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Question about higher wattage PSU's

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April 11, 2012 1:11:27 AM

I am currently getting the parts together to build a new tower. I am looking at getting a Corsair 850W PSU. What I need advice on is I don't know much about electricity and what all is wired into the house and such. I know the 850W PSU I am looking at says it has an input draw of 12 amps. My currect Corsair 750W says it draws 10 amps. From what I have learned, it's typical for a house to have 15 amp breakers. Should I have this computer in a room by itself with essentially nothing more than a light, or will it be ok to be in the same room where I have a TV, a Blu Ray player and a couple of lights?

EDIT: And obviously I have my monitor, speakers and on occasion an external hardrive plugged into the wall as well.
a b ) Power supply
April 11, 2012 1:35:47 AM

Its not drawing 10amps normally. Thats only under full load which you will likely never even come close to.

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a c 1172 ) Power supply
April 11, 2012 1:45:30 AM

Even at 80% load (680 Watts), which would be considered torture test conditions for a PSU, a Corsair 850 Watt 80 PLUS Bronze PSU would only be drawing 7 Amps from a 115V AC wall plug.

You haven't posted your system specifications so it's difficult to give you a more realistic/accurate AC current draw.
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April 11, 2012 2:56:20 AM

ko888 said:
Even at 80% load (680 Watts), which would be considered torture test conditions for a PSU, a Corsair 850 Watt 80 PLUS Bronze PSU would only be drawing 7 Amps from a 115V AC wall plug.

You haven't posted your system specifications so it's difficult to give you a more realistic/accurate AC current draw.


This is the PSU I'm looking at getting...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

I plan on getting one of the better socket 1155 Sandy Bridge mobo's with an i7-2600K CPU and about 8-12GB of RAM. I plan on having 2HDD, possibly with an SSD for the boot drive in addition to them. Also 1 DVD burner and 1 Blu Ray burner as well as a Sound Blaster Fatality PCI-X sound card. For the video card I am considering the Radeon HD 6870, the GeForce GTX 560 Ti or the Radeon HD 7870.

Now the 3 850W Corsair 80 PLUS Bronze don't show an input current, only the 80 PLUS Silver that I am considering shows that and shows the 12A which was what led to my question. Do the 80 PLUS Bronze PSU's draw less amps?

EDIT: And my case is the COOLER MASTER HAF X RC-942-KKN1 and I do intend to install the optional fans as well.
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a c 1172 ) Power supply
April 11, 2012 4:17:58 AM

Realistically, during typical gaming for instance, the system shouldn't be drawing any more than 450 Watts from the DC Outputs of the power supply unit.

The Corsair Professional Series HX850W (CMPSU-850HX) has approximately 89% AC to DC conversion efficiency at that power draw level.

This will result in a 506 Watt power draw from the AC wall outlet which is 4.4 Amps at 115 Volts AC.

The Corsair Professional Series HX850W (CMPSU-850HX) is actually able to supply up to a maximum of 1,000 Watts on its DC Outputs but unfortunately it's not at 80 PLUS Silver level efficiency. Drawing the full 1,000 Watts DC results in an AC power draw of 1,231 Watts @ 81.2% AC to DC conversion efficiency. That's 10.7 Amps from a 115V AC wall outlet.

With less than 4.5 Amps being drawn there's no need to rewire your house or have the system on its own circuit breaker.
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April 11, 2012 5:12:38 AM

ko888 said:
Realistically, during typical gaming for instance, the system shouldn't be drawing any more than 450 Watts from the DC Outputs of the power supply unit.

The Corsair Professional Series HX850W (CMPSU-850HX) has approximately 89% AC to DC conversion efficiency at that power draw level.

This will result in a 506 Watt power draw from the AC wall outlet which is 4.4 Amps at 115 Volts AC.

The Corsair Professional Series HX850W (CMPSU-850HX) is actually able to supply up to a maximum of 1,000 Watts on its DC Outputs but unfortunately it's not at 80 PLUS Silver level efficiency. Drawing the full 1,000 Watts DC results in an AC power draw of 1,231 Watts @ 81.2% AC to DC conversion efficiency. That's 10.7 Amps from a 115V AC wall outlet.

With less than 4.5 Amps being drawn there's no need to rewire your house or have the system on its own circuit breaker.

So I should be good then?

I appreciate your explanation, you've taught me quite a few things. Why do they say it needs a 12A input when it doesn't come close? Is it just to err on the side of caution?
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a c 1172 ) Power supply
April 11, 2012 5:57:20 PM

wildkitten said:
So I should be good then?

I appreciate your explanation, you've taught me quite a few things. Why do they say it needs a 12A input when it doesn't come close? Is it just to err on the side of caution?

You should be good.

The 12 Amps is suppose to be the worse case scenario. Sometimes the AC power grid, in some locations, will operate at a lower voltage than the standard 115 or 120 Volts AC and will require drawing a higher current to supply the equivalent amount of power. If you look at the power supply's label you will see that it can operate at as low as 100V AC which definitely will reach a little over 12 Amps.
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April 11, 2012 6:14:38 PM

Best answer selected by wildkitten.
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April 11, 2012 6:15:00 PM

Thank you so much. You've set my mind at ease.
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