Preventing Breaker from Popping

[madadd33]

Hello,

I moved into a new place and in 2 weeks, I've popped the breaker to the living room about 5 times. All I have on that breaker is the entertainment system (TV & Xboxone) and my Computer (old q6600, but psu is 1200W for upgrade potential). Anyway, when the breaker has popped, it's usually when the tv is on and I start up my computer (or wake it from sleep). Odd thing is that there are frequently times when both are on AND I also am playing a game on the xbox.

I feel like maybe putting the computer on a UPS would help, but I have no experience with personal UPS and if they regulate/stabilize voltage PULL. Other than that, I really don't want to pay for electrician and upgrade my wiring.

Oh and I assume 120v, the breaker is 20A, I've had this same setup in other houses and not had this problem, so I'm not sure why suddenly I'm having issues.

 

[GhislainG]

A UPS will make the problem worse because it will draw even more power (a UPS is approximately 65% efficient). The solution is to replace the weak breaker. On a 120 volt circuit, the breaker should be 15A, not 20A.

 

[hunter315]

When a computer PSU starts up, there is a very large inrush current as it charges up the primary capacitor. If you have the computer on, then turn on the TV your overall power draw hasn't increased by much, if you turn on the computer while you already have a reasonable load on the circuit you will see a massive inrush current which can be enough to trip a breaker, even though after 100ms the current would settle down to an acceptable level.

A UPS might fix the problem, but it would need to be inline so it saw the current spike and shielded the line from it.

 

[GhislainG]

A breaker that trips so easily needs to be replaced before doing anything else. If the new breaker trips, then there's a serious wiring issue or the PSU is defective; a PSU draws only as much power as is required by the system.

 

[hunter315]

If you read his description he says it only happens when he starts the computer or wakes it from sleep, that screams inrush current to me.

 

[GhislainG]

His PC certainly can't draw more than a few amps when he powers it up. The breaker trips when the load is way below 15 amps and he doesn't know how often that breaker has tripped before moving into that place. It's up to the OP to decide if he buys a $10 breaker or a $200 UPS to resolve his issue, but if it was my money I know what I'd do.

 

[hunter315]

PSUs have a massive inrush, startup for a PSU isn't a few amps, its a few dozen amps. Switching power supplies and motors have wayyyy larger inrush currents than their operating currents. The only truely useful part of Tom's PSU reviews, inrush current.
http://www.tomshardware.com/charts/120v-desktop-power-supplies/Inrush-Current,2565.html

So he could be drawing 50+ amps for only a couple of line cycles but if he is already at several amps of load that could be enough to trip the breaker

 

[GhislainG]

Let's say two dozen amps at 120 volts = 2,880 watts.

This video is more acurate: http://www.youtube.com/watch?v=fYfohC6qoXw 300 watts (2.5 amps) at startup is significant, but his CPU is overclocked. Just think about what happens when several servers connected to the same circuit in a computer room all power up at the same time after a power outage. If what you claim was true, the UPS would blow or shutdown to protect itself and that doesn't happen.

 

[hunter315]

You will never see it on a kill-a-watt, most of them only have a time accuracy of 100-250ms, which is 6-15 line cycles, you would need an Oscope or a true integrating meter.

For large servers they have staggered start up on their hard drives and on the servers to spread the load. If you have 15 10W hard drives start up at the same time you will see a massive current spike somewhere around 700W for about 10ms while the motors draw their stall current and get spinning.


Here's yet another review that keeps track of inrush current, and Seasonic's datasheet for a SS-650HT which specs that the inrush remain under 100A
http://www.techpowerup.com/reviews/Seasonic/SS-520FL/5.html
http://www.seasonic.com/pdf/datasheet/NEW/Bulk/PC/ATX/SS-650HT%20Active%20PFC.pdf


The reason it doesn't cook the UPS is because the UPS has a big output cap to stiffen its line to help against this initial spike, and a big battery in the middle to feed a extra current to the output circuitry, which while it would quickly cook if that was a sustained load, can deal with that for a few line cycles while everything is still cool. You can also end up reducing the inrush current because the UPS just can't supply it to the PSU, this is fine, the PSU will deal with it. Most good ones have a resistor in parallel with a thermal relay, the resistor significantly reduces startup inrush current and once the system is warm and the inrush is over the relay clicks and bypasses the resistor to improve efficiency.


Breakers are designed to be somewhat tolerate of inrush current otherwise everytime your fridge started up it'd trip the breaker, but they do have limits. See page 21 of the datasheet below for how long it takes to trip at a current level.
http://www.grainger.com/ec/pdf/QO-QOB-Miniature-Breakers-Catalog-2008.pdf
If he has say a 5A load already on the circuit, it could be enough to push the inrush from the side of the vertical line where it takes ~100ms-1 second to trip, to the side where it trips in a single line cycle. If its an older, or cheaper breaker that line could be a bit fudgier and a bit closer to 5x load than 7x load that it is for the SquareD QO breakers.

 

[GhislainG]

Sounds like we both agree he has a bad breaker and it should be replaced. I'm not saying the OP shouldn't buy a UPS (I have 2 quality UPS for my own systems), but he should start by replacing that breaker. A test that could also be easily be performed would be to connect everything to another circuit (using a quality extension cord) and see if the other breaker trips. If it does, then something else is wrong.

 

[madadd33]

I could try replacing the circuit, I just figured there wasn't much to a breaker, so it either worked or it didn't, not a sometimes/maybe/conditional type of functioning.

The reason I suggested/asked about a UPS was because I am unclear on whether a UPS will pull from it's battery for current spikes, or if the battery is only used when the input source is dead. Yes, a UPS will ultimately add more draw, but it will be consistent (this is the statement that needs verification).

One final thing I should note, the breaker looks new. Or rather it's a different type than any of the others on the panel which makes me assume it's been replaced before. The entire building and thus my unit is only 5 years old. It worries me that this breaker has been replaced already.

 

[GhislainG]

A standard UPS normally doesn't do much unless there's a voltage spike or drop and the input voltage is outside of the preset range. It doesn't help with the extra current required for a few milliseconds when you power up a PC. A solution is to buy an On-line UPS like an APC SMART-UPS RT 1500VA, but that's a rather expensive solution to an issue that could easily be fixed by a competent electrician. Have you at least checked the outlet is wired properly? Can't you connect the PC to a different outlet? How many circuits does your unit have?