The Ins and Outs of Automatic Transfer Switches

The Ins and Outs of Automatic Transfer Switches

A transfer switch moves an electrical load to alternate between two different power sources. With the help of these switches, you can safely connect or disconnect different power sources from an electrical load. But, while not using them, you must properly isolate power sources and control transitions from one source to another. There are two main categories of transfer switches: manual and automatic. Automatic switches activate themselves if one of the power sources experiences a change in voltage, whereas manual ones need human intervention. Let’s check out more important facts about automatic transfer switches.

What is an automatic transfer switch?

A low-voltage automatic transfer switch is a reliable way to move important load connections between main and backup power sources. Facilities that need continuous uptime, such as data centers, hospitals, and factories, usually have a backup utility feed or generator in case their main power supply goes out. If the main power fails, this switch will activate a secondary power source, such as an uninterruptible power supply (UPS). This is when a medium voltage automatic transfer switch acts as a relay, connecting the equipment to the power source. When the backup power source’s power is steady and within the acceptable voltage ranges, the transfer switch moves the load to that source. Also, the transfer switch can smoothly transfer the load from the emergency power source to the normal one when the utility power comes back.

How to install it?

The instructions for setting up an automatic transfer switch from various manufacturers could vary. Before the procedure, read the instructions carefully. 

Find the right automatic switch location

Choosing the right location for ATS is the first step, especially when installing one for generator backup. If an emergency happens, you should be able to find it close to the main breaker panel and easy to reach. You should position the solar transfer switch next to the solar inverter. Ensure that the switch is situated at an appropriate height and clear of any potential hazards. The standard advice for the mounting location is 18 inches from the service panel’s center. However, this can change based on the circumstances of the installation.


This procedure can be rather delicate since you will be handling electrical lines and potentially high voltages. If you’re not sure how to perform this task, consult a licensed electrician. The ‘Line’ terminals of the ATS are usually connected to the power supply, while the ‘Load’ terminals are used to connect the load. You often only need to attach the wires to the right connections when using an auto-transfer switch since it comes pre-wired.


After these steps, you should set up the switch. The details of this process are in the manufacturer’s user manuals. When you install ATS, be sure to follow these steps exactly. First of all, you must understand how to mount. You can install the transfer switch in many ways because some will need housing, while others, like the solar transfer switch, could already have cables attached.


It is important to test the ATS after installation to ensure it is functioning properly. Before activating it, make sure you turn on all the lights and appliances in the house. They should continue to work if there is a power outage. Remember that it is essential to install the transfer switch appropriately to avoid any potential safety hazards. 

How does it detect a power loss?

The incoming and outgoing lines notify the automatic transfer switch when the power goes off. A voltage sensor watches the incoming line to ensure the system gets enough voltage to work safely. If the power is lost, a warning will go out, and the ATS will activate the backup generator. A frequency sensor retains a focus on the outgoing line to check whether the gadget is safely producing adequate frequency for operation. If the frequency is not right, there will be a warning, and the ATS will begin to transition the backup generator.

Types of Automatic Transfer Systems

Open transition switch

With this type of switch, systems can manage the short power outage that occurs while transferring from grid power to local backup power. This pause, which is usually less than a second, permits a secure transfer. Programmed transition switches are a kind of ATS that halt while switching between utility power and generator power. 

Closed transition switch

The closed transition ATS serves best in places where even a short power outage would be a disaster. These ATS mechanisms use two power sources at once and facilitate a smooth transition while preserving safety requirements. However, they are more costly and complex.

Soft loading switch

The soft loading transfer switch can adapt the amount of load it carries depending on the case. This dynamic system gives companies more time if they have to deal with more cases that might need backup power. 

Bypass isolation switches

These are the most advanced and technically demanding systems available today. It usually involves a pair of systems working together for on-the-fly testing, maintenance, and inspection. They are vital for settings that include life support, telecommunication, air traffic control, and other sensitive areas.

When should you use them?

A transfer switch is an excellent backup power source for any commercial building that can experience a power loss. It also has many applications in hotels and other settings where people can weather power disruptions with ease and efficiency. It is especially important in institutions like hospitals, data centers, and telecom facilities. ATS minimizes downtime, protects data loss or equipment damage, and provides a smooth transition between main and backup power sources. This can guarantee operating stability and protect sensitive equipment and systems.


Giving your house or company electricity in case of a blackout or other electrical issues can greatly help. A generator is the way to go for this task. Power generators can temporarily replace the city’s or utility plant’s power supply by producing electricity from a fuel source, such as natural gas. Before choosing the right ATS model, you should carefully consider your needs and choose the best option. 


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