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Will a 700 watt psu literally consume 58 amperes from my current?

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  • Components
  • European
Last response: in Components
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June 20, 2014 9:24:41 PM

I did the equation 700/12 i got 58. Will it take 58 amperes from my electric current? Or is this another thing? I am not in an european country if it differs between countries

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June 20, 2014 9:33:21 PM

No - that's the current at 12V . It'll be a tenth of that from the wall.
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June 20, 2014 9:35:21 PM

I'll have to hunt down a good beginner's guide on PSUs, but the short answer is no.

A 700W PSU, if 80% efficient, and running at maximum load on a 110V supply:

P(output) = 700W
V(input) = 110V
Efficiency = 0.8 (80% in decimal)

P(input) = 700 / 0.8 = 875W.

I(input) = 875 / 110 = 7.95A (3sf)
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June 20, 2014 9:36:53 PM

No. you will have 58 amps runnionga round inside of your puter (assumng you actually "output" 700 watts.

What is your house voltage .... her ein US on 120 volt system w typically see 115 at the socket. So the way this works is

Assuming your puter is "bawlz to the wall" and actually outputting 700 watts.

1. With an estimated 85% efficiency, it's pulling 824 watts from the wall (700/0.85)

2. With a 115 volt supply, it's pulling 7.16 amps from the socket. (824 watts /115 volts)
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June 20, 2014 9:38:23 PM

I think they're 250V ac in Europe
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June 20, 2014 9:40:13 PM

I dunno where he is but he did say he is not in a European country.
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June 20, 2014 9:42:35 PM

Oh I thought he said he was. Funny to say where you're not from.
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June 20, 2014 9:45:52 PM

yes, had me do a double take....Only time ya typically hear that is when someone say they are not from this planet. :)  Those peeps are great fun to hang out with
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June 20, 2014 9:46:20 PM

+1 jack
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June 20, 2014 9:50:54 PM

i7Baby said:
Oh I thought he said he was. Funny to say where you're not from.


The UK power supplies are still different if he is from there.
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June 20, 2014 9:53:22 PM

yes they are (220 volt / 50 Hz) .... but he made it clear in the OP that he is NOT from there.
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June 20, 2014 9:58:30 PM

In my country the power is 220 volts. So i assume that it will take 215 as jack subtracted 5. THX a lot this thing scared the hell out of me.
PS: im arabian
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June 20, 2014 10:03:34 PM

If 220V:
P(output) = 700W
V(input) = 220V
Efficiency = 0.8 (80% in decimal)

P(input) = 700 / 0.8 = 875W.

I(input) = 875 / 220 = 3.98A

However, it will pretty much always use less power than that.
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June 20, 2014 10:03:37 PM

Well voltage is never constant..... during periods of high demand it goes down .... I see from 110 to 124 around my area varies seasonally and by time of day.....you might see 220 - 250. You always use the lowest voltage to calculate amps as volts and amps are inversely proportional.



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June 20, 2014 10:07:02 PM

I'm on nominal 230V power, and it's basically always within about 2V.

Remember that the PSU isn't going to be drawing the full 700W much anyway.
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June 20, 2014 10:25:59 PM

It much depends on where you live. I spent some years in the electric utility industry but even before that when designing plant power systems, we'd see wild fluctuations in seasonal communities for example. During winter time, we'd see 496 volts on 460/480 supply voltages and as low as 430 during peak summer loads. Mist equipment is designed to handle 15% lower than voltage rated but only 5% on over voltage so that's was blowing up VFDs on us.

I wuda went with an 850 watter but when I added a 46 watt dual water pump, bumped up to a X-1250 as I didn't like anything in the 1000 watt range at the time. Most I have pulled from the wall under Furmark was 770 watts but pump was like at 1/3 power and CPU was only drawing 40 watts.

One reason to pay attention tho to maximum wattage is that UPS can behave a little weird when PSU exceeds their power rating even if you are not approaching that level. Mine was making clicking noises when running at idle speeds (118 watts).
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