Reviewing the Basics of an Electrical Control Panel (Practical Example)

Okay, we get a lot of questions about
the basics of electrical control panels, such as what devices and
equipment we typically use, how the devices are wired, how to keep the control panel and the cabinet
within a normal temperature range and so on. A while back, we did a very detailed
and easy-to-follow video on this topic, and we received a lot of positive feedback. If you have not already watched that video, click on the link in the description and that will take you to the RealPars blog where you can watch the video
and read the article as well. But today, I am here at Pro-Control
workshop in the North of Amsterdam, They have some very cool industrial
automation projects going on, and we are going to shoot
a multi-series video reviewing an actual
electrical control panel, for you to see what the basic
components of a control panel are, how they are wired,
the function of a thermostat and so on. So in this video, we are going to review
the basic of an actual control panel, and I promise you this is not
going to be just a normal review, it’s going to be very in-depth, easy-to-follow
and you are going to love it. I promise. And in the next videos, we are going
to learn about the other aspects of this electrical control panel. But before we get into the video, don’t forget to like this
video if you find it useful. This keeps us motivated to create more valuable
and easy to follow videos in the future. And also as a heads up, since we know many of you love
Joshua’s professional voice, he is going to take
over the video from here and explain everything and then I will
be back again at the end of the video. Stay tuned! This is a control panel that is used for a
system that turns wastewater into clean water. An example of wastewater could be the water
that comes out of the bathroom or the toilet. This control panel controls the
system that cleans this wastewater and turns it into the drinking water.
Pretty cool, huh? This is a 2-door control panel. As you may remember from the previous RealPars
video about the basics of a control panel, we mentioned that we name control panels based on the numbers of
doors that they have. So you have one-door, two-door or
three-door control panel enclosures depending on how big of a panel you have. The more equipment and devices you have, the larger the control
cabinet you will need. This one that we have here
is a two-door control panel. Here on the front of the panel, we have some switches that are
connected to the PLC inputs and outputs. The first one says ’Mute Buzzer’. This is the button that you use and press
when there is an active alarm on the system. When there is an active
alarm on the system, the technician, engineer, or whoever
is responsible on the factory floor, presses this button to acknowledge
the alarm and mute the buzzer. That’s why we often call this
the acknowledge button as well. But you may ask, why do we need this? Why should we press this button and mute
the buzzer, acknowledging the alarm? Well, first off, to state the obvious, by pressing this button when
there is an active alarm, you only “mute” the buzzer. Muting the buzzer means
the alarm is still there and still visible on the HMI, but the buzzer has stopped sounding. But why should we mute the
buzzer and make it silent? Well, the answer is simple, because you don’t want that annoying,
loud sound of the buzzer in your ears while you are working to resolve the issue. So when there is an active
alarm on the system, and it’s making that crazy loud noise, the engineer or technician can press
this button to mute the buzzer, and in doing so, acknowledge that
they are aware of the alarm as well. Therefore, next time that
you see an alarm on the HMI, but there is no sound, it probably means that somebody
has already acknowledged the alarm. Next, we have the ‘ESD Reset’ here which I will get into shortly. Below this switch, we have the big red Emergency
Shutdown push button or the E-Stop as it’s often called. As the name indicates, you use this switch to shut down the
whole system when there is an emergency, and by doing this you can prevent
damage being caused to the system, or the people around it. As you can see, it has some
guarding around it, called a shroud. This will prevent the button
from being used unintentionally. Emergency Stop devices are
always close to where people work in order to be useful, but we have this shroud around
it to prevent any unwanted use. Why? Because if someone presses
this button unintentionally the whole system will
be shut down completely. Now, when you press the
Emergency Stop switch, a red alarm indicator
appears on the HMI screen. After the emergency is gone and
you want to run the system again, you can press the ‘ESD Reset’ button, or Emergency Shut Down Reset, here, to clear the alarm and
the indicator on the HMI. An Emergency Stop switch is designed to
work as a normally closed switch. That means this switch is
closed in normal operation and when it is pressed, the switch opens. Now you may wonder why we have this
Emergency Stop as a normally closed switch. Well, let’s say that you have this
as a normally open switch instead. That means the switch is
open in the normal state and will be closed when it’s pressed, right? Now, let’s say that unaware to you, a wire that is connected to the lower
part of the contact has been disconnected and you are not aware of it. Now, what happens when
there is an emergency? Well, when there is an emergency,
you press this Emergency Stop switch, BUT the switch will not work. WHY? Because the wire has been disconnected
and you are not aware of it. You never want to put yourself
in a situation like this. Because this is too late
and also too dangerous. So what’s the solution here? Well let’s repeat the same scenario but this time replace this
normally open Emergency Stop switch with a normally closed switch. With this normally closed
switch in the normal state, there is a 24-volt signal
connected to the PLC input, giving an Emergency Stop healthy signal
to the PLC, or other safety systems. When the switch is pressed,
the healthy signal will be lost, and that’s how the PLC, or safety system, knows to shut down the whole system. Right? Now imagine the switch is
back to the normal mode, but this wire gets
disconnected for some reason. What happens now? In this situation,
the healthy signal will be lost, and the PLC sees that as someone
pressing the switch, right? So it shuts down the whole system. So with this Emergency Stop switch, if the wire connected to the switch breaks, the PLC shuts down the whole system. Yes, I know, an unwanted shut down is not
what you want when a wire-break happens, but this is much better
