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Automatic Transfer Switch from Retelec

Today we will talk again about a very interesting topic: Automatic Transfer Switch(ATS). And if you don’t know why I mention “again”, it’s because you haven’t seen our first article on this topic. In this article we will make a journey from the classic Network Switching with contactors and relays, to see how to implement an Automatic Network-Group Switching and this time with the manufacturer Retelec.

Let’s get started!

What is Automatic Transfer Switch?

An Automatic Transfer Switch(ATS) is an automated system used in electrical power distribution. This system is responsible for automatically and quickly switching the power supply on a circuit, thus ensuring a continuous and reliable power supply.

When an interruption occurs in the main power supply (Grid) or a failure is detected in it, the switching system automatically activates a backup power supply (Group) to maintain the continuity of the power supply. This process is carried out quickly and transparently, sometimes without users noticing the transition between power sources, depending on the application and the secondary power source.

In addition to providing an uninterruptible power supply, Automatic Network Switching systems can also include monitoring and control functions, which allow monitoring the status of the power supplies, detecting possible failures and automatically triggering the necessary actions to restore the power supply in case of an anomaly.

Automatic Transfer Switch by contactors: Operation and diagrams

Automatic Transfer Switch(ATS) using contactor systems refers to a specific method used to control the transfer of electrical power between different power sources. In this approach, contactors are used as a source of switching force to perform the switching safely.

An Automatic Transfer Switch(ATS) system employing contactors generally consists of at least two contactors connected in parallel, each associated with a specific power supply. These contactors are designed to open and close the electrical circuits in a controlled, independent and counteracting manner (mechanical interlocking), thus allowing the selection of the desired power source. In addition, they usually consist of a device that controls the current supply in both systems, such as a voltage monitor and a relay.

When the power supply in the switching group needs to be changed, the contactor system is activated by a control signal. This results in the closing of the contactors corresponding to the selected power source (mains or group), while the remaining contactor associated with the other power source is opened. In this way, electrical power is safely redirected to the desired new power source.

Automatic Transfer Switch Scheme by Contactors

Conmutación Red-Grupo Contactores
Image taken from

Disadvantages of the systems of Automatic Transfer Switch Scheme by Contactors:

  1. System complexity: Contactor systems can become complex as the number of connected power supplies and loads increases. They require proper contactor configuration and precise interconnection, which means more complexity in design and installation.
  2. Maintenance and failures: Contactor systems may require periodic maintenance to ensure optimal operation. In addition, contactors can suffer wear and failure over time due to continuous use. These failures can cause interruptions in the power supply or even damage connected equipment.
  3. Switching time: Although contactor systems allow fast switching, they may still require some time to open and close the contactors. During this time, there may be a brief interruption in the power supply, which may affect sensitive equipment or cause discomfort in certain cases.

What is Retelec Automatic Transfer Switch?

Retelec’s Automatic Transfer Switch is a monobloc grid switching system that allows automatic load transfer from one grid to another in the event of power failures or interruptions. It is small in size and very easy to connect. When an anomaly is detected, such as a voltage drop or supply interruption, the system quickly activates a switching mechanism that redirects the load to a backup network. This process is done automatically and in real time, ensuring a smooth transition and minimal power interruption.

How to connect the Retelec Automatic Transfer Switch?

Conmutación Automática Red-Grupo Retelec
Mains-Group Power Connection

It has 2 power supply connection modules, which will be responsible for distributing the electricity from both sources, either Mains or Auxiliary Group. As you can see in the previous image we simply have to insert our wires in each phase and neutral and we are ready to work.

In the upper part we have two dry contacts that will give us two quite interesting functionalities.

  • The connector on the left is the dry contact for the on/off command to the generator set. At the moment that the switch detects a failure in the mains supply, it will switch to the genset supply, and at the same time it will close the contact giving the ignition signal to the genset.
  • The connector on the right is a fire signal indicator.

On the front of this ATS we find a switch that will allow us to select the working mode of our ATS Switching. It can be either Automatic (Auto) or Manual.

  • For the first case the system will work without the need for external intervention by anyone.
  • In the Manual mode the system will allow to control the Network-Group switching as desired by operating the round handle that we have in the front section of the device.

Finally, in the lower front section of our Switchgear, we will have two connectors for status signaling lamps. These lamps can be connected to externalize indicative signals outside the enclosure where our Switchgear is located, generally an Electrical Panel. They will allow us to see through luminous pilots the state of operation or of the Network signal or Group signal.

Advantages of Retelec´s Automatic Transfer Switch

The use of Retelec’s Automatic Automatic Transfer Switch brings a number of significant advantages to electrical systems. Here are some of the benefits of its use:

  1. Increased reliability: Ensures a reliable power supply by allowing automatic transfer to the backup grid in the event of main grid failures. This reduces the possibility of prolonged outages and improves the quality of electrical service at your facilities.
  2. Reduced response times: Thanks to automatic fault detection, response times to power supply interruptions are significantly reduced. This enables faster restoration of service and minimizes inconvenience to consumers.
  3. Cost savings: As a monobloc system that is easy to install and commission, the labor time required is reduced compared to a traditional contactor switching system. In addition, in case of failure or breakdown, it is only necessary to disconnect the power supply, remove the defective one and install a new one. Everything is done incredibly fast.
  4. Improved energy management: Enables more efficient energy management by facilitating the integration of renewable sources and electrical storage systems. This technology can optimize the distribution of energy generated from solar, wind or other renewable sources, ensuring maximum utilization and contributing to the reduction of carbon emissions.

Where to buy Retelec´s Automatic Transfer Switch?

The best way to acquire this device is by consulting the official Retelec website, which you can visit by clicking here.

On this website you will find all the technical information you need and in case of any doubt you can clarify it with their Technical Department. You will also find all the distribution network of their brand so you will know where to go to ask for an offer.


I would like you to let me know in the comments what you thought of this review and if you have had any experience working with Automatic Transfer Switch Systems.

If you liked this article leave me a nice Like to let me know and share it with all your contacts so they can learn more about this type of devices and never run out of power supply.

See you in the next article.

See you next time!

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