How to Read Electrical Diagrams | Wiring Diagrams Explained | Control Panel Wiring Diagram

Do you have struggles reading and using an electrical wiring diagram? If yes, don't worry! By end of this video you'll have a good understanding
of how to read understand and use it for your benefit 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 so that we can turn it on and off 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 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 As there are plenty of videos about vehicles’ wiring diagrams ceiling fans and other appliance out there in this video we decided to specifically investigate an industrial panel wiring diagram However, some rules of thumb will be applied to most of
the wiring diagrams in general So, before we continue please subscribe and click the notification bell and stay with me to the end as I have very interesting
points to tell you Let's start with an actual example of a wiring diagram This document includes more than 140 pages but we’ll check only some of the pages as the rest of them are somehow similar Every wiring diagram includes hardware components Power sources Ground chassis Terminals some wires of course and 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 To have a quick look at the symbols you see a three-phase AC
electric motor symbol here This one is the symbol for a solenoid valve This is a symbol for a contactor This is the coil and these are the contacts 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 software looks like this But, in AutoCAD electrical it looks like this! By the way, you’ll get used
to these symbols very soon Ok, let’s start with the first page to see how much it could be easy to read and understand a wiring diagram 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 For example, in England or Austria the voltage level is 400 volts
with 50 hertz of frequency But in the United States a three-phase power source will produce 480 volts with 60 hertz of frequency As you see, 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 As another rule of thumb the wiring diagrams are drawn
in the neutral condition Meaning that all of the contacts contactors circuit breakers, etc.


Are shown in their normal or non-energized condition Therefore, this contact is closed because it is a normally-closed contact and the rest of the contacts are open We have a great video
about NO and NC contacts and their actual application examples that you can watch it using the
link in the description if you wish 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” 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 this device is then you could find it in the panel using this tag This transformer converts the 400 volts to
a single-phase 230 volts 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 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 top of the page All of them have a 2.0 number just beside the arrow By “2” it refers us to page two And 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 number 130 and column number 6 I’ll turn to page 130 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 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 come back to this page very soon 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 terminals
have the same tag of “XC” 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 An interlock means a condition Let’s turn to page 130 again to see what those conditions are 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 In this page, we’ve a safety relay here 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 this is a very important
and inevitable stage of designing a wiring diagram and we should always do the same thing for the rest of the equipment used in the process By the way these two channels 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 and as a result these NO contacts become closed Thus the voltage will be transferred
to the A1 connection of the relays’ coils and finally, the coils will be energized Therefore, our 13-14 NO contacts
of the relays 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 and wiring I hope you’re excited for the next
parts of this multi-part series If yes please subscribe and click the notification bell to don’t miss the next videos

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