Electricians' Guide: Circuit Protective Device Selection
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- Опубликовано: 4 июн 2024
- Selecting the Correct Circuit Protective Device: Hints and Tips for Mastering Electrical Design
Selecting the right protective device is an absolutely critical part of designing an electrical circuit Get it right and the installation will run smoothly for decades, get it wrong and the consequences are unthinkable.
The selection process is quite simple, however in this video we have a look at some of the deeper complexities that hide away in the design process ready to trip up the unwary electrician.
We also cheerfully bust a myth regarding the use of B Type, C Type and D Type MCBs and their correct use.
Take a dive with Joe into the exciting world of electrical design in this series of videos that will help you if you're just starting out in this area at college or work. Even if you've been an electrician for years, there's something for everyone in this series of videos.
If you want to take the full course this video is part of then click the link below to access our completely free training package you can take at a time convenient for yourself. Free, flexible, fully certified CPD: 👉 training.efixx.co.uk/course/i...
Made with support from the @lucecogroup see their full offering of electrical installation equipment here: 👉 www.lucecoplc.com/
Check out the other CPD content we've created with the Luceco Group here: 👉training.efixx.co.uk/#/home
For more information on the @ElectricHeatingCo electric boiler featured in the video click the link here: 👉 www.electric-heatingcompany.c...
🕐 Chapters 🕕
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00:00 How is the correct protective device for a circuit selected?
00:07 Free Electrical Design Training: 👉 training.efixx.co.uk/course/i...
00:24 Previous video, Calculating Design Current: 👉 • Mastering Electrical D...
00:40 Introducing Nominal Current from the On-Site Guide
01:05 The shocking truth about the rating of an MCB!
01:50 Why use an MCB and not a fuse?
02:04 How to select the correct size MCB based on the design current
02:23 Avoid this pitfall
03:02 Side quest for an individual case of a resistive load
04:18 Joe's absolute top tip for electrical design
04:35 Decision on MCB size made
05:35 Back to the main quest MCB Types
06:40 LED inrush currents
06:57 The final selection made
07:10 Next video in the series, Selecting the Right MCB: 👉 • Electricians' Guide: C...
07:14 Free CPD: 👉 training.efixx.co.uk/course/i...
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❌ This content on this channel is for electrical professionals.❌ ==================================
📹 Presented by
Joe Robinson - Technical Editor
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#electricaldesign #electricians #electricalinstallation 
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A common fault with certain new items stored in ( damp ? ) sheds , ( air fryers , sandwich toasters etc ... ) , is that damp gets into the element's mineral insulation causing modern house's RCD to constantly trip , the owner might then throw this item away ! .... one trick is to take it to a house with ( old skool fuse box circuits ! ) , run the item for an hour or two , and hey presto ! the RCD no longer trips at the customer's house ..... ( tried - n - tested ) ............ DAVE™ 🛑
3:57 'Professional brands like BG' - I've never heard of this classification.
Is there a list of non-professional brands so I can avoid using them?
Yeah but what would the industry be without the grass roots leveI amateur brands that just make them for the enjoyment of the game, not for the money.
we have a voltage optimiser so when doing calculations i use the voltage i get yes? not 230v or 415v
Nope you use 230vac
@edc1569 do you know why? Like wouldn't my calculations be wrong when it comes to selecting mcb sizes ect?
We're I work in Swindon.. it's always around 243v
@3.34 If the boiler load characteristic is 'purely' resistive would kinda depend a little bit on the internals so definitely not ideal to infer as such. I mean its definitely fair that its not purely inductive either cause it wont be. But the exent of the phase change between I and V will depend on the types of pump. Most seem to be AC therefore have an inductance value of some sort (usually low uH)... so depending on the size of the motor it will definitely add an inductive element reducing the PF away from Unity (ie PF of 1, or 100%). Also the low power element need a AC-DC PSU, which will have filter caps on its input lines (Class XY) adding capactance to the load characteristic further reducing the load PF away from Unity.
I fully appreciate this is pedantic as hell... the PF is still going to be high as the above elements will only contribute a small amount, but this being a training module, it perhaps needs to be more 'accurate' than a casual video and to say a boiler is a 'purely' resistive load (ie PF of 100%) isn't technically correct.
Its gonna be close and (hazarding a guess) have a PF in the order of 80-99%. I would say the load is 'almost entirely resistive'.
This is pedantic as hell.... I get that, but this isna training video as part of a CPD certified course.
I hope I'm not missing something obvious.....
It's a fair point, and I debated this point back and forth a lot to be fair, but I think as it's an introductory course I've struck the right balance between being alert to manufacturer's direction and going too far into the finer details. Modifications due to power factor will likely be covered in future training modules.
In fairness though... Small controls aside... All of the actual load is resistive. Any electronics are going to be a negligible contribution to the whole. Obviously if there was a stated power factor you should use it but if there was one in this case it will probably say greater than 0.99 if anything and he did say manufacturers instructions should be consulted.
I don't think it is a question of striking the right balance.
It is easy enough to explain that a heating element made from a coil of wire will have some amount of inductance as it's also a solenoid passing a current and creating a magnetic field. This is quite literally school level.
So it can be explained that a heating element has both electrical resistance in order to generate heat, and have some amount of inductance because it's creating a magnetic field.
And therefore as it is not a 100% resistive load, the power factor is less than 1.
I have just explained it without going in to too much detail and using knowledge which the student already has, or should have.
So there is an explanation which is very simple to understand that doesn't go into heavy detail and is factually accurate.
How then do you explain an electrical clothes iron which sparks when turned off or unplugged? Doesn't that contain a heating element? What's the cause of that, the resistance element of the load?
@@deang5622 because there's enough voltage for the current to jump the gap as the contacts open or close. This happens even with convection heaters. It isn't unique to an inductive load but it is more visible on heating loads because of the current draw.
This is such an argument over nothing on this thread it's unreal. None of our designs or calculations are accurate to the level of needing to worry about power factor on resistive loads like this. It's verging on farcical.
@@travoltasbiplane1551 And you think that for an iron it only happens as a result of the 230 volts across the contact?
Utter nonsense. Ever heard of back EMF's?
Do you know what causes a Back EMF?
Real voltage in my area is 243v and its never changed in my 30 year off sparking.. you should always checked your local area voltage 1st..
3:40 in the video you say if the nominal voltage U0 goes higher it will cause more current to flow? ln = P/U0 if U0 is higher the current will fall. Worst case scenario Ln = 9000/253 =35.6A
I think it was just a mistake.
Resistive load. Bang the same figures into ohms law.
After you've derived a resistance
For example: 230/10ohms Vs 250/10 ohms... Which gives you the most current?
9000 is the power in watts. not the resistance
"Electrician's Guide"? Seriously?
Surely qualifued electricians studied this in their City and Guilds courses?