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Recently we had the UPS input feeder breaker trip due to a the wrong voltage supplied to a switch. the switch was rated for 120v and the electrical contractor connected 208v to the phone switch. The UPS sensed the problem and according to the alarm history transferred to bypass - inverter leg overcurrent - output undervoltage - bypass frequency out of tolerance - critical power supply failure. Why did the input breaker trip\r\n Thanks

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Posted on Jan 02, 2017

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SOURCE: UPS problem


Based on your post/description, two (2) possibilities:
1. electronic fault - main power/AC mains sensor which could be really just a relay; or
2. corroded fuse terminals or fuse holder.

The first is a bit of a challenge since different brands/models have different sensing circuitry design. Some can be as earlier stated, a simple AC relay while others could be a TRIAC switch with a DIAC trigger. Still, some could be an elaborate AD converter and a myriad of logic circuitry. Often, a service manual or at least a schematic diagram would be needed, however these are not that readily available and most often the tech or DIYer must resort to winging it. This of course would require familiarity with electronic circuitry and components, use of a DVM and a soldering iron. Extreme caution must be exercised since even with 12VDC supply most of the electronics are at least at 60VAC+ level.

The 2nd possibility would be of course be the easiest to determine and repair. Replace/clean.

Should the downtime & repair cost makes the project no longer economically reasonable, perhaps your best bet would be to simply replace the UPS since their prices are relatively low.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.

Posted on Apr 16, 2008

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SOURCE: emerge UPS 500va special power supply not working..

there is a fuse behind the ups which can be removed by opening the socket replace it if faulty
and you can operate the ups

Posted on Nov 27, 2008

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SOURCE: mge galaxy 20kva ups input breaker trip

Does it trip immediately or after a time? If it's immediate then there's a dead short on the line (or possibly inside the UPS). If it takes time to trip then there's a slow build up of too much current use. This is usually caused by defective capacitors in a power supply.

Posted on Apr 06, 2009

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SOURCE: I recently purchased a used Belkin F6C800-UNV UPS,

This is normal in some lower end UPS's, the voltage can swing quite a bit, a drop of 40 seems like quite a bit but it's out of the question. It will also adapt to what is plugged in yes. Ultimately to test you would want to try it with something like an actual PC plugged in and make sure it stays running. I'd say otherwise it sounds normal to me.

Posted on Jul 10, 2009

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SOURCE: bypass LED on the ups is on

This an excerpt from the UPS's manual:
The Bypass LED illuminates indicating that the UPS is in bypass mode. Utility power is sent directly to connected equipment during bypass mode operation. Bypass mode operation is the result of an internal UPS fault, an overload condition, or a user initiated command through an accessory. Battery operation is not available when the UPS is in bypass mode.

Posted on Jul 19, 2009

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If the battery is more than 3 years old then it may be due for replacement.

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What is the maximum amount of electrical energy that can be delivered durning a short circuit for low voltage 230v/400v

Tom, Not sure if what you're asking relates to the Maximum electrical energy (Voltage and Amps) that can occur during a short circuit through a properly protected electrical circuit (protected by a circuit breaker, etc.) or if the question is for the maximum amount you could potentially get from a short circuit on a 230V or 400V electrical line to ground OR another electrical line/supply.

IF the circuit is a 230V-AC circuit protected by a double circuit breaker, you could see the entire Voltage (230V-AC) and up to the full Ampere rating of the circuit breaker, (20, 30, 40, 50, etc Amps) during a short circuit condition to Ground.

IF the circuit is a 400V-AC circuit protected by a double circuit breaker, you, again, could get the entire Voltage (400V-AC) and up to the full Ampere rating of the circuit breaker protecting the circuit, when shorted to Ground.

Now, IF the short condition involves one of the above line voltages AND you are having it shorted against another Voltage/Amp circuit, the total potential Voltage and Amps you could experience, would basically be the sum of the two Voltages (and Amps) of the two (2) circuits being put into a short condition. So you would/could see a potential short circuit of whatever voltage is available, depending on what and where the short circuit is occurring.

By way of example, I've seen a 240V-AC 60 Amp circuit shorted to another 240V-AC 60 Amp circuit and the resultant "short condition caused enough damage, due to the voltage and Amps provided, to melt and weld the machinery's electrical connections, rendering the unit a total loss, not to mention that the person that caused the short to occur, received a face-full of melted copper metal bits all over their face and body. Thankfully they were wearing safety glasses, and their eyesight was saved, albeit, with some temporary blindness caused by the extremely bright flash and explosion.

The examples provided assume a properly working/functioning circuit breaker protection. However, if the circuit breakers are faulty, it is possible to recieve much higher vlotages and Amps, since there would be no protective circuit breaker that could trip the power off. In that case, the Main circuit breaker becomes the fail-safe protective device and that could have a much higher Amp rating, thus the maximum Voltage/Amps would be limited by the Main electrical ciruit breaker and electrical supply available at the location where the short circuit occurs.

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If you have more information about the particular situation, please post a follow-up comment and I'll provide you with some more info.

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Hi, I bought a 1500va APC UPS. Its not charging when connected to the mains power supply. It still beeps and stays on battery. I have set up the transfer voltage and sensitivity adjustment to no avail....

Hi, I am a licensed Master Electrician with 27 years exp.
Need more info. Did it work before? Are you positive your incoming voltage is correct? I will assume all of them things as yes and see what I can think of to fix ya up.
I would connect it to a load and let the batteries totally deplete, like a small drill or something that pulls close to the 12.5vac (1500va). Disconnect the load and unplug it for a minute, then plug it back in and then see if it charges. If it does, leave it alone til it completes charging then put a load on it. It shouldnt charge with a load on it if the battery is already fully charged. Then unplug it from the wall receptacle (main power) and see if it transfers and the batteries take over. If it does it should not charge again. A UPC should only charge when your load is being supplied by the main power, i.e., the UPS is plugged in and not transferred to the battery state.
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Mge galaxy 20kva ups input breaker trip

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