Automatic Transfer Switch: The Ultimate Guide

Home Automatic Transfer Switch: The Ultimate Guide

For transferring significant load connections, automatic transfer switches are a dependable source. Between the primary power source and the backup power source, a transfer takes place. Alternative energy sources are used in data centers, industries, and other facilities that must continue to function regularly. They utilize it for things like generators or any backup utilities when the main source is unavailable. An automatic transfer switch will tell the generator to start and back up a residence as if nothing happened during a blackout. Everything that is needed to know about automatic transfer switches will be covered below.

What is An Automatic Transfer Switch?

Operating an automated transfer switch
Source: Pinterest

When it detects a failure or outage in the primary source of power, an automated transfer switch (ATS) automatically switches the power supply from the primary source to the backup source. The ATS activates a standby power source, such as an uninterruptible power supply, when a primary power system fails. In order to run electric equipment until grid power is restored, an ATS can also start up longer-term backup power systems, such as nearby diesel generators.

The ATS functions as an electrical relay between the equipment and the power supply because it is linked to both the primary and backup power sources.

How Does It Work?

The automatic transfer switch is an intelligent power switch device that operates independently and is predominated by the control logic. Continuous power delivery is the basic goal of automated conversion. Its role is to connect the connected load circuit to one of the two power suppliers.

ATS is a useful mechanism, but it also exists to guard against minor power outages and interference with your operations. According to the requirements of the building, the size of the generator and ATS are chosen. 

Automatic transfer switches allow intelligent backup and power transfer that ensure business continuity. Additionally, it aids in averting costs that might be incurred as a result of environmental dread, including those associated with heavy industry, business, or even deadly hospital failures.

On a microprocessor, the automatic controller or control logic is built. The voltage and frequency of the two power sources, which serve as the primary and backup power sources, are continuously monitored. Should the power source fail, the ATS may be able to draw electricity from another source. By default, the majority of ATSs look to connect to the main power source. They are connected to a backup energy source, but only when necessary or required. The operation of automatic transfer switches is based on this idea.

Available Electrical Arrangements

ATS system for generators
Source: Pinterest

Multiple configurations are possible with both two and three power sources.

Two Power Sources


A generator for backup power and an electric utility service are both included in the typical transfer switch setup. A typical name for this system configuration is an emergency standby generator system. A number of engine-generator sets may be functioning simultaneously under the appearance of a single generator.


The utility case uses two utility sources that help provide redundancy and speedy service restoration to the distribution system to the load if there is an upstream equipment failure. The two sources aren’t dependent on one another, which means that there would be two electric services provisioned by the public utility provider. 


Transfer switches are used to switch the main power between two sets of generators, particularly in remote areas. The generator may need to provide constant electricity in remote areas because they experience frequent power cuts. 

Three Power Sources


When installing an emergency standby generator system, critical facilities will frequently include provisions for a second generator connection to act as a redundant emergency backup that can be used during bad weather or when the first generator is undergoing planned maintenance.

As demonstrated, the first generator is sometimes fixed onsite permanently while the second generator is a portable roll-up model that is only used when necessary.


This system adds an emergency standby generator supply to the redundancy offered by a dual utility setup. As demonstrated, the generator can be shared across several transfer switches using a priority management system, or it can be designated for use by a single transfer switch.

Different Types of Automatic Transfer Switches

A transfer switch produced by Beny
Source: Beny

There are four different types of transfer switch systems, and you can select the one that best meets your demands. All of them are working toward the same end result, which is to keep power safe. However, each of these systems complies with different standards and can be used in a variety of ways. Therefore, to decide which kind of system is ideal for your building, you need to speak with an expert.

Open Transition ATS

The first-break or open-transition approach is popular in the system. Dealing with power outages of a little duration is beneficial. Instead, they alternate between utility and reserve power. The one-second delay aids in a secure transfer. It guarantees that no one using the gadget nearby will have their utility endangered. 

A programmable transition switch is another form of this sort of ATS. Between mains and generator power, there is a pause that allows the circuit’s residual voltage to deplete before power is restored.

Closed Transition ATS

This kind of technology can be used in locations where the product’s maker will not accept any disruptions, no matter how small. Internal processes built into the closed transition ATS will enable simultaneous activation of both power sources. People can transition smoothly as long as they uphold safety requirements. It is much more expensive than current transitional systems, though, given the intricacy of these systems.

Soft Load Transfer Switch 

A closed transition ATS is comparable to the soft load transfer switch. It does, however, have the ability to change how much load it can handle depending on the circumstances. There is an additional charge for this skill. However, it gives businesses more options in scenarios where extra backup power is required.

Bypass Isolation ATS

Although this system is the most complex, its capabilities are the highest. It comprises two systems that often operate concurrently and allow for inspection and maintenance. The most delicate area is typically where people may notice this setting. This system consists of telecommunications, air traffic control, life support systems, and other priority settings.


