A power cut or voltage drop can damage a server disk, a database or a video recorder. VA vs W, runtime, UPS types and automatic shutdown — explained simply.
A power cut in the office usually means two things: unsaved documents and, worse, a server that shut down “unexpectedly”. That can corrupt a file system, a database or a recorder’s archive. A UPS (uninterruptible power supply) reduces that risk.
What a UPS protects against
- Power cuts — the battery keeps equipment running, depending on the model and the load;
- Voltage drops and surges — voltage is stabilised before it reaches your equipment;
- Brief flickers — devices don’t reboot.
VA vs W — what’s the difference
A UPS lists two numbers: VA (apparent power) and W (real power). Equipment load is measured in watts, so check the W rating rather than relying on VA alone. Leave headroom on the total load — don’t run a UPS at its maximum.
How long should it run
In most offices, the goal of a UPS is not to run for hours, but to:
- Ride out short outages;
- During a long outage — shut down the server and NAS cleanly and automatically.
Runtime depends on the load and the battery — it’s in the manufacturer’s tables, or we can size it for your equipment.
UPS types
- Line-interactive — regulates voltage and switches to battery during an outage; a typical choice for office equipment, networks and small servers;
- Online (double conversion) — equipment is always powered from the UPS inverter, so switching to battery is seamless; for critical servers and unstable power grids.
What to plug into the UPS
- The server and NAS;
- Network equipment — router, firewall, switches (otherwise the server stays up but the network doesn’t);
- The video recorder and the PoE switch that powers the cameras.
💡 Automatic shutdown: enable the UPS’s USB or network management so the server and NAS shut themselves down properly before the battery runs out. Without it, a UPS only “postpones” a hard shutdown.
The battery is a consumable
UPS batteries wear out over time. Regularly check the UPS self-test result and replace the battery as the manufacturer recommends — otherwise, when the power goes, the UPS might not last even a few seconds.