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Case Study: Effect of Heatwave on UPS

One of the difficulties associated with the Australian summer is that businesses often close for the last week of December through the first week of January, which means there are no staff onsite and no need to run air-conditioning. When combined with even moderate summer temperatures, let alone heatwaves in the upper 30/lower 40 degree range, this puts stress on computer equipment, because the warm air in the premises may not abate for as much as two weeks. This forces equipment such as servers, which are often tucked into enclosed spaces anyway, to run their fans very hard to expel warm air from around the processor, and this can shorten the life of many components.

Therefore it is good practice, if your business is to be unattended for a lengthy period, to make some arrangements for regular bouts of air-conditioning, or, where possible, switch some devices off.

The following chart shows the performance of an APC Smart-UPS 750 on one of our client's premises on 31 December 2015. On this day the forecast high was 39°C, but it reached 37°C in their area. The office had been unattended for the preceeding seven days, and the server was running the fan very hard.

The chart shows the internal temperature of the UPS (red) and the outside temperature (green) on the right, and the UPS load (blue) on the left:

It can be seen that the temperature of the unit reduced overnight, losing about 2½°C until 8:30am, then climbing to more than 47°C by 1pm. The air-conditioning was turned on at this time, and within 20 minutes the UPS' internal temperature had dropped by almost 1½°C. By 3:30pm, it had dropped to 41.8°C, a drop of almost 5½°C.

Correspondingly, over that period the load on the UPS dropped from 40.9% to 38.3% (2.6 points) as the server demanded less power to run the fan.

When the air-conditioning was turned off a few hours later, the UPS temperature climbed back up. This was due to, in this instance, a large area adjacent the office space which was not air-conditioned, so while the office was cooled very effectively with immediate results, once it was turned off, the warm air from the large space next to it flowed into the office and brought the ambient temperature back up.

In a more enclosed office space, it is expected that the air would remain relatively cool for the remainder of the day and into the night.

This demonstrates why large businesses run their IT and communications equipment in dedicated rooms with its own air-conditioning. For small business, this is not feasible, and so some manual intervention may be required during warm periods to let the office area cool down even if there are no staff onsite.

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