100A breaker?

[D Skelton]

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?

 

[Amp David]

A 100 amp main is a switch. Its rated to carry and be switch whilst carrying 100 amps

 

[telectrix]

the 100A rating of the main switch is the rated current it can carry as a constant load. nothing to do with breaking capacity, as it's just a switch, nothing more. as for RCDs, the A rating is the max. safe load current.

 

[D Skelton]

Ok, so in that case, why are there RCDs with different ratings? Why are they not all 100A?

 

[Amp David]

Cost?????

 

[D Skelton]

Hmm, so you reckon it's as simple as that? Makes sense I suppose.

Cheers chaps

 

[Amp David]

You're welcome, invoice is in the post:stuart:

 

[mogga]

You're welcome, invoice is in the post:stuart:

obviously not up to speed with the P.O. price rises Email ios cheaper these days

 

[D Skelton]

You're welcome, invoice is in the post:stuart:

I pay cash only I'm afraid. Feel free to come down and collect it however

 

[Amp David]

That's fine chief

 

[baldsparkies]

100 amps is a fair load by any estimate. Regardless of what the mainswitch, mcb, mccb, or rcd's are rated at, its always good practice to isolate loads before you energise. Then ramp up the loads/circuits one by one.
I have seen the less experienced looking for a fault due to mccb's not latching back in. When in fact no fault existed, just a simple case of trying to energise under load.

 

[Darkwood]

To note here! A switch disconnector will have an AC rating and its this that denotes its switching under load capabilities -
AC20 .... connecting and disconnecting under no load.
AC21 .... switching under resistive loads.
AC22 .... switching of mixed resistive and inductive loads.
AC23 .... switching of highly inductive loads.
You may be given 2 ratings on the switch ie. AC22 - 100amps and AC23 - 55AMPs (random guess but shows the reduction when using on inductive loads).

The number of times ive seen so called sparkies fitting say a 40A switch to a machine which is often used to switch off when motor running and assuming 40amp means 40amp regardless and not realising its a AC22 rating - thus isolator fails, welds loses phase etc.
Also to note is their is sometime a suffix at the end either A or B, AC22-A or AC22-B .... the A is for frequent switching and B for infrequent.
Always check the switch rating on its info if you have alot of inductive loads as most switches are sold under their AC22 rating.

 

[Guest55]

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?

I find it staggering that an approved electrical contractor would not know these details.
Truely speechless.

 

[vernam616]

I agree with the above post, frightening that you sign off work

 

[ipf]

Ok, so in that case, why are there RCDs with different ratings? Why are they not all 100A?

Same reason switches are not all 100A.

 

[Brightspark2]

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?

A main switch provides no overload protection and an RCD also provides no overload protection.

A 100A main switch isnt a double pole MCB nor does it have 100A breaking capacity. An isolator is an OFFLOAD device.

Ok, so in that case, why are there RCDs with different ratings? Why are they not all 100A?

What about for currents over 100A??...


Basics my friend....

 

[D Skelton]

I find it staggering that an approved electrical contractor would not know these details.
Truely speechless.

I agree with the above post, frightening that you sign off work

I do apologise guys, it seems I'm in the wrong job! I didn't realise that to be an electrician you had to know everything. Anyway, I'm off, I've got to start job hunting as clearly I'm not cut out for this electrical malarky.

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

 

[vernam616]

Erm it isnt About knowing everything , however knowing basics like that is a given

So yes if you didnt know that a main SWITCH is not a breaker you are in the wrong job pal, i take it your another one who doesnt have nvq level 3?

 

[Snapester]

vernam616 i think you are being slightly harsh, we all come on here to learn and better ourselves yet you make rash comments? I Think you should go a little easy as maybe one day you might require someones help to a question you are unsure of.

 

[vernam616]

Jesus christ get real man, theres no wonder Electrical Trainee get away with it because the world is full of people like you, i can imagine an apprentice asking this sort of question and id gladly answer them, however not an APPROVED CONTRACTOR, boils my blood it really does, someone who signs off work saying its safe is asking whether or not the main switch is a breaker

Your on the same level

 

[Amp David]

Erm it isnt About knowing everything , however knowing basics like that is a given

So yes if you didnt know that a main SWITCH is not a breaker you are in the wrong job pal, i take it your another one who doesnt have nvq level 3?

I've no NVQ 3 but still know the difference between an MCB, RCD and an isolator:freak:

 

[telectrix]

a few harsh comments here. OK, maybe a fairly basic question, but gaps in learning have to be filled at some time. i don't know exactly how a differential gear works, but i can still drive round corners. i don't know how my typing on here gets converted to 1's'and 0's and back to words to your pc/iphone/laptop, but that doesn't mean i can't communicate.

 

[Des 56]

NVQ 3 maketh the spark

Whats this obsession with nvq 3 or whatever else is the current fasion
There has never been and likely never will be a definition of what constitutes an electrician

I call myself an electrician ( others can describe me as whatever they feel is suitable) I know or want to know nothing of this nvq fad,I take it that it is an installation course

Being an electrician used to be about being able to operate in maintenance or installation
In that maintenance role,fault finding and assessment of safety (test and inspection) was and probably is part of the job
When installing electrical systems and equipment.yes we used to do both. Electricians had one day to wire a house and the next install conduit or pyro or tray etc in an industrial workplace and the next go and fix a complex broken down machine
If we were presented with an armoured cable,( the type that most nowadays dont even see)we may ask, is it double wired paper insulated ? or perhaps lead sheathed ? we had skills for wide ranging activities

We also tried, as best we could, to keep up with modern practices and technical knowledge

