An electrical wiring diagram could be a single page schematic of how a ceiling fan should be connected to the power source and its remote switches.
A wiring diagram may include the wirings of a vehicle. For example, how the horns are powered and connected to the controller on your steering wheel.
Or an electrical wiring diagram can be a 200-page document including all the electrical wirings of an electrical control panel in a huge factory or plant.
As some rules of thumb will be applied to most of the wiring diagrams, in Part 1 of this multi-part article you’ll learn how to read a wiring diagram by means of an actual industrial control panel’s wiring diagram.
And in Part 2, you’ll learn how to read a PLC wiring diagram and its modules.
Spend Some Time on Understanding the Standards!
Wiring diagrams may follow different standards depending on the country they are going to be used.
They may have different layouts depending on the company and the designer who is designing that.
They also may be drawn by different ECAD software such as EPLAN or AutoCAD electrical. So, when you see a wiring diagram for the first time, you may need some time to analyze it and become familiar with its layout and symbols.
Let’s start with an actual example of a wiring diagram.
The document we are going to check includes more than 140 pages but we’ll check only some of the pages as the rest of them are somehow similar.
First Things First! Wiring Diagram Symbols
Every wiring diagram includes:
– Hardware components,
– Power sources,
– Ground chassis,
– Some wires of course!
– Numbers, letters, and maybe some nomenclatures.
Normally the very first step to learn reading a wiring diagram is becoming familiar with the symbols of the equipment and each wiring diagram is supposed to have a page or two for this purpose.
This page is known as Legend and abbreviation page.
In the Legend and Abbreviation page you can see:
– A three-phase AC electric motor symbol
– A solenoid valve symbol
– An MCCB with thermal and short circuit protection
– A contactor (the coil and its contacts)
and all the other electrical symbols you need to read the wiring diagram.
Remember that these symbols may have some minor differences in different wiring diagrams depending on the ECAD software they have been designed with.
As an example, the Fuse in EPLAN Electric P8 (a Wiring Diagram Software) looks like this:
But in AutoCAD electrical, it looks like this:
By the way, you’ll learn more symbols in the rest of this article and you’ll get used to these electrical symbols very soon!
Wiring Diagram Rules of Thumb!
Ok, let’s start with the first pageto see how much it could be easy to read and understand a wiring diagram.
Rule #1: How to Follow a Wiring Diagram (Reading Direction)
First of all, there is a rule of thumb in standard wiring diagrams that you should read the diagram from left to right and from top-down.
Exactly like reading a book!
But sometimes, designers make some exceptions to have a better layout such as this page.
So as an exception, we should start from the downside and this is where the three-phase power enters the panel.
As a reminder, the voltage level and the frequency of the power depends on the country we’re implementing our project.
– In England or Austria, the voltage level is 400 volts with 50 hertz of frequency
– In the United States, a three-phase power source will produce 480 volts with 60 hertz of frequency.
The power enters the terminal blocks with the “X0” terminal strip.
The terminal strip is a mark that refers to a group of terminal blocks with the same voltage level or the same purpose.
From these terminal blocks, we move on to a three-pole circuit breaker with thermal and short circuit protection capability.
Rule #2: Wiring Diagrams Are Drawn in the Neutral Condition
Every standard wiring diagram should be drawn in the neutral condition.
This means that all of the contacts, contactors, circuit breakers, etc., are shown in their normal or non-energized condition.
Therefore, when you see a closed contact in an electrical wiring diagram, that is a normally closed contact and the rest of the contacts should be open.
We have a great article about NO and NC contacts and their actual application examples that you can read it here.
How to Read Wiring Diagrams
Ok! Let’s continue reading.
After closing this circuit breaker manually, the power flows toward some power distributer bars, from which some branches can be taken.
One of the branches goes into a two-pole circuit breaker.
and from there powers a transformer.
If you’ve noticed, there are some numbers on the wires.
These are called “wire tags”.
What is a Wire Tag? (And Device Tag)
Wire Tags are the combination of some letters and numbers installed on the wire or cable and are used to show you to which device or terminal block a wire or a cable should be connected.
Wire tags are very helpful in case of troubleshooting so that when a wire gets out of its connection point, you can easily look at the wiring diagram and figure out where it should be connected again.
There are the tags for the devices within the panel as well.
If you were looking at the wiring diagram and you didn’t know what a device is, then you could find it in the panel using its tag.
This transformer converts the 400 volts to a single-phase 230 volts.
