An input voltage or frequency problem prevents switching to bypass mode. -

[donwmack_apc]

This was originally posted on APC forums on 6/7/2011

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We have a Smart-UPS VT 30 kVA. We have had the UPS for about 4 months. It is running at 53% load.

This is the first time I have seen this message. Is there anything that I need to do?

06/07/2011 06:49:00 UPS: An input voltage or frequency problem prevents switching to bypass mode.
06/07/2011 06:49:00 UPS: On battery power in response to an input power problem.
06/07/2011 06:48:26 UPS: An input voltage or frequency problem prevents switching to bypass mode.
06/07/2011 06:48:26 UPS: On battery power in response to an input power problem.

[BillP]

This reply was originally posted by Angela on APC forums on 6/7/2011

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yup, as long as this message does not appear constantly as an alarm, i would not worry about it. if it did, i would say we need to see if there is a power issue going on at the facility.

[donwmack_apc]

This was originally posted on APC forums on 6/7/2011

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Thanks

[BillP]

This reply was originally posted by Angela on APC forums on 6/7/2011

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hi - i am not familiar with the Smart UPS VT and 3 phase UPSs but on the single phase UPSs, one of the UPS's primary functions is to constantly evaluate input power quality, including frequency, to make sure it is acceptable for the attached load incase the UPS has to transfer to emergency bypass incase of overload, etc so when that message comes up, it is indicating that the incoming power is not acceptable based on the configuration of the UPS. it usually corresponds to power fluctuations and brownouts.

did the error clear? did you make any setting changes recently? tech support may be able to review any power configuration settings as i am not familiar with those on the VT. or maybe someone else on the board more familiar with the product.

[donwmack_apc]

This was originally posted on APC forums on 6/7/2011

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The power did restore seconds later. I had included the log in the message but it was lost. We have had interuptions several times this spring. This was the first time I saw this particular message and wanted to confirm that as long as power returned to normal all was good with the system.

[upsguy_apc · Accepted solution]

This was originally posted on APC forums on 6/7/2011

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This UPS tracks the UPS Bypass Input which is also the power that feeds the UPS main input. The UPS inverter tracks the bypass input so that seemless transfers to bypass can be made with minimal exchange current and so the transfer is transparent to the load.

During times of minor input fluctuations the UPS can still run on the input voltage without having to transfer to battery however that input voltage is not satisfactory to operate the load on Bypass so the UPS will prevent itself from being switch to that source and you get the displayed alarm. The system was most likely operating as designed.