Anyone heard of a Mac Pro tripping a breaker when powered on?

lokiju

macrumors 6502
Original poster
Jun 10, 2008
275
1
I have two Mac Pro's in my house. The first one I got would always trip the circuit breaker in my office almost every time I turned it on but I just always assumed it was due to wiring in my office. Then I got a second one and when I was setting it up it was down in my living room at the time and it never tripped a circuit. Then I moved that one into my office and removed the other one that had been tripping circuits and the new one has never once tripped a circuit plugged into the same outlet as the old one did.

I then moved the circuit tripping Mac Pro to my living room and reloaded the OS and in the process tripped a circuit turning it on. I got it all built up and moved it to my bedroom and every time it comes out of sleep or gets turned on it usually trips the circuit.

What in the hell is going on with this thing?

Is this a known issue with the 2.66ghz Intel Xeon Mac Pros? If so, is there some kind of fix?

This is the exact model http://support.apple.com/kb/SP30
 

lokiju

macrumors 6502
Original poster
Jun 10, 2008
275
1
Do you have it plugged directly into the wall or into a surge protector first?
Tried both, doesn't matter.

UPS, surge protector, direct into wall, different circuits, different cords. None of it matters. Just this one specific Mac Pro usually trips any circuit it's plugged into when it comes out of sleep or is powered on for the first time.
 

gotzero

macrumors 68040
Jan 6, 2007
3,220
0
Mid-Atlantic, US
What kind of graphics cards do you have in there?

A Mac Pro should not be tripping a circuit. I think it is much more likely to be a wiring issue than a computer issue. Do you have something like a Kill-a-Watt where you can take a look at the quality of the power coming out of the circuit?
 

ThrawnTHX

macrumors member
Jul 20, 2009
46
0
What else is running on the same breaker? You could have it overloaded. Also, are you in an older house? You might have outdated wiring that can't handle some modern day punishment.
 

Disc Golfer

macrumors 6502a
Dec 17, 2009
582
0
What else is running on the same breaker? You could have it overloaded. Also, are you in an older house? You might have outdated wiring that can't handle some modern day punishment.
That's what I thought when I read the title, I live in a 100 year old house and my kitchen breaker trips when I use the blender, oven, dishwasher and toaster oven at the same time. But if OP's tried it on different breakers.. :confused:
 

lokiju

macrumors 6502
Original poster
Jun 10, 2008
275
1
What else is running on the same breaker? You could have it overloaded. Also, are you in an older house? You might have outdated wiring that can't handle some modern day punishment.
I don't see how that can be a factor. I have two of the same model Mac Pro's. One NEVER has tripped a circuit. One does almost every time.
 

nanofrog

macrumors G4
May 6, 2008
11,718
2
Startup and coming up from sleep mean a short duration (millisecond range), high current draw on the circuit (called ironically enough, startup current :p).

The tripping of the breakers could mean that at that instant, the load is too high (other items on the circuit + MP = load exceeding what the breaker is rated for), or the breakers need replaced (they do wear out, and will trip prematurely).

Another trick to tell if the breaker has gone bad (only works for the magnetic type found in the panel, not thermal types that would be in a surge suppressor), is does the switch on it feel "spongy/springy"; a properly working breaker has a solid "Snap" of a feel when moving it's position.
 

-aggie-

macrumors P6
Jun 19, 2009
16,793
50
Where bunnies are welcome.
Startup and coming up from sleep mean a short duration (millisecond range), high current draw on the circuit (called ironically enough, startup current :p).

The tripping of the breakers could mean that at that instant, the load is too high (other items on the circuit + MP = load exceeding what the breaker is rated for), or the breakers need replaced (they do wear out, and will trip prematurely).

Another trick to tell if the breaker has gone bad (only works for the magnetic type found in the panel, not thermal types that would be in a surge suppressor), is does the switch on it feel "spongy/springy"; a properly working breaker has a solid "Snap" of a feel when moving it's position.
There is no way the extra 4-5 amps from "normal" starting of a computer is going to trip ANY breakers.
 

elfxmilhouse

macrumors 6502a
Oct 15, 2008
579
97
Northeast USA
the OP has TWO of the same model mac pros and only ONE of them trips the breaker in the same places. it looks like a problem specific to the one mac pro that trips the breakers.

stop saying its the wiring in the house. unless the tolerance between power supplies is so wide that one can use that much more power on start up than the other, it looks like something isolated to one machine.
 

agbot

macrumors regular
Jun 11, 2007
143
0
Silicon Valley
There is no way the extra 4-5 amps from "normal" starting of a computer is going to trip ANY breakers.
Of course it can. If you're on a, say, a 15A circuit near capacity and turn on any 5A appliance, you'll probably trip the breaker.

