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  • UPS Bypass Switch Guide: How do they Work? | UPS System

UPS Bypass Switch Guide: How do they Work? | UPS System

What is a Bypass Switch?

A bypass switch is a non-essential addition to an uninterruptible power supply system that, while not integral to UPS operation, is definitely useful in the event of maintenance or repair. The core items you need in order to be protected in the event of power failure are a UPS and a battery to supply the power, under standard operation this should be all that is required. However, if there is a fault or you need to remove a unit for repair, a bypass switch ensures that power continuity is maintained in the event of a failure.

UPS bypass switch wiring diagram

How many types of Bypass Switch exist?

There are two main types of bypass switch that serve similar but distinct functions. These are the static bypass switch and the external maintenance bypass switch.

  • The static bypass is used as a failsafe for the inverter, if the inverter should fail the load will drop automatically onto the mains input feed which ensures continuous power. This switch is fitted to almost all on-line UPS systems as an added safety measure to ensure power remains continuous.


These are nearly always part of the UPS’ internal circuitry, with an external switch in case you need to manually invoke it. This isn’t ideal for repairing purposes as the bulk of the UPS is still connected to the power but is a great way to protect from inverter failure.


  • The external maintenance bypass switch is attached to the outside of UPS and is sometimes referred to as a wraparound bypass for that reason. This bypass is used in order to continue the flow of power while the UPS is isolated and easy to remove for repair. The alternative is to power down the entire network in order to remove the UPS which, for some businesses, may mean several hours downtime and cost them significant sums. Additionally, In the unlikely event your UPS itself experiences a fault, this switch makes sure that the load is transferred safely and leaves the unit easy to remove and replace.


How important is a UPS bypass switch?

A bypass switch is considered non-essential as the system will function without one, but the benefits of having a bypass switch is considerable. Without a maintenance bypass switch, the only way to repair or service your UPS system is to shutdown the power completely and can lead to a sustained period of downtime. If you’re working in a mission-critical environment, any period of downtime can have dire consequences and having a bypass switch is almost as important as having a UPS in the first place.


How do I know if my UPS has a bypass switch?

If your system comes with a static UPS switch it will be clearly labelled on the product description, it general comes as standard with an on-line UPS but it’s worth making sure.

A maintenance bypass switch of the external variety will need to be bought separately in most instances and fitted by one of our technicians. If your systems are mission-critical, we will likely advice fitting an external switch when you first purchase your UPS system and which product is the best fit for your needs.

For help and assistance with all your standby power requirements, please contact us via telephone or via our online contact form or let us call you back.