A Guide to Electrical Control Panels

If a product came from an automated assembly line, then an electrical control panel was involved in controlling it. This means anyone reading this has encountered a product made with the help of a control panel.

An electrical control panel is a system of several electrical devices that control and monitor the mechanical functions of industrial machinery. These machines have an array of applications, from assembly and manufacturing to food production and traffic lights.

Electrical control panel designs can vary based on the application. Control panels generally have either PLC’s or industrial computers that can have features like Supervisory control and data acquisition (SCADA). SCADA is a monitoring system on top of a control system. Usually one SCADA system is monitoring several pieces of equipment that each have one or more control panels.

Developing a more comprehensive understanding of electrical control panels can benefit anyone working in or managing industrial, especially manufacturing, enterprises. This article will discuss electrical control panels in depth by looking into each component and what they contribute to the system.

Components of Electrical Control Panels

The components of an electrical control panel can be classified into two main categories: electrical and non-electrical. It is important to look at both to get a complete picture of how the system works.

Non-Electrical Components

We will look into non-electrical components first because there are only usually two of them and they are straightforward to understand.


The enclosure is the metal box that houses the other components of an electrical control panel. It comes in varying sizes, materials, and specifications to match the exact needs of the processes the panel is used for and the environment the enclosure is in. The number of doors indicate the sections of the enclosure and plays a part in determining its size. The enclosure is typically made from steel, but different materials can be used based on the application.

Each enclosure will feature the following information on an attached metal plate:

  • Underwriters Laboratories or UL Safety Rating
  • IP Rating (if applicable)
  • NEMA classification (if applicable)

Together, these ratings let users know whether the enclosure is:

  • For indoor or outdoor use
  • Waterproof or water-resistant
  • Dust- or solid contaminants-proof
  • Explosion-proof
  • Fit for hazardous conditions

Back Panel

Back panels are metal sheets mounted inside the enclosure. These panels hold DIN rail mounting and wiring ducts. DIN metal rails provide a standardized mounting structure for the electrical devices that are to be attached. The wiring ducts serve as pathways for wires connecting the electrical devices. The ducts help in keeping components organized and noise between devices managed.

Electrical Components

These are the components that use electricity. They can further be classified into two categories: components that route power and components that control and monitor the mechanical processes. While most of these components are inside the enclosure, there are devices located outside such as the HMI.

Main Disconnect

Electricity for all of the devices comes into the control panel through the main disconnect. Disconnects can be fused, non-fused, or a circuit breaker. It usually has a handle outside the panel that lets users shut off power. The typical power that enters the panel can be anywhere between 120 to 480 volts.

Surge Arrester

After the power goes through the main disconnect, it will then be routed to a surge arrester. This component protects all the other devices inside a control panel from electrical surges. These surges can come from utility power surges or lightning strikes.

Transformer and/or Power Supply

Transformers change the voltage of AC power. Normally mounted externally to save space, these are essential for small AC loads, like conveyor motors, heaters, and pumps.

Power supplies convert AC power to DC power. Most industrial control is standardized on 24 VDC. Power supplies can be configured for a variety of incoming power.

Terminal Blocks

Terminal blocks are also used to route power to the devices inside the control panel. Each block has two terminals that can join wires together. These blocks can be arranged in a strip along the DIN rail to route the power to the other components.

Programmable Logic Controller or PLC

The PLC is akin to a computer’s CPU in that it serves as the brain of the entire panel. In fact, this component does have a central processing unit where the logic program is stored. The PLC has inputs and outputs where the terminal blocks are connected. These connections enable control of the mechanical processes.


Sensors such as proximity switches and photo eyes relay information to the PLC. They monitor the processes and give necessary feedback to the PLC in order to control the operations.

Relays and Contactors

Relays and contactors are essentially switches that turn devices on and off depending on the need of each process. Smaller relays are used to control simpler devices such as lights or fans. Contactors are used to control higher load devices like motors.

Relays and contactors are generally connected to the output terminal of the PLC.

Network Switch

A network switch connects multiple devices via ethernet. It serves as the communication hub connecting the PLC and network compatible devices outside the panel, usually along the assembly line.

Human Machine Interface or HMI

The HMI is one of the network compatible devices connected to the network switch. As the name describes, the HMI serves as the tool that lets users interact with the control panel. It usually has a screen, buttons, switches, joysticks and other input devices that allow the user to monitor and control the processes along the assembly line.

Electrical Control Panel

The electrical control panel is an essential part of any modern assembly line. It lets industrial companies easily control and monitor processes, ensuring efficiency and accuracy in every step. Industries that require complex operations need modern electrical control panels with added features and integrations to stay competitive.

Understanding each component in an electrical control panel is important because it lets organizations choose the most effective panel build and design. It helps keep operations streamlined. It also opens opportunities for cost-effective repairs and upgrades down the road.

If you want to learn more about electrical control panels, reach out to our teamJHFOSTER is an industry leader when it comes to industrial systems and automation. We have been equipping organizations since 1938.