Test Procedures

[BS3036]

Hi, first post here. I was thinking of sitting 2391, so I have been reading through Section 7 of Guidance Note 3, which roughly corresponds to Section 612 in BS 7671. I was trying to make some sense of the tests to see how logical it was.

What I don't seem to be able to find, is any case of a measurement of continuity of a neutral in a radial circuit.

The resistance of all three conductors is measured in the case of a ring final circuit, but in the case of a radial the neutral never seems to get measured. The only possible place relates to volt drop, but this is a fairly vaguely specified requirement.

It seems strange that the regulations would be suggesting that the way to know that a neutral in say a lighting circuit is checked by 'seeing if the lights work'. As a badly made high resistance connection could be missed, and potentially cause a fire.

Even in the case of a ring final, the neutral resistance is not actually recorded.

Doesn't it make a mockery of forcing people to buy and use expensive equipment, when bad connections in a neutral are not even checked by the procedure?

What is the value of a set of regulations, worked on by standards organisations all over the world, taught to people doing C&G 2391, resulting in a report which is given to customers to prove to them they are safe, which describes a mandatory procedure but forgets to include a basic measurement?

(Rant over! )

 

[Andy™]

What I don't seem to be able to find, is any case of a measurement of continuity of a neutral in a radial circuit.something to do with this not being required, although if you do N to E or N to L this will also confirm polatiry

The resistance of all three conductors is measured in the case of a ring final circuit, but in the case of a radial the neutral never seems to get measured. The only possible place relates to volt drop, but this is a fairly vaguely specified requirement.your circuit design should have already taken VD etc into account

It seems strange that the regulations would be suggesting that the way to know that a neutral in say a lighting circuit is checked by 'seeing if the lights work'. As a badly made high resistance connection could be missed, and potentially cause a fire.the regs dont always make sense

Even in the case of a ring final, the neutral resistance is not actually recorded.depends what certs your using. 7671 model forms dont, but some others do

Doesn't it make a mockery of forcing people to buy and use expensive equipment, when bad connections in a neutral are not even checked by the procedure?still need the same equipment to do the other tests.

What is the value of a set of regulations, worked on by standards organisations all over the world, taught to people doing C&G 2391, resulting in a report which is given to customers to prove to them they are safe, which describes a mandatory procedure but forgets to include a basic measurement?

(Rant over! )

my red

and welcome to the madhouse

 

[Apache]

hello and welcome and calm down

 

[Bez]

Welcome to the forum, can't answer any of your questions, but sit yerself down and have a beer Guinness

 

[SPECIAL LOCATION]

Hello BS3036....

welcome to the world of posting.....

but looks like you have been around the forum for a while?

Hi, first post here. I was thinking of sitting 2391, so I have been reading through Section 7 of Guidance Note 3, which roughly corresponds to Section 612 in BS 7671. I was trying to make some sense of the tests to see how logical it was.What I don't seem to be able to find, is any case of a measurement of continuity of a neutral in a radial circuit.

What about page 57 guidance note 3

sub section 2.7.19 verification of volt drop,

Second paragraph?

"Typically volt drop will be evaluated using circuit impedance."

The resistance of all three conductors is measured in the case of a ring final circuit' date=' but in the case of a radial the neutral never seems to get measured. The only possible place relates to volt drop, but this is a fairly vaguely specified requirement.

[/quote']

Volt drop see previous point....

What safety related reason can you give to need to measure Rn?

We measure the R1+R2 to eliminate or minimise the risk of electric shock in the event of a live-earth fault...

A live - neutral fault should trip the correctly rated MCB.

It seems strange that the regulations would be suggesting that the way to know that a neutral in say a lighting circuit is checked by 'seeing if the lights work'. As a badly made high resistance connection could be missed' date=' and potentially cause a fire.[/b']

No it couldn't because a Live-Neutral fault will be limited by the circuit protective device.... which will trip / or blow if too much current was passing down the cable exceeding the cables capacity!

Even in the case of a ring final' date=' the neutral resistance is not actually recorded.

