17th edition Can't find it in the book? help please. Part II

[ChristianG]

Hi people
again.

I have so far went through 22 pratice questions with only 2 problem questions. One thanks to notsosmart has been answered.

The next and last for today, Please bare in mind it is not the answer I am really after, but how to achieve that answer. The route taken through the book to get to that answer.

I'm sure if I had more knowledge of electrics i'd be able to help my self a bit more. but I am in the process of learning.

Question>>>

Correct co-ordination between circuit conductors and an overcurrent protection device is achieved when:

a) In exceeds the lowest current carrying capacity Iz.

b) In is less than the design current Ib.

c) Ib is less than Iz.

d) Iz is lower than or equal to Ib.

I have looked at Part 4 433.1.1 but just cannot find the answer amongst it.

Feel free to laugh or give advice.

Cheers

Christian

 

[Notsosmart]

Please bare in mind it is not the answer I am really after

Hey I'm not baring anything I hardly know you!


Question>>>

Correct co-ordination between circuit conductors and an overcurrent protection device is achieved when:

a) In exceeds the lowest current carrying capacity Iz.

b) In is less than the design current Ib.

c) Ib is less than Iz.

d) Iz is lower than or equal to Ib.

I have looked at Part 4 433.1.1 but just cannot find the answer amongst it.

Feel free to laugh or give advice.

Cheers

Christian[/quote]

You have looked in the correct place now narrow it down (for example does it say in the regs that In should be less or more than Ib?)
You will end up with only one of the statements to be correct.

Permission to laugh now
Really No-one should be laughing at you, because half of us experienced qualified sparks scratch our heads most of the time.

Keep-em coming because regs need to be regularly visited to keep us on the ball & without motivation they are Boo-oo-ring

 

[ChristianG]

Hi notsosmart

In 433.1.1 (i) it says "The rated current or current setting of the protective device (In) is NOT less than the design current (Ib) of the circuit, and (ii).......................................................

Hi notsosmart

In 433.1.1 (i) it says "The rated current or current setting of the protective device (In) is NOT less than the design current (Ib) of the circuit, and (ii).......................................................

I just cannot figure it out at the moment, I'm sure as you said more or less.....open my eyes! I just cannot seem to find the answer amongst it?

Any help is appreciated.

Cheers

Christian

 

[Notsosmart]

a) In exceeds the lowest current carrying capacity Iz.

b) In is less than the design current Ib.

c) Ib is less than Iz.

d) Iz is lower than or equal to Ib.

Hi notsosmart

In 433.1.1 (i) it says "The rated current or current setting of the protective device (In) is NOT less than the design current (Ib) of the circuit, and (ii).......................................................
I just cannot figure it out at the moment, I'm sure as you said more or less.....open my eyes! I just cannot seem to find the answer amongst it?

Any help is appreciated.
Cheers
Christian

Yeh Reg speak: good isn't it.

Try to look at it another way;

Ib = design Current
Iz = Conductor current carrying capacity
In = rating of protective device

Therefore which is true?;

a) rating of protective device should be higher than the lowest current carrying capacity? or,
b) rating of protective device should be less than the design current? or,

c) design Current should be less than Conductor current carrying capacity.

d) Conductor current carrying capacity should be lower than or (at MOST) equal to design Current.

 

[ChristianG]

I would say C.

I think that the answer I have been given in the back of these pratice papers is wrong and I am trying to find the answer still based on that so called correct answer, thus clouding my judgement.

This forum is quite good, i'd be ripped to shreds by now on site!

Thanks for your help notsosmart. hmmm hint of sarcasm there I reckon

Here is another for you......

An undervoltage device has operated and that restoring the supply may cause danger, I do know that the reclosure of said device should NOT be automatic. I also know that it should be manually operated, but is that just manually operated or with a tool or key?

Cheers for any help

Christian

 

[Notsosmart]

I would say C.

I think that the answer I have been given in the back of these pratice papers is wrong and I am trying to find the answer still based on that so called correct answer, thus clouding my judgement.
Christian

So what answer have they given in the back of the paper then?

 

[ChristianG]

B but the tutor did point out there may be mistakes.

Just like the one in the bs7671 that states that a radial circuit begins and ends at the board!!

 

[Mac]

I would say C.

I think that the answer I have been given in the back of these pratice papers is wrong and I am trying to find the answer still based on that so called correct answer, thus clouding my judgement.

This forum is quite good, i'd be ripped to shreds by now on site!

Thanks for your help notsosmart. hmmm hint of sarcasm there I reckon

Here is another for you......

An undervoltage device has operated and that restoring the supply may cause danger, I do know that the reclosure of said device should NOT be automatic. I also know that it should be manually operated, but is that just manually operated or with a tool or key?

Cheers for any help

Christian

Any machinery or equipment that has stopped due to a power failure(brown out or black out)should be restarted manually as this may cause injury/or danger to life.

 

[Notsosmart]

Chris an example of an undervoltage device for you

NG125 220..240Vac voltage release (MN) - Merlin Gerin - Voltimum UK - Electrical Installation Products and Contracting

No lock & key as you can see, however a normal household would not expect to see such an item, more likely an industrial situation where damage may occur if (say a motor) was subjected to lower voltage conditions.

Therefore only a skilled competent engineer (or sparky!, thats me before I get slated by you lot out there) would be expected to reset such a beast. So they will probably be contained within a lockable DB or (more likely) within an MCC

 

[ChristianG]

I'm going have to start sending you some money soon aint I?

Cheers Notsosmart.