# Thread: Question Corsair RM850i trips circuit breaker during "switch on "?

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## Question Corsair RM850i trips circuit breaker during "switch on "?

I have noticed that my circuit breaker trips when i switch on the PSU after being turned off for a long time , this doesnt happen during load or normal operation or when i start up my pc when the PSU switch has been left on
I looked at the breaker and its rated at 10A , My PSU Inrush current at 220V is probably around 66.7A but there is no information about the duration of such currents ( this is according to an HX850w review couldnt find one for my PSU)
https://www.tomshardware.com/reviews...su,5257-4.html

Is this inrush current enough to trip the circuit breaker ?

2. Originally Posted by Mezoxin
I have noticed that my circuit breaker trips when i switch on the PSU after being turned off for a long time , this doesnt happen during load or normal operation or when i start up my pc when the PSU switch has been left on
I looked at the breaker and its rated at 10A , My PSU Inrush current at 220V is probably around 66.7A but there is no information about the duration of such currents ( this is according to an HX850w review couldnt find one for my PSU)
https://www.tomshardware.com/reviews...su,5257-4.html

Is this inrush current enough to trip the circuit breaker ?

Then lets estimate it

Two 330µF capacitors charged to say 350V

I V Dt = 0.5 C V_c^2

where

I = 66.7 A
V = 220 V
C = 660 µF
V_c = 350 V

gives us a Dt of about 3 ms, which fits with the idea that things can charge up in the first ramp of the AC, which is a quarter cycle and so about 4 ms.

Now I recall about 30 years back there were special circuit breakers that were more tolerant to such inrush surge, I assume that they all are these days; how old are yours?

The attached tripping curve suggests it is quite possible as you are at about 7 times the rated current (for a few milliseconds)
Last edited by ashiekh; 11-28-2019 at 12:09 PM.

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Mezoxin (11-28-2019)

4. Originally Posted by Mezoxin
Is this inrush current enough to trip the circuit breaker ?
Yes.

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Mezoxin (11-28-2019)

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i need to change the breaker then, this brings other questions , which rating should i chose for the new breaker as the circuitry in room where the PC is only have lights and wall sockets I am not sure about the wire guage used but i dont think that a 60A breaker would be safe for it , ofcourse i'll call a technician to do the job and ask for his advice but they are not that reliable , soi appreciate getting a second opinion from you about what is correct rating for a breaker according to wire guage ? and if the circumstances push towards a 40AMP breaker would it be enough to prevent an inrush of 67A @ 3ms from tripping it ?

another question , is there any negative effects on the PSU if the circuit breaker trips while its charging up its capacitors , would it affect its commponents lifetime?

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Originally Posted by ashiekh

Now I recall about 30 years back there were special circuit breakers that were more tolerant to such inrush surge, I assume that they all are these days; how old are yours?
I just checked it has been around 30 years since they were installed

its the 2nd one from the bottom

8. Originally Posted by Mezoxin
i need to change the breaker then, this brings other questions , which rating should i chose for the new breaker as the circuitry in room where the PC is only have lights and wall sockets I am not sure about the wire guage used but i dont think that a 60A breaker would be safe for it , ofcourse i'll call a technician to do the job and ask for his advice but they are not that reliable , soi appreciate getting a second opinion from you about what is correct rating for a breaker according to wire guage ? and if the circumstances push towards a 40AMP breaker would it be enough to prevent an inrush of 67A @ 3ms from tripping it ?

If the wiring is only good for 10 Amp you can't just move to 40 amp, 4 times the current has 16 times the heating; but you can go for a slow-blow circuit breaker (if the electrician says it is OK)

One thing I would try is to swap two 10 amp breakers to see if that solved the issue; some look newer and might have more surge ability.
Last edited by ashiekh; 11-28-2019 at 07:22 PM.

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Mezoxin (11-28-2019)

10. Originally Posted by ashiekh
One thing I would try is to swap two 10 amp breakers to see if that solved the issue; some look newer and might have more surge ability.
This is a great idea.

Could just be a bad breaker.

11. Over 2000 posts... and finally a good idea! it had to happen... eventually.
Last edited by ashiekh; 11-29-2019 at 05:06 PM.

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got the technician today , he checked the wires and he changed all the circuit breakers as they were rated too low , and a 40A circuit breaker for the circuitry that include the power plugs in my pc room was installed , now the inrush current doesnt cause the breaker to trip