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XPS 8950, fan header power rating
I would like to know how much current the XPS 8950 , CPU fan header can supply ( I read that it is typically 1A) , the Dell stock fan Delta QUR0812SH is rated at 0.5A (I do not know if this is typical, minimum or maximum) . I am trying to add another Delta fan to the CPU vertical heatsink (I am not using the Dell stock heatsink) as a push-pull air flow configuration. Will I fry the motherboard if I add another fan (using a splitter) that demands more current than the motherboard can supply?
Or can I use the fan splitter at the chassis back fan header to run this second CPU fan? What current rating is this header?)
Or just use a SATA-to-fan cable to power this second CPU fan without tach control (is it a good idea to run one of the CPU fan at max speed (no tach) while the other with TACH signal?)
Thanks.
sam55todd
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November 7th, 2022 04:00
Tach signal is motherboard input, not output, and those can't be mixed from different fans,
therefore tach from only one fan is needed, the other tach (from secondary fan) will have to be disconnected.
The output bit is PWM signal (pulse width modulation), it should be supplied to both fans.
If there's no PWM input to fan - it's normally should spin at maximum duty cycle.
How you power fans - doesn't matter, it could be from MB jack or from SATA (etc.)
So it's absolutely fine to have power for two different fans coming from different sources (MB and SATA +12V/normally yellow for sata connector) as long as it adheres to right voltage/power (amps) specification.
moxxy
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November 7th, 2022 06:00
I have a Y splitter with no TACH wire on one branch of the Y tree, just worry about overloading the CPU fan header , so I guess I just get the SATA-to-Fan cable but the fan probably makes some noticeable noise at max rpm. I just wish Dell could include fan header electrical spec. in the documentations.
sam55todd
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November 8th, 2022 03:00
You still can use PWM signal as input to your secondary fan, it just would need slight rewiring of your Y-splitter (getting one specific wire from it and {correctly} connecting to your SATA-FAN cable if you know electronics a bit). And yes, most sources I see do reference 1A (12W at 12V) as max power draw for standard home-use motherboard Fan connector (on servers it's often more than that).
Unless of course it's generic standard fan and you don't mind to use simple resistor (or potentiometer) to a ground instead of more sophisticated PC fan speed controllers (incl. multichannel PWM with thermistors like HW-585 or ZFC39) for slowing RPM down to a reasonable levels.
ProfessorW00d
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November 8th, 2022 05:00
You can connect the two fans to the mobo fan header with your PWM Y-splitter adapter cable without overloading.