Circuit Breakers - How they Work, What's Inside 

I don't know where you live or what you studied but in Florida they rarely even mention the practical application of anything until well into the profession- if at all. And many electricians don't remember if they ever knew the applied science of it. Most don't apprentice, but are tied to a single licensed electrician. Engineers sit in front of computers for the most part.

They fit onto the same rail, but connections to the busbar and spacing of the terminals can be different between manufacturers. Consumer units are type tested assemblies, and that approval only applies if all of the devices in it are from the same manufacturer, so although it's often possible to physically fit devices from other manufacturers in there, it shouldn't be done.

No never, he has however freelanced as a presenter for ITV's Magaluf Weekender.

Akram Al-Hayek A HRC fuse my best guess.

Transformers appear as a short circuit before power is applied, so there is a significant surge when switching on. Once power is applied, the magnetic field of the transformer limits the current to almost nothing until something is connected to the output side. Whether it trips or not depends on where the AC mains cycle is - if it's at the peak value it will probably trip, but if at a low or zero value it probably will not.

T, Skipwadoo ww

change fridge bulb

Omar Alvi Yes, doesn't matter which way they are connected.

Thanks you for replying this quick. I like your channel and watching all of your videos. Very informative and educational. Its a great work. Pls keep it up.

Unlikely to be faulty, motors do have a significant surge when first switched on, often 5x-10x the running current, so can easily trip lower rated circuit breakers.

Thanks John.

They will work either way, it does not matter which is source and load.

Per Mejdal Rasmussen Lighting circuits usually, most homes have 6A lighting circuits with one for each floor, some older or smaller properties have a single 6A circuit for all of the lighting.

***** Interesting. Then you can use 1,0mm² instead of 1,5mm² thick wires.

+Sajid Rafique No, if circuit breakers have failed, they must be replaced. Zinsco were never sold in the UK, but a quick search reveals they are the type which welds closed and cause fires, so probably better to replace the entire panel.

+John Ward Thanks John, for informing me of the fire hazard ! Really appreciate that !

Yes, they don't last for ever. Repeated trips will cause damage inside and they will eventually fail.

@@jwflame Every product has a lifetime, that is clear. However, it looks like the performances are also effected (i.e. getting weaker: not able to withstand the same load and/or inrush peak current as before).

Kageitenshi For short circuit faults there will be little or no difference, both a B and C type will trip very quickly - typically less than 0.1 seconds. There won't be any discrimination between a 10A and 15A circuit breaker either, so either or both could trip.

***** Thank you for clarifying. Though I may be a bit paranoid about overloading the breakers, resulting in a walk of shame, I'd prefer to be on the safe side: Until I realized that my newer water kettle was rated at 2.6 kW, instead of the 1.8 kW it replaced, I routinely ran it alongside an 800W microwave and a lamp. It wasn't until I tripped the kitchen appliances breaker that I realized I was drawing very close to its rated 15A from the ~230V mains. Came as a surprise every time until I learned not to do that, rather slowly, thanks to how the microwave operates on "medium" and "low" settings for thawing, randomizing the intervals. Well, despite not having enough resistance at the business end of the kiln's heater to limit the current below 10A, but closer to 15A, the SCR dimmer and VA meter should be sufficient controls. Safety first.

bhupendra sharma yes, such devices exist. Either surge protectors for spikes / intermittent increases, or an overvoltage release for situations where the supply voltage increases above normal. Hager MZ209 is one example.

No, this would normally be behind the Shroud, and you should only remove this once the circuit is Safely Isolated, and then only if you’re Qualified! - Julie

Is that a One-punch man t-shirt?

brian whittle Possibly, larger motors often require the use of C type breakers as the starting current can cause B type devices to trip. Alternatively it could be that the motor had some problem such as sticking bearings, which would cause it to draw more current.

The bimetallic strip is for moderate overloads and reacts slowly, trips from 1.13x to 1.4x the rated current and above. It will typically take many seconds or 10s of seconds to trip. The magnetic solenoid is for short circuits and for a Type B will trip near-instantly from 3x to 5x the rated current and above.

@@jwflame Thanks, Mr Ward.

david freedman Possibly, although if the wiring to it is original, the wire insulation will certainly be unsafe. For switchgear and similar items, age in itself isn't a problem - it all depends on the condition it's in and how / where it's been used.

ok thankyou your help.

No, circuit breakers are specifically designed so the cannot be disabled, they will still trip even if the lever is fixed in the on position. The only way to disable them is to remove them completely, and with no overload or short circuit protection the cables will overheat and cause a fire when a fault occurs.

Why would you want to? Wont it just start a fire?

6 amps but that's at 240 volts, so the equivalent circuit power of a 12 amp 120V breaker. Newer properties generally have more individual circuits, older ones have a smaller number of higher power circuits that cover larger areas. 2500 sq ft would be a very large and expensive property in the UK, most are far smaller than that.

@@jwflame lol my 2 bedroom apartment is almost 2500 Sq ft