The Complete Guide to MCBs - Miniature Circuit Breakers

It's essential to keep our electrical installations safe and secure. In this learning module we'll explore how Miniature Circuit Breakers (MCBs) can provide protection, as well as what kind of MCB is best for your application.
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Also in this series the complete guide to RCDs
👉 • The Complete Guide To ...
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00:00 Minature Circuit Breakers - training
01:00 What types of fault to we need to protect against
03:25 How do minature circuit breakers work?
04:33 Overload protection
06:05 Fault protection
08:57 Nominal current
09:45 MCB types - B,C,D
10:10 Looking at the difference between type B & C MCBs
13:20 Problems with in-rush currents
14:25 Earth loop impedance and MCBs
17:15 Cmin correction factor
18:30 EN60928 manufacturer limits
20:16 Selecting the correct type of MCB
21:59 MCB Short circuit rating (Icn)
23:50 Prospective short circuit current
24:10 Service current Ics
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[@danyo1972]

These videos are fantastic. I am not an electrician, but I love to know how stuff works, and this tutorial really explains MCBs clearly and comprehensively.

[@abrahamben-]

Excellent! Concise, precise, useful and great fun to watch! Thanks a lot.

[@eddie_pegasus_electrical]

Great explanation Joe. I often get asked why I use mainly 6kA MCBs in control panels. The answer as you have explained so well, basically there maybe no need for the 10kA. As the Ipf is very rarely even close to 3kA never mind above 6kA at source, and even a lot less at the CP. 👊😎👍💙

[@kopspijker3515]

Taking an MCB to bits @ 3:35. BigClive would be proud!🥰.

[@AviKhali]

Thank you for the comprehensive information

[@michaelsimpson6603]

Excellent CPD video.

[@sologog8129]

Thank you, I have been researching B vs C switches recently but your explanation is really detailed.

[@greenpedal370]

You imply the MCB is new. It has been extensively in use for industrial and domestic installations since the 60s.

[@SeanBZA]

Yes had that short circuit issue where I used to work, seeing as the total length of cable, including the fuses and switchgear, was 15m, from the secondary terminals of the 250kVA transformer, via the 120mm2 cables to the busbars of the substation, and the 10m of 25mm2 SWA cable that fed the building disconnect. Did mean the voltage was stable at 238VAC on single phase though, though those 15kA breakers did cost a pretty penny when replacing a lot of the old Fuchs units for updates, though 2 of them stayed exactly the same at the original Fuchs units, no real replacement for the 100A 50kA breakers that fed the lifts, and all they got was dusting off and checking the screws were still tight. Board and breakers originally dated 1960, and, along with the substation, still going to be there for decades more no problem, with just a little regular maintenance.

[@kristiangoransson6104]

Where I work in Sweden I’d estimate that 95% of MCBs are type C, indifferent of it’s a commercial or residential installations. Doing a check it’s not often it’s actually a problem using type C but unfortunately most sparks don’t know that they’re taking a chance/risk when doing so.

[@thedangerzone9399]

Type B for residential in sweden. C for anything industrial or pro kitchens because of start load of motors. Same goes for rcb's. Residential is type A and anything three phase or single phase with frequency converter gets type B.

[@kristiangoransson6104]

@@thedangerzone9399 the wholesalers don’t stock any large amounts of type B MCBs. Fortunately it’s not very often there’s a problem with using type C in residential buildings.

[@MarkUKInsects]

@@kristiangoransson6104 How would that be scored on an EICR?

[@kristiangoransson6104]

@@MarkUKInsects we don’t have that system in Sweden. We’re supposed to do certain checks but nothing is saved or reported to any organization. That’s the most impressive thing about the UK and it would be great if someone would do a in depth video on what happens with the submitted documents and if there’s any follow up done. I could basically go out to a costumer and install a RCD next to an existing distribution board and only have to check the RCD, I’d not be taking responsibility for the rest of the installation and wouldn’t be able to make the customer change the entire board. It’s quite common with boards with different brands of MCB and accessories in.

[@TheManLab7]

I've got an old school 20A Variac and the smallest breaker that won't make it trip instantly, is a 40D. I ran 8m of 4mm armoured to my shed, which is the max the cable can take for that short of a run. But apart from my Variac with is a dead short on start up, the only other things I used that take that amount of power is my welder and heater.

[@AntonyoKnight]

Great informative vid

[@nicoladellino8124]

Very useful video, TNX.

[@30mAkills]

Very useful, educative and informative posting

[@wotireckon]

Here's an idea relating to diversity edge cases: a smart consumer unit that monitors and varies supply to individual circuits in order to prevent the main fuse blowing. This would be based on a priority system; to favour showers over cookers for example, but also to modulate/vary the power by means of voltage/current reduction or, as in the case of dimmer switches, alteration of the sine wave etc. A warning could sound when say 95% of available power is being used, and power could maybe tailored/controlled using an app. This type of CU doesn't seem to be available, (and is a logical extension of a smart meter) but might be an essential tool for future smart grids.

[@mpalaskokkalis1476]

Perfect

[@TheManLab7]

Can you talk about MCCB's panels and the breaker's to show other people who aren't sparky's. Thanks

[@girtsziverts3530]

Why persons who doesn't have electrical qualification need to now about electrical switchgear and MCCB's?

[@TheManLab7]

@@girtsziverts3530 because it's interesting

[@KristopherLee-fk5ll]

Is there a incoming and outgoing for termination? I struggle to debating with my coworkers.

[@efixx]

That depends on the device and manufacturer- usually not for MCBs

[@AdityaMehendale]

-Instantaneously- _Instantly_ - the MCB would not be very effective if the breaking was instantaneous ;)

[@girtsziverts3530]

You are absolute electrical genius.

[@greenpedal370]

Troll alert!!!!

[@boriss.861]

Why are you promoting PALAZZOLI MCB's from Italy? Available from Denman's Where is the UK made kit! I would say MK but they are owned by Novar and CircPro (UK) a division of Yihua