Which is misbehaving: My mains power or my Computer UPS?
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Which is misbehaving: My mains power or my Computer UPS?

by Greybeard#99 » Wed Jul 12, 2023 10:45 am

Concerned about the threat of possible power cuts, I installed a (CyberPower) UPS on my PC in October 2022. Subsequently I was unaware of its presence until I had occasion to look at the event log (as displayed in the UPS monitoring app). This indicates that, on occasions, the UPS has been active and switched to battery power due to high mains voltage.

The seemingly strange thing about these episodes is the switching frequency and their apparent duration.

The event log clearly shows the UPS continuously switching every second or two (either from main to battery or back to mains). It also shows that such episodes can last for several hours. It is less easy to determine the big picture from the log: such events appear to be relatively infrequent, but their cumulative duration is significant. The log is only recorded when the PC is running (but 8.5hours of excess voltage is shown during the last week).

I have contacted the UPS supplier who has confirmed that it should cut in at 256V and am taking more notice of the voltage as displayed by the UPS app (typically 242V). I am not aware that it is possible to extract data from the app to get a more detailed analysis of the "events".

My house is a Victorian terrace. It has been rewired (not that recently) and has a modern consumer unit.

Any thoughts?

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Re: Which is misbehaving: My mains power or my Computer UPS?

by ericmark » Fri Jul 14, 2023 7:32 am

Call the DNO (electric supplier not billing agent) as this can be caused by loss of PEN, it is rare, but if it does happen it can damage all sorts of equipment in the house.

It is unlikely due to any fault within the home, more likely a supply fault. If you want to know more, some reading here https://electrical.theiet.org/wiring-ma ... roken-pen/

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