type C rcbo's

[Nicky Tesla]

When did Delta T and Zeroth law get mentioned in BS7671.......If Electricians need to know all this stuff, then we would know all this stuff. There are many on here claim to know the adiabatic but know nothing of Zeroth law, yet claim i am wrong. So Sidey, it is not just for my benefit to do the calcs and explain later.

I also got the feeling that it was going to be a long road leading to a dead end (A cul-de-sac without calcs ) after hours of posts.

 

[Sidewinder]

Nicky,

I'm not going to start at the end.

If you don't like it, tough then I'm going no further, we start at the beginning, or not at all, sorry.

It will not lead to a dead end.

If you don't believe me then we can stop here as I'm not going to waste my time.

The theory behind the adiabatic should be familiar to any qualified electrician, sorry.

If you or the others can't follow it then I am wasting my time.

 

[Manator]

I think people will need to stand back and read the literature. I am not for one minute suggesting I know where Sidewinder is going in relation to Zeroth law, other than to suggest that if you have studied it, you will also understand that two elements can coexist, and still show the same temperature, ie water and ice at 0 degrees, and water and steam at 100 degrees.

If sidewinder is willing to give up his spare time to show us some very good information, and pass on his knowledge then I would like to do it step by step so that I understand each phase before jumping to conclusions.

 

[jopo]

you guys have lost me. dont know who's batting on what side. been fun to read.

However the formula mentioned is what we must apply in certain applications as most here have mentioned and it is to be used for times longer than >0.1S. We apply the equation knowing to ignore external losses as any answer will always be on the safe side.

i wish i could locate for fact. As opposed to just saying its so but i was sure it is the other way around in that the accuracy of the formula is lesser when under 0.1 second. i.e dont apply if under .1 seconds.

as $parks has said the rcd component looks after the earthing clearance times. To calculate the clearance time for the L-N. Obtain the trip curve for the protective device and see how long the clearance time for the device is with the known line fault current. if your cable can handle that clearance time. what is the problem.

i know everyone has mentioned the above, just not in one post. you all seem to be agreeing with each other on individual points but not the big picture.

i've just lost my way trying to explain myself to you lot.

 

[Steve3948]

Well we went from a C type RCBO to Zorro and his sword so I'me well lost :Blushing

 

[kerching]

Well we went from a C type RCBO to Zorro and his sword so I'me well lost :Blushing

I have ignored this post until now, then I read it!

Back in the day when at that established North West seat of learning 'The University of Salford' I was forced into doing thermodynamics as part of my course. Lecturer was 'Sith Iffrikin'...say it out loud and it makes more sense! Could not understand a fricking word he said, so tended to not turn up OR just ignore him. One lecture we went into Zeroth's Law, my mate at the time [now a senior researcher at NASA FFS!!] muttered something about

"A cow has 4 legs, a chair has 4 legs; so a cow must be a chair" he claimed this to be the antithesis of Zeroths Law, got up and walked out!!!! He had been partaking of a light libation of a product made by a certain Mr Jack Daniels at lunchtime and we feel this may have clouded the clarity of his thought process

Not that relevant to the thread but I [possibly wrongly] thought it worth sharing. I will now :coat as I have a leaking roof to fix........... :Y

 

[Nicky Tesla]

come on sides, put your dummy back in and explain if you can. There is not just me, Manator is interested and many others:consoling

 

[M107]

Well if nothing else it's made me have a read about Zeroth's law & then I've progressed on to photons and N systems....................need a beer now to cool the old grey matter down

 

[Nicky Tesla]

Well if nothing else it's made me have a read about Zeroth's law & then I've progressed on to photons and N systems....................need a beer now to cool the old grey matter down

You see sides

 

[Manator]

come on sides, put your dummy back in and explain if you can. There is not just me, Manator is interested and many others:consoling

I think those who can always will, and those who cannot will always call those who can.

Lets face it Nicky you are just as lost as all the others, and are now wondering what the hell has the Zeroth law got to do with the thermodynamics of cable selection and over current protective devises.

It is OK I am lost as well, its been over twenty years since I did the maths.

I do know that Sidewinder has not spat out any dummy, and that he does know his onions and could explain if you give him the opportunity.

 

[M107]

When Sidey has time I'm sure he will post a very interesting & informative lesson on the subject you have requestd Nicky, but as he has also said he is rather busy & maybe he doesnt need hassling into doing it just now?

 

[Nicky Tesla]

I wait with baited breath

anyway come on England Guinness

 

[Sidewinder]

Nicky,

I said I am busy.

Now I can work through this with/for you.

However, if you are going to demand I post on you terms, and abuse me why should I bother?

I'm a long way to spitting my dummy out.

However, you have to do your bit too.

Which, I am awaiting.

 

[Nicky Tesla]

How many more times ......ITS NOT JUST FOR ME!!!

I get busy Too!

Also if anyone else wants to do the calcs and explain how you did it, then feel free

Anyway, what are you "awaiting" for...........i can see any tutorial that you do would not take hours but weeks and i bet we still would not get to the destination.

 

[park1]

Forget Zoro's law and all the spiel.

The adiabatic enables a simple approximation, assuming no heat is lost from the conductor into the surrounding material, no heat transfer. Simple.

The Adiabatic is good for ratios of 0.1s/mm2, but as it errs on the side of caution the regs don't worry so much about that.

The expression/formula is straight forward, I believe jopo posted an example on another thread.

If you want to go down the line of the non Adiabatic approach, then all you need to do is apply a factor to the adiabatic, this is also straight forward.

There should be no reason for the non adiabatic to be used in most instances unless we're talking transmission or large industry.

Most reference books have examples of the adiabatic, try Guidance Note 6.

HTH.

 

[professional]

I have to say that it has been very interesting watching people confuse each other, quote inappropriate drivel and go round in circles ....

So does anyone feel able to cut all of the **** and post concise, relevant design criteria so that I can THEN pick them to pieces? ROTFWL

 

[Steve3948]

It's no good I got so confused I had to go on medication for a while :worship

 

[professional]

It never ceases to amaze me how readily people reach for a "packaged" solution to any problem.

Time to stand back and look at BASIC PRINCIPLES - the fancy formulae and drivel are fine for an "academic ego trip" BUT common sense must prevail.

It is the easiest thing in the world to hide behind unnecessarily complex explanations that few will understand - but far more difficult to simplify a (possibly) complex issue.

 

[park1]

I have to say that it has been very interesting watching people confuse each other, quote inappropriate drivel and go round in circles .... So does anyone feel able to cut all of the **** and post concise, relevant design criteria so that I can THEN pick them to pieces? ROTFWL

6 amp BS88, 45A2s at 415V

1.5mm2 coper conductor, E= 29765.25 A2s

Cable protected.

 

[professional]

6 amp BS88, 45A2s at 415V1.5mm2 coper conductor, E= 29765.25 A2s

Cable protected.

"So does anyone feel able to cut all of the **** and post concise, relevant design criteria so that I can THEN pick them to pieces?"

That would be a resounding NO then .... even allowing for spelling mistakes and text speak. ]