2391 and Ze Results.

[Nreed82]

Hi I have recently re-taken my 2391 exam and I am waiting on results in hope mostly!
I came across a question in Section B something like:

Q In a Distribution Board name 5 things that are no longer BS7671 and what has replaced them?

I answered with cable colour changes, from R,Y,B to B,B,G
Re-wireable fuses being changed for Mechanical Circuit Breakers and the use of RCD's when maximum Zs cannot be reached?

If any one could help as I really don't know and it was for either 8 or 11 marks.

Also at work I completed a Ze test on an SWA ( i think it was 10mm) Feeding a 3 phase motor pump and got the readings Brown 0.36, Black0.37, Grey 0.36 are these acceptable readings according to tabulated values?

 

[SJD]

Slightly odd question, for example "fuses in neutrals" are no longer BS7671, does anything that was once upon a time allowed but is not now count for marks?

 

[GaryM]

Also at work I completed a Ze test on an SWA ( i think it was 10mm) Feeding a 3 phase motor pump and got the readings Brown 0.36, Black0.37, Grey 0.36 are these acceptable readings according to tabulated values?

Ze is taken at the origin. You sound like you're talking about a final circuit so do you mean Zs?
If so, what's the size and type of protective device?

As for the main question - very odd indeed!

 

[Nreed82]

I'm not totally sure to be honest because I can't quite remember the full wording of the question?

I just know that it caught it me out!

 

[Nreed82]

Yes sorry I did mean the Zs, i can't remember the breaker size possibly 63A i was too busy trying to make it look like i knew what i was doing when i clearly didn't !

 

[GaryM]

Max Zs (uncorrected) for:

B63 - 0.73ohms
C63 - 0.36ohms
D63 - 0.18ohms

Assume it was a C63? If so then 80% corrected value would be 0.288ohms. It's not looking too good and may need further calculation if that's the case.

 

[Deleted member 26818]

Oh dear, re-wireable fuses are still allowed in BS7671.
Don't think fused neutrals is correct either, as BS7671 has never allowed fused neutrals.
I'd be thinging along the lines of the minimum CSA for PME bonding conductors being changed from 6mm² to 10mm².
BS3871 MCBs being changed to BS EN 60898.
BS1361 fuses being changed to BS 88-3.
Yes the harmonised wiring colours.
The increase in the minimum CSA for conductors of circuits for power from 1mm² to 1.5mm².

 

[Nreed82]

Max Zs (uncorrected) for:

B63 - 0.73ohms
C63 - 0.36ohms
D63 - 0.18ohms

Assume it was a C63? If so then 80% corrected value would be 0.288ohms. It's not looking too good and may need further calculation if that's the case.

Yes thanks for that I will check this up on Monday when I go back to work.

 

[Nreed82]

Ah you may be right there thanks for that

 

[Nik_lamb]

Ive done quite a few past papers recently as I did my 2391 exam last week and I don't remember a question like that. Are you shore it didnt say when looking inside a C.U name 5 deviations you might see and what you would rate them? That was a question I had.

 

[vernam616]

Oh dear, re-wireable fuses are still allowed in BS7671.
Don't think fused neutrals is correct either, as BS7671 has never allowed fused neutrals.
I'd be thinging along the lines of the minimum CSA for PME bonding conductors being changed from 6mm² to 10mm².
BS3871 MCBs being changed to BS EN 60898.
BS1361 fuses being changed to BS 88-3.
Yes the harmonised wiring colours.
The increase in the minimum CSA for conductors of circuits for power from 1mm² to 1.5mm².

Never heard of that last one before, what reg is that under out of curiousity?

I still see 1mm being used on installs

 

[Deleted member 26818]

Reg. 524.1, Table 52.3.

 

[vernam616]

Thanks will check it out !

 

[jdd]

Are you sure it doesn't mean what has replaced BS... as in BS EN

BS 3871 = BS EN 60898
BS 4293 = BS EN 61008
BS 5419 = BS EN 60947
BS 5486 = BS EN 60439
BS 1361 = BS EN 88-3

What do you reckon?

 

[vernam616]

Long day, just realised you said "Power" and not "lighting"

 

[jc_150]

Hiya
Cannot speak for C&G but for the board that I am involved with, if the question was in part B of our equivalent paper, then the question would have referred to the scenario, and not a stand alone question, therefore maybe the question was asking which parts of the scenario regarding the distribution board no longer meets current BS7671.
Regards
JohnC

 

[Sparkie30]

Ive done quite a few past papers recently as I did my 2391 exam last week and I don't remember a question like that. Are you shore it didnt say when looking inside a C.U name 5 deviations you might see and what you would rate them? That was a question I had.

you are right, 5 departures from brb. i belive it was Q 22