Why network gear needs a UPS
Power in most offices is reliable, but short interruptions, brownouts and voltage spikes happen more often than people realise. A flicker lasting half a second can restart every switch and access point in the building, dropping calls and disconnecting everyone for several minutes while devices boot. Repeated hard power cuts can also corrupt configuration and storage on network devices and servers.
A UPS sits between the wall outlet and the equipment. When mains power fails, it switches to battery quickly enough that the equipment never notices. It also filters out surges and dips, which extends the life of everything plugged into it. For PoE switches it does double duty, because it keeps every powered access point, phone and camera running too.
The main types
Standby UPS units are the simplest and cheapest, common for single desktop computers. Line-interactive units add voltage regulation, correcting minor dips and surges without using the battery, and are the usual choice for small office comms racks. Online or double-conversion units constantly run the equipment from the battery circuit, providing the cleanest power; they suit servers and sites with poor power quality.
Rack-mount models fit neatly into a comms cabinet, while tower models sit on the floor. Many business units include a network management card or USB connection that lets servers shut down automatically when the battery runs low, and lets monitoring systems alert someone when power fails. Check the outlet types on the back match the plugs on your equipment, so you are not tempted to add a power board.
Sizing it properly
Add up the power draw of everything that will plug into the UPS: firewall, switches including their PoE load, internet equipment, any servers or network storage, and the phone system if it is on site. Use the real or rated consumption in watts, then choose a UPS whose watt rating comfortably exceeds the total, leaving around a quarter spare for growth.
Then decide on runtime. Riding through brief flickers needs only a few minutes. Keeping the office online through a longer cut, especially if you have a backup internet connection, needs more battery. Manufacturers publish runtime charts for different loads, and extended battery packs can be added to some models. Remember that the fibre equipment and mobile towers outside also need power.
What should and should not go on it
Connect the network core: firewall, switches, fibre or internet equipment, backup internet router, and servers. Phones and access points are covered automatically if they are powered by a PoE switch on the UPS. Network storage should be on it so it can shut down cleanly. Cameras and their recorder are worth including if footage during a power cut matters to you.
Do not plug in laser printers, heaters, kettles or other high-draw devices. Laser printers in particular draw large bursts of power when warming up and can overload a UPS or drain its battery quickly. If the comms cupboard needs extra power outlets for the UPS, a registered electrician should install them.
Batteries wear out
UPS batteries are consumables. Most last three to five years, less in a hot comms cupboard. As they age, runtime shrinks, and eventually the UPS may fail exactly when it is needed. Many units run self-tests and show a warning when the battery needs replacement, but those warnings are easy to miss if the UPS is in a locked cupboard.
Record the battery installation date in your documentation, check the UPS status as part of routine maintenance, and replace batteries on a schedule rather than waiting for them to fail. Dispose of old batteries through a proper recycling service, as they contain lead or lithium. A replacement battery costs far less than the equipment it protects.
Testing and monitoring
Once a year, test the UPS under real conditions by switching off its input after hours and confirming the equipment keeps running and that any automatic shutdown works. Make sure the UPS alerts someone when it switches to battery, ideally through the same monitoring that watches the rest of the network.
A UPS that has never been tested, has a dead battery or is overloaded gives a false sense of security. A few minutes of care each year means it does its job on the day the power drops in the middle of a busy morning. Add the test to the same calendar as the failover test and the fire drill, so it happens without anyone needing to remember.
In short
- A UPS protects network gear from cuts, brownouts and surges.
- Line-interactive units suit most small office comms racks.
- Size for total watts plus a quarter spare, then choose runtime.
- Never plug laser printers or heaters into a UPS.
- Replace batteries every three to five years and test annually.