Question about double wires on PSUs

[For Science!]

Hello! I was wondering if I could ask about when dealing with double wires in PSUs, whether jumping a pin on the PSU side is equivalent/okay compared to soldering two split wires together. In small form factor builds, people typically want to minimze the amount of cabling that comes out of the PSU, and that often means reducing the number of cables by reducing the double wires to a single one typically by soldering/crimping the two wires together (Alternative 2).  I was wondering if it is electrically equivalent if you just jump the cable on the PSU side and whether it is okay to do so. I appreciate that in a fully-double wire scenario (Stock) maybe there is some kind of redundancy built in by having 2 wires go to the pin, but assuming that the cable is intact, is this fine too?

 

If it helps, I am speficially interested in the Corsair SF600, and will be using 15 AWG cables.

 

@jonnyGURU

 

 

[LukeSavenije]

@seon123 @Stefan Payne

[seon123]

Some of the wires are for measuring the voltage. They are most accurate when they are closest to the output. Should be fine, though. 

[Mira Yurizaki]

If they are current carrying cables/wires, then make sure whatever is receiving the current is not going to ask for more than what the cable/wire can safely support.

[Windows7ge]

The cables have a current carrying capability that is quite a bit higher than what they actually use. Alternative 1 should do you just fine especially if the system isn't going to be doing anything intensive, but like sean123 said you might go into the BIOS and see not so accurate voltage readings (not that they were accurate to begin with).

[mariushm]

Some wires are for voltage sensing, and they have to be connected as close as possible to the final connector (near device powered by connector).

 

The idea is that when current goes through the wire, there's some voltage drop on that wire.

 

For example, an AWG18 wire has a resistance of 21 mOhm  (0.021 ohm) per meter.  So, if there's a meter of wire between your power supply and the 24 pin ATX connector and there's 5A of current flowing through the wire, then between the power supply and the motherboard is a voltage drop of V = I x R= 5 A x 0.021 ohm = 0.105v

So, the power supply may output 12v exactly, but the motherboard receives 11.895v 

So the voltage sense wire's role is to "pick up" the voltage value near the connector - the power supply then can counteract this voltage drop... instead of outputting exactly 12v, it will output approx. 12.1v or whatever value is needed to see exactly 12v at the motherboard connector.

 

If you move the wire near the power supply, you're basically disabling this feature, you can no longer measure the voltage drop on the wires.

[Guest]

45 minutes ago, For Science! said:

Hello! I was wondering why my fingers are sore from typing.

 

 

Just leave out the sense wires altogether.

[For Science!]

5 minutes ago, mariushm said:

-

so given that I will be using fairly thick wires (15 AWG) and that it will be over quite a short distance anyway (10~15 cm on the longest cables) not having a super accurate voltage sense will probably not be detrimental anyway.

2 minutes ago, jonnyGURU said:

Just leave out the sense wires altogether.

It's actually not immediately clear to me which of the two double wires are sense, but I suppose since you mention I can leave it out all together, jumping them should not cause any adverse effects.

 

 

 

[Guest]

1 hour ago, For Science! said:

 

It's actually not immediately clear to me which of the two double wires are sense...

Then you need a better diagram:

 

http://www.jonnyguru.com/forums/showthread.php?t=13740

 

 

[For Science!]

5 hours ago, jonnyGURU said:

Then you need a better diagram:

 

http://www.jonnyguru.com/forums/showthread.php?t=13740

 

 

Thank you very much for the link. Much appreciated.