What Is an Automatic Transfer Switch (ATS) and Why Does Your Business Need One?

Power outages can bring your operations to a halt, costing time, money and productivity. An automatic transfer switch (ATS) protects against this risk by automatically switching your power supply from the mains to a standby generator when an outage occurs.

An ATS keeps your business running smoothly by ensuring a continuous flow of electricity without manual effort or delay.

You'll use many systems that depend on a steady power supply, from computers and servers to lighting and security equipment. When the main power fails, an ATS detects the problem and transfers electricity from your main power source to your backup system within seconds. This rapid response helps prevent data loss, equipment damage and costly downtime.

Here, we'll cover how automatic transfer switches work and why they are essential for business continuity. Understanding their role helps you make informed decisions about protecting your business from unexpected power failures.

Understanding automatic transfer switches

A reliable automatic transfer switch (ATS) ensures your electrical system keeps running when the main power fails. It detects supply loss, switches to your backup source and restores normal operation once the mains return. You can choose from several types and designs, each with specific components and control technologies that support safe, continuous power transfer.

What is an automatic transfer switch?

An automatic transfer switch (ATS) is an electrical device that automatically shifts power from the mains supply to a standby supply, such as a standby generator or UPS, when it detects a power failure. It restores the connection to the primary source once stable power is available again.

You can think of it as a motorised changeover switch that keeps your electrical equipment running without the need for manual intervention. The ATS monitors voltage and frequency from both sources to ensure a safe transfer.

In business settings, an ATS protects critical systems to ensure your business doesn't lose access to them in the event of a power outage. Its main purpose is to minimise downtime and prevent damage caused by sudden power loss.

How automatic transfer switches operate

An ATS works through a sequence of transfer switching operations. It continuously monitors the electrical power from the utility supply. When it detects an outage or abnormal voltage, the ATS sends a signal to start the backup generator or switch to a UPS.

When the mains return, the system automatically switches back. This process happens in seconds, maintaining a seamless power flow.

There are two main transfer modes:

• open transition, where power disconnects briefly before switching
• closed transition, where both sources overlap for a controlled period to maintain continuity without causing back feed.

Why your business needs an automatic transfer switch

An automatic transfer switch (ATS) keeps your operations running when the mains power fails. It protects electrical systems, supports compliance with safety standards and helps maintain the reliability of mission-critical equipment.

Business continuity and mission-critical applications

Power interruptions can halt production lines, disable IT equipment and disrupt healthcare services. An ATS automatically transfers the electrical load to a backup generator when it detects a fault or blackout in the main supply. This switch happens within seconds, keeping essential systems such as servers and lighting operational.

For businesses that rely on continuous operations, like hospitals or data centres, an automatic transfer switch is non-negotiable. The ATS works with uninterruptible power supplies (UPS) to provide layered protection. The UPS covers the short gap before the generator takes over, preventing data loss and equipment shutdown.

A well-configured ATS also supports load shedding, prioritising critical loads and reducing strain on backup systems. By maintaining steady voltage and frequency, it protects electronic drives and sensitive control systems from damage during transitions and generator synchronisation periods.

Compliance and safety considerations

Installing an ATS can help you meet important safety and performance standards such as BS EN 60947-6-1, which define the requirements for transfer switching equipment. Facilities that include emergency lighting, alarms or fire suppression systems must also comply with BS EN 8519, which covers fire-resistant power and control cable systems used for life-safety applications.

Using an ATS reduces the risk of short circuits and unsafe manual switching. It ensures that only one power source connects to the load at a time, preventing back feed into the utility grid.

Many ATS units include auto mains failure (AMF) control modules, which monitor voltage, frequency and phase conditions. These modules automatically start and stop the generator when needed, improving safety and reducing manual intervention.

Selecting the right automatic transfer switch

When choosing an ATS, consider your load type, supply voltage and environment. For industrial sites, a motorised switch offers precise control and remote operation. Smaller facilities may prefer a compact unit.

Enclosure type also matters. A steel enclosure provides strength and durability, while a polycarbonate enclosure offers corrosion resistance for outdoor or humid environments.

If your business integrates renewable energy, some ATS systems can connect with interface with solar inverters or battery storage systems for hybrid power setups.

Installation and maintenance best practices

Proper installation ensures long-term reliability. The ATS should be installed close to the main distribution board and connected through a circuit breaker rated for the system’s current capacity.

Routine testing verifies that your ATS operates correctly during an outage. You should inspect mechanical parts, tighten terminals if required and carry out functional and on-load transfer tests at least twice a year, ideally alongside generator maintenance.

Keep the enclosure clean and ensure the seal remains intact to maintain ingress protection. Regular software updates for AMF modules and monitoring systems help you track performance and detect issues early.

By following these practices, you reduce downtime, protect your assets and maintain compliance with both electrical and environmental standards.

Frequently asked questions

An automatic transfer switch (ATS) helps your business maintain power during outages, protects equipment from voltage issues and ensures safe transitions between power sources. It also requires proper selection and maintenance to match your electrical setup and operational needs.