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Whether for an office environment or server room, an uninterruptible power supply (UPS) should be implemented to protect computers and equipment—especially for mission-critical scenarios such as server rooms. But what UPS is right for your needs? It can vary depending on the usage scenario. For instance, in one Spiceworks thread, a user needed a UPS for network switches and had to be in a 1U rackmount form factor. To assist you in choosing a rackmount UPS, consider the following questions.

Line-interactive vs. on-line

When professionals think of UPS appliances, they often think of desktop UPS systems. Those are fine for desktop computers, but for data centers or server racks, rackmount UPS systems are better suited. Rackmount UPS solutions can be divided into types: line-interactive and on-line.

A line-interactive UPS regulates voltage fluctuations within a certain threshold. When the voltage falls below or rises above the threshold, a built-in transformer draws from the batteries to either boost or lower the voltage back to within the range. As long as the voltage stays within the accepted range however, power is not supplied by the batteries.

An on-line UPS provides superior voltage regulation because it constantly converts incoming power by using it to keep the battery charged. It then feeds the power from the battery to an inverter, which is then used to power your equipment. This method results in power with much better voltage resolution—though at a cost. On-line UPS systems typically cost more than line-interactive systems.

How many equipment plugs do you need?

Ensure that you pick a rackmount UPS with the appropriate number of outlets to meet your current and projected future needs. So if you currently require three outlets but plan to expand in the future, do not pick one with just three outlets. If you find that the UPS can no longer accommodate additional equipment, consider connecting a power distribution unit.

How much wattage do you need?

Similar to building a workstation or server, you need to calculate the amount of power your equipment needs. A simple method of calculating the power draw of your server equipment is to check the specifications of every machine that will be connected to the UPS. Without calculating your power draw, choosing the right UPS will present a challenge.

Rackmount UPS appliances are often rated in kilo volt amps (kVA) or 1000 volt amps (voltage × amps), though wattage specifications should be listed as well. Once you know your power needs, choose a rackmount UPS that exceeds that requirement.

Does your equipment require sine wave power?

Also sometimes marketed as pure sine wave power output, it means the output power can be measured as a pure sine wave. Generally, AC power from a wall outlet can have what is called power gaps, which can be graphed as steps rather than a pure sine wave. Using non-sine-wave power can cause issues for more sensitive devices, such as data loss in the case of storage or equipment failures in extreme cases.

As for whether it sine wave power is required, it depends on the equipment and scenario—though environments such as datacenters should utilize rackmount UPS systems with sine wave power output.

How long of a backup runtime do you need?

Should the UPS be required to run solely off the batteries because of power issues, the amount of backup runtime determines how long the batteries can supply power. This length of time depends heavily on the power load and the capacities of the batteries. Be sure to pick a UPS that can provide enough battery runtime for your backup generators to come online or safely power down your machines.

Answering the questions above will help you with choosing a rackmount UPS that fits your usage scenario with minimal fuss. If your equipment needs change dramatically, you may find your power protection needs changing as well. But with the right UPS appliance, you can expand its capabilities to meet new demands.

Considerations for Choosing the Right Rackmount UPS - HardBoiled
Article Name
Considerations for Choosing the Right Rackmount UPS - HardBoiled
Choosing the right rackmount UPS for mission-critical servers and equipment can be a challenge, but by asking the right question it can be made easier.
Wallace Chu

Author Wallace Chu

A self-professed tech hipster that loves computers and music. Uses an iPhone ironically.

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Join the discussion 3 Comments

  • it says:

    useless… all you did is tell what questions to ask with not a bit of useful information.

  • Wallace, I find it helpful that you said I should calculate the wattage needed of all my equipment connected to the UPS system to choose the right one. My husband has a full office set up at home because of the quarantine. He’s thinking of buying a UPS system since we get frequent power interruptions nowadays. I’ll share this with him later to use it as a guide in purchasing the right UPS. Thanks!

  • Choosing an inverter is a tough and complex task. I used Power Calculator by MSPWeb Store and it helped me a lot in selecting the correct UPS inverter for my home

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