PSU's---2 x 12v---The Dual Rail Myth

Frankenputer

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Let's stop hijacking this thread and create another one discussing specific PSUs.  This thread has really veered off course.



@flobiflex, I made your post into it's own thread: https://forum-en.msi.com/index.php?topic=110958.0

 

Svet

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Rossoevo said:
Found this:

How to Discover Your Power Supply Real Manufacturer

http://www.hardwaresecrets.com/article/370

Have fun
Just checked for my PSU with E307858 as well and returned search confirmed that its maked by Corsair:

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=QQGQ2.E307858&ccnshorttitle=Power+Supplies,+Information+Technology+Equipment+Including+Electrical+Business+Equipment+-+Component&objid=1078378885&cfgid=1073741824&version=versionless&parent_id=1073787374&sequence=1
 

Ahumado

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Frankenputer said:
Let's stop hijacking this thread and create another one discussing specific PSUs.  This thread has really veered off course.



@flobiflex, I made your post into it's own thread: https://forum-en.msi.com/index.php?topic=110958.0

That happens with 80% of threads and it bugs me but....... Whaddaya gonna do?


Ahumado
 

rhradacut

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I don't know if anyone has run across this one, PC Power & Cooling Turbo-Cool 1200 watt single rail PSU (+12V~90A (100A peak) but it seems to put another nail in the coffin for multi rail PSUs.

I just can't seem to keep track of all the different posts for PSUs.
 

wonderwrench

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Wow this is a long winded thread. I read several pages so I did not read every post. Multi rail PSU's were never made because they were better than single rail PSU's. Multi rails came about do to safety concerns.

As PC's power requirements increased it was realized that having a 12 volt power source in excess of 20 amps could be dangerous. This is because a short circuit would be harder to detect as the available amperage is increased. A PSU must be able to detect a short circuit and shut down for obvious safety concerns. Most PSU's call any load under about .5 ohms on a 12 volt rail a short circuit and shut down. This limits the output to 24 amps. If you want to make a PSU that can put out 40 amps at 12 volts the the acceptable circuit load resistance before short circuit protection kicks in must be lowered to .3 ohms. This would make it questionable as to if the PSU could correctly protect against a short circuit condition because you can DC weld at less than 40 amps. The higher the amperage available the worse it gets. Because of this Intel came up with the multi rail supply. Probably do to pressure from regulatory organizations such as UL etc.

Because multi rail supplies have been problematic do to load balancing problems many PSU manufactures have gone back to single rail designs. This is not necessarily a bad thing as I would trust a single rail PSU to run a wider range of system configs without problems. A single rail PSU will also allow the use of a lower wattage PSU because you do not have to over size the PSU to keep from having load balance problems. You can't have trapped amperage with a single rail PSU either. And if you need to do some arc welding you already have the equipment.

So the only down side to a single rail supply is overall safety.
 
 

Ahumado

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I am in no position to have a knowledgeable opinion. I would like to see references for your claims though.

Thanks for the post.

Ahumado


wonderwrench said:
Wow this is a long winded thread. I read several pages so I did not read every post. Multi rail PSU's were never made because they were better than single rail PSU's. Multi rails came about do to safety concerns.

As PC's power requirements increased it was realized that having a 12 volt power source in excess of 20 amps could be dangerous. This is because a short circuit would be harder to detect as the available amperage is increased. A PSU must be able to detect a short circuit and shut down for obvious safety concerns. Most PSU's call any load under about .5 ohms on a 12 volt rail a short circuit and shut down. This limits the output to 24 amps. If you want to make a PSU that can put out 40 amps at 12 volts the the acceptable circuit load resistance before short circuit protection kicks in must be lowered to .3 ohms. This would make it questionable as to if the PSU could correctly protect against a short circuit condition because you can DC weld at less than 40 amps. The higher the amperage available the worse it gets. Because of this Intel came up with the multi rail supply. Probably do to pressure from regulatory organizations such as UL etc.

Because multi rail supplies have been problematic do to load balancing problems many PSU manufactures have gone back to single rail designs. This is not necessarily a bad thing as I would trust a single rail PSU to run a wider range of system configs without problems. A single rail PSU will also allow the use of a lower wattage PSU because you do not have to over size the PSU to keep from having load balance problems. You can't have trapped amperage with a single rail PSU either. And if you need to do some arc welding you already have the equipment.

So the only down side to a single rail supply is overall safety.
 
 

Frankenputer

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The single-rail PSUs are still required to meet Govt. saftey rules and the UL wouldn't certify the PSU if it didn't.
All the single-rail PSUs by PC Power&Cooling meet all the safety standards and have certifications from the USA,
Canadian, and European agencies.
 

wonderwrench

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Frankenputer said:
The single-rail PSUs are still required to meet Govt. saftey rules and the UL wouldn't certify the PSU if it didn't.
All the single-rail PSUs by PC Power&Cooling meet all the safety standards and have certifications from the USA,
Canadian, and European agencies.
Well UL is giving them approval without meeting UL's own spec's because the VA limit on any output is 240va.
12x20=240 so the max amperage for a 12 volt rail is 20 amps max. http://www.formfactors.org/developer%5Cspecs%5CATX12V_PSDG_2_2_public_br2.pdf


 

