What size radiator do I need for my system?

A very hot airflow from radiator fans is a sign of a system, running at - or over - it's maximum cooling capacity.

Water needs to be adequately cooled with coldest ambient air temperatures therefore radiator should be getting as much as "fresh air" as possible. Hot air from radiator should also be dumped out of the computer chassis by the use of auxiliary chassis fans. Poor design and construction choice may result in insufficient radiator cooling which may lead to overheating of the components. In case of cooling capacity issues the symptoms are usually a slow, but steady increase in temperatures until the system reaches equilibrium and/or system encounters stability issues.

The best part of custom water cooling loop is that the system can be extended and the cooling capacity can be extended almost without limitations.

Rule of thumb is to use at least one 120mm radiator (section) per each water cooled component plus one 'spare'.

For example, if one is liquid cooling a CPU and a single high-performance graphics card it is recommended at least one 240mm (2x 120mm) radiator for good performance. Ideally, one would get a 360mm (3x 120mm) radiator for best performance. Motherboard- and memory water blocks usually have lower power output therefore they are not included in this equation.

Radiators also come in different sizes, but the 120mm type most common. For example, a 280mm radiator (2x 140mm), built for 140mm cooling fans, has 33% larger cooling surface than the 240mm variant (2x 120mm) thus it can dissipate substantially more heat given the same conditions. A 360mm radiator (2x 180mm), built for 180mm cooling fans, is 50% bigger than a 360mm radiator (3x 120mm), but fits only in a handful of computer chassis

The number and the size of radiators that can be installed in the system is usually limited by the type and size of the chassis, therefore EK recommends the use of larger, water-cooling friendly computer chassis.