Ring testing

[Gnasher]

Hi all can you help to settle a argument.

Situation

2 x 4mm in the top of a 32mm. MCB

Option 1

This indicates to me that it is either 2 radials in the same MCB, or a 4mm ring.
A ring continuity test should be carried out to prove that a ring exists or it is 2 radials.
If a ring exists carry on with ring tests. If 2 radials this should be raised further investigation required to identify if an incomplete ring is present, (fault) or it is indeed 2 radials from the same MCB (fault)

option 2

Doesn't matter if it is a ring or not as 4mm is good for 32A carry on and test.


Please vote option 1or 2

my option is 1

yes there are 2 conductors in the MCB
for this posting 4mm conductors throughout the circuit is not an issue.




Quite right should read my post prior to submitting, it's 2conductors. I agree with your option 2 comment I posted this as I am feed up fighting my corner I am looking for a bit of support in my argument

 

[trev]

Option one, there could be a live end flapping around somewhere. Why would you put 2 x 4mm cables into one MCB? VD/ lowering Zs are the only reasosn I can think of just now

 

[SirKit Breaker]

How many 4mm cables are in MCB?

Cant vote for either. Option 1, i assume you have 2 x 4mm cables, and instead of testing it properly to find out, you are guessing..

Option 2, gives me the impression that you don't really understand what you are doing.

You will get some real flack in response to this post.

Cheers...........Howard

 

[SJD]

4mm in the top of a 32mm. MCB

Do we assume you meant to say "Two 4mm cables in the top of a 32A MCB"?

 

[SJD]

And do you know if the whole circuit(s) is/are in 4mm, or perhaps just the first leg(s) (I came across this once)?

 

[trev]

Do we assume you meant to say "Two 4mm cables in the top of a 32A MCB"?

I assumed that

 

[telectrix]

option 1. it's either a ring or 2 radials. determine which it is. if a ring, then carry on with the usual tests for a RFC. if 2 radials, then test as 2 radials and preferably separate them to separate MCBs.

 

[Gnasher]

Yes but not an issue

 

[Jay Sparks]

This may have been a 4mm radial origanaly but some one may have added some extra sockets and decided this was the easiest and least desruptive way of doing it. You can do it this way according to the regs.

Jay

Obviousley, futher testing is required to determine if its a ring or not!!

 

[SJD]

I think the bottom line is you have to know what the circuit(s) is/are and test accordingly (option 1), you can't just make assumptions or not care (option 2).

 

[chrish_1977]

Are you sure it's 4mm if its old cable it does look thicker/ stranded cable. First thing you need to do as others have said is carry out the sequence for testing a ring eg end to ends to see if there is a ring if not, and there isn't a break then I would assume that it is possibly two radials and personally I would split onto two 16a breakers. But that's just my way of working

 

[Jimmyb]

option 2

Doesn't matter if it is a ring or not as 4mm is good for 32A carry on and test. Is it really ? think about installation methods

 

[Gnasher]

How can you say just carry on 4mm is good for 32A the green book may suggest that it is. However once you take into account downrating factors such as grouping or thermal insulation it will not be. The point I wea trying to get to was that we donot know why it was installed this way. There is a strong possibility that 4 mm may have been designed to comply with earh loop values. Volt drop. Or to compasate for any derating factors.
My feeling is that if you see 2 conductors in the top of a MCB there is a possibility that it may have been designed as a ring and this should be confirmed. If it is an open circuit further investigation should be carried out to determin why 2 circuits are fed from 1 MCB.
It may be that you have 2 high load circuits in 1 MCB and that a 32A MCB is to small.

 

[lee236]

Totally with ya on that Steve full investigation and sequence of tests required

 

[richardg]

In my opinion if u see two cables in one breaker irrespective of size I would first test end to end.
I have seen 2 x 4mm in a breaker recently feeding a high end power hungry entertainment system. Amazing how much power it used

 

[kingeri]

First establish whether it's a ring or a radial, then if it's a radial, establish if the CCC is adequate to be protected by a 32a breaker. Having 'two radials' in one breaker isn't an entirely accurate statement either, it is one radial circuit with two branches, and although perhaps not always the best practice, it can be done with the blessing of the IET. For all you know, one of those cables might only supply one double socket!

 

[Gnasher]

How many 4mm cables are in MCB?

Cant vote for either. Option 1, i assume you have 2 x 4mm cables, and instead of testing it properly to find out, you are guessing..

Option 2, gives me the impression that you don't really understand what you are doing.

You will get some real flack in response to this post.

Cheers...........Howard

the point I am making is that until you do an ring end to end you must assume it is a ring.

 

[telectrix]

the point I am making is that until you do an ring end to end you must assume it is a ring.

cobblers. until you test it you can't assume anything other than that there are 2 cables in 1 breaker.

 

[Gnasher]

cobblers. until you test it you can't assume anything other than that there are 2 cables in 1 breaker.

By assuming that it is a ring the first test you would carry out is a ring continuity test
This will prove if it is or is not a ring.
Once you have done you then decide on your next test.

If you do not assume it is not a ring what would be your first instinctive test?

 

[Octopus]

By assuming that it is a ring the first test you would carry out is a ring continuity test
This will prove if it is or is not a ring.
Once you have done you then decide on your next test.

If you do not assume it is not a ring what would be your first instinctive test?

My first instinst says that the OP doesn't know what he's doing

 

[Gnasher]

My first instinst says that the OP doesn't know what he's doing

My first instinst says that the OP doesn't know what he's doing

Hi Murdoch
i have been testing for years the problem I am having is that when you enter into a discussion with others who are a very set in there ways it is very difficult to get your point across especially when it is you against 3 of them. My intention was to post in a manner to create discussion that would help with my point of view. Most of the replays tend to agree with what I am saying.
That is that you must carry out the correct tests that will determine what is in front of you. As a tester you should have an above average level of knowledge and experience, this will allow you to understand that because the BGB states that a 4mm can carry 32A you still need to be able to understand and make allowances for correction factors that will down rate the CCC of conductors, all of a sudden a 32A MCB is to large to protect the conductor. It still worries me the amount of testers who do not understand this. We are not designers but we should have an understanding of the principles to aid in our decision making.
Not an easy job perhaps that's why the 2391 had the largest fail rate of all G&G exams

 

[UNG]

It still worries me the amount of testers who do not understand this. We are not designers but we should have an understanding of the principles to aid in our decision making.
Not an easy job perhaps that's why the 2391 had the largest fail rate of all G&G exams

An electrician with no idea of circuit design should not be doing the job. I think this is one of the most basic things that electrician needs to know not just have an understanding of it or how do they install a new circuit

With regards to the 2391 if you put enough inexperienced people through the exam then the fail rate will be high, when I sat the exam there were some who were having their 3rd, 4th or 5th attempt at it, some left after an hour I would be surprised if more than 50% passed on that day. It will be interesting how the replacements for the 2391 will fare and if the overall pass rate is higher then it will be interesting to make comparisons as to whether another dumbing down has occurred within the industry

 

[Silly Sausage]

2395 Pass rate:
April 2012 - 49%
June 2012 - 24%

Not a walkover then...

http://www.google.co.uk/url?sa=t&rc...FAcMOyfpDi3ikJQ&bvm=bv.42553238,d.ZG4&cad=rja