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Question about PWM Y-Splitters and cables (wattage)

2K views 8 replies 4 participants last post by  Aenra 
#1 ·
Let me start by apologizing if this has already been covered elsewhere.

Now on topic, i've been wondering how many Watts are safe to circulate through these things..

( if you need a visual, imagine something like this: https://www.amazon.com/PWM-Y-Splitter-Cable-Adapter/dp/B002OFP6QW )

A personal example:

8 EK furious Vardars, totaling (a maximum of) 45.12 Watts / 3.76 Amps. Is it safe for me to make/use an 8-to-1 splitter? Can it take such a load? Will solder it myself if i have to.

Would help a lot, too many fan cables going round, am trying to minimize what ends up on my Lamptron. If any of you have some notion of where the limit is, do let me know :)

As always, my thanks for reading.

Edit: To help avoid further misunderstanding, let me rephrase this:

- A fan's PWM cable can easily withstand the 0.47Amps; of said one fan.

- Can said same cable withstand 3.76 Amps (0.47x8)? 'Cause that's what happens when you go 8-to-1 in a single Y-Splitter.
 
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#2 ·
A splitter will handle that, but your motherboard won't. Motherboard fan headers are only 1 or 2 amps (12-24 watts). Put 40 watts of fans on them and you'll burn out the motherboard fan header. Also note that fans draw 150% to 200% more power on spin up (to get the fan up to speed quickly).

That's why people buy and install fan controllers that get their power directly from the power supply.

Also. the motherboard has to communicate with the PWM controller in the fan to be able to control it's speed. Hooking multiple PWM fan (more than about 2) just confuses the motherboard with all the data it is getting and it can;t control then anymore.

How PWN works vs how 3 pin fans work:



There are "splitters" that will power up to 8 fans with a single PWM signal (but note that all the fans connected to it will run at the same speed.

Swiftech 8 Way PWM Splitter-Sata


 
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#3 ·
Thanks for replying Bil;

Am afraid you've misunderstood me.. or maybe i misunderstood you? ^^

- I mentioned the word cable* in the OP for a reason, same reason i actually provide a URL for some visual assistance. I am not interested/worried about how much a controller can handle in itself, that can easily be glimpsed from their respective specs. Mine for example can handle up to 60W per channel, on 5 different channels.

- Good point mentioning the motherboard, i didn't as it's not involved in the process at all. All the fans are exclusively driven and controlled from my fan controller.

(the only thing plugged to the mobo is the pump [in the relevant 'pump' header] and that's only because i have to, as it wouldn't power up with an empty 'CPU' header)

* Now going back to the matter at hand, ie the cable itself. Yes, Y-Splitter cables exist, but no, not a one provides specs. Just a pic, lol

12V will always be 12V.. what defines the Wattage run through a cable is the Amperage. Typically, the Amperage a conductor (in our case, the copper wire inside the splitter cable) is capable of handling is directly related to its diameter. Lacking that actual diameter, i cannot know how many Amps i can run through the cable before it overheats->starts melting.

- PSU -> fine

|

- fans -> fine

|

- cable responsible for transfering 45.12Watts, ie 3.76Amps -> ???

|

- controller -> fine

*Editted the OP with the following:

- A fan's PWM cable can easily withstand the 0.47Amps; of said one fan.

- Can said same cable withstand 3.76 Amps (0.47x8)? 'Cause that's what happens when you go 8-to-1 in a single Y-Splitter.

That's what i'm asking. Have been told that it's probably unsafe expecting a cable so thin to be capable of such a draw, but they didn't know for sure either. I hope it's clearer now :)
 
#5 ·
Thanks for replying honegod, but i'm not really sure how one pertains to the other..

Will try emailing a company or two i think i have a chance of receiving a reply from; see if they have anything to tell me :)

In the meantime, assuming anyone reading actually --does-- use an 8-to-1 splitter, do by all means post?
 
#6 ·
I believe the most I've seen a fan controller state is the maximum was 4.5 A on the Corsair Commander. This is not so much due to the cable size, but the actual 3-pin or 4-pin connector itself, the small sheet metal used to form the pins is typically the limiting factor. This is why your GPU 6-pin and 8-pin connectors are limited in the power they can output when the cable sizes used can accommodate more current than the connector itself can.

Also with fans (well motors in general) they have much high start-up current, sometimes up to 6 times the rated current, that initial spike in turning on is what could end up killing a connector. I wouldn't go more than 4 fans being powered from a single 3-pin or 4-pin fan connector anywhere in the chain. I would keep it to a 4-1 splitter at the most, just make two of them and run them from two fan headers near each other and set them to the same settings in BIOS.
 
#8 ·
Quote:
Originally Posted by Aenra View Post

@axipher Good point about the connectors, had not occured to me :)

Will stick to my 4-to-1s, definitely better safe than sorry.

(can't give you rep for some reason.. but my thanks nonetheless)
Staff on this site are seen as demi-gods and we don't need silly things like REP :p

But actually REP is just turned off for staff <insert reason here>.

And no problem on the help, people often forget to think of the actual connections, or traces on PCB's and focus entirely on the wire size itself. I've done this myself when rushing a project, both in computers, and in but mining equipment. That's why you have multiple people looking at design choices and giving their feedback and input.
 
#9 ·
Quote:
Originally Posted by axipher View Post

And no problem on the help, people often forget to think of the actual connections, or traces on PCB's and focus entirely on the wire size itself.
Guilty as charged; it's funny how complicated it gets.. just like every other thing in life, the more you get to know, the less you realize you actually do, lol

My thanks again :)
 
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