Am I too fussy?

[Sidewinder]

Graham,

There is a DEFINITE distinction between live working and live testing there has been NO change.

it is NEVER acceptable to work live, it IS acceptable to undertake live testing.

---------- Post Auto-Merged at 23:25 ---------- Previous post was made at 23:25 ----------

r1+r2 has no direct correlation with Ze with regard to Zs.

---------- Post Auto-Merged at 23:26 ---------- Previous post was made at 23:25 ----------

If your calculated Zs is the same as your measured Zs then I would be amazed.

---------- Post Auto-Merged at 23:27 ---------- Previous post was made at 23:26 ----------

Why have you answered "no" to Steps point please?

 

[batty]

Working live is different to testing you cannot test correctly unless a circuit is live. r1 + r2 may give measurement of cpc and phase conductor it won't tell you if you have a missing neutrall. To me working live is changing a socket without turning circuit off. Its not live testing.

 

[Graham Lister]

Graham,There is a DEFINITE distinction between live working and live testing there has been NO change.

it is NEVER acceptable to work live, it IS acceptable to undertake live testing.

---------- Post Auto-Merged at 23:25 ---------- Previous post was made at 23:25 ----------

r1+r2 has no direct correlation with Ze with regard to Zs.

---------- Post Auto-Merged at 23:26 ---------- Previous post was made at 23:25 ----------

If your calculated Zs is the same as your measured Zs then I would be amazed.

---------- Post Auto-Merged at 23:27 ---------- Previous post was made at 23:26 ----------

Why have you answered "no" to Steps point please?

Why are you doing the same reading twice, the Zs wont be higher will it?

Answered no to steps as Zs is not a test to show correct functioning of equipment is it?

---------- Post Auto-Merged at 23:33 ---------- Previous post was made at 23:31 ----------

Working live is different to testing you cannot test correctly unless a circuit is live. r1 + r2 may give measurement of cpc and phase conductor it won't tell you if you have a missing neutrall. To me working live is changing a socket without turning circuit off. Its not live testing.

The fact the appliance doesnt work will tell you theres no neutral! thats picked up during the functional test at the end.

 

[Sidewinder]

Graham,

Steps never said it was a functional test.

Zs is an essential test to assess the performance of the circuit when energised.

I fail to see how there is any justification for this not to be undertaken.

Are you sure the Zs won't be higher?

How can you prove this without measurement?

What is the correlation between r1+r2 & Zs by the way?

 

[Graham Lister]

Parallel paths. Please explain how it could be higher? And yes steps said a Zs test is a functional test.

 

[batty]

Graham are you saying you would be happy putting an electrical installation into service without doing any live testing then?

 

[Sidewinder]

Graham,

I have just looked back through the posts by Steptoe and I can't find any reference to functional testing.

Where has this comment parallel paths come from?

There are many ways that Zs could be higher then Ze+(R1+R2), also this could depend on how the tests are undertaken.

You still have not explained the relationship between r1+r2 & Zs I cannot fathom where you are getting this from.

 

[Doc Hudson]

What is the correlation between r1+r2 & Zs by the way?

As your OP is about being fussy and correct terminology may I suggest that ((r1+r2)/4)+Ze will be not far off Zs just as R1+ R2+Ze is very close to Zs. As such they would be acceptable figures to write onto your certificate. Would that be a reasonable correlation?

Doc H.

 

[Sidewinder]

Yes Doc it would, however, Graham as only ever posted r1+r2, no reference to the calculations what so ever.

I am not criticising the lack of subscripts as this is excruciatingly difficult on the forum unfortunately.

I WAS hoping he would see the error of his ways!

 

[steptoe]

Parallel paths. Please explain how it could be higher? And yes steps said a zs test is a functional test.

did I ?

correct connection of equipment.

where?

or

when?

and as for a functional test, I dont go around turning peoples washing machines and TVs on, bit late then to find out you havce reversed polarity when tou have blew something up,

bit hard too if you are doing new builds and cant finish your testing until someone has moved in, :|

 

[Graham Lister]

Graham are you saying you would be happy putting an electrical installation into service without doing any live testing then?

No would do a Ze, polarity and rcd test . R1+R2 can prove correct connection of an appliance dont need a Zs is the point I am trying to make here. Of course I do a Zs sometimes its easier eg socket. Sometimes I do R1+R2 and add it to Ze. Doesnt make me a criminal does it? If its good enough for gn3 its good enough for me :good night:

 

[Sidewinder]

One other point r1+r2 does not relate to all circuits only some thus it is not a complete test.