than having an emergency but not being able to shut down the system. That’s why you always need to use a normally
closed switch, for your Emergency Stop. The Emergency Stop that I have here
goes to the lock mode when it’s pressed. So I press the switch, and as you can see, the switch goes back to the lock mode. Now to unlock the switch and turn
it back to the normal mode again, I can twist it like this, and the switch will get back to the normal mode again. On the back of the door, you see that the
switch is wired all the way to the PLC input. This is a BECKHOFF PLC. The blue wires that you see here
are digital input and output signals, the white wires are analog
inputs and outputs signals. These wires come all the way from the
sensors and actuators in the field and get connected to the PLC. Of course, we only have these switches
on the panel door connected to the PLC and the rest of the sensors and actuators will be connected to the PLC once we
install this control panel in the field. The Emergency Stop that we have on the door is connected to the PLC digital input card as it only sends an on and
off signal to the PLC input. Now you maybe be curious how you
should know which input on the PLC you should connect the Emergency Stop to. Well, this is simply done based on
the wiring diagram that we have here. In a later video, I will get into
the details of the wiring diagram and show you how simple it is to read
and carry out the wiring on this panel. Now let me give you an overview of all of the
important components that we have for this panel and also see how they are connected. As I mentioned before,
this is a BECKHOFF PLC. The first module that we have for this PLC is a CPU. The CPU works as the brain of the PLC. As you can see,
the CPU has a few LED indicators here, a couple of Ethernet ports and also a bunch of DIP switches right here. Next, we have the input and output cards. Of these cards, those with blue wires are “digital” input, and output cards and those with the white wires are
“analog” input and output cards. So you see that we use separate
cards for digital and analog signals. This PLC that we have here
is a unit that includes a CPU and a few input and output cards, which together make up the PLC hardware. Now let’s take a look at the wires
that are connected to the PLC. These wires come all the
way through the trunking, and then they are connected
to these terminals here. So one end of the wires are
connected to the PLC cards, and the other end is
connected to these terminals. Now later, when we install this control
panel on the field or the factory, the sensors will be connected to the
other end of these terminals. How? It’s very simple! First, we make some holes
on the bottom of this panel, like the holes that we have here. This is called a gland plate and allows
the cables to come into the panel. Then, we put them into the trunking and connect them to the
other end of these terminals. Please note that I am using the
term “cable” here instead of “wire”. What’s the difference? “Wire” is a single conductor, like this, but a “cable” is a group of wires,
like this, that is covered in a jacket. So wire and cable are different. A wire is a single conductor but a cable is a group of wire.
Very simple! Outside of the control panel, you use cables, but inside the panel,
you remove the jacket and use the wires. Why? Because inside the panel, you need to label every single wire. Why labeling? You need to label each wire to be able
to make the uniquely identifiable, which helps with troubleshooting
if there is an issue. The wire is labelled at both ends, so you know exactly where
each end terminates. Moving on, as you can see, the PLC is connected to an
Ethernet switch via these cables. From the other end, the Ethernet
switch is connected to these devices which we call Communication
Interface Unit or CIU. These interface units connect to the
pumps that are installed in the field, and that’s how the PLC
can control the pumps. So the PLC is connected to
this Ethernet switch first, then the switch is connected
to these Interface Units, and then the other end of the
units are connected to the pumps. Some field devices are connected
to the PLC directly via wires, and some others are connected
via Ethernet cables. All right, here we also
have the power supplies. The bigger one has 24-Volt DC output voltage and 20 Ampere or sometimes shortened
to Amp or Amps output current. The small one has 12 Volt DC output voltage and 10 Amp output current. Both of these power supplies
receive 220 Volt AC as input. This bigger one gives you 24
Volt DC in the output here, and the smaller one gives
you 12 Volt DC on the output. Now you may ask why we have two
power supplies in this control panel with different output voltage. Well, that is simply because we have
some devices in the control panel that work with 24 volt DC and some
other devices that work with 12 Volt DC. We use this one to power the
devices that work with 24 Volt DC and this one for powering the
devices that work with 12 Volt DC. Wonder why the 24 Volt power supply
has a greater output amperage compared to the 12 Volt power supply? This is because the number of devices, or the devices themselves, powered by the 24 Volt power supply require more input current to operate than those powered by
the 12 Volt power supply. We usually size the power supplies based on
the amount of current output that we need. For example,
we have power supplies with 1 Amp, 3 Amp, 5 Amp, 10 Amp,
and 20 Amp output current. The more devices we have,
the more current we need and the bigger the
power supply gets. Easy, right? So this was an in-depth overview of
the essential components that you see in an electrical control panel. This video was brought to you
by RealPars in partnership with Pro-control here in the Netherlands. They are experts at control system
design and industrial automation. They have a team of world-class
automation engineers and have been designing and implementing industrial control systems in
different industries for many years. If you want to get in contact with them, you
can check out their website at That’s We will put a link to their website in
the description below the video as well. Ok, that’s all for today’s video. If you have learned something
new from this video, it would mean the world to us to like this video. If you haven’t already subscribed
to the channel, please do so. When you subscribe, don’t forget to hit the little bell next
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that we post a new video. And if you have got any thoughts or questions, add them in the comments below. We read each and every comment and
reply to it in less than a day. Thanks for watching and we’ll
see you in the next video.

