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Discuss Primary supply overcurrent protective Device in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

S

solavie

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While completing the Elecsa certificate, it asked for the nominal current rating and short-circuit capacity of the primary supply overcurrent protective device. The system is a TNC-S and there is nothing written on the fuse at all to say what rating it is. Also it is riveted and it cannot be open to check the fuse inside.

Do I leave the Nominal current rating - Blank?

And how do I measure its shortcurcuit capacity using a Megger 1552 :confused:

And are we allowed to isolate the supply to change the consumer unit by removing this fuse . I am not too sure where I stand as there is no other isolating switch.

Thanks.
 
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G

Guest123

  • Thread Starter Thread Starter
  • #2
Hey.

If you are unable to verify the rating of the main fuse then you can either ring the DNO or if they cant help then put LIM in the box and note the reason in the comments box.

You dont usually measure the short circuit capacity of the fuse but note the maximum allowable like you would for an MCB, i.e 6KA for standard type B breakers.

For BS 1361 it's between 16.5KA and 33KA I always note the higher number
For BS 88-2 it's 50KA.

Check OSG for all types

Technically you are not allowed to break the seals and pull the cut-out fuse but it is done, sshhh;).

Hope this helps.
 
D

DanBrown

  • Thread Starter Thread Starter
  • #3
Hey.

If you are unable to verify the rating of the main fuse then you can either ring the DNO or if they cant help then put LIM in the box and note the reason in the comments box.

You dont usually measure the short circuit capacity of the fuse but note the maximum allowable like you would for an MCB, i.e 6KA for standard type B breakers.

For BS 1361 it's between 16.5KA and 33KA I always note the higher number
For BS 88-2 it's 50KA.

Check OSG for all types

Technically you are not allowed to break the seals and pull the cut-out fuse but it is done, sshhh;).

Hope this helps.
Lenny, what does LIM aquate to?
 
G

Guest123

  • Thread Starter Thread Starter
  • #4
LIM stands for Limitation i.e you weren't able to record a result or carry out a test due to circumstances beyond your control. Like on a PIR for instance on the tick box page where it asks "cables routed in prescribed zones" obviously you cant tell if they are or not so you put LIM in the box.

Hope this helps.
 
S

solavie

  • Thread Starter Thread Starter
  • #5
Thanks.
 
S

Scott F

  • Thread Starter Thread Starter
  • #6
Hey.

If you are unable to verify the rating of the main fuse then you can either ring the DNO or if they cant help then put LIM in the box and note the reason in the comments box.

You dont usually measure the short circuit capacity of the fuse but note the maximum allowable like you would for an MCB, i.e 6KA for standard type B breakers.

For BS 1361 it's between 16.5KA and 33KA I always note the higher number
For BS 88-2 it's 50KA.

Check OSG for all types

Technically you are not allowed to break the seals and pull the cut-out fuse but it is done, sshhh;).

Hope this helps.
GN3 page 60 (16th) or osg"Except for london and other major cities the max fault current for 230v single phase supplies up to 100a will not exceed 16 ka ."
 
H

hughesy

  • Thread Starter Thread Starter
  • #7
GN3 page 60 (16th) or osg"Except for london and other major cities the max fault current for 230v single phase supplies up to 100a will not exceed 16 ka ."
Thats what i thought also was told if you ringthe DNO and ask them they will tell you its below 16.
 
G

Guest123

  • Thread Starter Thread Starter
  • #8
Are we not talking about the capacity of the fuse, as opposed to what the fault current would/should be??
 
S

Scott F

  • Thread Starter Thread Starter
  • #9
Are we not talking about the capacity of the fuse, as opposed to what the fault current would/should be??
Hi Lenny the original post was what was the short circuit capacity of the primary overcurrent protective device What should he put in the box and osg and gn3 both state"where a service cutout containing a cartridge fuse to Bs 1361 type 2 supplies a consumer unit which complies with bs 5486 or bs en 60439-3 then the short circuit capacity of the overcurrent protective( ]devices within the consumer units may be taken as 16ka)

Not noticed that bit before . Usually takes all my mental prowness to read beyond a few lines.In table 2.4 it does indeed rate type 2 at 33ka

I was taught 0n 2391 that it was 16ka and have always put that down. Death to lecturers
 
S

solavie

  • Thread Starter Thread Starter
  • #10
hi Scott

I will use that value. However is it anywhere in the onsite guide, 16 or 17th edition or the same for IEE wiring regulations as I could not locate it.

:)
 
S

Scott F

  • Thread Starter Thread Starter
  • #11
Solvie ONG page 56 and 57 table 7.4 If you have time on your hands it wouldnt hurt to ring your Dno to see what they have to say
 
Hey.

If you are unable to verify the rating of the main fuse then you can either ring the DNO or if they cant help then put LIM in the box and note the reason in the comments box.

You dont usually measure the short circuit capacity of the fuse but note the maximum allowable like you would for an MCB, i.e 6KA for standard type B breakers.

For BS 1361 it's between 16.5KA and 33KA I always note the higher number
For BS 88-2 it's 50KA.

Check OSG for all types

Technically you are not allowed to break the seals and pull the cut-out fuse but it is done, sshhh;).

Hope this helps.
Hi Lenny. Whilst I understand DNO refers to what used to be the Regional Electricity Supplier I can't get my brain to work out what DNO stands for! I know I'll kick myself when you tell me but I can't sleep at night not knowing!
Thanks in anticipation.
 

Des 56

-
Arms
Esteemed
Hi Lenny. Whilst I understand DNO refers to what used to be the Regional Electricity Supplier I can't get my brain to work out what DNO stands for! I know I'll kick myself when you tell me but I can't sleep at night not knowing!
Thanks in anticipation.

Distribution Network Operator
regards Des
 
E

Engineer54

  • Thread Starter Thread Starter
  • #14
Welcome,.... So with your first post, you reopen a 4 year old thread, with information that's already been given!!

Not a great start!!
 
S

shagbite

  • Thread Starter Thread Starter
  • #15
one and two thirds to be precise.

which begs the question........if you knew, why repeat it?
 
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