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ITGlossary · Protection and installation
Overload
A condition where the connected load exceeds the UPS’s rated output in VA or W.
Technical level:Intermediate
When the equipment connected to a UPS draws more power than its VA or W rating, the UPS is overloaded. An alarm usually sounds and an indicator lights up; most models tolerate a small overload for a few seconds or minutes, depending on its size, and then switch to bypass or shut down the output.
Importantly, an overload while running on battery cannot be handled by bypass, so the load goes off. A heavy load also shortens runtime noticeably and stresses the batteries.
A practical tip: do not connect laser printers, heaters or other devices with high inrush or peak currents to a UPS, and keep the continuous load at around 70–80% of the rated capacity to leave a safety margin.
Questions that mention it
All frequently asked questionsCan a system shut down or restart while connected to a UPS?
There are two scenarios: 1) UPS overload → degraded operation; avoid it by choosing the right specifications and watching the indicators. 2) Battery discharge → reduced runtime. Charge for 8-9 hours before first use, then for 4-6 hours, and recharge immediately after a full discharge.
What is a Static Transfer Switch (STS)?
An STS automatically transfers loads from the main source to the backup source when the main one fails, within a few milliseconds, a gap server power supplies ride through without interruption. It has overload and short-circuit protection.
Related terms
- BypassA path that feeds the load directly from the mains, without protection, when the UPS is overloaded, faulty or under maintenance.
- Capacity SystemParallel UPS units that share the load with no spare unit (N configuration), so the failure of one unit overloads the rest.
- Static BypassAn electronic path inside the UPS that instantly and automatically transfers the load to the mains on overload or internal fault.
- Altitude DeratingReduction in the rated power of a UPS, inverter or generator when it is installed above a certain altitude, usually 1,000 metres.
- Ambient TemperatureThe surrounding temperature of the environment where UPS or batteries are installed.
- Emergency Power Off (EPO)A safety feature that allows immediate shutdown of power to connected systems in an emergency.