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I have a UPS unit that I would like to use for a workstation installation that does not have a valid ground (in the Philippines, a true ground is a luxury).

I am not an Electrical Engineer, but I have always believed that a UPS needs a ground to operate. Out of curiosity, though, I tried plugging this one in and it seems to be working just fine without any warning lights/sounds/etc.

Does running it this way represent a risk either to the machine or person using the machine?

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migrated from serverfault.com Aug 2 '11 at 7:28

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2 Answers 2

up vote 9 down vote accepted

There are several potential issues with not using a ground for your UPS or workstation. Most notably is the risk of operator injury. For instance, in the UK, if your appliance (UPS, PC, handheld drill) is not double insulated (identified by having 2 boxes, one inside the other and an almost complete plastic covering shell) it must, by law, be grounded. This is to prevent a short inside the unit from making the outer shell "live", in this instance, if an operator were to pick it up, they would act as the conductor to ground. However, if there was a grounding wire in place, the copper/aluminum/other should be a much better conductor than a human body in most cases and will harmlessly discharge the current to ground, usually tripping a circuit breaker or blowing a fuse.

The other reason is for electrical noise, a non-grounded appliance can introduce a 50/60Hz hum or other interference into the devices that it is plugged into, or in some cases, near.

A true ground is actually remarkably easy to obtain, it is "simply" a matter of driving a (usually) copper spike into the earth and having this connected to your electrical system and any exposed metal fixings (copper pipes for radiators, water pipes for taps etc). In the UK it must be easily inspected but a total cost for the parts required (earthing rod, couplers and inspection pit) is well under £50 or 3500 Peso.

To answer your question succinctly, no, it should not harm your UPS not having a ground but it could potentially harm you. It may also introduce "peculiar" networking errors, especially if your are fully utilising a gigabit ethernet connection, i.e. running iSCSI to multiple machines etc.

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Thanks much for the detailed answer. In terms of the UK law, I appreciate the data point, but there are a ton of electrical devices in use around the world that do not have a ground. Thus I'm inclined to write this off as "overly cautious". Is there some reason why a UPS is different? As for the ground, we're in the middle of a mall with no nearby metal fixtures, so it is unfortunately difficult. Finally, thanks for the heads up with the networking issues. We'll be sure to keep an eye out for those. Thanks again! –  Scot Aug 2 '11 at 8:29
    
Of course, if they don't have a ground to start out with, and the plug the PC in, they are basically still in the same situation electrically, so at least they have the benefit of the battery. –  KCotreau Aug 2 '11 at 12:07
    
@Scot as long as there is no way for you to contact any of the conductors in the UPS unit, I wouldn't worry too much. Just be aware of the potential dangers, and even if you're not near anything that could ground you, I'm sure there's other electronic devices around you that could present another path. –  Breakthrough Aug 2 '11 at 21:44

As Dan has answered, it is for safety, and to prevent 50/60hz hum entering into the electrical paths and causing networking/other faults.

Low voltage devices (as described by EU legislation, but probably applies to other countries aswell), do not require a ground, because even if they DID become live, the voltage and current present do not pose a harm to the user. Other metal shelled devices may not have an earth because there is a very very VERY low probability of a short occurring inside the device (think VCR with a figure of 8 connector).

I am not sure about your country, but if there was a member of public, or staff, harmed by this device, you may be liable because you have tampered (well, not even connected), one of the safety features.

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These are all valid points, but I believe @Scot didn't tamper with the device - it came from another country without the ground. –  Breakthrough Aug 2 '11 at 21:45
    
Although it is a bit vague, I believe he does not have a ground in his electrical installation, rather than the UPS not having a ground –  Marineio Aug 7 '11 at 17:41

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