Case Fans

nheather · 13 Jan 2020 at 08:19

Got some Artic PWM case fans arriving today. One of Artic’s selling point is that they can be daisy chained together so they can work off one fan header - the CPU fan header to be precise.

I have my doubts about why you would daisy-chain and would appreciate your thoughts.

Power - taking the power for six fans from one header - I expect that isn’t an issue as each fan draws little load but would it still not be better to use all the fan headers to distribute the load.
Arctic claim the benefit of daisy chaining is that they all work from the same temperature sensor, the CPU, therefore the fans shut down if the CPU is cool. Fair enough but what temperature do the SYS fan headers work off. Generally in the BIOS, the only threshold profiling is against the CPU temperature. So wouldn’t all the SYS fans work of the CPU temperature anyway.
One benefit I could see is if you don’t have more fans than headers, or that not all the MoBo fan headers are 4 pin.
The real benefit I can see is cable management - you can secure the fan cabling to the chassis with just one wire going to the motherboard and I am inclined to daisy chain just for this reason. But Artic don’t present that as an advantage.

Anyway appreciate any thoughts that you have.

Cheers,

Nigel

gupsterg · 13 Jan 2020 at 10:06

Most of the headers on my C7H allow 1A (12W) power draw from a fan header, only 2 allow 3A (32W). So I would check you mobo manual to see what your headers allow before daisy chaining more than 4 on a header.

Be also aware that PWM signal strength can weaken as more fans are connected to a header, AFAIK you can get away with 8 or so.

nheather · 13 Jan 2020 at 11:06

gupsterg said:
Most of the headers on my C7H allow 1A (12W) power draw from a fan header, only 2 allow 3A (32W). So I would check you mobo manual to see what your headers allow before daisy chaining more than 4 on a header.

Looked through the manual, doesn’t say as far as I can tell.

But that besides is there any value in daisy-chaining other that keeping the wiring neater.

The SYS fan headers support speed control, as far as I can see you can’t select what temperature sensor this is driven from so I assume that it is the CPU.

Cheers,

Nigel

Jay85 · 13 Jan 2020 at 12:27

I have 7 of these fans so i know exactly what you're going through.

The daisy chain system works really well IF you run them off a pwm fan controller with Sata powering them. For my config, i run 5 off a pwm fan controller, and 2 off 1 motherboard header, all work as intended. The 2 off 1 motherboard header is probably the max i would daisy chain together (maybe 3 - @0.3A per fan so upto 0.9A), provided your motherboard can handle upto 1amp on a header (some can do more but they usually state on the board itself or in the manual).

For your second question, a lot of modern higher end boards actually allow you to set the temp sensor your pwm header should follow. For instance on mine i can set it to cpu, mobo, internal sensor (if connected) profiles etc.

doyll · 13 Jan 2020 at 15:01

As already said, be careful to not overload headers. Good rule of thumb is figure fan will draw 2-4+ times as much power starting up (or impeller stopped) as it's amp rating. Only company I know of that gives both running and startup load rating is Nidec Servo. Below link shows rating and starting load specs for fans commonly known as Gentle Typhoons
http://www.nidec-servo.com/en/digital/pdf/D1225C.pdf

As others have suggested, use PWM splitter hubs that use mobo PWM signal and PSU power. I have used PWM hubs for many years and will continue using them.

gupsterg · 13 Jan 2020 at 15:03

nheather said:
Looked through the manual, doesn’t say as far as I can tell.

But that besides is there any value in daisy-chaining other that keeping the wiring neater.

The SYS fan headers support speed control, as far as I can see you can’t select what temperature sensor this is driven from so I assume that it is the CPU.

Cheers,

Nigel

I daisy chain fans. I have 2 rads in my rig, each rad has 3x AC F12 PWM, then each set of 3 fans is connected to a 4 in 1 cable, these use PWM from mobo header but the fans are powered from PSU via molex. This allows each set to run at on same profile. The AC F12 PWM on website are shown as 0.25A @ 12V.

I would assume it's CPU temperature. On my ASUS ROG Crosshair VII Hero WiFi you can base it off several sensors, I have my fans based off water loop temperature.

EsaT · 13 Jan 2020 at 17:24

Arctic P12/P14 PWMs are very low power fans.
Certainly wouldn't put six to one motherboard header, but 3/4 shouldn't be problem.

Mcnumpty2323 · 13 Jan 2020 at 17:29

Usually 1A on a fan header
Ones marked pump/AIO usually 2A
Fans should have voltage and amps on the label
And can multiply those if want to know watts

doyll · 13 Jan 2020 at 18:27

Fan rated 0.08amp can easily draw 0.35amo at startup/stalled. Three fans pulling 0.35amp at startup pulling about 1.05amp on a 1amp header is more than header's 1amp rating. Four fans would be 1.4amp, 0.4m more than 1amp fan header rating.

Ever notice most of the time when someone reports a fan header burnt out it happens when they started system? That is the time fans are all pulling 3 times as much power running amp rating normally published.