Top Mount Radiator fan direction

[JustJeff]

I'm getting back into watercooling after well over a decade away. I'm not planning any overclocking right away, but I'll probably muck about with it once the system is built. The system in my specs is what is being built. The CPU, Mobo, RAM are all sitting in their boxes. PSU is in my current main PC. All the watercooling has been sitting in a box for well over a decade. I'll test the D4 to confirm it's still working. Radiator needs to be purchased (leaking radiator is what prompted me to stop watercooling). CPU block needs to be purchased.

For now I have a full tower under my desk. 360 top mounted radiator with fans, 120 fan in front, 120 fan in rear. One thing other thing to note is that I dont' keep the side panel on. From the top of my case to the bottom of the desk I have about 6 inches. It seems that I should pull air in from the top and push it out from the front and back. If I push air out of the top it's going to deadend into the desk and build up heat.....or so I would think. The full tower is temporary though. I'm planning wall-mounted system...but for now I want to get the new stuff in the case and up and running. I'll finish planning the wall-hung, build it and transfer the hardware to it later.

 

[ThrashZone]

Hi,
I would intake on rads simply because they like coolest air possible
Top and front of cases are also filtered already so rads won't collect dust as fast if maintained weekly

Leaving the side panel off most of the dust will collect in the rad instead of the cases designed filtering system which can also be improved with other materials

Open wall mount not you'd still be smart to concoct a filtering system for it somehow.

 

[JustJeff]

I would intake on rads simply because they like coolest air possible

Yes, that is how I seem to remember it should be.

Open wall mount not you'd still be smart to concoct a filtering system for it somehow.

I'm not worried about dust too terribly much. I have access to compressed air and can regularly blow out radiator fins, fans, GPU, etc.

 

[MxPhenom 216]

If you are putting rad at the top, those fans should be used as exhaust. Not intake, unless you want to defy physics and push hot air down and into your system....

 

[FireFox]

If you are putting rad at the top, those fans should be used as exhaust.

Exactly.
I still don't understand why people recommend/suggest top fan as intake
Knowing that someone will quote my post and contradict what i am saying please don't.

 

[ThrashZone]

Hi,
As said because front and top of cases have filters lol

 

[FireFox]

Hi,
As said because front and top of cases have filters lol

this

unless you want to defy physics and push hot air down and into your system....

 

[JustJeff]

If you are putting rad at the top, those fans should be used as exhaust. Not intake, unless you want to defy physics and push hot air down and into your system....

You didn't address only have 6 inches of space from the case to the desk. Does that provide adequate air space for the hot air to get out and disperse into the rest of the room? I just ran into this identical situation as a heating and air technician. Homeowner put a deck over top of their condenser and were burning up fans due to the hot air being pulled through the coil not being able to get out. All the air was deadpanning into the bottom of their deck, heating up all the air around the unit and getting recirculated back into the condenser. Their system wasn't running properly and they were smoking their motors.

I'm looking for the best alternative for a temporary situation. Which is better to draw the coolest air from the top in and let it escape out of the open side panel, or to deadpan the hot air coming off the radiator out the top. Keeping in mind that the side panel is off and nothing is heat soaking inside the case..

 

[MxPhenom 216]

Hi,
As said because front and top of cases have filters lol

That's irrelevant. If your concern is dust going into a system, well:

1. As exhaust for the top, dust will never enter from that side of the case in that configuration
2. Set up the airflow in the system to be either neutral or positive pressure. Negative pressure will make for a dusty system no matter what.

You didn't address only have 6 inches of space from the case to the desk. Does that provide adequate air space for the hot air to get out and disperse into the rest of the room? I just ran into this identical situation as a heating and air technician. Homeowner put a deck over top of their condenser and were burning up fans due to the hot air being pulled through the coil not being able to get out. All the air was deadpanning into the bottom of their deck, heating up all the air around the unit and getting recirculated back into the condenser. Their system wasn't running properly and they were smoking their motors.

I'm looking for the best alternative for a temporary situation. Which is better to draw the coolest air from the top in and let it escape out of the open side panel, or to deadpan the hot air coming off the radiator out the top. Keeping in mind that the side panel is off and nothing is heat soaking inside the case..

Thats fine. I see nothing wrong with that. Its not going to really circulate back into the system unless you forcefully make it do that.

Keep it simple,

All you need to do it make sure the air pressure in the system is neutral or positive.

Neutral: Same amount of air leaving the system as entering
- Can by done by having the same amount of fans for intake vs exhaust

Positive: This is the best option for a clean system, and cool running - More air entering than actively leaving
- More intake fans than exhaust

 

[ThrashZone]

That's irrelevant. If your concern is dust going into a system, well:

1. As exhaust for the top, dust will never enter from that side of the case in that configuration
2. Set up the airflow in the system to be either neutral or positive pressure. Negative pressure will make for a dusty system no matter what.


Thats fine. I see nothing wrong with that. Its not going to really circulate back into the system unless you forcefully make it do that.

Hi,
Wrong again exhaust will draw from where ever it can back/ cracks in the case... unfiltered air plus dude does not use a side panel either lol

this

Hi,
Thanks
Rad hot air is nothing compared to other components

 

[MxPhenom 216]

Hi,
Wrong again exhaust will draw from where ever it can back/ cracks in the case... unfiltered air plus dude does not use a side panel either lol


Hi,
Thanks
Rad hot air is nothing compared to other components

That will only happen if the pressure in the case is negative. It will have to pull air from somewhere if its got more leaving then entering....

He was referring to what I said as 'this' in response to what you said....

