type C rcbo's

[park1]

yes i know what the "O" stands for, but L/N Loop eh! Earth faults need a very low ohm range to make sure you get high enough currents to trigger off the MCB before 0.4 seconds. ie before someone dies (in theory)

Overcurrent is different. A flow of 30A may flow through a 10A MCB but will not trigger off the MCB before 0.4 seconds cos the fault is not seen as passing through a person for eg.

What i think you are getting at is short circuit protection ie a direct short from live to neutral and not to earth.

Well no.....All the Zs figures are to do with the 0.4 second Diss time for earth faults and have nothing to do with short circuit faults. But if you can prove they do, then do it.

In the case of MCBS, they have everything to do with it, as I said, they are all or nothing.

 

[Nicky Tesla]

oh forget itheadbang

 

[Steve3948]

yes i know what the "O" stands for, but L/N Loop eh! Earth faults need a very low ohm range to make sure you get high enough currents to trigger off the MCB before 0.4 seconds. ie before someone dies (in theory)

Overcurrent is different. A flow of 30A may flow through a 10A MCB but will not trigger off the MCB before 0.4 seconds cos the fault is not seen as passing through a person for eg.

What i think you are getting at is short circuit protection ie a direct short from live to neutral and not to earth.

Well no.....All the Zs figures are to do with the 0.4 second Diss time for earth faults and have nothing to do with short circuit faults. But if you can prove they do, then do it.

In the case of MCBS, they have everything to do with it, as I said, they are all or nothing.

For the purpose of the thread please expand.

 

[park1]

Ok

Do we need to protect live conductors thermally, yes we do.

Overload and fault current in accordance with chapter 43.

Rather than me expanding, how do we protect live conductors from overload, how do we protect against fault current using a MCB.

Chapter 43 explains all.

 

[Nicky Tesla]

well go and get chapter 43 and pull off the relevant paragraph and quote the bit where you take L/N loop and how this is relevant to the Zs figures and OVERcurrent protection if you can find one.

 

[Steve3948]

OkDo we need to protect live conductors thermally, yes we do.

Overload and fault current in accordance with chapter 43.

Rather than me expanding, how do we protect live conductors from overload, how do we protect against fault current using a MCB.

Chapter 43 explains all.

435.1 - Protection afforded by one device.

A protective device providing protection against both overload current and fault current shall fulfil the requirements of the relevant

regulations in section 433 and 434.

 

[park1]

Hence the Line / Neutral loop measurement. If this value was higher than the corrected maximum Zs value for this breaker (c type rcbo). The circuit may not comply !
No Sorry you've lost me!............Line / Neutral loop ? Nothing to do with ZS, touch voltages, electric shock times, adiabatic equations, nothing nada!.......who on earth (if you pardon the pun ) does that?

No adiabatic, are you sure about that?

As I have mentioned, chapter 43 tells pretty much all. This is something practising electricians should know. I'm not going to hand it on a plate, research what is being said and learn.

 

[Nicky Tesla]

Zs values and relevance to L/N Loop ?...........Im still waiting:z

 

[park1]

434 being the relevant section Steve.

---------- Post Auto-Merged at 16:33 ---------- Previous post was made at 16:32 ----------

What can you derive from a level of fault current?

 

[Nicky Tesla]

Im still waiting:z

 

[park1]

Make an effort lol.

 

[Steve3948]

434 being the relevant section Steve.---------- Post Auto-Merged at 16:33 ---------- Previous post was made at 16:32 ----------

What can you derive from a level of fault current?

Well it says it fulfils (meets) the requirements of 434

Providing the device is M4, M6 and PSC is less, where's the issue.

 

[Nicky Tesla]

Steve did you find any relevance for Zs to a L/N loop?

 

[Steve3948]

Steve did you find any relevance for Zs to a L/N loop?

I have not found a relevance, nor any relevance to small overloads in earlier posts.

I think $park is referring to the P/N Line Impedance.

The RCD provides protection against indirect contact (perhaps as well as supplementary protection against direct contact), in which case the MCB element of the RCBO isn't doing that job, so table 41 etc don't apply. That's how I read it.

 

[park1]

Yes I am referring to the P/N loop impedance.

 

[park1]

Should this be in the student learning forum?

 

[Steve3948]

If you are a student $park then I suppose yes :yawn

 

[park1]

Well, I'm surprised nobody seems to know, a New thread in the student forum, people may be more inclined to answer.

 

[Manator]

I have followed and not replied to this thread, as for the question should it be in the student and learning zone? I would say no, there are some debate here that has gone from the sublime to the outright obvious and yet some participants of the debate have missed some vital thoughts or points.

Students will be baffled and confused, and so it is best that the conclusion to this particular debate is carried out within this section of the forum.

If anyone would like to write a synopsis of this debate for inclusion into the student section then please feel free to do so and start a new thread with your findings.

 

[Nicky Tesla]

Absolute rubbish.Where on do earth have you got this drivel from - if you exceed the tabulated value for efli you must carry out design CALCS to ensure that you still meet the requirements for thermal constraint with regards short circuit protection.

Once you deviate from the OSG you can longer use it as an excuse for any lack of relevant design knowledge.

I`ve had a bad day ....

Absolute rubbish.....a higher impedance will produce a lower amperage not a higher one

ie.240v / 1666.66ohms=0.144Amps..........so tell me, what cable and what RCBO/MCB cannot handle 0.144Amps???????

The only difference the P/N loop(as you put it) will make to the current flow if it is higher than Zs values is it will be restricted as in less current not more

The only thing to look at is to check if the P/N loop is LOW cos your RCBO may not be able to handle a high PFC.