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ITGlossary · UPS technology
Maintenance Bypass
A manual switch used to isolate the UPS for servicing while still supplying power to the load.
Technical level:Intermediate
The maintenance bypass switch transfers the load directly to the mains, bypassing the UPS electronics completely. A technician can then switch off, inspect or even remove the UPS while the equipment keeps running. It can be built into the UPS or fitted in an external panel, which also allows the unit to be replaced entirely.
It is essential for a UPS that supplies equipment which must not be shut down, such as servers, telecoms or industrial production lines.
While in bypass, the load is unprotected against outages and fluctuations. Follow the manufacturer's switching sequence strictly: the wrong order can drop the load or damage the UPS.
Related terms
- IsolationSeparation of input and output with no conductive connection, usually through a transformer, to protect against faults and noise.
- BypassA path that feeds the load directly from the mains, without protection, when the UPS is overloaded, faulty or under maintenance.
- Redundant Power SupplyA second power supply inside a server or switch that takes over without interruption if the first one fails or loses its feed.
- Double Conversion EfficiencyThe share of input power that an online UPS delivers to its output, lower at light load and highest at medium to high load.
- IEC C19/C20 ConnectorsPair of connectors rated up to 16 A under IEC 60320, used on higher-power UPS units, rack PDUs and servers or switches with high-consumption power supplies.
- Offline (Standby) UPSA UPS that leaves the load on the mains and switches to battery only when the mains fails, with a short transfer time; the simplest and cheapest topology.