How Does an ATS Panel Work?
Description: An ATS panel is a specialized electrical enclosure equipped with a motorized transfer switch that connects the output to one of two input sources: Generator or Mains. A neutral position disconnects the output entirely. The motorized transfer switch is paired with an advanced ATS controller, featuring a front-panel access port for a manual override lever that bypasses all electrical and electronic circuits.The panel also integrates essential protection and auxiliary components.
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ATS Systems: Certified, Plug-and-Play Reliability
Never fear a power outage again. Discover our professional, certified ATS panels for seamless automatic power transfer. With 40 years of expertise, we provide high-performance solutions for residential and industrial needs. Our Automatic Transfer Switch panels, paired with the BeK3 AMF / ATS controller, feature extraordinary load and generator protection against:
Over/Under Voltages
Over/Under Frequency
Overload / Overcurrent
Phase Sequence mismatch
Reverse Power
Alternator Failure
Not mentioning a granual protection of the engine with traditional I/O methods or J1939 compliant Canbus and the flexibility of our remote control & monitoring options.
What is an ATS panel?
Bernini Design clears up all misunderstandings once and for all with a "solid rock" technical approach
An ATS (Automatic Transfer Switch) is an electrical switch with three distinct states: [1], [0], and [2]. For each state, the ATS connects a common output [C] to a specific input. The [0] position serves a critical mechanical purpose: it ensures a physical break, preventing any electrical connection between input [1] and input [2].
The position of the switch is driven by mechanical levers coupled to a powerful electric motor. Automatic operation is only possible when this mechanism is paired with an electronic controller. Typical applications include electrical panels designed to connect a load to a primary power source (the mains, or position [1]) or an emergency source (a generator, or position [2]). Despite the simplicity of this technical definition, there are many misconceptions regarding ATS devices in standby applications—particularly when integrated into AMF (Automatic Mains Failure) systems. This guide resolves those issues:
ATS Control Panels: the "When"
It is crystal clear that you need an ATS panel when building a standby system based on a diesel generator.
An ATS panel is the correct choice when your power needs exceed 60kVA in a 3-phase configuration. You can choose a standard ATS panel or ask for a tailored version. When it comes to residential applications, unless you need 200 Amps of current, the best solution is to trust in the Bernini Design AMF Single-Phase residential control panels. Choose the right product on this page:
Single Phase Residential Panels
ATS Control Panels Complete Tutorial
An Automatic Transfer Switch (ATS) control panel is the core component of a standby power system. It looks like a distribution electric panel, but it additionally features an ATS controller on the panel's door that controls all functions.
The inside includes a "Motorised Transfer Switch" and various electrical components.
The ATS control panel monitors your primary power source (Mains) and automatically switches your building's load to a secondary source (Generator) during a power failure. This guide explains how it works, the technology behind it, and essential safety considerations.
Tutorial Links Summary:
The Risks of Basic/DIY Systems
The Solution: The ATS Control Panel
Power Connections Diagram
How an Automatic Transfer Switch Works
Source Monitoring: The ATS controller constantly monitors the Mains voltage.
Automatic Switching: When the Mains fail, the controller signals the generator to start. Once the generator is stable, the ATS transfers the load.
The "Break-Before-Make" Concept: To protect inductive/capacitive loads (like motors), the switch stays in a neutral 'zero' position for a programmable time (usually 2 seconds). This ensures no overlap between power sources, preventing backfeeding.
Contactor vs.Motorised Transfer Switches: the following table summarises what is about. A generator control panel that features a contactor-based solution is correctly identified with the term "AMF Control Panel" instead of "ATS Control Panel".
| Feature | Contactor-Based | Motorised Switch |
| Ideal Current | Up to 100A | Up to 2000A+ |
| Power Consumption | Constant (coil active) | When Switching |
| Mechanism | 2 Contactors
Electrical interlock |
Motorised
spring/gear |
| Best For | Smaller residential | Industrial/
High-power |
The common misunderstanding: "ATS Switch"
Often incorrectly referred to as an "ATS switch" (Automatic Transfer Switch; a redundant term), an ATS is a 3-position transfer switch (TS) driven by an automatic control system. When properly wired and enclosed in a suitable box with the necessary ancillary components, it allows you to transition your building’s power source between the utility mains and an emergency generator.
In other words, it ensures seamless, automatic power continuity during outages.
A 250 Amp motorised switch example
On the door of the ATS control panel is the ATS controller and, in the case of an emergency, the manual lever to override the TS (Transfer Switch).
ATS Control Panel Manual Override Lever
What is a Changeover?
