What a UPS is for
An uninterruptible power supply (UPS) sits between the building's power and your critical equipment. It does two jobs: it carries the load on battery when power fails, and depending on type, it cleans up the sags, surges and noise that happen every day.
A UPS is not a generator replacement. Its battery usually runs for minutes, not hours. Its purpose is to keep equipment running through short blips, allow an orderly shutdown, or bridge the gap until a standby generator starts.
Typical protected loads in Edmonton businesses include servers and network gear, phone systems, point-of-sale terminals, security and access control panels, medical and lab equipment, and PLCs and controls on production lines.
Even businesses with a standby generator need a UPS. The generator takes several seconds to start and transfer, and that short gap is enough to reboot servers, drop calls and corrupt data in the middle of a write.
The three common types
- Standby (offline): the cheapest and simplest. Fine for a single workstation. There is a brief transfer when it switches to battery.
- Line-interactive: adds automatic voltage regulation, so it handles sags and swells without using the battery. A good fit for small server closets and network racks.
- Online double-conversion: the load always runs from the inverter, so there is no transfer gap and the output is fully regenerated. The usual choice for server rooms, sensitive equipment and anything fed by a generator, whose output can wander in frequency.
UPS units are rated in both VA and watts. Size to the watts your equipment actually draws, with headroom, and check that the VA rating also covers it.
Sizing for runtime
Runtime depends on load and battery capacity. Halving the load more than doubles runtime on many units, so it pays to protect only what truly needs it.
- List the equipment that must stay up and its power draw (from nameplates or, better, measured).
- Decide what the UPS must achieve: ride through blips, shut servers down gracefully, or hold until a generator starts.
- Pick a runtime target for that goal, then size the UPS and any external battery cabinets with growth headroom.
- Set up shutdown software so servers power down cleanly before the battery runs out.
Leave room to grow. A UPS running near its full rating has little runtime and no space for the next switch or server. Many businesses size for their current load at around half to two-thirds of the unit's capacity, then confirm with the manufacturer's runtime charts.
Electrical work around a UPS
Small plug-in units just need a suitable receptacle. Larger rack and floor-standing units are hardwired and need proper electrical design.
- Dedicated circuits sized for the UPS input, with the correct receptacle or hardwired connection.
- Maintenance bypass switch so the UPS can be serviced or replaced without shutting down the load.
- Output distribution to racks through PDUs, ideally with A and B feeds for equipment with dual power supplies.
- Bonding and grounding done properly, which matters for both safety and data integrity.
- Heat and ventilation, since UPS units and batteries both give off heat, and batteries last longer when kept cool.
- Generator compatibility when a standby generator feeds the UPS.
See powering a server or data room for the bigger picture.
A UPS output can be energized even when its input breaker is off. Only trained personnel should open UPS or battery cabinets.
Batteries and maintenance
Most UPS failures are battery failures. Sealed lead-acid batteries wear out over a few years, faster if the room runs hot. Lithium-ion options last longer but cost more upfront.
- Run periodic self-tests and act on alarms.
- Track battery install dates and replace on the manufacturer's schedule.
- Keep the UPS on a network card or monitoring so alerts reach someone.
- Recycle old batteries properly. Do not put them in regular waste.
A UPS that alarms quietly in a locked closet is not much help. Make sure someone receives its alerts, and that the self-test results get looked at. A battery that fails its test should be replaced promptly, not at the next budget cycle, because the next outage will not wait.
When replacing batteries, plan the work for a quiet period and use the maintenance bypass if the UPS has one, so critical equipment stays powered.
Getting it right the first time
A good UPS project starts with a short assessment: what must stay on, for how long, what is on the circuit now, and whether a generator is part of the plan. Our UPS systems team installs, wires and commissions units, and works with your IT provider on monitoring and shutdown.
If you are also weighing a generator, read sizing a backup generator.
Common questions
How long will a UPS run my server?
It depends entirely on the load and battery capacity. Most rack UPS units are sized for several minutes to allow shutdown or generator start; longer runtimes need external battery packs.
Do I need an online UPS?
For servers, sensitive electronics and anything fed by a generator, online double-conversion is usually recommended. Line-interactive suits small network closets and point-of-sale.
Can I plug a UPS into a power bar?
No. Plug it directly into a suitable receptacle, and do not plug another UPS or a space heater into its outputs.
How often do UPS batteries need replacing?
Lead-acid batteries typically need replacing every few years, sooner in warm rooms. Follow the manufacturer's guidance and the unit's battery test results.
Codes and permit rules change and every building is different. For work on your system, talk to a licensed electrician and your local permit authority.