Keeping the Cash Register Humming

By Richard P. Bingham | Oct 15, 2003
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Have a backup solution for when the lights go out

It has been several months since the “Blackout of 2003” captured headlines around the world. After the initial coverage of what happened and how many people were sleeping in unusual places, attention eventually focused on how much business was lost during the 12 to 24 hours during which electricity was being restored.

Pictures of piles of spoiled goods filled newspaper pages, TV broadcasts and Web sites, along with statistics on the hundreds of millions of dollars in revenues lost per major city involved.

It may not be practical for every retail establishment to have its own backup generator to carry the load during such a widespread event. However, it also doesn’t take a large cash investment to protect those same businesses and their critical operations against the typical power quality disturbances that can interrupt business.

Most surveys of the quality of the supply in North America have pointed to sags, or short reductions in voltage, as being the primary power quality disturbance. What happened on Aug. 14 is classified as a sustained interruption, or, to most people, a blackout. This is a more severe form of a sag. Transients, also called impulses or spikes, are not nearly the most prolific, not even coming in second place. A typical facility will experience less than 10 percent of the power quality disturbances being related to transients (unless you are in a lightning belt region, such as Florida). Transients can cause damage to equipment, such as when lightning couples into the electrical or communication systems, and the deployment of transient voltage surge suppression may prove beneficial if properly installed and grounded.

An important note is not to overlook providing transient protection on the phone lines and other communication links, such as WAN or cable modems, as they can provide the path that results in destructive events as well. However, they provide no protection against sags or interruptions, which are the loss of energy available to keep the equipment running in a facility, and account for 60 to 70 percent of the power quality problems at a typical facility.

Interruptions inexcuseable

There are compact uninterruptible power supplies (UPS) available on the market for a couple of hundred dollars that can keep the point-of-sale terminals and cash registers running for quite awhile. They aren’t designed to last 12 hours, but the scale of the most recent power outage event was actually a very infrequent occurrence, similar to a “100-year storm.” Protecting power and its quality has again come to the forefront of the news. Even short duration sags lasting only tenths of a second can disrupt electronic equipment. The figure above shows how a facility on the “other side” of the blackout saw the voltage vary during that time. This caused all non-UPS backed computers within the facility to shut down. During the blackout, there were numerous reports of retail outlets having products to sell—such perishable items as ice and dairy products—but they had no registers operating to carry out the transaction.

Larger UPS units and portable/standby generators can provide voltage for a longer period of time. Make sure that any portable generators are properly installed according to the National Electrical Code, as well as properly ventilated. These also require periodic maintenance to be ready to operate when the call comes. There are countless stories of generators not starting or running properly during the blackout. Generators should be run once a month or so as a test, and the typical UPS has batteries that require periodic replacement.

Another consideration for sustained interruptions is the delivery of fuel for the generators. Extra fuel storage within a facility generally is not permitted. The smaller, gasoline-powered generators require refueling after several hours of operation, but going to the local service station to get more gasoline wasn’t an option in August, as those electric pumps were out of service.

The larger diesel-powered generators had larger fuel tanks on them, but are also powering larger loads, resulting in larger gallons per minute consumption. When the fuel started to run low and the facility manager went to call the local fuel supplier, the supplier’s phone system was off-line, as those, too, were powered by the nonexistent electricity. In New York City, there was a scramble to find a delivery person who could deliver the diesel fuel needed to keep the generators running.

Some foresight and planning, along with a small capital investment, can keep the cash register ringing up those sales during most power quality disturbances that a typical facility would encounter. Nothing could stop the blackout of 2003, but hopefully, a problem of a lesser magnitude could easier be rectified.

BINGHAM, a contributing editor for power quality, can be reached at 732.287.3680.


About The Author

BINGHAM, a contributing editor for power quality, can be reached at 908.499.5321.

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