What is a UPS Bypass Switch?

A UPS 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.

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UPS Bypass Synchronisation

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 generally 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 electrical systems are mission-critical, for example in manufacturing or healthcare, we will likely advise fitting an external switch when you first purchase your UPS system and which product is the best fit for your needs.



How important is a UPS bypass switch?

Our strength lies in our ability to work with you to determine your exact needs for power protection for both now and in the future, and then create a bespoke solution to match your needs and your power strategy in the future. As a UPS Systems customer, you can be assured of the greatest level of service during planning, installation and commissioning of your project as well as being provided with the best level of after-sales care available.

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

UPS Bypass Frequently Asked Questions (FAQ)

What is static bypass?

Static Bypass is the line which effectively joins the input supply to the output and continues to support the load without going through the UPS system.

How does a UPS Bypass Switch work?

UPS Static Bypass switches allow the normal UPS normal operation to be circumvented, in cases of an overload or fault situation. A properly designed system should enable this to be performed without loss of power to the load.

What is UPS Bypass Mode?

UPS Bypass mode is when you switch the circuit from going through the UPS to going around or bypassing it. A manual bypass switch is used to remove the UPS system from the circuit for servicing or maintenance or if it is no longer working correctly. An automatic transfer switch functions in the same way as a manual, but will also switch the UPSs load to mains electric automatically if the UPS experiences an internal failure.

What is bypass switch in inverter?

As a static inverter is a more specialised version of a UPS system it works the same way, the Bypass switch allows a static inverter system to be bypassed if there is an issue or maintenance is required.

What is UPS THDi?

Total Harmonic Distortion (THDi) is a measurement of the harmonic distortion and is the ratio of the sum of the power of all harmonic components to the power of the fundamental frequency. THDi is also used to characterise the power quality of electric power systems and the linearity of audio systems.

Still unsure of some about a UPS Bypass Switch? Contact us and we can help.

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.

Alternativey you can find our range of Riello UPS Bypasses here. 

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