External Maintenance Bypass for UPS – The What & Why

What is an External Maintenance Bypass?

A maintenance bypass allows you to work on the UPS without interrupting power to your equipment. The main purpose of the external maintenance bypass is to isolate the UPS from utility power for service. It is used to redirect power around the UPS when it requires maintenance, repairs, or replacement. The maintenance bypass ensures power is available to the connected load devices or to the power distribution unit(PDU).

An external maintenance bypass unit consists of an NEMA-rated mechanical enclosure that has circuit breakers or rotary switches. This equipment allows for power to pass between it via the UPS and to a power distribution unit or critical loads. It can be mounted onto the wall or be placed in-line within a matching cabinet enclosure as the UPS.

Configurations for External Maintenance Bypasses

External maintenance bypass systems for UPS equipment come in varied sizes, shapes, and ratings. For example the switches utilized could be regular breakers or rotary switches, they could be wall mounted or stand alone, they could have built in distribution, and they could have interlocking circuits to prevent mis-operation, Most importantly is the option of ‘make before break’ and brake before make’ which describes the switching function of the maintenance bypass system.

Make Before Break

A make before break maintenance bypass system is configured in a fashion where the UPS system can be electrically isolated from incoming utility power and the critical loads the system powers. With this system properly configured and installed a UPS & Battery system can be uninstalled and anew replacement system installed without ever taking down power to the critical loads.

Brake Before Make

A brake before make maintenance bypass system is configured in a fashion where the critical load must be de-energized as it disconnects the utility power from the load while isolating the UPS system prior to being able to turn on the maintenance bypass switch to provide utility voltage to the critical load.

Maintenance Bypass Setups

When setting up the maintenance bypass, it will be the first piece of equipment that is directly connected to the available power supply mains. Then the maintenance bypass is connected to both the UPS and to the power distribution unit. There will be an input line and an output line connected between the UPS and maintenance bypass. This setup allows workers to manually control the UPS so it can be de-energized for serviced and repair without impacting the critical load.

Internal Static Bypass Setup

An external maintenance bypass should not be confused with an internal static bypass switch. An internal static bypass switch allows for some maintenance to be performed internal to the UPS. While most of the internal components are de-energized while on internal static bypass, there are still areas within the UPS equipment that are still energized and would not be service able without an outage.

Benefits of External Maintenance Bypass for UPS

The main benefit for external maintenance bypass is to allow the UPS and battery system to be isolated from critical loads for service and trouble shooting. A properly designed and installed UPS system with an external maintenance bypass will provide years of reliable service allowing for battery and aged based component replacements without interruptions to your critical loads.

Facility Gateway Corporation: UPS Maintenance Services

Here at Facility Gateway Corporation, we are a UPS equipment and service supplier. We offer UPS equipment, batteries, capacitor, fans, and part replacement. Our company also provides comprehensive UPS maintenance contracts and emergency services. If you are interested in external maintenance bypass for your backup power systems or want to learn more about our maintenance work, reach out to our company today.