It is used to feed the power receptacle or socket, the heater, and the fan.
The “-ST19” tag refers to a thermostat to turn on and off the heater or the fan on its specified temperature setpoints.
You’ve also noticed the earthing chassis and its branches wherever it’s needed.
How to Address a Component in Wiring Diagrams
Before we continue to the next page, you may ask what these numbers on top of the page are. This is a very good question!
Actually, these are the column numbers and they have divided each page of this drawing to 10 columns.
As you see, there are some devices in each column and we can use these column numbers in combination with the page number to address different devices, contacts, terminal blocks, and so on, in other pages.
Let me explain it by some examples!
For instance, the main three-phase power is shown with some arrows and numbers on the top right-hand side of the page.
All of them have a 2.0 number just beside the arrow.
– By “2” it refers us to page two.
– By “0” it points out to the first column of page two.
And there you go! It’s our power source on page two.
As another example, the number below this contact says page 130 and column 6.
I’ll turn to page 130 of the wiring diagram and this is column number 6.
And there it is! The same tag, KA1306 as we had expected.
It looks like a coil. But not the coil of a contactor; the coil of a relay.
And how do I know that?! If you have seen the legend and abbreviation page of the drawing you know that the “-KA” is a nomenclature for a relay in this drawing.
Below the coil, you see the 13-14 contact (NO Contact) of page two and also the other NO and NC contacts of this relay with the addresses they have been used in this drawing.
We’ll get back to this page again.
On page two, the mains power source is feeding a 24-volt power supply and it provides us with a voltage of 24 with 10 amps of capacity.
From there, we have extended this voltage using some terminal blocks so that we can deliver the power to different instruments, PLC cards, PLC CPU, or whatever device which needs 24 volts to power on.
But wait! This part of the drawing, seems a little bit strange as all of these terminal blocks have the same tag of “XC”.
What are Double-Level Terminal Blocks?
There are a variety of terminal blocks in the market. In this case, to save some space in the panel, we have used some double-Level terminal blocks.
They occupy the same space as the ordinary terminal blocks but we can connect two wires to each side of them.
In the following, we have a branch that delivers the 24 volts power to page 12 column zero, but with two interlocks!
What is Electrical Interlocking?
An interlock means a condition.
For example, here, without having those interlocks enabled, our 24 v cannot reach page 12, column 0.
Let’s turn to page 130 of the wiring diagram again to see what those conditions are.
NOTE:Did you notice that we have to get back and forth between different pages? This is the only way we have to take to fully understand these drawings.
On page 130, we’ve a safety relay, and it will be used to protect people, material, and the machine itself when the machine is operating.
Remember that the designer of this wiring diagram had to refer to the datasheet of this equipment to complete his job.
In fact, reading the datasheet of the equipment is a very important and inevitable stage of designing a wiring diagram.
We should always do the same thing for all of the equipment used in the process.
By the way, channels S11/S12 and S21/S22 are used to be connected to the safety components at the site (For example the safety barriers) and if the area is evacuated then these channels will be activated.
As a result, the NO contacts of the Safety Relay (Output Contacts 13/14 and 23/24) become closed.
Therefore, our 13-14 NO contacts of the relays (KA1306 and KA1307) become closed.
In this way, our 24-volt power will be transferred to page 12, column zero.
Let’s pause this part here and we’ll continue the next part by reading and understanding the PLC, VFD, and their power and signal cabling section of this control panel wiring diagram.
You can read Part 2 of this article here.
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The electrical schematics are read from left to right or from top to bottom. This is important to get right, as the signal direction indicates the flow of current in the circuit. It is then easy for a user to understand when there is a change in the course of the circuit.
Rule #1: You should read a PLC Panel wiring diagram from left-to-right and top-to-down, just like when you're reading a book. Rule #2: To understand the addressing system of a PLC panel wiring diagram use the combination of the provided column numbers and page numbers.
- Schematic Diagrams.
- Wiring diagrams.
- Block diagrams.
- Pictorial diagrams.
When interpreting a single line diagram, you should always start at the top where the highest voltage is and work your way down to the lowest voltage. This helps to keep the voltages and their paths straight. To explain this easier, we have divided the single line into three sections.
- Battery. The symbol for a battery is shown below. ...
- Resistor. The schematic symbol of the resistor are drawn in two different ways. ...
- Potentiometer. ...
- Schematic Symbols of a Transistor. ...
- Schematic Symbol for an Integrated Circuit. ...
- Logic Gates. ...
- Inductor. ...
