Electrical Noise & Battery Backup

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Keri_WW

Keri_WW

Senior Member
We've been have a problem at work where two cubicles on one circuit will have their their computers switched from normal power to the APC battery backup rather frequently throughout the day. The software indicates electrical noise.

We've tried changing out UPS systems and lowering the sensitivity through the software package with no change. An electrician took the panel cover off and checked all of the wiring to that circuit, the panel, and the transformer feeding the panel and found nothing out of the ordinary. So my question is whether it could be something rather simple causing the problem or what we can suggest the electrician to look into...? This is a recent problem in an existing building / setup that has been running fine for years.

Any ideas?

Thanks! :grin::grin:
Keri
 
I got a pretty good idea what the problem is, its the UPS, a cheap UPS. Basically for backup power for a PC they make two kinds. One with Modified Sine Wave inverters (cheap and noisy), and True Sine Wave inverters (2 to 3 times more expensive and clean outputs). Bet you your inverter has a MSW type inverter? Look at the inverter specs and see what type of inverter it uses.
 
They are APC UPS-ES 500 and ES 650's. You may be missing the point however. Yes the back up is a stepped approximation of a sine wave, but that is irrelevant to the fact that the units keep detecting electrical noise.

We aren't having problems when running on battery power, only that they keep switching between the normal/emerg frequently (they don't stay on battery for more than 2-3 seconds, which is killing the batteries)... Does that make sense?

Thanks
Keri
 
You need to either replace the unit or monitor the circuit to determine if the metering component of the UPS is accurate. If you find that it is accurate, then the signature of the power quality measurement will help you determine the cause. Also try to make measurements on other nearby circuits to see the differences, sometimes that help in the detective work.
 
Did the electrician monitor the voltage AND CURRENT long enough to determine what the ups is seeing. Might have a laser printer common to the circuit--sounds like voltage drop to me !
 
Other Loads

Other Loads

Is there anything else on the circuit from the panel? I have seen laser printers (fuser heater cycles) causing major dips. If the voltage is low for other reasons and the fuser roll heater turns on, that may be enough to cause the UPS to switch. Small "personal" laser copies are the same.
 
It is quite common for there to be frequent power "events" which cause a UPS to kick in.

With large computer room UPS, I've seen where the UPS will print out "power line events" and there will be something happening with the power which the UPS is "not happy with" on the average of once an hour!

It could be that these UPS are newer or a different design than others in the building and they would "complain about the power" no matter which circuit they were on in the building? Might try swapping these with another unit elsewhere.

Then if all UPS have the problem only on that circuit, there could be something plugged into that circuit which is causing problems or a problem with the circuit itself. Might want to identify everything on that circuit, then plug these various things into another circuit with extension cords and see if the problem moves/disappears.

Or if you can set-up the UPS so it does not "beep" when switching power and move it where the worker will not hear the noise of it "clicking", then than may be another option. I assume everything keeps working just fine backup or not.
 
i have found that our ups's dont like being pluged in a circuit that has a copier on the same circuit, i had to dedicate a circuit just for the copier, to get the noise problem to go away, after that it worked just fine.
 
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