Obvious question more than likely.

[jwc]

Second question of mine on here and it's one I've never got round to getting an answer for.


Mains comes into a building through a 60A main fuse for instance.
Why then are main switches rated at 100A or 80A?
Does this mean any load above 60A would blow the main fuse before it blew the main breaker?


Don't be harsh people. I'm fully aware the answer's probably an obvious one.

 

[brightspark2010]

as far as i can see it this scenario is the same as a 100a main fuse supplying a db with 2x 80a rcd with the load split so you wont overload that 80amp and by overload i dont mean trip the rcd as it wont i just mean pull more than the components cuurrent carrying capacity

surely if this is ok then so to would the 32amp radial? I would have always said the isolator needed upgrading to 32amp and the circuit was not designed well for its intended use.

It was a simple question with a simple anser that I obviously had not had taught to me in this way I am mister careful and have always done very well whereever I have worked and dont not expect to be called a crap dumb electrician as this is definately not the case

 

[brightspark2010]

so that scenario is ok? so what about then 32a circuit 1.5mm cable 5amp (whatever aplliance no fuse) that is again ok as the cable will not pull more than the load of that appliance?

 

[shagbite]

So you knew that from birth did you? Wow!

You can help how I define what you've stated, and that is by not stating it. What you define as basic knowledge is completely subjective and even still, how can someone who was taught this most 'basic' of knowledge from the word go by more than one 'qualified' tutor and by his site supervisor be at fault for accepting what he was being told? I don't know the OPs situation, whether or not he is a Electrical Trainee or a time served spark, but what I do know mainly through personal experience is that questions like this can be answered without jumping to conclusions.

What I can't abide by is supposed 'qualified' sparks asking stupid questions like: "Why can't I use one neutral conductor for two different circuits?", "does the water need bonding if it comes in in plastic?" and "can you put a socket in a bathroom?" when the answer is there in black and white in the BGB. Unfortunately, there are things that aren't in the BGB that need to be taught, sometimes they just happen to be taught wrongly or not at all. There was a recent post on here from a valued member asking questions about adiabatic equations and how 't' is applied in different circumstances. This is basic stuff for me, calculations, formulae, thermal effects, inductance, capacitance, trigonometry, transposition blah blah... but clearly it isn't basic for him. Still, I know through some of the advice he has given others, stuff that is basic for him is good advice and that he knows what he is doing but most importantly, knows his limitations at this point in time. Should I be slating him for his lack of 'basic' (in my opinion) knowledge?

Like I said, I was learning ladder logic before I even knew about bonding! At the time I still thought that an RCD had overload protection (not that it affected my work at all) I was wiring and programming complex automation systems, fault finding motors and designing installations, but by your definition I would be a $hit electrician because I lacked 'basic' knowledge. Well sorry mate but we all lack a little basic knowledge here and there.

I refuse to accept that someone who can realise that they need to ask questions, however basic at times, must be crap at what they do!

I bet you couldn't tell me off by heart the minimum distance control gear can be placed from a swimming pool or basin? I know it, it's basic knowledge Eng!?!?!. Does that make you a crap spark? Of course not!

you make some excellent points here mate, especially about basic knowledge being subjective and hopefully i'll remember it the next time i jump down someone's throat. (but don't hold your breath!!).


having said that, when i think about your confusion over the role of RCD's, i realise that your mistake was borne out of misinformation. if you have your teacher and your gaffer challenging your beliefs, it's more than likely that you're going to be swayed towards their way of thinking.

what you say about "not knowing the op's situation" is a valid point, but try as i might, i can't imagine anyone telling him that the double-pole main switch on a domestic consumer unit is used to break overloads.

i've met a few people that struggled to get their heads around the role of a RCD, but i've never met anyone who thought the main switch was a MCB (on a domestic cu).

 

[shagbite]

In my day, we had to sit a series of aptitude and math tests to be accepted by my company as an apprentice!! There was no such thing as multiple choice C&G exam questions either. Each question if answered, needed to be answered in full, so if you didn't know, then you failed, it was as simple as that!!

you were lucky; you entered the industry before the accountants started running the show. the quality of education shouldn't be sacrificed in order to make a profit.

 

[Jay Sparks]

I once worked with a sparky that had completed the apprenticeship and been in the trade, for the same firm, for over 10 years. I heard him on the phone one day talking to one of his mates. He was talking about a normal thermostat, in a house. He told his mate that the stat controlled the temperature of the rads!!! Of course after he finished on the phone, I corrected him but not in a billitiling way. In his defence, he did say that all he's ever been shown about stats, is how to fit em, not how they work! He has given me invaluable advice on stuff that Ive never come across before and thats what this game is all about...learning!

It comes down to how you were taught at college by your tutor and by your mentor (sparky), if they were good at there job, you SHOULD be good at yours!!!

 

[shagbite]

I once worked with a sparky that had completed the apprenticeship and been in the trade, for the same firm, for over 10 years. I heard him on the phone one day talking to one of his mates. He was talking about a normal thermostat, in a house. He told his mate that

the stat controlled the temperature of the rads

!!! Of course after he finished on the phone, I corrected him but not in a billitiling way. In his defence, he did say that all he's ever been shown about stats, is how to fit em, not how they work! He has given me invaluable advice on stuff that Ive never come across before and thats what this game is all about...learning!

It comes down to how you were taught at college by your tutor and by your mentor (sparky), if they were good at there job, you SHOULD be good at yours!!!

to be fair, indirectly, they do.

if the air temp' drops below the thermostat's setting, then it fires the boiler which heats the radiators.

but i get what you're saying - they're not directly linked.

 

[7029 dave]

who remembers the old 12 way wylex cu,1980's that had 60amp main dp switch just like all domestic cu's back then. ps give us a like if you remember!!

 

[Andy78]

Vaguely remember them, from childhood..... lol certainly never fitted one if thats what you mean

 

[Andy78]

Never come across one as a sparks come to think of it. Plenty of 2, 4, 6, and 8 way, but can't recall seeing a 12 lately.

 

[shagbite]

who remembers farah's from the 80's? sometimes worn with a snake-belt. ps give us a like if you remember!!

 

[7029 dave]

Never come across one as a sparks come to think of it. Plenty of 2, 4, 6, and 8 way, but can't recall seeing a 12 lately.

the dp main switch is bang in the middle 6ways either side

 

[Andy78]

In that case no, never seen one.

 

[Jay Sparks]

to be fair, indirectly, they do.

if the air temp' drops below the thermostat's setting, then it fires the boiler which heats the radiators.

but i get what you're saying - they're not directly linked.

Yes but he was saying, if you set the stat to say, 25*C, then thats what the radiator temperature will be at.....but the radiator temperature is controlled by the TRV.

As I said, its just miss/ill information from his tutor/mentor.....but then again, this may have never come up over the 4 years!!

 

[shagbite]

he didn't work for bailey's did he?

everyone i meet from there seems to spend their entire working life doing the same thing, day-in day-out.

 

[Jay Sparks]

he didn't work for bailey's did he?

everyone i meet from there seems to spend their entire working life doing the same thing, day-in day-out.

No, a firm near me. Ive done some subby work for them over the past few years. There work does vary, or it did when I was working for them.