In a PLC system there will usually be dedicated modules for inputs and dedicated modules for outputs. An input module detects the status of input signals such as push-buttons, switches, temperature sensors, etc.. An output module controls devices such as relays, motor starters, lights, etc.
The main components of a PLC consist of a central processing unit (CPU), power supply, programming device, and input and output (I/O) modules. The CPU is the brain of the PLC and carries out programmed operations. These operations or outputs are executed based on signals and data provided from connected inputs.
- Processor: The processor is also called the CPU which means central processing unit. ...
- Rack/Mounting: A PLC unit is formed by combining a number of components. ...
- Input Assembly: ...
- Output Assembly: ...
- Power Supply: ...
- Programming Device/Unit:
- Cleat Wiring. This wiring comprises of PVC insulated wires or ordinary VIR that are braided and compounded. ...
- Casing and Capping Wiring. ...
- Batten Wiring. ...
- Lead Sheathed Wiring. ...
- Conduit Wiring.
A wiring diagram shows the relative layout of the components and the wire connections between them. This type of diagram shows the physical relation of all devices in the system, the conductor terminations between these devices, and are commonly used in motor control installations.
Types of Electrical Diagrams or Schematics
There are three ways to show electrical circuits. They are wiring, schematic, and pictorial diagrams.
Dyslexia is included in the Individuals with Disabilities Education Act (IDEA, 2004) as a specific learning disability (SLD). Dyslexia impacts reading, specifically decoding and accurate and/or fluent word recognition and spelling.
Three categories of SEN are associated with learning disability: moderate learning difficulty ( MLD ), severe learning difficulty ( SLD ) and profound multiple learning difficulty ( PMLD ).
Single-line diagrams are where upper-level details like generators, main transformers, and large motors are shown. Schematic diagrams show the functionality of more mid-level electrical circuits without getting bogged down in the details of individual connections (which are shown on wiring diagrams).
Electrical symbols are the most commonly used symbols in circuit diagramming. Amplifiers (denoted by triangle shapes) increase the output signal in your circuit. Capacitors (parallel lines) store energy in your system, while resistors (zigzag lines) reduce current flow.
- Cables and wires in a circuit are drawn as straight lines.
- Wires should not cross over each other.
- We need to use the correct symbols for each component in the circuit.
- When drawn, the circuit forms a closed loop.
There are five commonly used symbols in Electrical – Switch, Wire, Contactor, Motor, Transformer. These symbols can be used in any electrical drawings. Switches are used for ON/OFF any control circuit.
Circuit symbols and names are small images that represent an electrical or electronic device or function. Circuit symbols and names are used for creating diagrams. And these diagrams show how a circuit is connected. They are essential in designing circuits or making printed circuit boards for a project.
There are several types of solid state outputs available with PLC's. Three popular types are transistor, triac and TTL. All three of these output units will generally have a common terminal although triac output units are available in an isolated configuration.
These three PLC components are: processor, power supply, and an input/output (I/O) section. The processor, or the brain of the PLC system, is a solid-state device designed to perform a wide variety of production, machine tool, and process-control functions.
There are two main types of inputs: data inputs from devices and machines, and data inputs that are human-facilitated. The input data from sensors and machines are sent to the PLC. Inputs can include on/off states for things like mechanical switches, buttons, and encoders.
- Ladder Logic.
- Function Block Diagram.
- Sequential Function Charts.
- Structured Text.
- Instruction List.
- What do we want all students to know and be able to do?
- How will we know if they learn it?
- How will we respond when some students do not learn?
- How will we extend the learning for students who are already proficient?
- 6 Essential Characteristics of a PLC.
- Shared mission, vision, values, goals. ...
- Collaborative teams focused on learning. ...
- Collective inquiry. ...
- Action orientation and experimentation. ...
- Commitment to Continuous improvement. ...
- Results orientation.
Basic PLC operations
PLCs are made up of input points or modules, output points or modules, and a CPU (central processing unit). Inputs accept a wide range of analog and digital signals from different sensors/ field devices and work to convert them into logic signals that are CPU compatible.
Electricity takes different forms: coal, water, solar, wind, nuclear, hydro and solar.
The most common type of home electrical wiring is the NM cable, also known as the Romex cable, after the most popular electrical wiring brand name. The NM cables contain three or more individual conductors, wrapped together in a sheathing, which is a flexible plastic jacket.
The raceway and conductor method is one of the most common types of electrical wiring. It involves either a metallic or a nonmetallic conduit or tubing with multiple insulated phase.
