Electrical control panels are designed and used to control mechanical equipment. Each one is designed for a specific equipment arrangement and includes devices that allow an operator to control specified equipment.
Electrical panel components control every piece of equipment in every industry. It’s difficult to describe all possible combinations because every industry and most companies have defined component preferences.
If you need to come up to speed on control panels fast, take your time. Find someone to help you, someone who knows what you’re trying to do. Start with the basics and build from there. Below are the basics.
Electrical Control Panel Descriptions
If control panels are new to you and you want to learn about them the first step is learning the terms used to describe them. What are the major descriptive categories and how is each one described? Below is an example of how to describe important control panel attributes.
1 • Safety Ratings
- 3rd Party Safety Certification = UL508A (cULus)
- Short Circuit Current Rating (SCCR) = 5kA
2 • Enclosure Ratings
- NEMA Rating: NEMA 4X Outdoor
- Material: 304 Stainless Steel
- Mounting: Wall Mount
- Door Mechanism: Lockable Handle with 3 Point Door Latch
3 • Main Power
- Incoming Power
- 480V 3 Phase through a Main Circuit Breaker
- Outgoing 480V Power
- 480V 5.0 HP Fan through a Motor Starter
- 480V 1.0 HP Pump through a Motor Starter
4 • Control Power
- 120V and 24VDC
- 480V-120V Transformer
- 120V-24VDC Power Supply
- Outgoing 120V Power
- Chemical Pump through a Power Relay
5 • Door Mounted Operator Devices
- Power
- Main Circuit Breaker Operator
- Fan
- Hand-Off-Auto Selector
- Fan Running Light
- Low Flow Light
- Recirculation Pump
- Hand-Off-Auto Selector
- Pump Running Light
- Low Flow Light
- Sump pH Meter (Signet)
- Chemical Pump
- Hand-Off-Auto Selector
- Running Light
- Tank Low Level Light
6 • Sequence of Operation
- Supply Fan
- In Hand
- Run Supply Fan
- In Auto
- Monitor Air Flow Switch to verify Air Flow above minimum Flow Rate
- Alarm and stop Supply Fan if Air Flow below desired Flow for X Seconds
- In Hand
- Recirculation Pump
- In Hand
- Run Recirculation Pump
- In Auto
- Monitor Water Flow Switch to verify Water Flow above specified Rate
- Alarm and stop Recirculation Pump if Water Flow below minimum Rate for X Seconds
- In Hand
- Chemical Pump
- In Hand
- Run Chemical Pump
- In Auto
- Monitor Chemical Tank Level Switch to verify Chemical Level above minimum Tank Level
- Alarm and stop Chemical Pump if Chemical Level below minimum Tank Level for X Seconds
- In Hand
7 • Remote Control Interface
- Digital (Dry Contact) Inputs
- System Enable Contact
- Digital (Dry Contact) Outputs
- System Local-Off-Remote Selector in Remote Contact
- Fan Running Contact
- Pump Running Contact
- Chemical Tank Low Contact
- Analog (4-20mA) Outputs
- pH signal from Door Mounted pH Meter (Signet)
Electrical Power Components
Control panels use electrical panel components that control the flow of power to physical equipment (Pump Motors, Blower Motors, Heaters, rtc.). These are power components. Below are the terms used to describe them with a description of each type. See Electrical Power Components for beginners for more information.
Circuit Breakers
A circuit breaker is a manually operated electrical power switch that can detect short circuit and overload conditions and turn itself Off when one of these conditions is detected. Short circuit conditions are detected magnetically and overload conditions are detected thermally.
Fused Disconnects
A Fused Disconnect is the combination of a manual operated power switch and a fuse. A fuse is a thin metal wire in a sand packed paper wrapper. A fuse breaks the flow of electricity a when short circuit or overload causes the metal wire to literally burn up. A fuse breaks the flow of electrical power by graceful self destruction.
Motor Starters
A Motor Starter is a device or combination of devices (Circuit Breaker, Contactor, Overload Relay) used to power and control a motor. It generally includes a Contactor and Overload Relay to control the motor, but they can be replaced by a Soft Starter or Variable Frequency Drive to improve motor control.
Soft Starters
A Soft Starter is a simple solid state motor power controller. Instead of simply opening and closing the power circuit like a motor contactor, it ramps the motor voltage up or down to turn the motor on and off more smoothly to eliminate electrical surges and mechanical shock. A Soft Start (SS) is more expensive than a motor contactor, but provides the added benefit of reducing electrical and mechanical shocks associated with starting and stopping a motor.
Variable Frequency Drives
A Variable Frequency Drive (VFD) is an advanced solid state power controllers. Instead of simply ramping the motor voltage up or down like a soft start to turn the motor on and off, a VFD controls the motor speed at all times. A VFD is more expensive than a Soft Start (SS), but provides the added benefit of controlling motor speed.
Electrical Control Components
Control panels use electrical panel components to control the logical operating sequence of physical equipment. These are control components. Below are the terms used to describe the major control component types with a description of each. See Electrical Control Components for beginners for more information.
Control Relays
A Control relay is the simplest electrical control device. It has a coil that can be energized (logical 1) and de-energized (logical 0) by an electrical voltage (120V, 24VDC, etc.) and contacts that change logic state based on its coil (logic input) state. Control relays are used to turn other devices like contactors, pilot lights, etc. on and off.
Timing Relays
A Timing relay is the next simplest control device. They are control relays with built-in timers to control when their contacts change state, and are used to turn other devices (contactors, pilot lights, etc.) on and off at specific times.
- ON TIMER – it’s contacts change to On state after ON delay when coil is energized.
- OFF TIMER – contacts change to Off state after OFF delay when coil is de-energized.
- ONE SHOT TIMER – contacts change to On state when coil is energized for ONE SHOT time setting.
- REPEAT CYCLE TIMER – contacts repeatedly change states (On / Off) when coil is energized.
Programmable Logic Controllers (PLC)
A PLC is a collection of components (relays, timers, etc.) in a package. PLCs are packaged in various forms and can range in price from under $100 to several thousand dollars. They are flexible and allow communications but you need people with computer skills, programming tools (computer, software, cables, etc.) to program them to function properly in your application.
Electrical Operator Devices
If you’re new to control panels, operator devices allow an operator to monitor and control the mechanical equipment attached to the control panel. Below are the terms used to describe the major operator device types with a description of each. See Best Panel Operator Devices for our recommendations.
Pilot Devices
Pilot devices are door mounted manually operated electrical switches or indicators. They come in many forms and colors; Indicator Lights and Non-Illuminated and Illuminated Pushbuttons, Push-Pulls, Selector Switches.
Digital Meters
Digital Meters are door mounted digital display that allows an operator to monitor analog process variables (Level, Pressure, Temperature, etc.). They can include relays making it a controller and an analog output making it a signal conditioner.
Operator Interfaces
Operator Interfaces are door mounted touchscreen computer displays that communicate with programmable logic controllers (PLC). They can replace pilot devices and digital panel meters. They allow an operator to control the PLC and display the status of signals connected to the PLC digital (On-Off) and analog process variables (Level, Pressure, Temperature, etc.).