Frankenputer

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I know the calculation. Since you source comes from Intel, I don't see it as meaning a violation of the UL or Federal Saftey guidlines. I'd want to see excerpts directly from UL/Federal Safety sources, not from an Intel reference. I'm sure they are sighting a reference from the UL and EN, but I'm also sure that there are other standards that are allowing the UL certification.  Just as in statistics(which you can make say what you want), references can be used to also support your own purpose. Intel's reference does not mean it's the only standard or specification. There is no way the certification would be given unless it met the standards.  UL would not violate their standard, nor would the Govt. allow it.  I'm not saying some company isn't capable of stating or printing some approval on their product, but it would be caught rather quickly.  PC P&C is not the only company producing single +12V rail PSUs with high amps and getting UL approval.
 

wonderwrench

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Frankenputer said:
I know the calculation. Since you source comes from Intel, I don't see it as meaning a violation of the UL or Federal Saftey guidlines. I'd want to see excerpts directly from UL/Federal Safety sources, not from an Intel reference. I'm sure they are sighting a reference from the UL and EN, but I'm also sure that there are other standards that are allowing the UL certification.  Just as in statistics(which you can make say what you want), references can be used to also support your own purpose. Intel's reference does not mean it's the only standard or specification. There is no way the certification would be given unless it met the standards.  UL would not violate their standard, nor would the Govt. allow it.  I'm not saying some company isn't capable of stating or printing some approval on their product, but it would be caught rather quickly.  PC P&C is not the only company producing single +12V rail PSUs with high amps and getting UL approval.
I would like to see the real documents also. I did some research and found the documents but if you can believe it you have to buy them or subscribe to their service. What BS it should be public. I guess all we can do is trust Intel is telling the truth.
http://www.ul.com/info/standard.htm
http://www.comm-2000.com/productdetails.aspx?sendingPageType=BigBrowser&CatalogID=Standards&ProductID=UL60950_3_S_20001211(ULStandards2)
 

wonderwrench

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Found this info but if you want the complete document they want $$$
IEC 60950
"Hazardous Energy Level

A stored energy level of 20J or more, or an available continuous power level of 240 VA or more, at a potential of 2V or more."
http://www.i-spec.com/IEC_60950/glossary.html
 

Frankenputer

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I found the same things, but I'm not in the mood to spend hours scouring the net trying to find free documentation. I'm sure the govt. safety standards are free, but, again, I'm not really in the mindset to go hunt them down.
 

ex_forum_user_3

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wonderwrench said:
Found this info but if you want the complete document they want $$$
IEC 60950
"Hazardous Energy Level

A stored energy level of 20J or more, or an available continuous power level of 240 VA or more, at a potential of 2V or more."
http://www.i-spec.com/IEC_60950/glossary.html
But it also writes this:

- Chemical Hazards

The product must limit contact with hazardous chemicals, their vapours and fumes under normal and abnormal conditions.

How is a PSU going to do that? :lol_anim:
 

wonderwrench

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Some good info on this subject.
http://www.playtool.com/pages/psumultirail/multirails.html
 

ex_forum_user_3

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I have seen that article before...it's saying the same as I have been saying from day 1 when "multiple 12V rail" PSU came to the market.
Heck, my footnote still mentions it :lol_anim:
 

jason str

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looking for input here thats all.
I have worked with electronics for years but have never done much work on power supplies and wish to learn more.
Now i realise there is a 12 v rail but does everything run off of this or does the 12 v rail (s) only power outputs running @12 volts ?
This is where i get confused maybe if i saw a schematic it would be easier for me to understand.
Just for basics not to argue about single and multi-rail supplies.
 

ex_forum_user_3

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Not quite understanding your question, but systems moved to use the 12V line as the most used line in your system.
It used to be mostly 3.3v & 5v and 12v was to power motors mostly.
This changed a long time ago to mostly use 12v and hardly use the 3.3v & 5v to power your system.
In my opinion it won't be long before all other lines will vanish and only 5vstb and 12v will be left over.
 

jason str

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lets say for instance we are talking about a single rail psu to make things easy. Multi rails seem to confuse people.

Does the 3.3v and 5v lines run off of the 12 v rail or a seperate circuit ?

Im also having issues about people using watts to convert power draw i dont understand what they are talking about. I have always used amperage to measure current draw.

Does anyone have a detailed schematic of a single rail psu to post here for reference this would make understanding the circuitry much easier. I have looked around but cant seem to find any.
 

Del UK

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jason str said:
lets say for instance we are talking about a single rail psu to make things easy. Multi rails seem to confuse people.

Does the 3.3v and 5v lines run off of the 12 v rail or a seperate circuit ?

Im also having issues about people using watts to convert power draw i dont understand what they are talking about. I have always used amperage to measure current draw.

Does anyone have a detailed schematic of a single rail psu to post here for reference this would make understanding the circuitry much easier. I have looked around but cant seem to find any.
Just ask a manfacturer, for schematic .

Main circuits used in modern system are +5V & +12V.  Look at cabling from PSU, Red is +5V / Yellow is +12V and Blacks are ground (There is 5 & 12 grounds)

The mainboard uses the +3.3V rail

The main advantage of single +12V rail, is the amperage is set rate. There are xx amps to supply system.

With more than 1 +12V rail, the amperage is still xx amps, but can be split.

Example:

+12V Rail 1 = 25Amps  :biggthumbsup:
+12V Rail 2 = 25Amps  :biggthumbsup:

Combined total amps is 30Amps for both rails...........(smalll print)  :biggthumbsdown:

So if graphics card needs 22Amps on the +12V rail & CPU needs 8Amps, what is left for other devices like fans and hard drives etc.....

Some quality PSU's will boot OK, but you will lose performance and over stress all components in system.......which shorten component life and cause problems with software..........

Hence why I use, a single +12V rail psu or a dual channel with lots of AMPS on the +12V rail :yes:



 
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