Grammatically, a "changeover" refers to a complete transition from one system or condition to another. In the industry, it is commonly used to describe an AMF configuration utilising two contactors with mechanical and electrical interlocks.
A CONTACTOR-BASED CHANGEOVER
These ensure that only one contactor is active at a time: one connects the mains to the load, while the other connects the generator to the load. Both share a common output point: your facility. The contactor-based changeover panels are better defined as "AMF Control Panel".
Learn how a contactor-based changeover actually works
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The Risks: Why Basic TS, ATS, and Changeovers Fail
Attempting to build a system from individual components often leads to failure and safety risks:
1-Complexity and Risk:
A basic Transfer Switch (TS) is an industrial component with 3 positions (0-1-2). It is intended for use only by professional panel manufacturers, not for DIY installation.
2-Incomplete Solutions:
An ATS is simply a piece of hardware. Without specialised external components and complex engineering, it cannot function as a complete backup system.
3-Lack of User Control:
Most standalone ATS units lack user-friendly manual overrides and present significant challenges when interfacing with standard "electric-start" generators.
4-Safety Hazards:
Manual override operations on basic units often expose users to high-voltage electrical hazards.
5-Regulatory Compliance:
Without professional integration, you cannot achieve an "up-to-code" installation. In the event of an electrical fault or fire, you may face significant legal and insurance liabilities.
6-The Solution:
The ATS Control Panel is safe, compliant, and a reliable solution. We build professional ATS Control Panels, custom-manufactured to your specific power requirements.
7-Tailored Capacity:
We provide solutions ranging from 80kVA up to 200kVA with a 3-Phase + Neutral (3Ph+N) configuration.
8 Bullet Points For Purching a Bernini Besign ATS Control Panel
1- Turnkey Compliance: Every unit is supplied with full international certifications.
2- Universal Compatibility: Powered by the Bernini Design Be242RB universal interface board, any qualified electrician can integrate virtually any generator type.
3- Certified Safety: Because our panels meet strict standards, your electrician can certify the installation as "up-to-code," ensuring you are 100% protected in the event of an inspection or insurance claim.
4- Precision Control: Our user-friendly controller features over 50 customizable settings, allowing you to fine-tune automation without compromising system integrity.
5- Safe Manual Override: Operate your system safely from the exterior of the panel—no exposure to live electrical hazards.
6- Advanced Monitoring: Optional GSM, TCP/IP, and Modbus tools provide real-time status updates and alerts wherever you are.
7-Custom Configuration: We offer granular load control and protection by utilising high-quality contactors instead of standard, off-the-shelf Transfer Switches.
8- The Bernini Design 24/7/365 Support: Benefit from our global technical support, ensuring you are never left without assistance.
Safety and Legal Compliance
Installing an ATS involves high-voltage power. For legal compliance and safety, always hire a qualified electrician. Proper installation requires current-limiting devices, appropriate cable sizing, and adherence to international standards like IEC 61439. Improper installation risks fire, injury, and legal liability.
A good installation of an ATS control panel will provide safety and long-term functionality ot your backup power system.
ATS: The Technical Design
Circuit Protection:
Always use 10A circuit breakers for auxiliary control circuits wired inside the Automatic Transfer Switch panel.
Engine Interface:
The ATS controller acts as a universal bridge for engine auto-start modules. Use pilot relays to protect controller outputs.
Design Philosophy:
Measure twice, cut once. Always bench-test your automation logic with lamps before connecting the main building load.
The Controller:
The installation of the Be242 ATS controller is a mandatory choice for all Bernini Design ATS control panels.
System implementation example: industrial ATS panel
To demonstrate the concepts above, let’s look at a typical professional setup using a high-performance Motorised Transfer Switch paired with an advanced ATS Controller.
ATS Panel Core Components List
Logic Controller: Advanced ATS Controller (e.g., Be242).
Switching Device: 250A Motorised Transfer Switch (e.g., Telergon CCF/1 3PH+N).
Auxiliary Protection: 10A Circuit Breakers (MCB/GCB) for control circuits and 1A fuse for the motor.
Operation Logic Neutral Position [0]: The system uses an electric pulse of 12V to ensure the switch enters the neutral position before changing sources.
Mains/Generator Selection: A pulse on the [M] terminal drives the switch to the MAINS position. A pulse on the [G] terminal drives it to the GENERATOR position.
Safety Timing: The controller automatically enforces a 2-second "dead time" during every transfer. This is the Break-Before-Make rule in action, protecting your load from inductive back-EMF.
