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GCN Home > 11/18/02 issue

What keeps the up in uptime? UPS

By John Breeden II, GCN Staff

Network health depends on a smart, smooth, survivable power supply

Network users take electrical power for granted, like oxygen, until the supply suddenly shuts off. Then a reliable uninterruptible power system, like a full scuba tank, becomes supremely important.

Network UPSes are basically large, manageable batteries. Their chief specification is long run time—40 minutes of battery power is better than 15.

In testing UPSes, the GCN Lab considered several other factors, too. How many outlets did each UPS have? How many plugs were directly battery-attached as opposed to giving only surge protection? And how easy was it to monitor each UPS with the included software?

A pure sine wave is the cleanest type of power, but most computers don’t require a pure sine wave; they draw their power from the top and bottom of the signal. We looked at the waveforms to judge their quality. And as always, price was a factor in our ratings.

We set up a test workgroup of three desktop computers and a monitor, enough to tax but not overload our test UPSes, which were rated between 1,000 and 1,500 volt-amperes.

Most computer power requirements are stated in watts, although VA gives a better indication of capacity. Watts multiplied by 1.4 gives the VA rating. For example, our largest test workstation drew 220 watts, which meant its VA rating was 308.

Some monitors’ power requirements are in amperes, which can be converted to VA by multiplying by 120. A 1.3-amp monitor would draw 156 VA from a UPS, for example.

No matter what devices are connected, their total VA load should be less than the UPS’ VA rating. A 1,000-VA UPS can generally support three average desktop computers plus a monitor, or two servers and a monitor.

The total power demand of our test network was 950 VA—close to but less than the top VA ratings.

The Para Systems Minuteman SmartSine S1400 was the best all-around performer with the longest run time and a small form factor. It sat on the floor and, at 6 inches by 17 inches, took up little more room than a shoebox.

The SmartSine was the only unit in the review with eight plugs for devices; others had six or four. Plus, all eight of the plugs connected to the battery unlike other units, some of whose plugs gave only surge protection and not backup power.

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