The common elements in a wiring diagram are ground, power supply, wire and connection, output devices, switches, resistors, logic gate, lights, etc. A list of electrical symbols and descriptions can be found on the "electrical symbol" page. A line represents a wire.
Black wire: This is a hot wire that carries electricity from the power source to the first switch in a typical 3-way setup. It's also called the “common wire” or the “line wire.” Unless the breaker is off, this black wire is always hot.
Appliance Plugs or Power Cords
If you're looking at exposed wires: The neutral wire is identified by a white stripe, ribbing or white insulation. The hot (live) wire has no ribbing or stripe; it may have black or red insulation. If the cord has a green wire (rare), it's a ground wire.
Live, neutral and earth mains wires
The plug contains three wires – the live, neutral and earth wires. In a plug, the live wire (brown) and the neutral wire (blue) are the two wires that form the complete circuit with a household appliance.
The present study examined the role of language capacities in explaining differences in social information processing (SIP) among three school-age groups: high-functioning children with autism spectrum disorder (ASD, IQ > 75), children with specific learning disorder (SLD), and children with typical development (TD).
There are five aspects to the process of reading: phonics, phonemic awareness, vocabulary, reading comprehension and fluency. These five aspects work together to create the reading experience. As children learn to read they must develop skills in all five of these areas in order to become successful readers.
The benefit of using an SLD is that it has lower coherence than the light of an LD, which enables coherence noise to be reduced. For example, if an SLD is used for light interference measurement, it reduces diffused reflection (speckle noise) on the surface of the object to measure.
A specific learning disability in reading, also known as dyslexia. A specific learning disability in writing, also known as dysgraphia. A specific learning disability in mathematics, also known as dyscalculia.
Find out about profound disabilities and how to get the right support and communication for someone with PMLD.
Specific learning disability is the major or overriding disability condition that best describes the person's impairment. SLD. Speech or language impairment. Speech or language impairment is the major or overriding disability condition that best describes the person's impairment. SLI.
A schematic shows the plan and function for an electrical circuit, but is not concerned with the physical layout of the wires. Wiring diagrams show how the wires are connected and where they should located in the actual device, as well as the physical connections between all the components.
In power engineering, a single-line diagram (SLD), also sometimes called one-line diagram, is a simplest symbolic representation of an electric power system.
Learning how to read an electrical schematic drawing is an important skill for maintenance workers and managers even if they aren't licensed electricians. Understanding schematic drawings helps identify faulty components, troubleshoot systems, and improve safety.
In AWG, the larger the number, the smaller the wire diameter and thickness. The largest standard size is 0000 AWG, and 40 AWG is the smallest standard size. It may also be called Brown & Sharpe wire gauge or simply the gauge of the wire. AWG is for single-strand, solid, round, electrically conductive wire.
Load Wire - Generally connected to the top half of your switch. If the wire is coming from the top of the switch box, it is likely your load wire. Line Wire - Generally connected to the bottom half of your switch. In some cases, line wires are marked with “line”, “pwr”, or a lightning bolt symbol.
Electrical symbols are a graphical representation of basic electrical and electronic devices or components. These Symbols are used in circuit and electrical diagrams to recognize a component. It is also called a schematic symbol.
- Phase 1 - Black.
- Phase 2 - Red.
- Phase 3 - Blue.
- Neutral - White.
- Ground - Green, Green with Yellow Stripe, or Bare Wire.
Basic Wire Color-Coding
A black or red-hot wire usually connects to a brass-colored screw terminal or black wire lead on electrical devices. A white neutral wire usually connects to a silver-colored terminal or white wire lead.
Current is usually denoted by the symbol I. Ohm's law relates the current flowing through a conductor to the voltage V and resistance R; that is, V = IR.
With simple on-off light switches, mixing up the line and load wires won't affect the operation. The power will be either off or on. It does become critical is when installing a GFCI outlet. Because it contains an internal circuit breaker, incorrect installation can cause a safety failure.
Hot wire is identified by its black casing. This is the main color of hot wire for most homes. However, other hot wires can red, blue, or yellow, although these colors can indicate a different function besides powering an outlet.
- Wires (Connected) This symbol represents a shared electrical connection between two components. ...
- Wires (Not Connected) ...
- DC Supply Voltage. ...
- Ground. ...
- No Connection (nc) ...
- Resistor. ...
- Capacitor, Polarized (Electrolytic) ...
- Light-Emitting Diode (LED)