Also, given the OP said that the problem machine works sometimes, it's not some flat out short in the power supply. If you have a clamp on ammeter and know what you're doing, monitor the current at breaker with and without the machine running, or see if it spikes > breaker rating for an instant.
 

quantum003

macrumors 6502a
Apr 27, 2009
541
0
Superposition
Yeah, that's true... when a small fish tank filter was added to the circuit in the kitchen at my old place, the breaker would suddenly trip whenever the microwave was turned on. The fridge and microwave were the only two other items on that circuit, but removing the fish tank filter from the wall permanently solved the problem.
 

-aggie-

macrumors P6
Jun 19, 2009
16,793
50
Where bunnies are welcome.
Of course it can. If you're on a, say, a 15A circuit near capacity and turn on any 5A appliance, you'll probably trip the breaker.

Also, given the OP said that the problem machine works sometimes, it's not some flat out short in the power supply. If you have a clamp on ammeter and know what you're doing, monitor the current at breaker with and without the machine running, or see if it spikes > breaker rating for an instant.
Well, I certainly know that, but he already said the other computer works fine on the same circuit, so I don't think we're talking about a circuit with 11 amps from other stuff (which would be kind of silly for something with a computer on it...he'd need to have some pretty high amperage loads and light are not going to get there).

I'm pretty sure the problem is what I said it was. But perhaps my experience as an electrician means nothing. (Unless something is shorting the secondary, which doesn't make sense if it doesn't do this on initial startup.)
 

lokiju

macrumors 6502
Original poster
Jun 10, 2008
275
1
the OP has TWO of the same model mac pros and only ONE of them trips the breaker in the same places. it looks like a problem specific to the one mac pro that trips the breakers.

stop saying its the wiring in the house. unless the tolerance between power supplies is so wide that one can use that much more power on start up than the other, it looks like something isolated to one machine.
THIS!
 

Sun Baked

macrumors G5
May 19, 2002
14,874
57
If it was a GFCI circuit, i'd blame the wiring ... since some are very sensitive to fan and electric motor starts.

If the machine does this with only the main box plugged in, and nothing else hooked to it ... i'd say the machine.

If the computer only does this with monitor, external i/o, i'd say one of the power bricks, monitor, or i/o devices is creating a short of some sort. Which can happen if a couple power bricks get mixed up.
 

nanofrog

macrumors G4
May 6, 2008
11,718
2
the OP has TWO of the same model mac pros and only ONE of them trips the breaker in the same places. it looks like a problem specific to the one mac pro that trips the breakers.

stop saying its the wiring in the house. unless the tolerance between power supplies is so wide that one can use that much more power on start up than the other, it looks like something isolated to one machine.
I was just trying to get the OP to think about the load. If the load is close to the breaker's rating, it can trip during startup.

There are variances with PSU's even if it's the same make/model, and even batch (think transformers, caps,... from multiple suppliers for example), and the resulting QC tends to be spotty.

I've seen bad batches before (a bit too common lately IMO), as they're in a hurry to fill orders (they have a habit of missing lead times, and other sources have to be used to keep the assembly line operational). New units may not even meet ATX/EPS spec OTB. :eek:

Given the OP mentioned a UPS, it seems brown outs aren't the cause either (this does assume the UPS is functioning properly, and at least uses a mulit-tap transformer for voltage correction in undervolt conditions when the supply is still high enough to prevent the battery from being used).

I do suspect the PSU BTW, but want to be able to eliminate other possibilities.

There is no way the extra 4-5 amps from "normal" starting of a computer is going to trip ANY breakers.
It can though if the nominal load is high enough (not at the breaker's rating, but close). I just don't have any real idea of the load, including if both systems are on the same circuit.

Only one is suspect it seems, and the mention of a PSU swap is the best way to isolate the PSU.