50 comments on “Reviewing the Basics of an Electrical Control Panel (Practical Example)”

  1. Alpesh Jadhav says:

    Please make a video on wiring of PLC I/O and power supply in panel…

  2. charles dlamini says:

    Thanks a lot electrical wiring is now becoming very clear

  3. Bottn says:

    A video by making an exhausted review of each electrical component teaching how they work and how to troubleshoot can make a boom on this channel, love realpars

  4. Thagmal Geddes says:

    Very comprehensive and detailed video, honestly one of the best Channels for Electrical, Instrumentation, and automation!!

  5. Craig Rollinson says:

    Great video. Please can you do one to help with reading schematics in the field, anything would help

  6. Ahmed Amer says:

    Thank you for the helpful video. I love to watch your videos. You did a very good effort. What I would like to see in the next videos is what rules should be followed in shielding, earthing and grounding the control panel, VFDs, PLC and sensors.
    Thanks again. you rock.

  7. Kunjabihari Jena says:

    Thank you sir giving ideas of PLC.

  8. Nivid Shah says:

    More practical videos please 🙂

  9. Rabah Boussada says:

    Thank you

  10. Derin A. Maleek says:

    Perfect stay tuned

  11. An Tran Duc says:

    I have question. What is communication interface unit in this video. Could you please explant me about and function of it. Thanks

  12. An Tran Duc says:

    Good teacher

  13. حامد پاشایی says:

    is it reliable to connect emergency system to plc,i mean i thought plc isnt reliable to shutdown whole system in emergency situation ? thx for your videos,i love realpars

  14. rahulbindhu r says:

    Love you real pars

  15. ARUN KUMAR says:

    Thanks for sharing your knowledge

  16. Silver line says:

    Nice video..
    Why are the pumps directly not connected with PLC using contactors or relays, what is the use of CIU between PLC and pumps ? by using relays or contactors you would have saved the cost of Ethernet switch..
    Please clear this doubt

  17. Monkey Dee Dav says:

    Can't wait for the next video !

