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Exhaust fans for network closet

Linwood

Active Member
JimS said:
If you make a hole in the wall for a fan it would be easy to slip some short 2 x 4s in to line the "duct".  A few dry wall screws to hold them could be covered by the grills.  Would make it much more solid to mount the fan also.  I have also wondered about the heat.  I am putting my things in a large cabinet.  Nothing with a lot of power - a few routers and Pi boards, a ups...Passive ventilation will probably be adequate if I make the openings fairly large for a little more flow.
 
Yeah, maybe.  I'm struggling a bit with the new house as it has all metal studs.  While it is nice to think there are no termites, they are problematic when it comes time to do... well, most anything.  They are REALLY flimsy and rely on the sheet rock to tie together for strength.   Adding a horizontal 2x4 I have not done, but I think I would have to open up the opposite side of each stud to screen them in from the back side of the metal stud.  I hung a TV, and I took out a large section of sheet rock and put in ply wood instead, screwed it into the studs and then screwed the TV to the ply wood.
 
So framing up inside the wall is all new to me.  I really rather miss wood studs.
 

LarrylLix

Senior Member
Linwood said:
Yeah, maybe.  I'm struggling a bit with the new house as it has all metal studs.  While it is nice to think there are no termites, they are problematic when it comes time to do... well, most anything.  They are REALLY flimsy and rely on the sheet rock to tie together for strength.   Adding a horizontal 2x4 I have not done, but I think I would have to open up the opposite side of each stud to screen them in from the back side of the metal stud.  I hung a TV, and I took out a large section of sheet rock and put in ply wood instead, screwed it into the studs and then screwed the TV to the ply wood.
 
So framing up inside the wall is all new to me.  I really rather miss wood studs.
I had a house with metal studs back in the 1970s. I would avoid them like the plague now. I remember drilling trial/finding holes every 1" across 40 inches of wall looking for a stud. I didn't know it was metal studs.
 
Then you get a stud finder and it won't find them either. When you do find a stud and try to self-start a sharp pointed screw into them they just push out of the way. Now you drill a hole through  the drywall to make a screw catch hole in the stud but  there is a hole where the screw hole is. Wiring had to be grommetted in some areas and armoured cable used in others.
 
Wait until you try to hang your kitchen cabinets.
 
For domestic building they should be outlawed. I would rather have UFI in my house.
 

Linwood

Active Member
If anyone is interested will show you my solution.
 
First, I got forced into the solution.  I added a computer to the closet, and shot the door and watched the temperatures.  It was running mid 80's before the computer, but rose quickly to the high 80's without.  I was going to let it go until mid-90's, thinking that was reasonably safe -- my router started crashing about 88 degrees.  And the router was 3' lower than the temperature sensor.  I guess home use stuff is just not made very well (Linksys WRT1900ACS). 
 
i-xMbfBXk.jpg

 
The first hump is yesterday when I started to test it but decided to go to bed and opened the door.  The right hump is where things started crashing.  I do not know how much hotter it would have gotten.   The significant drop is my turning the AC down while working (it was not running much as not very hot out). 
 
This does not show the max temp with my solution running, will see that over night.
 
Here's what I did: Home depot for duckboard; they had none so got a sheet of foam insulation  ($14).  I used about 5% of it, quite a waste, could probably have used a piece of sheetrock as well.  I made it the size to hold 2 computer fans.
 
i-SQZGZ78-M.jpg

 
I taped the fans together and put a 12v socket on it.  I had a bunch of old 12v bricks, and the fans were left over from a computer build, so essentially free but pretty cheap if I had to buy.
 
The hardest part was cutting a hole in the wall  that matched up on each side.  I cut one then tried to mark the other, in retrospect it might have been easier to take a long drill and drill each corner (though whether I could go straight enough is a good question).   Fortunately duct tape (the metal kind) covers a lot of sins.
 
i-W3Cw5nt-L.jpg

 
Now the fans: 
 
i-8txMK84-L.jpg

 
To mount the fans I just put four toothpicks on each side, holding them in place (angled away so they would not vibrate into the blades).  Looks silly but took all of a minute and no cost.
 
