circuit breaker trips when turning on RM750i *after a long time off* ?

so I noticed that when I turn on the PSU switch, sometimes the circuit breaker will trip. no biggie cause I just reset it (and usually the PSU will remain on anyway unless I leave home for a long time maybe)

 

so question is is that normal? my seasonic never did that iirc

 

and the cause can't be inrush current since Tom's Hardware shows inrush even for 230V is quite low (less than 45A) for this PSU

 

so what could be causing this? :confused:

might need to install a new circuit breaker

but my old seasonic (x650 KM3) shows the prob aint with the circuit breaker so what's the real cause??

circuit breakers fail occasionally, they are not expensive

 

get a power monitor unit and see if the PSU is drawing that much power

dunno if I can find a good affordable power monitor anytime soon

 

anyway is there any scientific explanation as to why this happens???? what exactly it going on? is it inrush or is there another possible cause?

 

(for recap those are the symptoms: when PSU switch is off for a long time, then PSU switch is turned on, then one of the circuit breakers sometimes trips. why?)

dunno if I can find a good affordable power monitor anytime soon

 

anyway is there any scientific explanation as to why this happens???? what exactly it going on? is it inrush or is there another possible cause?

 

(for recap those are the symptoms: when PSU switch is off for a long time, then PSU switch is turned on, then one of the circuit breakers sometimes trips. why?)

 

Cold power on can use a lot more power for a few seconds to charge capacitors etc

The issue is inrush current. Your opinion that it isn't is based off of a bar graph on a tech website that only gives the amperage .

Inrush current is more than just an amperage, if you look at inrush current on an oscilloscope you have a y axis and x axis where is

the y-axis is the amperage and the x-axis is time.

 

When you look at inrush current on an oscilloscope you'll see a big wave and at the top of the wave is your Peak inrush amperage

that's the number that the tech websites use for their bar graphs and that's the only number they give you.

 

When you first turn on the power supply you will see the inrush current and let's say the peak of the inrush is at 10 milliseconds(ms) at 45 amps,

at 15ms you're at 25 amps, at 20ms you’re at 10 amps, and 25ms it levels out to 5 amps, your normal load.

For over 18 milliseconds you were over the rating of a 15 amp breaker.

 

(these numbers are just for demonstration and have no real correlation with your power supply it's just to make this easier to explain)

 

Breakers are able to handle inrush current to a point but if the inrush current lasts too long it gives the breaker a chance to trip as it heats up.

If you have other things on the circuit, monitors,printers, a TV ,lamp, these also add to the amperage that is already on the breaker.

The higher the amperage on the breaker when you turn on the power supply the longer the breaker will be over it's rated amperage giving you a

higher chance of the breaker tripping.

 

So let's go back to the oscilloscope now and put it at the breaker. Before the power supply is even on your already sitting at let's say

10 amps on the breaker, when you turn the power supply on your peak is now 55 amps at 10ms, at 15ms you're at 35 amps, at 20ms you’re at

20 amps and at 25ms you’re at 15 amps leveled out to normal load. For 24ms you were over the rated amperage of a 15 amp breaker.

The PSU peak inrush amperage stays the same (40 amps) and the amount of time the rush lasts is the same(25ms) but the amount of time it

was over the breaker rating is longer(18ms vs 24ms)

 

When you put two different power supplies side-by-side they could have the same Peak amperage but the amount of time the inrush lasts could

be longer on one and shorter on the other. For example the rush on a seasonic could last 25ms but on a Corsair could last 30ms.

 

(Again these numbers are just for demonstration)

 

The amount of inrush current a breaker can handle and for how long it can handle it depends on the trips curve of the breaker. Without knowing what

model of breaker you have I can't tell you how much your breaker can handle. Some breaker manufacturers do you have a graph that shows you the

trip curve of their breakers so in a way you can calculate this yourself but without proper tools you won't be able to do this.

 

A possible solution for you would be to get a uninterrupted power supply.

ow! that could explain why my Seasonic didn't trip anything: I always used it behind a UPS from the 1st day I used it

 

wheras the Corsair was used on a 2nd test PC directly plugged into wall

 

so now I dunno if my Seasonic would also trip without the UPS

 

and I didn't know it depended on both amperage AND amperage/time good to know

 

 

though the tripping's just a very minor inconvenience my real concern is are there any real risks? (physical damage to PSU or to anything else)

I mean amps are what cause real damage when you think about it so the thought of that much current going through a device aint exactly reassuring :/

From motors to power supplies most electrical devices have some form of inrush current breakers are designed to handle this. And in most scenarios the higher the wattage of PSU the higher the inrush you might see, but this isnt always the case. It comes back on the design and componets that make up the PSU. Example: Peak inrush for, Corsair 1600i = 21 amps, Seasonic SSR1200 = 72 amps, EVGA Supernova 1600t2 = 83 amps. The rush your PSU is getting aint nothing.

 

Another thing to remember is inrush lasts for a second or less,this wont cause a problem as long as stays within spec.

It could be a short. I had a power strip that used to have a short and would trip the breaker on occasion. Got rid of the power breaker and the problem was gone. If the only change was the power supply and you narrowed it down to that, don't take a chance and RMA it ASAP. I wouldn't mess with power issues.

tbh I didn't "change" anything that PSU was tested with a new PC, without a UPS (the old PC is still powered by the Seasonic & that Seasonic was always used behind a line-in UPS)