There were good sparks,average and some who should have never been in the job,but there never was a defined piece of paper or even an organisation and that includes the JIB, that determined the role (the role of electrician was around for eons before this over hyped young JIb system was dreamed up)yes it is very short lived


No definition of electrician is the reason these days we have short course sparks, and also sparks, like some I could name on this forum, who in a way have no right to call themselves electricians, because their knowlege and abilities go way beyhond an average spark

In this wide ranging field of electrics,it is impossible to be a know it all
The various roles that members of this forum perform in and succeeded by making it the top,it shows this is a forum for sparks of all experiences and abilities

There may sometimes be anger and frustration at quick fix training etc,but that is the way of the world and it will continue

The opening post seemed to contain obvious gaps in knowlege and there is no doubt,he needs to knuckle down to his definitions,but who are you to say he is not an electrician,he may very well and probably does do an excellent job,we can never know, insults like saying get another job shows lack of understanding of your own trade,because of the variation of that trade

To any who deem it OK to throw around the superior attitude I say beware your comments dont come back to bite you
Even the high achievers. I have seen them make simple and surprising comments at times,all are fallable

Its time that judgement and personal critisism was laid to rest,because who in the end are you to judge what constitutes a spark


Why I have written the above,is to try to demonstrate to some.who have the opinion that a piece of paper or experience in a section of the industry suddenly gives them the right to determine who or what constitutes an electrician,it has never been defined

 

[telectrix]

an admirable post, des.

 

[RogertheBodger]

Very well said Des. I have just scrapped my own post on similar lines because I couldn't put it any better than that.

I will say however that I for one am sick to death of reading comments from the worlds best Electricians who's only point in posting is to rubbish someone else's opinion, and I am sure there are lots of others who share my opinion.

This problem seems to be getting worse, if you don't like a post, just move on to the next one.

 

[Andy78]

I agree that some of the comments were harsh, but these are things that I would definately raise an eyebrow at if a self employed domestic installer said them to me. I would say some knuckling down and revision is a very good idea indeed. Every sparks should be aware that every item of electrical equipment has ratings of the voltages and current it is designed to carry. How can you use them properly if you don't ?

We are all learning every day however, no matter our experience. This forum is for questions to be asked and answered. I am a new member so don't know if this is the way round here, but a lot of people come in for abuse when asking for help. How helpful is that really ?

 

[Andy78]

D Skelton, just for some info, maybe interesting, maybe not. On 3 phase distribution boards you do get MCCB incomers, RCD incomers, and switch disconnectors that fit in the same board, although this will differ by brand. Domestic CUs main switches are just switch disconnectors however.

 

[D Skelton]

Erm it isnt About knowing everything , however knowing basics like that is a given

So yes if you didnt know that a main SWITCH is not a breaker you are in the wrong job pal, i take it your another one who doesnt have nvq level 3?

Jesus christ get real man, theres no wonder Electrical Trainee get away with it because the world is full of people like you, i can imagine an apprentice asking this sort of question and id gladly answer them, however not an APPROVED CONTRACTOR, boils my blood it really does, someone who signs off work saying its safe is asking whether or not the main switch is a breaker

Your on the same level

For the record, I'm no Electrical Trainee, but who are you to question the job I do and why on earth should I have to come on here and have justify myself to you?! I worked dam hard to qualify as an electrician, excelling above and beyond my fellow students at the time! I have gaps in my knowledge yes, I'll be the first to admit that, but I'm also sure I have knowledge in other areas of eletrical work that would far surpass yours. I guarantee that some of your gaps in knowledge would be what I would consider to be basic but I assure you that you wouldn't catch me on here shooting you down for asking a basic question.

You badger on about the importance of an NVQ and yet you only completed your 2391 last month where as I completed it years ago! A qualification that many regard as having much greater importance than the NVQ. Not that I proclaim to be an expert because of one poxy qualification!

I know that a 100A main switch is double pole, I know that it is rated to only carry 100A, I know that it is suitable to provide isolation, I know it is linked and I know when I do and don't need one. I also thought for a moment that it might have functioned as a breaker, whooptie doo!

If I'd never have asked, I'd never have known, and funnily enough, no one at college ever explained to me exactly what a main switch is. If this is such crucial knowledge, tell me why no one ever thought it neccessary to tell me whilst I was studying??? Probably because it doesn't matter in the grand scheme of things!

Although it's good to know for example exactly how an RCD works, why is it neccessary? As long as you know where the regs tell you to put one, and what type it should be then there's never going to be a problem is there.

You sir have not been helpful or informative in any way, you have not advised me or even made known a professional or useful opinion. You have written nothing but abuse, and for no reason at all?! My only question is what made you so insecure that you had to shoot down a fellow qualified electrician? Saying that, I don't even care, I have nothing more to say to you and I can proudly welcome you as the first member of my ignore list!

Finally, special thanks to Des and to all of you who have either educated me, informed me or even just stood in my corner. I salute you all

 

[D Skelton]

D Skelton, just for some info, maybe interesting, maybe not. On 3 phase distribution boards you do get MCCB incomers, RCD incomers, and switch disconnectors that fit in the same board, although this will differ by brand. Domestic CUs main switches are just switch disconnectors however.

Thank you Andy, I am aware of this

 

[Andy78]

Thank you Andy, I am aware of this

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.

 

[D Skelton]

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]

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]

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]

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.

 

[D Skelton]

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

Oooh hello! Hopefully you'll get banned for that remark but just in case, welcome to the second slot on my ignore list

Good day

 

[Spudnik]

Two members have now received a temporary ban.

If anyone else would like to join them, please let me know.