(Unless something is shorting the secondary, which doesn't make sense if it doesn't do this on initial startup.)
Definitely not a dead short. But a bad transformer can cause the behaviour, as can bad caps (common btw, as electrolytics can leak, and/or swell causing shorts under specific temp conditions before they're totally shot).
 

Phantom Gremlin

macrumors regular
Feb 10, 2010
216
8
Tualatin, Oregon
get a kill-a-watt

Someone already mentioned the kill-a-watt. It's very inexpensive and would be of great use in diagnosing problems like this. It doesn't just read Watts, it can also display voltage, current, power factor, etc.

Using the kill-a-watt to compare the behavior of the two Mac Pros at startup will probably be sufficient to make a proper diagnosis.

We don't know if the OP has a "modern" circuit breaker. But if he does, startup current should never be a problem. Breakers allow a huge amount of surge for a brief period. I looked this up a while ago and am far too lazy to Google again, but IIRC the numbers work out to something like 1000% of rated load for at least a significant fraction of a second. So that's 150 Amps! The breaker will even allow something like 200% of rated load for about a minute.
 

CaptainChunk

macrumors 68020
Apr 16, 2008
2,142
6
Phoenix, AZ
Not unheard of... My old apartment building in LA was built in 1955 and had equally ancient wiring. I would trip a breaker (causing half the apartment to black out) from time to time powering on my MP if a lot of other stuff in the house was on (like A/C, microwave, living room TV, stereo, etc.). I couldn't even run the A/C and microwave simultaneously without tripping the breaker. Very annoying.

I don't miss that place at all.
 

elfxmilhouse

macrumors 6502a
Oct 15, 2008
579
97
Northeast USA
So swap the power supplies between both machines and test again.
yes good idea!


I was just trying to get the OP to think about the load. If the load is close to the breaker's rating, it can trip during startup.

There are variances with PSU's even if it's the same make/model, and even batch (think transformers, caps,... from multiple suppliers for example), and the resulting QC tends to be spotty.

I've seen bad batches before (a bit too common lately IMO), as they're in a hurry to fill orders (they have a habit of missing lead times, and other sources have to be used to keep the assembly line operational). New units may not even meet ATX/EPS spec OTB. :eek:

Given the OP mentioned a UPS, it seems brown outs aren't the cause either (this does assume the UPS is functioning properly, and at least uses a mulit-tap transformer for voltage correction in undervolt conditions when the supply is still high enough to prevent the battery from being used).
yes exactly! i think the variance between the psu could be a cause. Its just frustrating to see people not read the entire original post and respond.
 

lokiju

macrumors 6502
Original poster
Jun 10, 2008
275
1
Someone already mentioned the kill-a-watt. It's very inexpensive and would be of great use in diagnosing problems like this. It doesn't just read Watts, it can also display voltage, current, power factor, etc.

Using the kill-a-watt to compare the behavior of the two Mac Pros at startup will probably be sufficient to make a proper diagnosis.

We don't know if the OP has a "modern" circuit breaker. But if he does, startup current should never be a problem. Breakers allow a huge amount of surge for a brief period. I looked this up a while ago and am far too lazy to Google again, but IIRC the numbers work out to something like 1000% of rated load for at least a significant fraction of a second. So that's 150 Amps! The breaker will even allow something like 200% of rated load for about a minute.
My house was built in 2005.
 

JacaByte

macrumors 6502
Dec 26, 2009
315
0
Dudes, this is a simple black and white problem; he has two Mac Pros, one which trips circuits and one that doesn't. Yet you draw the conclusion that his house wiring's at fault.

Two and two don't add together; Apple's been using (pretty much) the same make and wattage of power supply since they built dual processor G5s. There's not enough disparity between two models of Mac Pros to say that one draws 4 or 5 amps more than another model, which is what is being suggested by saying his house wiring's the issue. There has to be something wrong with his power supply, and/or a component inside the computer that's drawing more current from the power supply than need be.

I suggest opening up the MP that trips circuits and unplugging everything except the hard drive with the OS installed on it and the motherboard. If that still doesn't work, you can try unplugging everything, pull up a wire diagram of the logic board connector for the MP and try crossing the "Power ON" pin with a COM pin using a paper clip or something. (and insulated gloves; don't zap yourself) This will power up the power supply with essentially zero load on the power supply itself and will isolate any problems with the power supply itself. Some power supplies can't run without any load and will short themselves out, but I think the MP power supplies are new enough to prevent that from happening.