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Electronics => Beginners => Topic started by: openthomas on October 22, 2012, 10:05:13 pm

Title: Help with a UPS fault
Post by: openthomas on October 22, 2012, 10:05:13 pm

Hi all,

My APC UPS's are coming up with building wiring fault. According to the documentation there are 3 possible causes.

1 overloaded neutral wire
2 reversed polarity
3 missing ground wire

I am sure its not the polarity, used a socket tester. How can I measure the ground connectivity and how can I check for an overloaded neutral wire ?

Title: Re: Help with a UPS fault
Post by: BigBrother on October 22, 2012, 10:10:24 pm

I have two APC Back-UPS XS 1500. They complain with this same thing if I use them on a surge protector or power strip.

Title: Help with a UPS fault
Post by: openthomas on October 22, 2012, 10:28:42 pm

In this case its plugged into the wall socket. I am guessing overloaded neutral. Interestingly when I plug this UPS in, apc smartups 1400, my 3m 724 sends out an alarm saying my dissipative mat which is being monitored is not functioning. That device uses two ground connections. One is sourced from a radiator and the other from the wall socket. When I plug this UPS into any socket in the building, the alarm goes off on the ESD workstation monitor. The monitor compares the two grounds. Puzzle....

Title: Help with a UPS fault
Post by: openthomas on October 22, 2012, 10:44:07 pm

I have measured the ground to neutral. With the UPS plugged in its 20V. Without it, 5.18V.

So ......what does that mean ? Its overloaded and the UPS makes it worse but does that mean the UPS is faulty ?

Title: Help with a UPS fault
Post by: openthomas on October 22, 2012, 10:47:30 pm

With a different UPS ground to neutral goes to 17V but in this case the workstation monitor does not sound. Perhaps because it uses a 16V signal to test the mat ?

Title: Help with a UPS fault
Post by: openthomas on October 22, 2012, 10:48:06 pm

Will 20V on the neutral damage my equipment ?