 

[FireFox]

@JustJeff
My best advice is to try both, intake/exhaust and see what suits you.

 

[ThrashZone]

That will only happen if the pressure in the case is negative. It will have to pull air from somewhere if its got more leaving then entering....

Hi,
Since there is no side panel being used this is irrelevant read the op lol
He's also going to be using an open wall mount where there is No Walls except the back lol

Besides once again hottest components are not the radiator but is the CPU depending on clocks/ GPU usually the hottest/ Memory all these components create and run at hotter temperatures than the water will ever get which even under hard oc'ing should top out at 35c

 

[Deleted member 24505]

Imo top out, front in. The cool air coming in the front will naturally go out through the top rad cooling it. Why have top in which will basically pump warm air from the rad into the case. Say 3 in front and 3 out top will make it neutral so less dust.

 

[MxPhenom 216]

Imo top out, front in. The cool air coming in the front will naturally go out through the top rad cooling it. Why have top in which will basically pump warm air from the rad into the case. Say 3 in front and 3 out top will make it neutral so less dust.

That is what I have been saying, but at the same time idk if that holds up when you have a case without the side panels on it.

 

[ThrashZone]

Yes, that is how I seem to remember it should be.


I'm not worried about dust too terribly much. I have access to compressed air and can regularly blow out radiator fins, fans, GPU, etc.

Hi,
Your call
It's much easier to remove a filter and vacuum the dust off or take it outside and blow it off "which I do both" rather than doing all this inside the house where the dust bunnies are still in the house.

That is what I have been saying, but at the same time idk if that holds up when you have a case without the side panels on it.

Because seems like everyone is commenting on the title not the second paragraph in the op lol

 

[maxfly]

I would do which ever is easiest. With no case door it isn't going to matter. Your components are going to be pulling cool air no matter how you set up your rad fans (including the rad). Its a temp build anyhow, so just build it to be taken apart easily is my best advice.
Once you go with your wall mount, figure out which way your fan orientation is going to be most effective.
Btw the only time natural convection is actually a factor in an enclosed environment is if your running a fan less rig. The moment you introduce fans you introduce pressure. This immediately forces the air to go where the fans are pushing it or pulling it. If convection were any kind of real factor in case cooling, every case would be built with fans on the bottom and top only.

 

[eidairaman1]

Passing through a Rad you need high static pressure fans. If the rad is inside the case you need to ensure hot hair has other means of escaping.

 

[Deleted member 24505]

with no side panel, put the rad where it is most convenient, as air flow is irrelevant.

 

[mtcn77]

If you are putting rad at the top, those fans should be used as exhaust. Not intake, unless you want to defy physics and push hot air down and into your system....

This is wrong. If you make it the exhaust side, the fan motor ambient temperature will increase - reducing MTBF. Also, I would be reticent to put any cheap sleeve bearing fan in a vertical axis orientation for the proper lubrication can only work horizontally.
The exhaust side can work on its own pressure difference if you seal the case properly. Cold air has higher inertia, if multiple fans work as intake, the air turbulence can reduce air insulation.

 

[claes]

This is wrong. If you make it the exhaust side, the fan motor ambient temperature will increase - reducing MTBF. Also, I would be reticent to put any cheap sleeve bearing fan in a vertical axis orientation for the proper lubrication can only work horizontally.
The exhaust side can work on its own pressure difference if you seal the case properly. Cold air has higher inertia, if multiple fans work as intake, the air turbulence can reduce air insulation.

Sorry to troll but this post doesn’t make sense.

My best reading is that you’re worried about fan motor temperature and therefore think intake is better than exhaust. This might be true (although probably irrelevant), but doesn’t address any of the claims made in the post. Therefore you haven’t made any claims as to why they’re wrong, only an aside (fan operating temperature) that could be a potential downside to exhaust that the OP should consider.

The second paragraph makes logical sense but ignores that the OP is planning on running the case without a side panel.

 

[Outback Bronze]

I would intake on rads simply because they like coolest air possible

Agreed. Been WC for decades...

 

[JustJeff]

@JustJeff
My best advice is to try both, intake/exhaust and see what suits you.

Yep, I have thermometers for the purpose of measuring supply and return air. I'll just set my thermometers in the system and measure the deltaT.

I got my answer and it seems that people are going to muck up the thread debating the general issue without actually having read the specifics of the OP

 

[mtcn77]

Sorry to troll but this post doesn’t make sense.

This might be true (although probably irrelevant), but doesn’t address any of the claims made in the post.

Well, since it is 'my' post to address, it does relate to the claims I set as long as it is still true, which you have also recognised. That makes it self explanatory doesn't it? I don't claim something, I just simplify the train of thought.
If you want to digress, I'd be happy to, but that would be beside the point. Why and how cooling works are different inflection points. I'm trying to sequence the second part. If you think you can increase cooling by not attending to the pressure losses, or thinking air can go where it takes sharp turns(as in oversize fan blowing on the open case) think of it like a car engine and some seals...

The clearest path and the shortest trajectory of fan volute wins.
PS: I forgot some fans do not operate in "pull" quietly, but since we are discussing radiators, I'm expecting there is a way to stack the fans before the radiator?

 

[claes]

Mxphenom was talking about pulling hot air from under the desk
You’re talking about hot air affecting fan life span

I’m not arguing with you, I’m just explaining that telling someone that they’re wrong without addressing their claims doesn’t address why they’re wrong.

Besides being a little rude, in the context of this thread, if we’re to assume that what mxphenom said is true and that hot air will collect under the desk, then you’re technically agreeing with them.

Have a good one