An automatic transfer switch has advantages that can be reaped by any firm, no matter how big or little. And our group promises that the expense is well worth it. However, certain companies come to mind when you think of an automatic transfer switch, such as:

  • Hospitals
  • Governmental structures
  • Commercial buildings 
  • Factories 
  • Warehouses
  • Restaurants
  • Schools

Why Do We Need It?

Automatic transfer switch in display
Source: Pinterest

A transfer switch improves efficiency and assurance for your company. You will benefit from selecting the appropriate switch for your purposes if:

Power Security

Your business comes to a complete halt if you lose access to power for whatever reason. Although a generator might somewhat minimize this, you still need to physically connect your generator to the operations you want to resume. This task not only takes a lot of time and causes downtime, but also restricts how well your generator works. 


Handling any power source at all can have negative effects. An unexpected power outage can be dangerous for workers, and managing a manual generator hookup can be disastrous—especially at night! Your whole needs are met by a transfer switch, which completely eliminates the risks connected with an outage.

The NEC mandates a transfer switch for any electrical connection to a house. The only secure method of connecting a generator directly to your home is by using an ATS. Your house is separated from the power lines by an automatic transfer switch. By doing this, back-feed—which happens when the power flows back down utility lines—is avoided. 

Backfeed has the ability to start fires in addition to harming the generator. Even worse, back-feed might electrocute personnel trying to restore utility power who are working on the power lines, injuring or even killing them.

Operational Simplification

The quickest and safest way to connect a generator to your house is via a transfer switch. Especially during a power outage, running extension wires to and from appliances can be an uncomfortable and time-consuming headache. With the aid of a transfer switch, you may quickly and conveniently use your generator to power any appliance in your home’s electrical system. 

A transfer switch is necessary to power certain appliances during a utility power outage since others, such as furnaces or well pumps, cannot be linked to a generator with an extension cord.

You choose which processes to power automatically when you install your automatic transfer switch. Everything from your lighting to HVAC systems, business machinery, or even refrigerators, can fall under this category. This procedure greatly streamlines power restoration and enhances the performance of your generator.

Things To Consider When Choosing An Automatic Transfer Switch 

An automatic dual power transfer switch
Source: Pinterest


The rating type could be a crucial first factor, depending on your project or application. A coordinated circuit breaker rating, which is comparable to a circuit breaker series rating, is used for less competent switches. You can be sure the switch will reach the required short-circuit withstand closure rating if it has a coordinated rating.

It’s a good option as long as you can discover a breaker that can fix a problem in the needed amount of time. This method has a drawback because some projects can be quite “dynamic.” It’s possible that the ATS you specify at the beginning of the project won’t satisfy the demands of the final design. It makes sense to level up your ATS choice to one that carries a time-based rating, formerly known as an Any Breaker rating, in circumstances when that’s a possibility.


With sensors that supply a variety of data, industrial and commercial power distribution and control equipment are smarter than before. This information not only improves operational control but also makes it possible to maintain systems more effectively, increase reliability, and support energy-management plans.

Most switches can be detected from outside. That gives the required data but necessitates extra hardware and connections for external meters, adding complexity. Devices with sensors built into the container often have a reduced physical footprint and offer better simplicity.

An ATS with sensors that keep track of current, voltage, harmonics, and other power quality factors is available. You can also get temperature sensing with some switches. This information is very helpful in recognizing possible difficulties because high temperature is one of the earliest and most significant signs of power problems. The ability to establish thresholds for each of these measured values is a feature of higher-performing switches. When that limit is exceeded, the switch may sound an alarm, prompting service technicians to look into the matter.


Communication is the last important factor that sets ATS options apart. When the data from the available devices can be disseminated widely, whether it’s within the plant or via the cloud to managers and operators wherever they are, the benefits are substantially increased.

The standard ATS products from the majority of ATS manufacturers rely on Modbus TRU (serial) communication. A higher-level switch is necessary if you desire more flexible communication possibilities. Switches from several OEMs may interact using numerous protocols, including Ethernet IP Modbus TCP, PROFINET, DeviceNet, and Profibus. Your ATS can connect to the cloud via some of these protocols, allowing operators and maintenance managers to get alarms and warnings on their mobile devices.

You might get a headache and cross your eyes after reading the lengthy list of ATS specifications. Fortunately, depending on the application, many of these specifications are simple. There are, however, a select few specifications where you must look past the technical prerequisites and examine whether the chosen device will satisfy your larger strategic needs and organizational goals. To make a wise decision, take into account the adaptability, measurement, and communication capabilities of your available ATS choices.


An automatic switch typically costs between $400 and $2,000, while a manual switch typically costs between $200 and $800.


