Uninterruptible Power Supplies and Electrical Wiring Concerns

Home offices in newer homes should not have any problems with wiring issues. However, older homes may or may not have the proper outlets to protect delicate computer hardware. All UPS boxes should use the typical three prong connector with either straight blades or curved twist-lock prongs. The latter is handy for working in tight spaces when you need to plug two three-wire connectors into one receptacle.

In an older house, unless the wiring has been upgraded to the office area, you may find after installing a new UPS that a warning condition of an ungrounded outlet appears. Many simple surge protectors also have an alert light to this condition, so it pays to check your outlook for grounding before buying a UPS. Simple ground test equipment is available in hardware stores as well. You cannot tell a grounded receptacle simply by looking at it. Even if there are three holes, this does not guarantee a ground connection. Disassembling the outlook to look for three wires is not advised without a background as an electrician. In any case, even the presence of three connected wires at the receptacle is not a guarantee because the ground wire may not be connected at the service panel. Given the dangers of working around home electrical wiring, paying strict attention to electrical safety is vital.

A UPS will function even when not connected to a grounded circuit. Grounding is a safety issue, not a battery backup or surge protection issue. It could be an issue with line interference. More importantly, there are significant safety concerns in the event of a serious failure. This could result in the appliance itself re-directing current to connected devices or a person. It is unlikely that any UPS manufacturer would recommend operating a UPS through an ungrounded outlet. Probably most would also exclude warranty coverage on a UPS used in this way. Running a heavy duty extension cord to a known grounded outlet is a possibility for a short-term alternative but not recommended as a permanent solution.

The best approach, particularly in wiring a home office in an older dwelling is to have an electrician install a dedicated line. This way there is no chance that a sudden load on another appliance in the house that shares the circuit to the computer will cause a problem. The dedicated line also ensures there are no other connections in the house sharing the ground wire to the computer/UPS outlet. If there are some ground wire sharing possibilities, this can be a source of line noise resulting in some problems with data communications.