PC Problems: Smoking UPS

Question, how do you know your earthing is ok? you have very much resistance when testing with a ohm meter, how about with a Megger? doy ou get the same lower resistances? if you increase the current in the Earth, does the resistance increase (hot spots generated at the connection point between conductors)

Are you running any suppression equipment before the UPS?

Hi,

It seems the UPS T/Fs primary winding weakens due to overvoltage. When you removed earthing from UPS , now there is no leakage current from T/F to earthing terminal.It is risky to run UPS in present condition as your T/F is faulty . Try with interchaging the Phase & neutral at incoming side of UPS ,reconnect earthing to UPS.If the condition is same or got worse, replace T/F of UPS.

The first thing to go smoking in e.g a thunder caused power failure is the small metal varistor(s) located near your input voltage connector that is supposed to leak overvoltage surges to earth. If it's overstressed (too hi amps for too long) it can deteriorate in random (both ways up or down) change in voltage level of activation, in your case probably down.Check if tis is the case by temporarily disconnecting it but DONT under any surcomstances work with a no-ground powered computer

I have found in the last that those devices don't just fail and come back to life, they either blow their sides off with a small hole thru the disc, or vanish from the PCB with only the stumpy legs left on the PCB

Your Uninterrupted Power Supply (UPS) has a fused link to ground that needs to be replaced this is internal and in addition to it obvious circuit breaker which is on it's positive side. check both supplies and verify that these ground links are intact IE... if one is faulted it will act as if the ground " load / Nuetral" leads are reversed and cause the symptoms you have experienced when both PC's are plugged in.

Just replace it. UPS devices only last about 5 years due to the lead-acid battery failure.

Some UPS's have the batter "Pack" as a separate box.

The UPS I setup once used 96 x 2V cells wired in parallel/series configuration for 48 VDC terminal voltage, the cells were 3600Ah.

The battery "Pack" took up about 6 square meters of floor space and stood about 1200mm in height, including the cage they needed

Dear friends

Please see following links to understand What is earthing in electrical system

http://picearthingtech.com/

http://blogs.siliconindia.com/picearthingtech

Regards

Raju