I have a request from a customer to investigate possible power quality issues concerning installed communications equipment. The symptoms are as follows: 1) UPS has dropped offline at least once a day for the last 2 weeks. 2) A voltage of 5 volts was measured on the neutral output of the UPS. 3) An individual received a mild shock when he touched the case of the UPS. In my opinion, all evidence points to a faulty or failing UPS. I am not a Power Quality expert by any means and I would like some input as to what specifically I should look for in the system that could be causing this problem to occur other than a faulty UPS. Can anyone help?
Communications Power Problems
- Thread starter cnjerocqn
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
Re: Communications Power Problems
1. What do you mean when you say "dropped offline"?
2. Is the 5 volts measured N-G right at the UPS? If so, that would be unusual since on every small 120V UPS I have seen there is a bond inside the UPS between N and G. There should be no chance to develop any voltage drop in the 2 or 3 inches coming from the bond point to the output terminal. If the 5 V is measured downstream somewhere and the thing is heavily loaded, it could well be normal. But since you did not give us much info about the UPS itself, it is hard to make any kind of educated guess.
3. A mild shock as in a static electric type shock? Or one that continued as long as he touched the case?
If this is a relatively small unit, I'd be inclined to just replace it rather than screw around with it. They are fairly cheap and diagnosing their problems is not worth the effort.
cnjerocqn said:
1. What do you mean when you say "dropped offline"?
2. Is the 5 volts measured N-G right at the UPS? If so, that would be unusual since on every small 120V UPS I have seen there is a bond inside the UPS between N and G. There should be no chance to develop any voltage drop in the 2 or 3 inches coming from the bond point to the output terminal. If the 5 V is measured downstream somewhere and the thing is heavily loaded, it could well be normal. But since you did not give us much info about the UPS itself, it is hard to make any kind of educated guess.
3. A mild shock as in a static electric type shock? Or one that continued as long as he touched the case?
If this is a relatively small unit, I'd be inclined to just replace it rather than screw around with it. They are fairly cheap and diagnosing their problems is not worth the effort.
charlie tuna
Senior Member
- Location
- Florida
we once had a deltec power conditioner that had these same problems -- found out the unit was not bonded to the power source. the feeder was via a manual transfer switch and the installer never connected either of the two power source bond wires to the unit.
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