I'm building my first PC for Christmas and I've run into an issue. My motherboard, a Gigabyte A520M DS3H V2, only has one fan header for the system fan. I've heard a rule of thumb is to connect about three fans per header, though it's recommended to stick to two if possible.
I'm using a Jonsbo D32 Pro case and plan to install two 140mm intake fans at the bottom, a 140mm exhaust fan at the top rear, and a 120mm exhaust fan at the rear. Since the CPU tower cooler seems to push air out the back, I'm considering whether I could skip the rear fan and connect the top-rear exhaust fan to the CPU fan header instead. Then I'd connect the bottom intake fans to the system fan header.
If I don't get a fan hub in time, is this setup feasible? Also, if I had to choose, should I prioritize bottom intake fans or top exhaust fans, considering this case doesn't have front intake options?
3 Answers
You should definitely double-check your motherboard manual for the maximum current ratings on your headers. They generally have limits on how many fans you can daisy chain based on their amperage. Most modern boards can handle 1A per fan header, which means you could run 2-3 normal case fans if their combined current stays within that limit. If you’re unsure, it’s often safest to connect only two fans to each header.
If you're running fans with somewhat higher power draws, consider buying a simple fan hub, which will take power from your PSU while still letting your motherboard manage speeds through its headers.
As for your question about bottom intakes versus top exhausts: for an optimal airflow setup, having both should ideally be balanced for good cooling. However, if you had to choose, I'd suggest two good bottom intakes, especially since you're not adding front fans. You can always add the exhaust fans later when your hub arrives.
It's completely fine to connect a couple of case fans to the CPU_FAN header temporarily, as long as their total current draw is within the header's limit. Both your CPU_FAN and SYS_FAN headers are standard 4-pin PWM types capable of powering multiple fans with splitters. The general practice is 2-3 fans on each header, assuming none are high-performance fans. Make sure your actual CPU fan is on the CPU header to avoid boot errors. This way, you can daisy chain your top-rear exhaust fan with the CPU cooler, and the two bottom intake fans can go on the SYS_FAN.
Definitely take a look at the specs of your fans and your board's manual. In most cases, motherboard fan headers have currents of about 1A. Your 120mm fans generally pull 0.1 to 0.3A each, which should let you connect two of them to the CPU header without issues. If your fans are standard models and not the high-speed industrial types, your plan to connect them sounds good. Just make sure to keep everything under the limit to avoid any issues.
Good advice! Just remember, if you use the CPU header for case fans, they will ramp up according to CPU usage, which isn't always ideal. But for a temporary solution, it works!
Totally agree! And just keep in mind, keeping your CPU cooler fan on the CPU_FAN header makes sense too since it will adjust based on the CPU temperature, which helps with overall performance.