Do i need 20 amps on a breaker circuit if the graphics Card needs 20 amps on a 12 volt rail?

[lovdagame]

the graphics Card i got says it needs 20 amps on a 12 volt rail so does that mean i need 20 amps on a breaker circuit so it does not overheat. So what if i used 20 amps on a 15 amp breaker circuit what would happen?

 

[pm4]

the graphics Card i got says it needs 20 amps on a 12 volt rail so does that mean i need 20 amps on a breaker circuit so it does not overheat. So what if i used 20 amps on a 15 amp breaker circuit what would happen?

No you dont need 20 amp breaker. Your PSU will handle that.

There is equation
watt = amps * volt

Which means that 20 apms * 12 volt = 240 W.
Your psu need to supply that power for your GPU. To do so, it need to draw same power from your outlet, but that is not 12V but depending on where you live it may be for example 240V. In that case to get same power at 240V it will be current of 1A.

240V * 1A = 240W

So from your outlet/breaker to your psu it will be current of 1A at 240V but from your psu to gpu it will be 20A at 12V.

This is simplistic version as your psu is not 100% efficient, so you got some extra power needed. If you wouldd have for example 90% efficient, to draw 240W you would need to take about 267W. So real current would be higher than 1A. (267W / 240V = 1,1125A)
This should give you general idea.

So on your 15A breaker you can supply 15A * 240V = 3600W (if you got 240V outlet).