  18. Frits Zonneveld says:

    Please don't learn people to wire a emergency stop function direct to a plc. Never trust a program to handel your safety. Always wire a safety controller, this checks for wire continuety. So wen a wire got lose your emergency conyoller shuts down. A few examples PILZ pnoz , twinsafe from beckhoff. You can wire a feedback signal from your safety controller directly to your plc

  19. naib at world says:

    Besten Dank! RealPars™ ⏩⏩

  20. Vahid Tamimi says:

    My favorite channel in Youtube. Keep up the good work.

  21. A M says:

    Thank you for this tutorial.

  22. Noran Kunda says:

    Keep up the good work realpars

  23. Lawrence Farinelli says:

    Videos like this can really help me when it comes time for me to take my practical test at work. I’d love to see more videos like this! Thanks for all your videos

  24. Bob Stout says:

    RealPars rocks! Josh makes these videos more awesome!

  25. Ye Htut Naung says:

    Another informative video , thanks a lot

  26. kiy kio says:

    Thank you. I need connect analog s7-200

  27. Iftikhar Ahmed says:

    Plz explain the wiring diagram ,in detail like this

  28. akshit reddy says:

    very helpful to understand the practical situations…..with such a simple explanation of the panel components

  29. Nosratollah Abedi says:

    hi first Thank you for the helpful video
    i have a question on the subject of vfd and inverter, where i can propound it to get answer?
    it's a specialized question.

  30. jermans kingsly says:


  31. Mohamed Atef says:

    Please add assembly guide, where we should put the power components and the control components in the panel, thanks

  32. Alikhan Zulkashov says:

    As always, realpars makes the most informative and helpful videos, looking forward to watching new videos in this video series. 👍👍👍

  33. Anton Horai says:

    What's the point of carrying sensor cables from the bottom, thrue the whole cabinet, to the terminals at the top, and then back, to controller at the bottom? Why dont You place sensor terminals near the PLC? Thanks for your videos!

  34. Vladislav Supron says:

    Thank you for interesting video and good explanations.

  35. Abd Oud9 says:

    Thanks guys I will share it everywhere keep it up 👍

  36. Tony Nguyen says:

    Thank you! I love these detailed explanation videos! Keep it up please!

  37. Wilberth Enrique says:

    Thank you…

  38. Soualmi Aymen says:

    wow very exiting video, i've learned alot and you have made clear of alot of what i see in the field thanks alot realpars keep the honey runin in your channel love you all

  39. Mostafa Seyedan says:

    That's my first comment on YouTube.
    I'm Persian and I work in automation.
    I never have been educated this good in my life!!
    Love you guys. Keep up the perfect work♥️

  40. Jermy Ermi says:

    very interesting video thank you

  41. Abdo Mohamed says:

    Very useful video, can you make video about SIL (safety integrity Level), please?

  42. Vikki Jukes says:

    How can I get a job in automation sector

  43. Ben Hurley says:

    Just what I needed. Thanks 😊

  44. Habeb Sabri says:

    Thanks for this video I want a way to read your blueprint for the control

  45. Mayank Tandon says:

    Superb man

  46. Emad Eddin says:

    Great as per usual . You always think out of the box .

  47. Melquíades Delgado Ramírez says:

    As usual, the best time-investing in learning industrial automation comes from you RealPars. Thank you and Pro Controls for taking the time for bringing to us new valuable and informative material. I'll be expecting more.

  48. Maysam Mirzakhalili says:

    Thank you very much. I am learning so many amazing facts from your brilliant videos. Thank you.

  49. Arentas REC says:

    Nicely shot video but when you listen it sounds like this video made for primary school kids to tech basics of automation panel and very long video for amount of information explained. Nice work thought.

  50. XC Z says:

    hope have a video to Introduce the specification's grounding system

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