Closed cabinet with only one hole!! - cold air intake question! - AVS Forum
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post #1 of 11 Old 06-10-2013, 08:35 AM - Thread Starter
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I have a large 2.5m width x 50cm depth x 50cm height that has 8 pop open cupboard doors at the front and a large cable management access port at the back for feeding the cables: I've included a picture of half of the unit just so you get a feel for how it's put together! The unsitely blue retangle is a hole that goes right through the unit and out the back....

My question is... "As i can create a gap of around 10mm between the unit and the cabinet doors how would i pull cold intake air from around the bottom of the doors and exhaust it out the cable management gap? (blue retangle)"

Obviously i can exhaust the hot air out of the access hole which is roughly 40cm x 10cm on both side of the cabinet... but it's
important for me to be able to pull cold air in from around the main doors... I was thinking of mounting a cross flow \ squirrel cage fan on the bottom of EVERY door pulling cold air from the cab pointing at the floor and blowing it into the cabinet.... would this suffice? or is there a better way of doing it?

the challenge really is in not modifying or cutting\drilling the unit at all as its an expensive unit that i just cant deface it! I can remove the middle shelves so the air flow can be a less complex.

Any ideas welcome! The diagram is an old diagram and i feel that maybe having the intake and and blower fans mounted at the bottom and top of the swing out doors and keeping the middle shelf to divide the intake and blowing fans might be an idea?

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post #2 of 11 Old 06-10-2013, 09:07 AM
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I'm not sure I understand your question. Is the 10mm (0.4 inches) the gap between doors when closed?

I set up a cooling solution for my enclosed cabinet not too long ago. My cabinet is about 3' wide x 3' high x 2' deep; it houses an AVR, a stereo receiver, a blu-ray player, and a DVR. I used 2 fans configured to exhaust hot air out the back, and let the cold air intake be the gap between doors. This setup has worked very well, with the only drawback being a "ribbon" of dust that forms along the equipment (where the doors meet).

I used the coolerguys website for my components. They have some nice options for a clean finished look; they've also got programmable thermostat options and temperature displays...very slick. You might also want to look at reviews about fan noise when selecting your fans, especially if you're watching in a quiet room or sitting close to the unit.

Like you I was also working with an expensive cabinet and had concerns about cutting into it. Is it correct to assume you would prefer to cut into the back only? If so, I might try a few fans in the back to start, and see how that works. You can always go back at a later date and add cold air intake fans, but you might not need them. Just make sure that the power supply you choose is expandable to add additional fans in the future.

Is there a gap between the shelves and the back of the cabinet? I would be cautious about removing the shelves if it forces you to stack your components; that could make things run even hotter.
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post #3 of 11 Old 06-10-2013, 09:07 AM - Thread Starter
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I've included this AWFULLY DRAWN diagram! Too demonstrate further what im trying to do ... would it work? There is a gap in the middle dividing shelfin that is quite big for feeding cables from the top shelf to the bottom shelf so cold air COULD pass through the shelfing quite easily...

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post #4 of 11 Old 06-10-2013, 09:12 AM - Thread Starter
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"I'm not sure I understand your question. Is the 10mm (0.4 inches) the gap between doors when closed?"

Yes. Its the distance between both of the flip out cabinet drawers AND also the distance that hinges hold the door away from the main body of the unit...

"I set up a cooling solution for my enclosed cabinet not too long ago. My cabinet is about 3' wide x 3' high x 2' deep; it houses an AVR, a stereo receiver, a blu-ray player, and a DVR. I used 2 fans configured to exhaust hot air out the back, and let the cold air intake be the gap between doors. This setup has worked very well, with the only drawback being a "ribbon" of dust that forms along the equipment (where the doors meet).

I used the coolerguys website for my components. They have some nice options for a clean finished look; they've also got programmable thermostat options and temperature displays...very slick. You might also want to look at reviews about fan noise when selecting your fans, especially if you're watching in a quiet room or sitting close to the unit."

Yes. I plan on doing the same thing... Ive already specced all the gear from them... However if i cant get the internal temp down low enough then its silly spending the money on it all...

"Like you I was also working with an expensive cabinet and had concerns about cutting into it. Is it correct to assume you would prefer to cut into the back only? If so, I might try a few fans in the back to start, and see how that works. You can always go back at a later date and add cold air intake fans, but you might not need them. Just make sure that the power supply you choose is expandable to add additional fans in the future."

I cant make any ammendments to the unit but the rear cable access port is sizaable and i was planning on using hot glue to mount the fans purely because it peels right off the gloss! smile.gif

"Is there a gap between the shelves and the back of the cabinet? I would be cautious about removing the shelves if it forces you to stack your components; that could make things run even hotter"

Yes. There is a large access that is about a quarter of the entire shelf that is cut away allowing easy cable access between the upper and lower shelves. And i would really like to keep the shelves but am wondering if it will hinder getting cold air into the top shelf or not frown.gif
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post #5 of 11 Old 06-10-2013, 09:19 AM
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Quote:
Originally Posted by phoenix_rising View Post

I've included this AWFULLY DRAWN diagram! Too demonstrate further what im trying to do ... would it work? There is a gap in the middle dividing shelfin that is quite big for feeding cables from the top shelf to the bottom shelf so cold air COULD pass through the shelfing quite easily...

