2391 question paper help!

[liddley]

just going through some past papers in prep for my 2391 course and exam next week and am having trouble with some questions.

Any ideas?

for a construction site state

a) the electrical supply to be used for portable hand held tools

b) maximum disconection time for the system above

c) meaning of 25 in the formula Zs.In<25

 

[Strima]

Why don't you give us the answers that you think are correct and we'll go from there.

 

[liddley]

Not sure regarding the wording of some of the questions and what the question is getting at.
When it states the type of supply is it getting at ie.TNC-S TNS TT ect ect...
or my thoughts 110v reduced voltage SELV supply?

 

[Plonker 3]

Yes that is answer 1. You really have to read the questions properly when doing the exam. Remember this question is worth 3 points so 3 one word or very short answers are all that is required.

There are no questions about earthing systems there so come away from that sort of thinking.

Electrical supply and earthing arrangement are 2 totally different thing.

 

[spark 68]

Have a look at section 704 in the BGB (BS7671) :smilewinkgrin:

 

[SJD]

Re (1) I'd also suggest reading 704.410.3.10 including the notes.

 

[liddley]

Thanks guys, can anyone tell me where in the BGB i can find info relating to question c) above, can not find where i need to be looking

 

[topquark]

Thanks guys, can anyone tell me where in the BGB i can find info relating to question c) above, can not find where i need to be looking

If you multiply a resistance (Zs) by a current (In) you get?

 

[SJD]

Try thinking what the unit of measurement would be of the "25" in such an equation, which might give you some clue?

 

[liddley]

I really am rubbish at this.

25 volts

 

[telectrix]

look up touch voltage.

 

[ringer]

Where are you taking the 2391 exam next week? It's not long since the last one. Surprised there would be another one so soon.

 

[liddley]

Hi ringer,
Wakefield skill centre, the four day course is next week but the written paper is on the 12th July.
Apparently its the last 2391 they have running before the new version starts.

 

[ringer]

Ah, fair enough. That gives you two weeks then Took mine June 14th. If yours is anything like the June one then as long as you know GN3 pretty well you should be ok. Saying that, I don't have my results yet, so may be talking too soon when I say that I am quietly confident it was reasonably straight forward. Best of luck to you.

 

[liddley]

did you sit the four day course or the 12 week night course?