Should I passively cool?

[Cramig88]

Ok first first

x570, 64g (4x16), 2x 1tb Kingston nvme’s on raid 1, and a strix OC 4090. Oh a 5950x too

i do overclock, usually to stability. If I push the envelope, I’ll ask about fans lol. But, with all the radiators I have and rebuilding the pc (x570 WiFi/hero to x570 dark hero), kinda taking a… different approach

 

now when it was setup before, all the rads were in there blah blah. If I wanted to spike my temps I could easily run 90c sustained all day. It seemed no matter how hard the fans would run, after time, to where the office would be as hot as the flipping cpu!  Totally not kidding… during winter out here it can be 3F or lower at night. My pc would heat the entire top floor, the office being the… radiator?

 

guess the question is simple. Do I need to install fans at this capacity of liquid cooling?  I don’t see how they would serve a benefit since after a while, the room itself reaches thermal equilibrium - I need an AC unit for the window!

 

just wondering if it’s worth installing a 3 fans per radiator, being 9 total. I don’t personally see a need considering, any ideas?

 

thermaltake d5/500ml

ekwb dark hero monoblock

byzinski monoblock/4090

120x30mm rad

360x30mm rad

140x60mm

360x80

420x80

 

holds little over 3.5L in total

Yes it’s heavy when installed. The case is 75# with all the stuff on it (glass and crap)

should I?

[Levent]

Wter cooling isnt magic, those radiators need fans. They are not built for passive cooling. Use a sensible block combination with low speed fans and you will be more than fine.

[Cramig88]

15 minutes ago, Levent said:

Wter cooling isnt magic, those radiators need fans. They are not built for passive cooling. Use a sensible block combination with low speed fans and you will be more than fine.

The x570 has a custom monoblock, it isn’t a generic anything, it’s made for the board and covers the VRMs/MOSFETs too

same for the 4090.  Both were 500 each (I think, maybe 300) in their hayday 

 

I just figure I got way more than enough sq/meter/cubic whatever of water per degree of heat. With fans, I still hit a peak - that’s the room temp.

 

it would be nice if I could shove all this into a case, troublesome as that will be, and not deal with fans. Idk ugh

[Psittac]

You still need airflow, radiant at the least

[Cramig88]

47 minutes ago, Psittac said:

You still need airflow, radiant at the least

Ok there’s a person on my side

ok radiant, gotcha. Heat rises, cool air initially around the pc

i figure that’s radiant, or adiabatic or something enough?  Figure it this way, minus expansion n such, if I took a blowtorch to 1inx1in of any radiator, it wouldn’t matter. There’s so much surface area overall…

 

air should naturally flow just due to heat, high pressure/low pressure yada yada?

figure I’ll bench it first without fans, gonna have to anyway. Just didn’t plan on benching like 5 rads

 

hey it’s science!

[thrasher_565]

90c a bit hot imo.

even cheap fans would probably help or hell even a box fan.

if it was like 85c i guess it be fine. 

the more the room heats up the less heat will come out of the rads.

think evaporation will happen faster so have to refill more often. posable to spike presher and pop fittings. dry out past so have to re past more offend. 

 

you can use a old psu to power the fans you can jump it to to stay on. 

 

$50 usd Phanteks XT PRO cheap big case

can hang a rad out the back too if need be

 

you can get rad mounts too if you dont want a case. 

Edited December 24, 2025 by thrasher_565

[Blue4130]

2 hours ago, Cramig88 said:

. My pc would heat the entire top floor, the office being the… radiator?

 

guess the question is simple. Do I need to install fans at this capacity of liquid cooling?  I don’t see how they would serve a benefit since after a while, the room itself reaches thermal equilibrium - I need an AC unit for the window!

 

 

If 1000w (being generous) heats your whole top floor, you must have a really small house.

[Pusbucket]

4 hours ago, Cramig88 said:

Ok there’s a person on my side

ok radiant, gotcha. Heat rises, cool air initially around the pc

i figure that’s radiant, or adiabatic or something enough?  Figure it this way, minus expansion n such, if I took a blowtorch to 1inx1in of any radiator, it wouldn’t matter. There’s so much surface area overall…

 

air should naturally flow just due to heat, high pressure/low pressure yada yada?

figure I’ll bench it first without fans, gonna have to anyway. Just didn’t plan on benching like 5 rads

 

hey it’s science!

what will end up happening is you will hit a thermal wall as the liquid and radiators heat-up and then the entire system will just be pumping hot liquid around.

You NEED some means of actively exchanging the heat from the liquid to the environment. Radiators alone are horrible for passive cooling.

 

I do recall years ago a 100% passive cooling case. The entire case was literally an aluminum heatsink with 2"- 4" fins on the outside surfaces.

Your radiators simply do not have enough exposed surface area to work passively. 

[J_Zet]

8 hours ago, Cramig88 said:

just wondering if it’s worth installing a 3 fans per radiator, being 9 total.

 

Just buy two 5 packs of Arctic P12 PST. Their minimum RPM is 200. Even at 400 it will be very quiet and should give you enough airflow. (You can obviously go for Noctuas if thats ok with your wallet).

However, you might get something like "semi-passive" cooling. Like using the airflow from one fan, twice. If you put radiator on intake with 3 fans, radiator on exhaust might not need any fans because it will use airflow from intake going through your case and escaping because of positive pressure. This however heavily depends on your case and configuration of radiators. 
 

[Lurking]

Elevate the radiators so the air can flow through (from convection). In your picture, they don't get air. 

with enough radiators the surface increases and passive is possible.

 

What you try to do is natural convection. The air in the fins warms up and rises. This draws in fresh air from below. A fan added wood be "forced" convection. This is more effective requires a smaller radiator surface area. But both rely on fresh air being available. 

 

But the heat going in your home will be the same regardless of cooling. All the electricity going in your PSU will become heat regardless. 500W electricity will become 500W heat. 

 

 

[steamrick]

Even a Mo-Ra 3 420 was only claimed to have about 200W worth of passive cooling capacity, and that thing has huge surface area and the sparse fins needed for passive cooling.

 

Your thick 80mm radiators are basically a whole bunch of dead area because air isn't going to move through those long thick dense finstacks without a fan forcing it to. 

 

If you really wanted to passively cool a truly highend system, you'd need one or multiple of the Mo-Ra IV 600. It'd also help a lot if you set them on their side so that air can flow through the fins upwards, though that'll take up a huge amount of floor space.

[Cramig88]

On 12/24/2025 at 1:18 PM, Lurking said:

Elevate the radiators so the air can flow through (from convection). In your picture, they don't get air. 

with enough radiators the surface increases and passive is possible.

 

What you try to do is natural convection. The air in the fins warms up and rises. This draws in fresh air from below. A fan added wood be "forced" convection. This is more effective requires a smaller radiator surface area. But both rely on fresh air being available. 

 

But the heat going in your home will be the same regardless of cooling. All the electricity going in your PSU will become heat regardless. 500W electricity will become 500W heat. 

 

 

Yep, u were right

so I just took out the 120 and 140, stuck with the 2x 360s and the 420

the thin 360 is passive, the thick one has 3 intakes on the front

the 420 is on top with only 2 fans

 

now idk if the loop order matters but given what I *had* and what is, I’m at 38 idle, less?  28k on r23 with only 78c, barely hits 80 - nowhere near 90

 

the fans ramp up a little, just to compensate for Vdroop I think. Hey whatever, works, it’s a clean setup and… case closed and done with!

 

pump to gpu to 420 to cpu to gpu to 360/thick/front to 360 thin/passive to the pump again

 

Bazam!  Thank you all!!!!

[Cramig88]