ATS controller
Source: Pinterest

For their demands, power plants employ enclosed circuit breakers, much as homes do. In increasingly complex configurations, Automatic Transfer Switches are used to suit the special requirements of research or equipment that requires continuous power. These solutions must be used during the generator automatic switch installation process to cater to the specific requirements of homes and buildings.

For the facilities themselves, electrical engineers might build control rooms for a variety of uses, such as in hospitals or data centers. These could also be utilized in alarms that monitor buildings for fires, hazardous ventilation that removes harmful compounds from rooms, and emergency lighting that directs people to escape as necessary.

These automatic switch systems may employ alerts that signal diminished power. When creating the generator automatic transfer switch installation, this instructs the switches to turn on the backup generators. Once they have done so, the settings then distribute power throughout the facility.

All businesses strive to provide transfer switch products for various applications and to service and maintain them after installation.


The interaction diagram of an ATS between the generator and the main grid power
Source: Pinterest
  • Visual scrutiny on the outside. Look for any visible indications of wear or damage. Make careful to have the unit replaced or repaired right away if there are any cuts or breaks in the lines or damage to the unit itself!
  • Look for moisture indicators. Serious risks can arise from accumulated moisture brought on by excessive humidity levels or interaction with outside sources. Never try to activate a transfer switch that is wet or damp. Find the moisture source and deal with it right away.
  • Watch for indications of extreme heat. Cracking, deformation, contact damage, and discoloration are all indications that your automated transfer switch is operating at an excessively high temperature. Make an appointment with a specialist as soon as any signs of overheating are discovered.
  • Elimination of dust. Dust might obstruct connections and lessen your ATS’s efficacy. Use a vacuum or other comparable instrument to get rid of accumulated dust and dirt. Please stay away from using compressed air! While these are quick and simple tools for dust removal in some situations, you are more likely to shove dust into critical components with anything delicate like a transfer switch where it will stay lodged and cause issues.
  • Your transfer switch needs cleaning. Never clean electronic components with moist products. Use a recognized industrial solvent instead. Make sure to completely remove any accumulated debris, grime, or foreign objects.
  • Verify contacts. Corrosion symptoms are common in small amounts, but once erosion is visible, it may be time to replace the contacts or the ATS altogether.
  • Plan a professional visit. Despite being quite simple, these checks are really crucial. To be sure your system is receiving the attention it needs, choose a qualified electrician or staff members who have received special training in transfer switch maintenance.

Tests To Run While Maintaining An Automatic Transfer Switch

Working of ATS
Source: Pinterest

When completing annual automatic transfer switch maintenance, be ready to test the switch in a number of ways to make sure it’s in good working order. These tests consist of:

  • To make sure that dc millivolt and microhm drop values don’t go above the upper limits of the typical range specified by the switch manufacturer, do a contact/pole-resistance test. If you are unable to locate this information in published form, keep an eye out for any values that deviate by at least 50% from similarly situated poles or switches.
  • Use a thermographic survey, a low-resistance ohmmeter, or the calibrated torque-wrench approach to examine all bolted electrical connections. Keep an eye out for unusually high resistance and be ready to investigate any values that are greater than 50% of the lowest recorded value. Check to see if the bolt/torque levels correspond to the manufacturer’s stated data as well.
  • Complete a number of automatic transfer tests, and then watch how the transfer switch behaves in the simulated situations of a total loss of normal power, a re-energized normal power source after an outage, a total loss of emergency power, and various single-phase conditions. As you continue the automatic transfer switch maintenance cycle, look into any issues or anomalies.
  • Test the transfer switch’s timing and functionality by completing a number of tasks. Transfer time delay, engine starting, frequency- and voltage-sensing relays for normal power sources, frequency- and voltage-sensing relays for emergency power sources, re-transfer time delay when normal power is restored, automatic transfer functionality, limit switch function, interlocks, and full engine cool down and shutdown should all be tested. Please be aware that all testing results must correspond to the system’s and the manufacturer’s design requirements. As you carry out the rest of the automatic transfer switch maintenance, look into any issues and anomalies.
  • Make sure all transfer switch controls are set up and functioning according to the manufacturer’s recommended settings. Check the settings on each connected timer and make any necessary modifications.


Between primary and backup electrical power sources, important load connections can be safely transferred using low-voltage automatic transfer switch assemblies. When their regular (primary) power supply becomes unavailable, data centers, hospitals, factories, and a wide range of other facility types depend on an emergency (alternative) power source, such as a generator or a backup utility feed.

For years, Beny has offered high-quality automated transfer switches and other energy solution products to commercial enterprises of all sizes. We understand the value of dependability and reliability in your goods and services as a family-run company, and we constantly strive to be the best. Contact Beny for high-quality automatic transfer switches.

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