An Automatic Transfer Switch (ATS) is the device that keeps your lights on when the grid goes down.
It constantly monitors your main power source and, within seconds of detecting an outage or voltage drop, it automatically routes electricity from a backup generator or battery system.
When utility power returns, the ATS seamlessly shifts the load back, ensuring your home or business experiences virtually no interruption.
In the following article, we’ll explore exactly how an ATS does this, the different switch-over methods available, and why choosing the right ATS is critical for uninterrupted power reliability.
The primary function of an ATS is to monitor the main power source and identify supply issues, including outages, surges, and dips. If it notices any instabilities, the ATS will activate and connect your backup power supply:
Although this process may seem drawn out, it typically occurs within a matter of seconds. So, any operational downtime is negligible, making ATS devices integral for homes and businesses that require constant power.
Each transfer sequence of an ATS is programmed to ensure reliable and safe switches between power sources. Here’s how the stages work.
When a normal power supply is available, the ATS assumes a more background role. It continues to monitor the utility source’s frequency and voltage, ready to identify any fluctuations or instabilities. Your generator will remain on standby when your normal electricity supply is steady.
If the ATS detects a loss of power, or drops or surges in the frequency/voltage, it will react. Most Automatic Transfer Switches can detect issues in a matter of milliseconds and will send a signal to your generator, asking it to start up.
The generator will initiate its start-up cycle, which can result in a short delay. It needs to reach its optimal operational speed, and the voltage must be stable. Once this happens and the generator is stable, the ATS will be ready to begin the load transfer.
The ATS transfers the utility load to your generator using exact timing to reduce the risks of electrical hazards and backfeeding. It achieves this by disconnecting the utility line and connecting the generator to the load circuit, ensuring stable power delivery.
While the generator runs, the ATS will monitor the utility power to check whether it’s ready to activate. When the utility power activates, the ATS will verify that it’s stable before transitioning back. If it remains stable for a set time (typically five minutes), the re-transfer sequence will begin.
The re-transfer sequence works similarly to the initial load transfer. It disconnects from the generator and reconnects to your utility supply.
The generator will then enter its cool-down mode, which is a vital step as it protects the components and its lifespan. When the generator is cool, it will shut off automatically.
Automatic Transfer Switches have multiple transitions, which suit different load sensitivities and operational requirements. It’s essential to remember that the type of transition you use has a significant impact on the generator’s performance and the safety of your equipment.
There are four main types of ATS transitions:
Open transition is the most common type, as it disconnects the load from utility power and then connects it to the secondary power supply. This process typically takes between one and five seconds and is used for non-essential commercial loads, HVAC systems, and lighting.
Closed transitions have a short power overlap, which ensures there are no delays. They’re particularly beneficial for environments where the slightest loss of power can disrupt operations.
However, the transition is more complex, as both the primary and secondary power supplies must be perfectly synchronised. Examples where closed transitions are used include hospitals and data centres.
As the name suggests, delayed transitions involve a pause between the disconnection of one power source and the reconnection to another. The method is most beneficial for mechanical systems that could suffer damage under stress.
For example, delayed transitions are beneficial for industrial settings with sensitive equipment.
You might hear soft load transfers referred to as load blending or ramping, as they slowly move the load between power sources. The applications for soft load transfers include sensitive electrical equipment and environments that rely on stable voltages.
ATS units can operate in multiple modes, depending on your system’s requirements. These modes include:
Advanced ATS models may offer additional features, including remote monitoring, which simplifies diagnostics and maintenance.
ATS setups differ depending on the sensitivity, size, and complexity of your operating environment. For example, residential applications often have fewer needs than large-scale commercial or industrial applications.
Residential Applications: These ATS units are smaller and come in pre-packaged sets, which can power the entire home or different circuits.
Commercial Applications: Commercial environments require larger-capacity switches that can support multiple power sources. They also have options for both bypass and closed transitions.
Industrial Applications: Industrial environments have high-load systems, and they require power ATS setups. Most facilitate integration with power management systems.
Healthcare Applications: In healthcare environments that must align with strict compliance guidelines, ATS systems require robust safety features and should guarantee an uninterrupted power supply.
Data Centres: Data centres also rely on constant operation, which means that ATS systems use soft load or closed transition modes to avoid disruptions.
Solent Power specialises in helping residential and commercial clients benefit from reliable power. Our tailored ATS solutions align with your power needs and give you ongoing peace of mind.
Once you speak to our generator sales team and find a suitable model for your needs, we’ll discuss ATS options and ensure you have access to reliable power.
We’ll conduct a comprehensive site survey and assess your needs based on both current and future backup power requirements. Whether you have a current generator in place and need to add an ATS, or require a complete system, we can support you.
As an authorised distributor of diesel generators and ATS systems, we only stock models from trusted manufacturers. You can also take advantage of a convenient installation service that seamlessly connects the generator and ATS to your systems while ensuring compliance.
Each ATS goes through extensive testing procedures, and our experts will provide advice. This allows you to protect vital equipment and ensure people’s safety.
With a dedicated maintenance service in place, we’ll also address any issues, ensuring you continue to benefit from a reliable backup power source.
If you operate in a highly regulated industry, compliance is essential. For example, the healthcare industry, industrial environments, and even data centres must meet strict legal requirements.
We’ll provide complete documentation of maintenance activities, ensuring your business aligns with requirements.
Automatic Transfer Switches aren’t just components of your backup power supply—they give you long-term peace of mind and can prevent operational downtime. Adding them to an existing or new generator setup gives you more control and ensures power continuity.
Whether you need an open transition switch or a closed transition setup for data centres and hospitals, Solent Power has everything you need. Our experts will assess your needs and develop custom solutions.
Please get in touch with us today for more information, or view our many ATS systems.
Solent Power Ltd (Company Number 12622565) is a company registered in England and Wales. Our registered office is located at Station yard, Bowes Hill, Rowlands Castle PO9 6BP. VAT No. 363504018