Typical ATS Panel Connection
Typical ATS panel connection
ATS control panel specifications
Before installing an automatic transfer switch in your standby power system, make sure that your product m
| Description | Notes |
| Manufacturer - Production Date | ernini Design Srl -........ |
| Model-ATS (Serial No.) | 60 kVA - BEK3 (Nr....) |
| Structure / Protection | Steel 1,5mm IP62 |
| External Dimensions | 70 X50 X26 / 25KG |
| Rated Power | 80 kVA @ 35°C |
| Continuous Rated Power | 60 kVA @ 35°C |
| Rated Voltage | 400 V / 360-440 |
| Insulation Voltage | 1000 V |
| Rated Current AC1 | 125 A |
| Continuous Current / Short Circuit | 0-100 A @ 400 V /50 kA |
| Frequency / Range | 50 Hz / 45-55 Hz |
| Electrical Protections | Min-Max V-Hz, Max Amp |
| Changeover | 3-Ph+N TELERGON 125A |
| Norms / Standards | IEC 61439-1-2-34-5-6-7 IEC 60529 |
| Internal Protections | 2 x Circuit Breakers 10 A |
| Humidity Class | 5-85 % |
| Operating Temperatures | -5 /+35 °C Nominal (50°C max.) |
| Temperature-Dependent Power Reduction | Reduce power by 5% for each °C above 35. |
| Connections | 12 X 25 mmq |
| Battery Charger | 12 V / 2 A |
| Standby Power Supply | 10 VA |
1) The panel must be installed only by qualified personnel.
2) Electrical protection devices must be installed to limit the power and current flowing through the panel, from the mains or generator, to a maximum of 100 A at 400 V.
3) Neutral and ground connections are mandatory.
4) The negative battery terminal must be grounded on the engine side.
5) Do not open the door when mains or generator voltage is present. The panel's interior contains components that present a risk of direct contact (IP00).
6) Consider placing advice about the presence of a standby generator
The Auto Mode
Activation: Push the [AUTO] button until the yellow LED illuminates.
Automatic Start & Transfer: The engine starts automatically when the panel detects a mains failure. The transfer switch disconnects the [LOAD] after the [MAINS BREAKER] timing expires. After the [WARM UP] time, if voltage and frequency are within configured settings, the transfer switch moves to the "GENERATOR" position.
Mains Restoration: When mains power is restored, the transfer switch moves to the neutral position for a programmed duration before connecting the mains.The engine stops automatically after a [ COOL DOWN ] time.
NFPA-110 Compliance Notes
If the engine shuts down due to an alarm, the transfer switch connects the mains independently of its status. If NFPA-110 mode is disabled in your settings, the transfer switch only transfers to the mains when its parameters are within safe limits. In AUTO mode, the BeK3 periodically tests the engine (if properly programmed), during which the yellow AUTO LED continues to blink. The BeK3 can also start and stop the engine via an activated remote control.
The Test Mode
Activation: Press and hold the [AUTO] push button until the yellow LED blinks. The panel will initiate a start sequence.
Operation: The engine will keep running until you exit TEST mode.
Exiting: Press the [AUTO] button briefly or select the OFF mode.
The Manual Mode
Starting the Engine: Push the [MAN] button to select MAN mode. Press and hold the [START] button until the engine
starts. The display automatically loads the ENGINE STATUS PAGE to show start-sequence information. (Note: During
cranking, the BeK3 turns off the display backlight to conserve battery voltage).
Generator & Load Transfer: Wait for the green engine LED to turn on. Wait until the green generator LED turns on. Push the [ I KG ] push button to activate the transfer switch and load the generator.
Mains Transfer: Wait for the green mains-available light to turn on. Push the [ I KM] push button. The transfer switch enables the mains after a 2-second changeover delay. (Note: The programmable changeover delay timer only functions in AUTO mode). Stopping the Engine: Push the [0-STOP] button. The [STOPPING] message will be displayed.If the engine has already stopped, you can reset the stop sequence by pressing the [0-STOP] button again.
The Off Mode
Turning OFF: Press and hold the [ 0-STOP ] button for 2–3 seconds to turn OFF the BeK3 and clear the fault alarms log. Parameter Programming: In this mode, you can program parameters or modify settings. Turning Back On: Push the [ MAN ] or [ AUTO-TEST ] button on the front panel to turn the controller back on.
The Setup Mode
Default Configuration: The BeK3 controller features default settings for a 400V 3-phase system and
standard I/O engine controls. On-Site Programming: You can program the controller directly on-site without external
equipment. The panel accepts single-phase or three-phase systems for both utility power and the generator. Follow the
instructions detailed in the installation manual to proceed.
