100A breaker?

D Skelton · Apr 5, 2012

So a conversation with a fellow spark brought into question what exactly are main switches?

Is a 100A main switch a 100A double pole MCB or does the 100A mean its breaking capacity? I'm sure it's the former but I'm beginning to question my own knowledge as he thought differently.

Also, with different rated RCDs, 25, 40, 63...etc, Does that mean that it will trip if the current passing through it exceeds that amount essentially acting as an RCBO? If so, why do we need RCDs to double up as overcurrent protective devices as well?

This is probably quite a basic question but the reason we wondered is because we all seem to fit CU's with 100A main switches even when the cut out fuse is only rated at 60A or 80A. If the main switch is indeed a 100A overcurrent protective device, why is this?

D Skelton · Apr 6, 2012

Andy78 said:
Lol no worries. Hope I haven't insulted you, just don't know what you know. Plenty of domestic installers have never worked on 3 phase.

You haven't insulted me at all, you provided a useful and informative post. Whether I already knew it or not is irrelevant

And I'm not a DI as I carry out larger scale commercial work as well as domestic.

vernam616 · Apr 6, 2012

Certainly not insecure hahaha, just sick of reading these idiotic posts from so called "electricians"

You have a 2391 cause you learnt to pass the exam, otherwise you would have had the knowledge to know that. It wasnt a overload device

I pride myself on my qualifications and how hard i worked to get where i am today, if only everyone was the same

Apologies if you have been insulted as thats not in my nature to insult purposly, just really sick of reading stupid things like this

Guest55 · Apr 6, 2012

D Skelton said:
I assure you both that in my new line of work, whatever that may be, I'll be sure to remain ignorant.

I hear McDonalds are taking on burger flippers.
More arrogance by someone responsible for electrical safety in customers homes.
Idiot.

Darkwood · Apr 6, 2012

Biff55 - i suggest you actually contribute to this forum before shooting ppl down then we can see what exactly you think you know and your background, whos to say OP hasn't been working in other electrical areas and just re-newing himself or maybe he worked for a company with a boss like you who just shot him down at every opportunity knocking his self confidence, if you read his other threads and posts you'll find hes quite capable but just tidying up his knowledge here and there, yes he might have been told it at college but can you honestly say you recall every detail.