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Advice on fan layout in a horizontal HTPC case (intake vs outtake/positive pressure vs negative prssure)?

post #1 of 4
Thread Starter 
I need some advice on how to orient my fans (intake vs outtake) in my Apevia BK-500 HTPC.

I have it right inside a TV cabinent in a horizontal position, with the front facing the left and the left side right up against the inner wall of the cabinet.
There are 4 fan slots: Fan A is 1x 120mm fan slot on the left side of the case next to the inner wall, Fan B is 1x 120mm fan slot on the right side of the case facing outward (towards the people), and Fan C is 2x 80mm fans on the rear of the case, facing the right side of the TV cabinent. The front of the case faces the left side of the cabinet. I have it this way since it's the only way it would fit inside.

I have a pancake CPU cooler that doesn't expel air out the back.

My current layout is to have Fan A as intake, Fan B as outtake, and the 2x80mm Fan C as outtake. This is a negative pressure setup that sucks hot air out of the case. However, this means my pancake cooler doesn't have access to cool room temperature air, and has to recycle warm case air. (the only intake Fan A blows cool air into the GPU).

Thus, I'm wondering if I should turn Fan B into an intake fan as well (have both 120mm fans be intake and have the two 80mm fans be outtake). This would create a positive pressure situation. This would bring cool air directly onto my CPU HSF cooler, but I'm concerned the lack of fans to exhaust heat would result in heat buildup inside my case.

Another option is to turn Fan B into intake, turn Fan A into outtake, and leave Fans C as outtake. Bu this means Fan A might dump air inside the cabinent (which traps heat), which may or may not be effective. But then again, this isn't a very high power consumption rig, so even if it does dump heat into the cabinent and the heat gets trapped, it may not matter that much.

I could turn 80mms into intake fans, but I don't have fan filters of that size and would prefer not to.

See picture:
The case is layed down horizontal - the left side of the case is the front of the case with HDDs, PSUs, 3.5 drives, etc. The right side of the picture is the rear of the case, and contains the parts such as the CPU/GPU/etc. The top of the pic is the left side of the case, and the bottom of the pic is the right side of the case.


Edited by Bluescreendeath - 8/25/16 at 12:52pm
post #2 of 4
Airflow is not easy to explain, but it's not 'suck hot air out'. What ever air is being sucked out of case is replaced by the same amount of air coming in. case. Think of the air as water. case as a tank full of water, and vents as pipes in and out of tank. Because tank is full we cannot put any more water in unless we are taking the same amount of water out .. and we cannot take any water out unless we are putting the same amount in.

First thing I would do is remove all unused PCIe back slot covers. They are blocking an area that will serve as an nice exhaust vent.

Where is the heated exhaust air going when it comes out of case in your TV cabinet? It needs some way of leaving the cabinet without mixing with the cool air going to HTPC.

At a guess I would use both 120mm vents as intakes. One will flow cool air toward CPU cooler and hopefully help push CPU heated exhaust toward and out of 80mm exhaust vents. The other 120mm fan will supply GPU and help push it's heated exhaut out the back where the PCIe slot covers were.

I usually do not use the motherboard I/O shield (in back of case) becuause leaving it out increases back vent area and allow more airflow from CPU back and out of case helping cool mobo components in that area.

Depending on how powerful your 120mm fans are they may be able to push more air out of the 80mm vents than vents with fans in place will flow.

Like this.

Edited by doyll - 8/26/16 at 2:42am
post #3 of 4
Thread Starter 
Thank you for the information. I will consider taking out the PCIe slots to improve exhaust.

Your diagram of 2x120mm intake and 2x80mm exhaust is my current plan.

Do you think I should turn the 2x80mm fans into intake fans and the 1x 120mm fan next to it into exhaust (so even more exhaust)? Would that negative affect airflow?
post #4 of 4
Quote:
Originally Posted by Bluescreendeath View Post

Thank you for the information. I will consider taking out the PCIe slots to improve exhaust.

Your diagram of 2x120mm intake and 2x80mm exhaust is my current plan.

Do you think I should turn the 2x80mm fans into intake fans and the 1x 120mm fan next to it into exhaust (so even more exhaust)? Would that negative affect airflow?
If you do not remove the PCIe slot covers their is no exhaust airflow for that side of case except over the GPU and into the CPU cooler.
2x 80mm need to be exhaust or removed.

The back of your TV cabinet needs to be open so the heated air coming out of back of case has somewhere to go. You might need to put a divider in the cabinet between side intakes and back of case .. including below and above the case .. so none of the heated exhaust can move forward and contaminate / heat up the intake airflow. I know this may sound extreme, but every degree warmer the air going into case and components is a degree warmer that component will be .. and the faster their fans will need to run to keep them cool, so the louder it will be as well.
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