At a glance: automatic transfer switches
- An automatic transfer switch (ATS) helps switch your power supply from the mains to a compatible backup generator when mains power fails.
- With a compatible setup, the generator can start automatically when a loss of mains power is detected.
- When mains electricity returns, the system transfers back and the generator can shut down automatically.
- An ATS can make backup power more convenient, particularly when you want essential equipment to keep running during a power cut.
- Not every generator is ATS-compatible. Check for the correct ATS input and manufacturer compatibility before choosing your setup.
- ATS options are available for compatible petrol and diesel generators, so automatic backup isn't limited to one fuel type.
- An ATS should form part of a properly specified backup-power setup, including a generator with enough output for the equipment you need to run. An automatic transfer switch takes much of the manual work out of using a generator for backup power.
When mains electricity fails, an ATS can detect the change and, with a compatible generator, signal it to start. The system then transfers the electrical load to generator power. Once the mains supply returns, it can transfer back again and allow the generator to shut down.
That means you don’t necessarily need to be there to start the generator and manage the changeover during every power cut.
There are a few important things to get right, though. The generator and ATS need to work together, the generator needs enough output for your backup load and the system needs to be correctly installed.
How does an automatic transfer switch work?
An ATS monitors the mains electricity supply and responds when it detects a loss of power or a change that meets the system’s switching conditions.
With a compatible generator setup, the process typically works like this:
- Mains electricity supplies your property or equipment as normal.
- The ATS detects a problem with the mains supply.
- The ATS signals the compatible generator to start.
- The electrical load transfers to generator power.
- The ATS continues to monitor the mains supply.
- When mains power returns, the load transfers back.
- The generator is allowed to stop.
Our diesel generator ATS, for example, monitors changes in mains voltage and controls the automatic start and stop process when paired with a compatible generator.
For you, the main benefit is simple: the backup system can respond without you having to manually start the generator and manage the changeover.
What is an ATS used for?
An ATS makes most sense when losing power could cause disruption and you want a compatible generator ready to take over.
At home, that could mean maintaining power to essential equipment such as heating controls, refrigeration or alarms during an outage.
Automatic transfer can also be useful in commercial and other settings where having someone manually start and change over a generator every time the mains fails isn't practical.
The important point is that an ATS doesn't create any additional generator capacity. It changes how the backup supply is brought into use.
Can you use an ATS with a petrol generator?
Yes, some petrol generators can form part of an automatic transfer setup, but compatibility is very model-specific.
Don’t assume that any petrol generator with electric or remote start will support ATS. The generator needs the correct ATS connection and the transfer equipment needs to be designed to work with it.
If you’re considering a petrol ATS setup, check the exact generator and ATS combination before buying.
That’s why it’s better to start with the power you need, then identify generator and ATS combinations designed to work together.
What about dual-fuel generators?
If you prefer the flexibility of petrol and LPG, a dual-fuel generator can be useful for backup power because you're not relying on a single fuel option.
ATS compatibility is a separate question, though. A generator being dual-fuel doesn't automatically mean it can connect to an automatic transfer switch.
If automatic backup is important to you, check the ATS specification alongside the generator specification before buying rather than assuming the two will work together.
Can you use an ATS with a diesel generator?
Yes. Compatible diesel generators are commonly used with automatic transfer switches for standby and heavier-duty backup applications.
Our diesel ATS is designed for compatible Warrior/Bimson Power diesel models from 4kW to 15kW, across single- and three-phase setups. Crucially, the generator must have the required ATS input socket.
There are exceptions even within a generator family. For example, our wireless remote-start 6.25 kVA diesel model doesn’t support ATS, while the electric-start version has an ATS input.
That's why it's worth checking the individual specification rather than assuming compatibility based on fuel type or generator size.
What’s the difference between an ATS and a manual transfer switch?
The main difference is how the change between mains and generator power happens.
An automatic transfer switch detects a problem with the mains supply and manages the changeover automatically when used with a compatible setup.
A manual transfer switch requires someone to carry out the changeover manually.
If you want backup power to come into use without you being there to operate the changeover, an ATS may be a better fit. If power cuts are occasional and you’re happy to manage the changeover yourself (perhaps after turning off a few non-essential appliances first), a manual transfer system may meet your needs.
Whichever option you choose, it needs to suit your generator, electrical installation and backup requirements.
Does an ATS start the generator automatically?
With a compatible system, yes. Auto-start is one of the main reasons for choosing an ATS setup.
But there's an important distinction: having an electric-start generator doesn't automatically make it an auto-start generator.
The generator needs the correct ATS connection and compatibility so the transfer switch can signal it to start when mains power fails. Always check for a dedicated ATS input and confirmation that the generator and transfer switch are designed to work together.
What size generator do you need with an ATS?
The ATS doesn't determine how much power your generator can provide. The generator still needs to be sized for the electrical load you want it to support.
Start by deciding what needs to stay powered during an outage. That may be a selection of essential appliances rather than everything connected to the property.
Add up their running requirements and account for any additional starting demand. You can then choose a generator with enough rated output before checking that the generator and ATS are compatible.
This is particularly important with automatic backup. The fact that a generator starts without you being there doesn't remove the need to specify the system correctly.
What should you check before choosing an ATS?
Before putting together an automatic backup-power setup, check:
- Whether the generator supports ATS
- Whether the ATS is compatible with that specific generator
- The generator's rated output
- The electrical load you need to support
- Whether you're working with single- or three-phase power
- The voltage and current requirements of the installation
- Which equipment needs backup power
- How the system will be installed
Don’t choose an ATS just because the connector appears to fit or assume that transfer switches are interchangeable.
Our diesel generator warranty information specifies requirements around the transfer systems used with our generators, so it’s worth checking with us before installing third-party equipment.
Do you need an electrician to install an automatic transfer switch?
An ATS used to transfer power between a mains electrical supply and a generator becomes part of the electrical installation. This isn't a plug-and-play DIY job at the consumer-unit side.
Bimson's ATS is designed to connect with compatible generators using the supplied connection, but installation of the transfer system between the mains supply and household consumer unit needs to be handled correctly.
Use a suitably qualified electrician for installation and make sure the generator, ATS and electrical load have all been properly specified before the system is put into service.
Is an automatic transfer switch right for you?
An ATS is worth considering if you want your backup generator to respond automatically when mains power fails.
It can make particular sense where essential equipment needs a reliable backup supply or where you may not always be there to start the generator manually.
The key is compatibility. Choose the generator based on the power you need first, then make sure the ATS is designed to work with that generator and your electrical setup.
If you're unsure whether an ATS will work with the generator you're considering, use our chat system to help you check compatibility before you buy.
