How do you know what kind of rads you need?

[geoc]

I am wondering how you seasoned watercoolers know how much radiators are needed in a build?

Do you guys quesstimate and while being on the safe side? Since there is no specific dissipation power for each rad (i.e. 120, 240, 360) how would you know how much you need?

[Squeetard]

Guestimate. A 240 will do a CPU + Vid card. I added a single 120 between my cpu and vid card that didn't make any difference. I'd say you need a 360 for cpu+ SLI.

So lets say you need 120mm for every component you want to cool. Your mileage may vary.

[Squeetard]

Let me add that a proper amount of cooling hits a certain max temp under load and stays there, it doesn't slowly creep up over time.

[AmuseMe]

I just fill the case with the maximum allotted size. My Little Devil PC-V8 can hold a maximum of three 120.4/ 480mm rads. So I put in three 120.4/ 480mm rads.

As for actually knowing. It really depends on what your cooling, if your over-clocking, and what fans your using.

[SugarJ]

I'd caution that Squeetard's estimate would be more accurate for Sandy Bridge and current AMD processors. The LGA1366 and LGA2011 SB-E chips run hot, and you won't reliably cool a max OC CPU with a single 120mm rad. Not that I'd ever do a custom loop with a single 120 rad anyways.

[chrisk]

I tend to just look for other folks who have similar builds and see what rads they have. If you check out 10 builds that have triple rads and they are all accommodating a similar cpu and gpu setup (ie. a 920@ 4.0ghz, single GTX 580), then that is a great clue as to what you might need. This might be risky, but gives a good starting point when costing out a loop.

Then, I find a place like HWC and post my proposed parts :)

Also, yes I also do what Amuseme does and I also try to figure out what will most easily fit in my case and setup.

[geoc]

So 120mm per CPU or GPU is the usual average then for mid range components(ie. gtx560, amd phenom x6 oc, etc)? Assuming we're not talking about chips that run exceptionally hot.

[jibz]

you can also factor in sound level. if you want a silent build you can go for massive surface area and low rpm fans or even passive.

if your strapping a delta on a 120 it could handle a little more load.

if you want to get really picky look at the surface area of popular air coolers and what fans they use and compair your w/c surdace area and fans.

[lowfat]

It really depends on your fan choices. A single 120mm radiator can expel a lot of heat w/ a high speed fan. But slow the fans down to 1000rpm or less and it won't do anywhere near as well.

[Feanor]

For decent performance at medium sound levels, go for around 1500 rpms fans and 120 mm of radiator per item water cooled (for a cpu plus gpu loop, that would be a 240 rad). Don't expect miracles, just high-end air-cooling performance level at much lower decibels. Again, noise level is different for each individual.

For the best silent operation, you really have homeworks to do. Choosing the right fan with the right rad is critical if you want to have some cooling potency. Large rad with low rpm is the way to go.

For best performance, just push/pull any radiator your case can fit, 38mm 3000 rpm fans are the way to go. It's when your computer slighty lift of the ground that you have enough fans...