UPS: Compensating for a low input voltage - Bit confused!!

[Anonymous user]

Hi I hope someone can help, we have 4 APC ups's in our server room.

2 x SUA3000RMI2U (one of which has a management card installed)
2 x SU3000Inet (tower)

We've load balanced them between our servers and the load is minimal on all of them.

Late on Monday night we had a powercut, it lasted a couple of hours. When I got into the server room the next day power had been restored the and ups's were all fine (I mention this for information - it may not be related to my query)

Today (wednesday morning) I have just recived notice from my UPS with the management card that the 'UPS: Compensating for a low input voltage'

+"13.06.2012 09:02:14 UPS: No longer compensating for a low input voltage.+
+13.06.2012 08:55:02 UPS: Compensating for a low input voltage.+
+13.06.2012 08:54:53 UPS: No longer compensating for a low input voltage.+
+13.06.2012 08:38:54 UPS: Compensating for a low input voltage."+

Upon looking at the UPS's the two SUA3000RMI2U both have the low voltage light lit the two SU3000INET's don't.

I'm unsure how to tackle the problem we've used these units for years without issue, the only way i've managed to stop the notifications is to lower the threshold but its not really a solution. Should I be concerned by this?

Any help or info appreciated.

[BillP]

the different types of units you have are on different hardware platforms and firmware platforms - thus they may have difference voltage or sensitivity settings set which is causing one UPS to see the input voltage as a little low below threshold and the other one does not see the same thing.

i'd first check the device with the network management card and analyze the data log at the time the events are reported - what is the actual input voltage? ultimately you'd need to find out with an electrician or someone who can help determine what has happened to your incoming voltage to address the problem.

[Anonymous user]

Many thanks for the reply,

I'm not sure if the low voltage was fluctuating somewhat but it seemed that when ever I checked the voltage was at roughly 211VAC and the threshold was set to 208VAC

When I altered the notification threshold to 204 the error stopped and the light is now clear on the UPS.

However the other identical until still has the light on which suggests to me that the input is still low. (I have no management card or powerchute install to check the readings on this unit) I assume if the power goes backup then the light should go out?

I've now re-set the threshold on the managed ups back to 208 to see if it starts complaining again.


Edit : straight away i'm notified of the low input yet the unit shows 210. Threshold is 208 ......


Message was edited by: ittim

[BillP]

this might help too depending on whats been happening.. http://nam-en.apc.com/app/answers/detail/a_id/715

[Anonymous user]

Thank you, I'm not entirely sure I understand the table but i'm not getting anywhere near those voltages as far as I can tell.

[BillP]

i was thinking that maybe the UPS is implying a hysteresis type thing where it wont come back online unless it goes back up to a certain voltage value - to avoid teetering on and off from AVR boost to online.

can you give me all of the logs to review (instructions here|http://nam-en.apc.com/app/answers/detail/a_id/9321]? these are 230v nominal voltage units, correct? i am saying that based on the model numbers you provided.

[Anonymous user]

I've just arrived into the office this morning to find that all my UPS's are now happy.

I'm wondering if the Electricity board were doing something which caused the errors.

[Anonymous user · Accepted solution]

Thank you for helping me with this. Yes they're 230.

I've attached the logs as requested.