There are two separate layers of connections: the automation power layer and the "power" layer. The automation layer must be implemented first. The main goal is to connect the engine and perform all tests on it. After that, you can approach the second layer: the connection of the Load, generator, and the mains. The following picture cleraly illustrate the 400 V connections. To dive into the engine connection details, visit the tutorial page:
ATS PANEL CONNECTIONS TUTORIAL
Up-To-Code Standby ATS Panel Installation
Our ATS panels are tested 100% before delivery. You must rely on a licensed electrician capable of providing an "up-to-code" installation. You can benefit from our support 24-7-365.
The installation must be carried out by a qualified electrician. He will release the certificate in force in your country. A bad installation may cause backfeeding, that is the most dangerous situation when dealing with standby power installation.
The ATS control panel, in a standby backup power system, is connected between the utility power and your building. It is also connected to the generator. A control panel made by Bernini Design offers additional connections for remote control, monitoring and most importantl, the connection to the engine. In other words, the ATS control panel is capable of starting and stopping the generator when necessary. The installation must be carried out by a qualified electrician. At the end of its job, he weill release an Up-To-Code installation certificate. For a complte undersyour clarity, follow this 3-step overview.
Step one: Understanding the ATS control panel environment
In this picture, we present a general overview. The simplest case is interfacing with a power generator that features its own auto-start electronic module.
In this case, connect the ATS control panel's "FUEL SOLENOID OUTPUT" to the auto start module's "REMOTE START INPUT".
Maintain a high level of insulation of the low-voltage wiring from the mains. In case of extreme overvoltage during a thunderstorm, the parasitic capacitance can couple the overvoltage with the generator. This will cause severe damage to electronic parts like the voltage regulator, engine automation systems or auto-start modules.
A good practice of keeping low-voltage wires and high-voltage wires very well separated will provide long-term safety.
Step two: the right connection
Even though the ATS panel is designed to prevent backfeeding, you must wire all connections with caution, especially in a 3-phase system with neutral. This prevents fatal damage in the first place. You must wire the mains input to the utility power, the generator to the generator input and the load to the ATS control panel output. It is a mandatory practice to maintain the same phase sequence. This will avoid electric motors rotating in the opposite direction when switching from mains to generator and vice versa. Even in the case of a single-phase system, you must respect the phase and neutral connection. Some equipment strictly requires a precise LINE and NEUTRAL connection. In some cases, you must create a virtual NEUTRAL by using a resistive impedance.
Step three: connection recap
Before setting your system in the automatic mode of operation, make sure of the following
1- Limiting the current device on the mains supply according to the maximum ATS switch rating.
2- Limiting the current device on the mains supply according to the maximum ATS switch rating.
3- The size of the cables is in accordance with the rated current.
4- The terminal blocks are properly tightened.
5- Full insulation test between load-generator-mains.
6- The generator is capable of supplying the current needed in the worst-case scenario.
7- Double-check if the installation is up-to-code.
8- Check the protection settings of the ATS controller.
9- Check the mains failure settings on the ATS controller.
10- Put warning indicators about the presence of an automatic backup generator.
11- Carry out a full manual test of the system.
Last but not least, double-check the environments around the backup generator: it must meet the manufacturer's specifications.
MECHANICAL INSTALLATION
To install an ATS control panel, you must find a suitable place for it. It must be fixed to a stable and robust wall. The total weight can reach 40kg. In this case, you have to drill 4 holes of 10mm diameter minimum. Use metallic wall fixing plugs. If the wall is made of concrete and subject to thermal variation, consider to use 5mm-thick spacers to allow a good air flow over the back surface of the box. This prevents condensation and fungus proliferation inside the metallic cabinet. There is no problem for ATS control panels over 160kVA being assembled into heavy racks suitable for floor mounting. In either case, you must provide good protection against rain and elements,far away from direct sunlight.
PROTECTION AGAINST ELEMENTS
If the ATS panel is installed outdoor and exposed to marine environments, you must consider using a BeK3-based ATS panel. This ATS box features all gaskets based on silicone compounds preventing long term aging.
ELECTRICAL INSTALLATION
There are some basic electrical configuration to be considered:
-SINGLE PHASE ATS PANEL
-3 PHASE ATS PANEL
-ONE GENERATOR SERVING TWO OR MORE LOADS
-TWO GENERATORS SERVING ONE LOAD
There are two basic ways to connect the LOAD to UTILITY POWER or GENERATOR: via a contactor-changeover or a motorised changeover. The ATS panel wiring diagram varies by typology. On this page, we provide details for a 3-phase ATS panel wiring diagram based on contactors, a single-phase ATS wiring diagram based on contactors, and a 250-amp ATS panel with a motorised changeover.
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