to get pretty noisy at the exit point and that maybe i was putting unnecessary pressure on the fans?

So what im saying is, if im exiting both fans through the same hole does that hole need to be the same size (or greater than) both fans combined? If so, then that isnt great from a practical point of view as you cant get fittings and vent covers and such in that size, and it would look dodgy too.

Or would i be better off making 2 holes, one for each fan? (Which again, would look dodgy)

Or am i just being paranoid and one 6" hole for both fans is fine?

What do you guys with more than one fan do?

:unsure:

#2 roundsquare

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Posted 11 April 2012 - 07:35 PM

Why you exhausting with both? :unsure: are you not intaking with one fan?

If you're exhausting with both fans it makes sense you want to allow for the extra pressure created by the combined fans going through one exit.


e2a speeling lol

e2a i forgot to say, why might more holes look dodgy? going to outside of house or the like? that may seem dodgy i suppose.

Edited by roundsquare, 11 April 2012 - 07:37 PM.


#3 cypher79

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Posted 11 April 2012 - 07:40 PM

Sorry i should have mentioned, one fan is for my veg tent, the other is for my flowering tent. Both tents have passive intakes.

And as my next place will be rented, i really dont want to make two holes, one will be bad enough lol.

#4 Chris P

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Posted 11 April 2012 - 07:43 PM

I had a setup a few years back with 2 x 6" extraction fans (1 was dedicated to the lights), I got a 2 x 6" to 8" connector and put a hole into the loft.
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#5 Frank Lopez

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Posted 11 April 2012 - 07:48 PM

.

Edited by Frank Lopez, 11 April 2012 - 07:49 PM.

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#6 roundsquare

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Posted 11 April 2012 - 07:51 PM

I had a setup a few years back with 2 x 6" extraction fans (1 was dedicated to the lights), I got a 2 x 6" to 8" connector and put a hole into the loft.

That sounds like a good idea then :yep:

#7 mrchang

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Posted 11 April 2012 - 08:03 PM

cant you vent from veg room into flower room and then out?

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#8 cypher79

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Posted 11 April 2012 - 08:08 PM

I had a setup a few years back with 2 x 6" extraction fans (1 was dedicated to the lights), I got a 2 x 6" to 8" connector and put a hole into the loft.


Nice one :wink:

Now my next problem is i cant find an 8" cavity wall adaptor to go with it (dont really wanna vent into the loft either)

could do with something like this in 8" (or more)
Posted Image

biggest i can find is 150mm (6")

Any ideas anyone?

#9 Chris P

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Posted 11 April 2012 - 08:22 PM

cant you vent from veg room into flower room and then out?

That's what I do now, but he can't do that as both setups use passive inputs.

Any ideas anyone?

I just got mine from a grow shop, can't remember which one. It was like a big plastic Y connector, with the 2x6" as input going to an 8" output.

Do you have the option of switching from passive to active intake in the flower area, then you could use the output of the veg as the input for the flower room, then you can just stick with your 6" exhaust.

Edited by Chris P, 11 April 2012 - 08:24 PM.

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#10 cypher79

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Posted 11 April 2012 - 08:29 PM

Hmm, not sure about venting my veg tent into the flowering tent because i think that would make the fan in my flowering room work flat out all the time = noisy.

Anyway, i think ive got it sussed now. I will cut a 250mm hole through the brick work with a core drill, stick a matching size louvre on the outside with the matching plastic pipe through the cavity, then stick a 250mm y-piece on the inside, and just use reducers to stick my ducting onto that :guitar:

cheers fellas

Edited by cypher79, 11 April 2012 - 08:30 PM.


#11 Chris P

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Posted 11 April 2012 - 10:21 PM

Hmm, not sure about venting my veg tent into the flowering tent because i think that would make the fan in my flowering room work flat out all the time = noisy.

Yeah not the best solution for your setup. I've only got a 125w envirolite for vegging so temps are low but notice you have a nice 400w halide.

Anyway, i think ive got it sussed now. I will cut a 250mm hole through the brick work with a core drill, stick a matching size louvre on the outside with the matching plastic pipe through the cavity, then stick a 250mm y-piece on the inside, and just use reducers to stick my ducting onto that :guitar:

cheers fellas

Sounds like a plan.

When you are joining extraction ducting into one, the output should ideally be a size bigger than the two inputs. If not the two extraction fans will not be able to work at full power because of the resistance caused by compressing the air from 2 sources into the same space. This would also likely cause a louder gushing noise of the air coming out. I think if the fans are wired on a slow speed or you have a fan speed controller it will probably not be as bad.
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#12 cypher79

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Posted 12 April 2012 - 08:15 AM

Good point mate, i think i will step it up to 300mm just be on the safe side :yep:

#13 Chris P

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Posted 12 April 2012 - 11:46 AM

Good point mate, i think i will step it up to 300mm just be on the safe side :yep:

8" would probably be ideal for 2 x 6" inputs, but I would be really paranoid about putting a large hole in an outside wall, depends where you live I guess. As long as it doesn't look conspicuous. Have a good think about what is best to do.
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#14 cypher79

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Posted 12 April 2012 - 03:08 PM


Good point mate, i think i will step it up to 300mm just be on the safe side :yep:

8" would probably be ideal for 2 x 6" inputs, but I would be really paranoid about putting a large hole in an outside wall, depends where you live I guess. As long as it doesn't look conspicuous. Have a good think about what is best to do.


Yeah ive been thinking that too mate, i wanna make the smallest hole i can get away with really. You think i would be ok with just an 8" (200mm) hole then? When i read your other post i thought you meant the hole needs to be a size bigger than both fans combined. :unsure:

Edited by cypher79, 12 April 2012 - 03:39 PM.


#15 cypher79

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Posted 15 April 2012 - 07:56 AM

hi

ive tried this a few times over the years and it never works

if one is even slightly more powerful than the other it will completely knock it out

last time i had 2 * 200mm extracts, both the same fan, same size, however it still didnt work, one room ran perfectly, the other had no extraction at all and after one day the roof was covered in condensation

i just went with one hole for one room and did a window extract ( boarded up window with a hole in the board ) for the other room


Thats strange, i never had any problems like that

the only issue i had was a noisy exit point, and my temps were generally fine

what size y-piece was you using?


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