Net result outside the closet:
 
i-dqsKwcV-L.jpg

 
In this case I have the vanes angled so you cannot easily see into it from the ground.  In the closet I reversed it so I could easily see if both fans are running:
 
i-zf3p5j5-S.jpg

 
Silent, at least compared to the switch and router much less computer.
 
While I put this note together and did some cleanup it has been maybe an hour and the closet is about 3 degrees above ambient and appears to be leveling off, though it may go a bit higher.
 
Incidentally, at about 2 watts each it seems pointless to control the fans, I plan to have them run 24x7.  In a computer such fans usually last many years, hoping that will be true here also. 
 
The grills were about $6 each so about $30 in pieces and parts invested, and a few hours (some of which waiting for touchup paint to dry -- I cut the hole with a sabre saw that left a lot of marks on the wall). 
 
Hopefully that will fix things. 
 
Would the hole with no fans have been adequate, depending on convection?  Maybe, but the low temperature at which the router failed concerned me.
 
Did I need the duct as opposed to just blowing into the wall?  Probably not, but when I decided to use foam I realized how simple it was to build, and the fans probably are more efficient in a relatively sealed tunnel.
 
This was my second choice, by the way.  it looks like it has a fan and thermostat for relatively cheap ($50).  And it is pretty.  But my cheap concoction is pretty enough I think, from the outside.
 
https://www.amazon.com/gp/product/B00QFWLGPU/ref=ox_sc_saved_title_5?smid=A2AW0W4FKP16S5&psc=1
 
(In case amazon link breaks it is an AC Infinity Airplate T3)
 
Linwood
 

LarrylLix

Senior Member
I found both my Netgear, and ASUS AC1900 routers  both work much better when mounted vertically. Despite both looking designed to sit horizontal, they both crashed at about 34c in my smaller cabinet.(CAO Tag sitting on the top case surface) Standing them vertically seemed to cure the problems by making them more tolerant,
 
Strangely enough, although I couldn't really detect much of a temperature difference, it always happened in summer, and never winter months, despite being constant temperatures in the house. Humidity would fluctuate some though.
 
So you may want to help the heat get out of the components by considering mounting angles in addition to fan cooling.
 
Nice job!
 

Linwood

Active Member
@LarryILix, thanks.  I'll take another look at it.  it sits on a wire rack not solid, and the case is filled with holes, but maybe being vertical the air flows across the board better or something.
 
Lots of wall space in the closet. 
 
34c is pretty darm warm but I guess I am spoiled by working with more business oriented gear, I just don't expect crashes under 100F or 38C or so.  Not servers, but AP's, routers, switches... 
 
I guess why that's we pay 10x the price for business gear vs home.
 

Linwood

Active Member
In the FWIW department I may need to buy a couple fans with more power.  Today it has stayed locked right at 84 degrees, which is higher than I would like (ambient outside the closet is 76).   Not hot enough to crash things, but hotter than desired.
 
So in terms of lessons if someone is considering it -- the Tim the Tool Man Taylor lesson (for those wasting time watching sitcoms) is "More Power" is good.
 

RAL

Senior Member
It's all a question of how many CFM of air you need to move to keep the temperature where you want it.  One thing to consider is whether you want to go with 2 fans with a higher CFM rating.  For a given fan size, higher CFM usually means higher RPM and more noise.  A better choice may be larger diameter fans, or additional fans at the same or lower RPM to keep the noise down.
 

Linwood

Active Member
RAL said:
It's all a question of how many CFM of air you need to move to keep the temperature where you want it.  One thing to consider is whether you want to go with 2 fans with a higher CFM rating.  For a given fan size, higher CFM usually means higher RPM and more noise.  A better choice may be larger diameter fans, or additional fans at the same or lower RPM to keep the noise down.
 
