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The Importance of Load Balancing

post #1 of 6
Thread Starter 
Load Balancing or Cross Loading is an often overlooked aspect of PSUs. Due to the design the PSU, it is very often the +12v rail will not perform as specified unless there is sufficient load on the +5v and +3.3v rails. This is especially true with older and/or cheaper PSUs. This is the reason why I do not recommending running a 2nd PSU with proper testing. Especially if you plan to run a video card or any sensitive component off the 2nd PSU. ATX specifications require the positive rails to maintain 5% voltage regulation. All good PSUs can do less than 2%. Honestly, if your PSU is over 3% off... get a new one.

The first numbers represent the PSU voltages without a load.
The second set is the PSU voltages with 3 fans and 2 HDs (~12v@2A and 5v@1A)

__________________________________________
Dell 250w PSU
11.58v -> 11.80v
5.13v -> 5.05
3.32v -> 3.32v

3.5% -> 1.7%
2.6% -> 1.0%
0.6% -> 0.6%

__________________________________________
Generic TurboLink 400w PSU
11.82v -> 11.95v
5.16v -> 5.02v
3.34v -> 3.29v

1.5% -> 0.4%
3.2% -> 0.4%
1.2% -> 0.3%



Look at the difference in PSU voltage regulation!
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post #2 of 6
Thread Starter 
Bump... 22 reads and no responses?

A little load makes a HUGE difference!
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post #3 of 6
if there's only a pump and a pair of fans (all running off the 12v line) hooked into a 2ndary PSU how could i go about balancing aside from adding devices?

I've never really thought about balancing honestly
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post #4 of 6
Thread Starter 
Quote:
Originally Posted by Firestorm252 View Post
if there's only a pump and a pair of fans (all running off the 12v line) hooked into a 2ndary PSU how could i go about balancing aside from adding devices?

I've never really thought about balancing honestly
You don't need to. It is just fans and pumps... they are designed to run from like 7-13v. Being .5v off will not affect them.

This is more for users trying to run a video card off a second PSU.
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post #5 of 6
duckie this is why you cheat and get some wire wound resistors to simulate a load and then run that second PSU

now if I could only get some for cheap I would be happy and my g/f could quit complaining about all the vacuum tubes sitting in the house.
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post #6 of 6
Thread Starter 
Quote:
Originally Posted by rx7speed View Post
duckie this is why you cheat and get some wire wound resistors to simulate a load and then run that second PSU

now if I could only get some for cheap I would be happy and my g/f could quit complaining about all the vacuum tubes sitting in the house.
Yup, PCP&C sells one: http://www.pcpower.com/products/view...t.php?show=VLR



However, I just want others to be aware of this since this is a very often overlooked issue.
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