Cooling2.jpg 58k .jpg file

I think you would be better off with the fans on the back, trying to exhaust the hot air out. It's best to place them as high as possible, where the hot air collects at the top of the cabinet. If the shelves restrict too much airflow you could place a fan high and a fan low. You might not need the cold air intake fans at all, if there are enough gaps at the front for air to get in.
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post #6 of 11 Old 06-10-2013, 09:26 AM - Thread Starter
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Yeah im going to try a mock up tonight with some old fans and see if it makes any difference.. Here is a pic of where the 10mm gap is that i referred too...

gap.jpg 20k .jpg file

Would you place them directly over the cable access port at the top/back of the cabinet...blowing out or a few inchs away from it?

Any ideas on how i could suck the air from the 10mm gap around the cabinet doors? would a crossflow fan be best? (noise would be an issue though)
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post #7 of 11 Old 06-10-2013, 10:06 AM
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I actually don't think it's necessary to use fans at the base of the unit - if you have a fan (or fans) blowing air out of the access hole, with the appropriate intake area you'll suck sufficient air in through all available apertures. As a very rough rule of thumb, the total cross sectional area of the gaps available to suck air into the cabinet should match your exhaust "hole", so in your case, the sum of all the gaps around the doors would need to be roughly 400 sq. cm. Ideally, you'll want to make a seal around the exhaust fans so that you are actually drawing air across the units - without a reasonable seal, the fans will just suck a lot of air in using the path of least resistance, which could easily be from immediately adjacent to the actual fan unit. What you need to make sure is that air is actually drawn across the units you want to cool - if air can get sucked into cabinet and exhausted without actually passing over/around the equipment, it won't do you any good.

I couldn't quite tell from the two diagrams, but ideally the access hole you're going to use as the exhaust port should be as high in the cabinet as possible, otherwise you'll end up with a 'puddle' of hot air above the stream of cooler air.

Another consideration is to make sure there's good vertical air flow between each piece of equipment, again, you don't want to a pocket of trapped hot air. And just to offer a slightly different perspective to PSUMazda, if the shelves are preventing the natural upward flow of air, you may be better served my removing them (stacking the units with greatest heat output - like amps - on the top). Also, what you don't want is cooler air coming into the cabinet lower down and just shooting up the gap between the shelf and the back of the cabinet before being exhausted - putting strategically placed holes in the shelves is one way of managing the path that the cooling air takes through the cabinet.

Dave
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post #8 of 11 Old 06-11-2013, 05:06 AM - Thread Starter
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Thanks guys i really appreciate you taking the time to give me your input i think you both make some really solid points and you've confirmed in my mind how i'll try and tackle it... If for any reasen i need additional air intake using fans pulling air from the bottom of the cab doors... what would you guys suggest in terms of creating adequate airflow? Crossflow fans? Normal fans and making air ducts? Are there special types of fan for doing this?
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post #9 of 11 Old 06-11-2013, 10:08 AM
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Suggest you take a look at the products made for this purpose, and the information / white papers on cabinet cooling at the manufacturers' websites:

http://activethermal.com/index.html
http://www.coolcomponents.com/cabinetventing
http://www.coolerguys.com/ho.html


Jeff


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post #10 of 11 Old 06-11-2013, 09:07 PM
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Quote:
Originally Posted by DGF View Post

I actually don't think it's necessary to use fans at the base of the unit - if you have a fan (or fans) blowing air out of the access hole, with the appropriate intake area you'll suck sufficient air in through all available apertures. As a very rough rule of thumb, the total cross sectional area of the gaps available to suck air into the cabinet should match your exhaust "hole", so in your case, the sum of all the gaps around the doors would need to be roughly 400 sq. cm. Ideally, you'll want to make a seal around the exhaust fans so that you are actually drawing air across the units - without a reasonable seal, the fans will just suck a lot of air in using the path of least resistance, which could easily be from immediately adjacent to the actual fan unit. What you need to make sure is that air is actually drawn across the units you want to cool - if air can get sucked into cabinet and exhausted without actually passing over/around the equipment, it won't do you any good.

I couldn't quite tell from the two diagrams, but ideally the access hole you're going to use as the exhaust port should be as high in the cabinet as possible, otherwise you'll end up with a 'puddle' of hot air above the stream of cooler air.

Another consideration is to make sure there's good vertical air flow between each piece of equipment, again, you don't want to a pocket of trapped hot air. And just to offer a slightly different perspective to PSUMazda, if the shelves are preventing the natural upward flow of air, you may be better served my removing them (stacking the units with greatest heat output - like amps - on the top). Also, what you don't want is cooler air coming into the cabinet lower down and just shooting up the gap between the shelf and the back of the cabinet before being exhausted - putting strategically placed holes in the shelves is one way of managing the path that the cooling air takes through the cabinet.

Dave
This puts into words exactly what I was thinking of your setup. You need fans high, no need for intake fans, just make sure the pathway from intake to outtake is exclusive.


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post #11 of 11 Old 06-12-2013, 09:17 AM
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Quote:
Originally Posted by AV_Integrated View Post

This puts into words exactly what I was thinking of your setup. You need fans high, no need for intake fans, just make sure the pathway from intake to outtake is exclusive.

THIS. The exhaust fans will pull the air through the intake. That's the way to get rid of heat. smile.gif

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