The hardest part (and was not that hard) was cutting the hole, so I am a bit reluctant to get bigger fans now.
 
But your comment raises a question.  I was thinking two fans with about twice the CFM.  
 
Btu what if I just put in two more fans like what I have here -- in line.  I.e. back to front.  What does that do aerodynamically, will that move 40% more air (I'm guessing there is an inverse square relationship in there somewhere)? 
 
Most of the twice-the-CFM ones I see are a LOT louder (like 25-30dba vs. 17, one was 35, which I have no idea if they will be audible, but that's a lot more noise; hard to compare with "silent" to know). 
 

RAL

Senior Member
Linwood said:
The hardest part (and was not that hard) was cutting the hole, so I am a bit reluctant to get bigger fans now.
 
But your comment raises a question.  I was thinking two fans with about twice the CFM.  
 
Btu what if I just put in two more fans like what I have here -- in line.  I.e. back to front.  What does that do aerodynamically, will that move 40% more air (I'm guessing there is an inverse square relationship in there somewhere)? 
 
Most of the twice-the-CFM ones I see are a LOT louder (like 25-30dba vs. 17, one was 35, which I have no idea if they will be audible, but that's a lot more noise; hard to compare with "silent" to know). 
 
My gut feeling is that stacking the fans won't help much.  But I'm far from an expert on air flow like that.  I've just never seen it done.
 
If you don't want to deal with enlarging the hole in wall right now, I'd try higher RPM fans and see how bad the noise is.  If it's acceptable, that's great.  If not, at least you'll have a better idea of whether the added CFM helps, and then you can decide about enlarging the hole or not.
 
Also think about whether at some point the grate over the fans might be restricting the higher CFM.  Easy to remove the grate to see if that has an effect or not.
 

kurtmccaslin

Active Member
I assume you have your fans set up to exhaust from the room.   How much flow area do you have for the return (under the door?)   It should be at least as big as the exhaust flow area-- preferably bigger.
 
Another idea would be to install two additional fans near the floor on the same wall.   Same setup only in reverse flow direction.   
 

Linwood

Active Member
rockinarmadillo said:
I assume you have your fans set up to exhaust from the room.   How much flow area do you have for the return (under the door?)   It should be at least as big as the exhaust flow area-- preferably bigger.
 
Another idea would be to install two additional fans near the floor on the same wall.   Same setup only in reverse flow direction.   
Exhaust yes, but the issue of intake size is a good point, I had not given much thought to it because there is a good sized gape, but it is likely a real constraint.  The door seals pretty well on the sides, and there is only about 30 sq in at the bottom, maybe a bit more and 50-60 for the fans.  A grate in the door would help, or I could cut a bigger opening, or put another opening in the bottom of the closet to the hall.  Have to give that some thought, all of which are a lot more effort than a bit more power in the fans, though obviously I will reach a point of diminishing returns quickly if there is not adequate intake. 
 

kurtmccaslin

Active Member
The easiest way would be to cut an inch off the bottom of the door with a table saw or circular saw.   Just need to make the cut real straight.   And will probably need to paint afterward.
 

LarrylLix

Senior Member
If the sides of the door leaks you will have to dust frequently as you will see a ring on the frame every week.

Are the bottom it will not be as obvious and easier to clean one linear dust streak..

Sent using Tapatalk
 

Linwood

Active Member
rockinarmadillo said:
The easiest way would be to cut an inch off the bottom of the door with a table saw or circular saw.   Just need to make the cut real straight.   And will probably need to paint afterward.
 
Maybe.  Or rather "yes but".  There's an inch or so now and it looks pretty big, a 2" gap would really be visible, and it faces the den/great-room.  I think I am more likely to go in from the side out of view if I really have to.
 

BraveSirRobbin

Moderator
Is my suggestion of obtaining louvered doors out of the question?  I really believe this will solve your issue.
 
Louvered doors look really good, especially if left in natural wood and not painted (but you will want to match your other doors of course).
 
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