# Fan is to large for outake hole.

Discussion in 'Grow Room Design/Setup' started by Purpleface, Mar 24, 2012.

1. I have a 3" fan and a 2 1/2" inch hole for my outake. I don't have anything to cut a larger hole so would this reduce my airflow to much?

2. I'm no pro, but I doubt half an inch will matter, we'll see if I'm right though lol.

3. Anyone else? That wasn't too reassuring.

4. I have the same question, although my fan is 6 inches so I'm losing 3 /12 inches. It doesn't seem to be affecting the airflow too badly for me. I'll have to give you another not so assuring answer, you're probably ok.

That's not the question I asked.

7. [quote name='"Purpleface"']

That's not the question I asked.[/quote]

8. simply in terms of physics, that statement is incorrect. If you can push X air through Y hole, then all you need is Y hole for X air to enter.

That being said, from what ive read its a good idea to have more than 1 intake hole to give even air distribution, along with osculating fans to help move it around better.

9. [quote name='"Clidefr0g"']

simply in terms of physics, that statement is incorrect. If you can push X air through Y hole, then all you need is Y hole for X air to enter.

That being said, from what ive read its a good idea to have more than 1 intake hole to give even air distribution, along with osculating fans to help move it around better.[/quote]

Alright this is all good info but my question still stands guys.

10. Obviously a smaller hole will restrict airflow, if you have no way of fixing it then im not sure why you are even here tbh but what you will have to do is, the math.. , or test it.

Im not 100% sure on this equation, but im guessing if you take the CFM of your fan at 3" and then find out what the % of missing space is in your hole and then take that number and apply it to the original CFM, you may find the number you're looking for.

its about 7"sq for the 3" and 4"sq for the 2.5" which means that the 2.5" will only give about 57% the airflow capabilities.

All this is assuming that the fan can actually push more air than a 3" pipe can take, which is why testing becomes the better option.

11. What he said, airflow is greatly reduced and puts much more strain on a fan motor.

12. the answer is simple... try it and see... just make a funnel to ensure you don't loose air... once its installed monitor temps... if you space does not cool down, you need to enlarge the hole...

and i liked the other guys response about intake... hahahahaha

13. [quote name='"Tihspeed"']the answer is simple... try it and see... just make a funnel to ensure you don't loose air... once its installed monitor temps... if you space does not cool down, you need to enlarge the hole...

and i liked the other guys response about intake... hahahahaha[/quote]

Thanks, making a funnel didn't even cross my mind.

14. I just installed two 120mm fans in my box (see sig for reference). The holes I cut for the fans are about 1/2 inch smaller than the diameter of the fans. I don't have any trouble. I don't think a half inch or so makes a whole helluva lot of difference. YMMV.

15. The fans you have couldnt push enough air to fill a 3" hole if you stacked 20 of them on top of each other and ran them so hot they burnt out.

16. They're working fine in my box right now. What's your beef with my fans?