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Do I need to balance load on two +12V rails on PSU?

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July 22, 2011 6:34:57 AM

I have a 700W PSU which I know is an overkill for my i5-750 and hd5770
It is the Aerocool E85-700:
http://www.aerocool.com.tw/index.php/products/power-sup...

The PSU has two +12V rails, and each rail has 30A.
The question is, do I need to balance the load I put on each rail, by connecting the CPU to one rail and the GPU to the other? Or does it not matter or the PSU will distribute the load automatically?
a b ) Power supply
July 22, 2011 7:41:42 AM

You do not have to do that, dual +12 ral bias is used for SLI or CrossFireX (2 cards) even if you use the 1 +12 volt rail that does not detract from the power.
July 22, 2011 1:19:12 PM

What is the dual +12 rail bias you mentioned?
I'm not using SLI or CF I'm just using one 5770.

I know that even one rail on my PSU is enough for my i5-750 + 5770, but I was just wondering if it would be better to balance the load between the two rails, and how do I know which connector connects to which rail?
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a c 247 ) Power supply
July 22, 2011 2:29:00 PM

Just like most multi-rail PSUs, yours already has the connectors balanced. If you look about 3/4 of the way down the Aerocool page it has a table showing you which connectors go with which rail.

From that table, your hard drives, motherboard, and some of your CPU and GPU comes from rail one, the rest of the CPU and GPU comes from rail 2
July 22, 2011 4:41:41 PM

thanks hunter315 for pointing that out, and I noticed that it said "dynamic load distribution", so i suppose that the PSU balances the load automatically.
a b ) Power supply
July 22, 2011 6:01:25 PM

You just need to mindful of your load and how you distribute it. It is almost impossible to balance the load since the dynamic load varies a lot. You can only account for the max load when you allocate.


This is one of the reason i switched to single rail supply. I don't need to worry about these things and it allows the user to maximize the rail capacity.

On my Antec supplies (Multi Rail) is separate the Hard Drive and Optical drives on certian rails. I put these devices with motors on separate rails.
a c 1102 ) Power supply
July 22, 2011 8:27:00 PM

The Aerocool E85-700 is manufactured by HEC/Compucase and has the voltage regulation design flaw that is common to all brands and models based on this HEC design.

If you exceed 560 Watts of power consumption from the E85-700 the +5V and +3.3V rails will deviate outside of the ATX12V specifications. This will make your computer behave erratically.
July 23, 2011 6:29:14 PM

leon2006 said:
You just need to mindful of your load and how you distribute it. It is almost impossible to balance the load since the dynamic load varies a lot. You can only account for the max load when you allocate.


This is one of the reason i switched to single rail supply. I don't need to worry about these things and it allows the user to maximize the rail capacity.

On my Antec supplies (Multi Rail) is separate the Hard Drive and Optical drives on certian rails. I put these devices with motors on separate rails.


How do you know which rail you are connecting stuff to?
July 23, 2011 6:35:41 PM

ko888 said:
The Aerocool E85-700 is manufactured by HEC/Compucase and has the voltage regulation design flaw that is common to all brands and models based on this HEC design.

If you exceed 560 Watts of power consumption from the E85-700 the +5V and +3.3V rails will deviate outside of the ATX12V specifications. This will make your computer behave erratically.


that seems like a pretty serious problem! can you give me a link to any articles or discussions with more details of that?

I thought this PSU was good and its mentioned here as a "good examples of products to watch"

Best solution

a c 1102 ) Power supply
July 23, 2011 6:43:29 PM
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00derek00 said:
How do you know which rail you are connecting stuff to?

By looking at the wires with the yellow color coded insulation. These are the +12 Volt lines.

The solid yellow insulator jacket is usually considered to be the primary +12V rail.

If the yellow wire also has a different colored stripe (e.g. blue) this means it's on a different rail.

On power supplies with multiple +12V rails each rail has a different colored stripe on the yellow insulator jacket.
a c 1102 ) Power supply
July 23, 2011 7:10:14 PM

00derek00 said:
that seems like a pretty serious problem! can you give me a link to any articles or discussions with more details of that?

I thought this PSU was good and its mentioned here as a "good examples of products to watch"

This is Hardware Secrets' review of the Cougar CMX 700W (CGR B2-700 ) made by HEC/Compucase :

http://www.hardwaresecrets.com/article/Cougar-CMX-700-W...

I doubt very much that you'll be drawing enough power from the power supply to even encounter this problem but if you ever experience erratic behavior from your computer this would be something to consider.
a c 144 ) Power supply
July 24, 2011 2:15:54 PM

What the PSU specs are telling you is that either rail will provide 30 amps max. From ko888's link, it looks like the total 12 volt capacity is around 48 amps, not 60 amps.

Or avoid the whole question next time and get a single rail PSU.
July 30, 2011 10:12:58 AM

Best answer selected by 00derek00.
a b ) Power supply
July 30, 2011 10:25:02 PM

This topic has been closed by Mousemonkey
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