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Old 10-21-2009, 08:17 PM   #1
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UPS & PC combo trip AFCI


I have a homebuilt PC that has been on a 7 year old UPS for a long time now. Turning on the PC never tripped the AFCI. I upgraded the UPS to a newer heavier duty one and the AFCI started tripping quite frequently when the PC was turned on. I ended up getting a replacement unit for the UPS and the problem went away for a week and now it is back with a vengeance.

The PC alone never trips the AFCI,
The UPS just sitting there never trips the AFCI.
Only when the two are together do they trip the AFIC.
The UPS has an LED display that comes on to show the voltage change when a load hits it and it simply shows anywhere between 119 and 121 volts.

The PC has a 750 Watt power supply, possibly too small for the PC in question, the UPS is a 1250 Watt unit (APC BN1250)

Any thoughts as to what is wrong here? Should I just replace the AFCI to see if it will get rid of the problem?

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Old 10-21-2009, 09:55 PM   #2
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UPS & PC combo trip AFCI


How long and what brand AFCI breaker you have on this set up ?

I know some brands did have issue with it especally with early generation models.

Merci.
Marc

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Old 10-21-2009, 10:00 PM   #3
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UPS & PC combo trip AFCI


Quote:
Originally Posted by Keith Wheeler View Post
I have a homebuilt PC that has been on a 7 year old UPS for a long time now. Turning on the PC never tripped the AFCI. I upgraded the UPS to a newer heavier duty one and the AFCI started tripping quite frequently when the PC was turned on. I ended up getting a replacement unit for the UPS and the problem went away for a week and now it is back with a vengeance.

The PC alone never trips the AFCI,
The UPS just sitting there never trips the AFCI.
Only when the two are together do they trip the AFIC.
The UPS has an LED display that comes on to show the voltage change when a load hits it and it simply shows anywhere between 119 and 121 volts.

The PC has a 750 Watt power supply, possibly too small for the PC in question, the UPS is a 1250 Watt unit (APC BN1250)

Any thoughts as to what is wrong here? Should I just replace the AFCI to see if it will get rid of the problem?
Sure! You're overloading the circuit. (No matter what) Don't Drink and Drive, Ever!!!
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Old 10-21-2009, 10:20 PM   #4
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UPS & PC combo trip AFCI


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Originally Posted by frenchelectrican View Post
How long and what brand AFCI breaker you have on this set up ?

I know some brands did have issue with it especally with early generation models.

Merci.
Marc

All the AFCI's in this house are from late 2003 early 2004, we bought the house in March of 2004 and they are Siemens 15A AFCI's
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Old 10-21-2009, 10:30 PM   #5
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UPS & PC combo trip AFCI


I do not want to push a " panic button " here but I have a feeling that you have one of the early generaton of AFCI breaker and Siemens are pretty good what I know.

however I will admit I don't deal a whole alot with Siemens in the USA but in France yeah I get a tons of it anyway let me cut to chase that I think they { Siemens } did update the AFCI breaker but excat number I don't have with me at the moment.

There is two options you can do is run a tempory cord to see if that clear up if so maybe the AFCI breaker is going bad if so you can replace with new one but I do not know how senstive they set at.

For breaker cost it will be about 30 or so

Merci.
Marc
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Old 10-21-2009, 10:37 PM   #6
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UPS & PC combo trip AFCI


I appreciate the input. I was at a point where I was going to drop by the local hardware store and pickup a new breaker, but the idea of running a drop cord to another room and testing the breaker that way (using another room) to see if it trips is a good idea.
What gets me is that without the UPS it never trips the breaker. Other devices hooked to the UPS cause no problem but they don't pull as much power either. Something about the combination of the two is upsetting the AFCI.
After replacing the UPS unit I figure I don't have a bad one of those and I can put the PC on the very old UPS and the AFCI doesn't trip.
So I'll watch the forum for other replies but in the meantime will most likely drop a cord to the next room.
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Old 10-21-2009, 11:37 PM   #7
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UPS & PC combo trip AFCI


Just hang on I know couple of members here may know a trick or two how to deal with pesky AFCI but I am thinking something along the switching mode in UPS may affect the AFCI due I know some UPS do have double conversion which it mean it will convert to DC plus whatever battery with inverter or direct connection to battery then convertet back to AC somecase it may casue a small arc but I doubt it unless someone else is famuair with small ups system

Merci.
Marc
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Old 12-10-2009, 12:30 AM   #8
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UPS & PC combo trip AFCI


FWIW, I believe the UPS charging its battery would also place a load on the circuit, in addition to the 750W PS. If your comp is pulling the full 750 at start or all the time, like a RAID array *and* the batt is charging *and* you have anything else like a lamp on the circuit and you could be maxing out a 15A circuit.
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Old 12-10-2009, 09:00 AM   #9
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UPS & PC combo trip AFCI


Has the UPS been able to fully charge before plugging the PC in ?
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Old 12-10-2009, 11:18 AM   #10
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UPS & PC combo trip AFCI


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Has the UPS been able to fully charge before plugging the PC in ?
That's the thing...I know my UPSs at home and work discharge quite regularly when they need to step in for "brown out" conditions, even if only for a second, even if you don't notice it. Then they cycle back to charging as soon as the power goes back to normal. OP says an old UPS started tripping and new one tripped out of the box. I'd be curious to know the VA difference between the old and new UPS.
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Old 12-10-2009, 02:36 PM   #11
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UPS & PC combo trip AFCI


Is this a 15amp AFCI Breaker? 750w + 1250W = 2000W/120V = 16.66Amps
This not including what all else is on this circuit.

Last edited by Chasm; 12-10-2009 at 02:39 PM.
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Old 12-10-2009, 03:18 PM   #12
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UPS & PC combo trip AFCI


The 1250w UPS is how many watts it can handle of items plugged in
It will not take anywhere near that number while running
And the 750w PC power is the capacity, again it should not take anywhere near that number
Unless it is a server with 5 drives running all the time
Even then not close to 750w

Since its the AFCI part that is tripping (button) & not the breaker (capacity reached) it seems its an incompatibility
Someone else just posted that a battery charger was causing the problem on his AFCI circuit
Since the UPS has a battery charger built in that may cause the problem
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Old 12-10-2009, 08:04 PM   #13
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UPS & PC combo trip AFCI


I bought a new Mac Pro and now my Siemens 15amp AFCI trips whenever I turn ON the computer or wake it up from sleep. I have done countless hours of research. My current AFCI circuit breakers were probably mfg. around 03-04. I just bought a new Siemens direct replacement that was made between 08-09. I am planning on replacing the older AFCI with the newer one to see if that fixes it. This is really frustrating! I wish Apple asked me "Where I plan on plugging this thing into?" rather than "What are you going to do?".

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