[/quote']

It is on an NICEIC certificate.

Doesn't it make a mockery of forcing people to buy and use expensive equipment' date=' when bad connections in a neutral are not even checked by the procedure?

What is the value of a set of regulations, worked on by standards organisations all over the world, taught to people doing C&G 2391, resulting in a report which is given to customers to prove to them they are safe, which describes a mandatory procedure but forgets to include a basic measurement?

(Rant over! )[/quote']

Because there is no need for that particular measurement,

as there are NO serious safety related issues ....

Unless you can think of one? :|

 

[BS3036]

What safety related reason can you give to need to measure Rn?

We measure the R1+R2 to eliminate or minimise the risk of electric shock in the event of a live-earth fault...

A live - neutral fault should trip the correctly rated MCB.

I'm referring to a high resistance connection in the neutral. Imagine a 3kW immersion circuit. Imagine that the screw in the FCU neutral hadn't been tightened up. In the worst case (around 17 ohms) this connection will dissipate 750W and catch fire. In another case it might dissipate less, appear to work, but not catch fire till the electrician had left the house. The MCB would in neither case be tripped.

Judging by reports on various forums, faults in the neutral (high resistance) are actually quite common.

No it couldn't because a Live-Neutral fault will be limited by the circuit protective device.... which will trip / or blow if too much current was passing down the cable exceeding the cables capacity!

See above

Because there is no need for that particular measurement,

as there are NO serious safety related issues ....

Unless you can think of one? :|

See above.BTW I joined the group when it started, but have been a bit distracted by work since then.

 

[a1]

BTW I joined the group when it started, but have been a bit distracted by work since then.

Not good enough excuse. Detention for you after class Tonight.

Welcome and Thanks for posting.

Members can post as often or as little. When they like.

 

[kme]

I'm referring to a high resistance connection in the neutral. Imagine a 3kW immersion circuit. Imagine that the screw in the FCU neutral hadn't been tightened up

If ANY of the screws haven`t been tightened correctly (or partially tightened onto partly insulated cable), that may well not show on your test.

Furthermore, you may have taken the phase out its terminal, to link to the cpc. Then tested. What if you don`t tighten THAT up correctly after testing - same scenario as you suggested above, even though your test resuls were excellent!

No matter what the subject, you can only go so far...........

AFAIAC

KME

 

[batty]

If you do a loop test with most testers a neutral is needed.

Batty

 

[Risteard]

It's an interesting point, however doesn't the inspection process require the inspector to check that connections are mechanically and electrically sound? Therefore shouldn't a loose connection be discovered (probably during erection). And isn't inspection the major part of the inspection and testing process and likely to expose faults which testing may not show up?

 

[Nicky Tesla]

The reason for R1 in the R1+R2 is only to get the R2 reading without having to use a flying lead not for getting the R1 reading.

 

[kme]

The reason for R1 in the R1+R2 is only to get the R2 reading without having to use a flying lead not for getting the R1 reading.

This is indeed one reason for using it. It will also confirm polarity, as you can switch off, and the meter should read ">2000", or whatever your particular meter displays (O/C).



It will also provide cable size, if distance is known, or vice versa.

 

[Andy™]

This is indeed one reason for using it. It will also confirm polarity, as you can switch off, and the meter should read ">2000", or whatever your particular meter displays (O/C).

It will also provide cable size, if distance is known, or vice versa.

R1R2 alone will not confirm polarity. gotta be some seriously wrong witing to get it wrong though!

 

[kme]

Andy...

If, for example, we`re testing a radial S/O cct.

You link out at the DB, then test at each S/O - with the socket switch in the "off" position & "on" - how have you not confirmed polarity?????????

KME

 

[Andy™]

if you have earth in the live terminal and live in the earth terminal.

 

[kme]

:OAgreed :O

Didn`t think of that, as I couldn`t envisage stupidity of that caliberheadbang

However, you`d find that on the subsequent tests......

Then dismember the prattock who`d carried it out? :| :coat

 

[BS3036]

Guys, thanks for the input. I've enjoyed reading the replies.