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ITGlossary · Protection and installation
Altitude Derating
Reduction in the rated power of a UPS, inverter or generator when it is installed above a certain altitude, usually 1,000 metres.
Technical level:Advanced
With altitude the air gets thinner: it cools electronics less effectively and insulates less well between conductors. That is why manufacturers state full power up to a certain altitude, often 1,000 metres, and above it give a derating table or factor. Generators are affected even more, because the engine gets less oxygen.
In Greece this concerns mountain villages, ski resorts and telecom sites on peaks. A 10 kVA UPS at 1,500 metres may not deliver its full rated power; the exact factor is in the manual.
Size the installation using the power after derating, not the nameplate rating, otherwise the UPS may overheat or overload with loads it would normally cover.
Related terms
- GeneratorAn engine-driven alternator that produces electricity when the grid fails, often started automatically through an ATS.
- InverterThe component inside a UPS that converts DC power from batteries back to usable AC power.
- Ambient TemperatureThe surrounding temperature of the environment where UPS or batteries are installed.
- ATS (Automatic Transfer Switch)A device that automatically moves the load from the grid to a generator during an outage and back again when grid power returns.
- Emergency Power Off (EPO)A safety feature that allows immediate shutdown of power to connected systems in an emergency.
- OverloadA condition where the connected load exceeds the UPS’s rated output in VA or W.