 

[Graham Lister]

Graham,I have just looked back through the posts by Steptoe and I can't find any reference to functional testing.

Where has this comment parallel paths come from?

There are many ways that Zs could be higher then Ze+(R1+R2), also this could depend on how the tests are undertaken.

You still have not explained the relationship between r1+r2 & Zs I cannot fathom where you are getting this from.

He seemed to imply a Zs proves correct connection of equipment? that is not what its for is it? Sidewinder you answer my question as I asked first thanks. How can it be higher and please give me an example as I would love to know. I asked you first so please explain. Dont come back with more questions just an answer many thanks.

 

[Sidewinder]

OK, I will once you explain what tests you are looking at, because and r1+r2 test is nothing to do with a radial circuit such as a lighting circuit.

What is your question exactly please then I can answer it.

Your posts are some what confused at the moment and you seem to be mixing terms and are not clear in the measurements that you are taking.

My OP was not restricted to certain circuits, however, your posts are.

There are differences in the tests and the issues that could be seen, so once you clarify the errors in your information i can truthfully and accurately answer your posts.

IF I make assumptions it seems that you will merely flame me.

---------- Post Auto-Merged at 00:04 ---------- Previous post was made at 00:02 ----------

Oh, I can't see where Steps suggested that a Zs value implies correct connection of equipment.

There is more to the Zs test than may first be obvious depending on how you undertake it.

 

[Doc Hudson]

No would do a ze, polarity and rcd test . r1+r2 can prove correct connection of an appliance don't need a zs is the point I am trying to make here. Of course I do a zs sometimes its easier eg socket. Sometimes I do r1+r2 and add it to ze. Doesnt make me a criminal does it? If its good enough for gn3 its good enough for me :good night:

Hello Graham, may I just hint that r1 & r2 are not the same as R1 & R2, e.g. ring continuity r1,r2,rn as compared to R1+R2+Ze to calculate Zs. This I think is some of the point Sidewinder is making. If it were a City and Guilds exam marks would be lost. As such correct terminology should still be used in the industry as a whole. It is a subtle difference between knowing what somebody means and misinterpreting data giving wrong results. It is his lecturers instinct coming out I think, trying to get all forum members reading this thread to think about what they are saying.

Doc H.

 

[steptoe]

you asked

what is it confirming that isn't already confirmed

I simply gave one of the many things testing for Zs could prove,

that is nothing to do with functionality, merely to prove the living room socket has been correctly connected after you had removed it to do your continuity test,

or simply that you have replaced the cables back in the consumer unit correctly after doing your IR test, or even that you have actually re-instated the earthing conductor after testing Ze

a Zs test is in actual fact for proving disconnection times can be met, but it also proves quite a lot of other things at the same time, does it not?

 

[Graham Lister]

did I ?where?

or

when?

and as for a functional test, I dont go around turning peoples washing machines and TVs on, bit late then to find out you havce reversed polarity when tou have blew something up,

bit hard too if you are doing new builds and cant finish your testing until someone has moved in, :|

Oh please mate if you follow gn3 doing a zs loop test isn't where you pick up reversed polarity. Doing a ring test or R1+R2 for a radial will pick up up wrong polarity in switches or sockets.

---------- Post Auto-Merged at 00:11 ---------- Previous post was made at 00:09 ----------

Hello Graham, may I just hint that r1 & r2 are not the same as R1 & R2, e.g. ring continuity r1,r2,rn as compared to R1+R2+Ze to calculate Zs. This I think is some of the point Sidewinder is making. If it were a City and Guilds exam marks would be lost. As such correct terminology should still be used in the industry as a whole. It is a subtle difference between knowing what somebody means and misinterpreting data giving wrong results. It is his lecturers instinct coming out I think, trying to get all forum members reading this thread to think about what they are saying.Doc H.

Sorry I know what i meant! find it hard enough to type without getting all the terms spot on :^O . Will try harder in future.

---------- Post Auto-Merged at 00:16 ---------- Previous post was made at 00:11 ----------

OK, I will once you explain what tests you are looking at, because and r1+r2 test is nothing to do with a radial circuit such as a lighting circuit.What is your question exactly please then I can answer it.

Your posts are some what confused at the moment and you seem to be mixing terms and are not clear in the measurements that you are taking.

My OP was not restricted to certain circuits, however, your posts are.

There are differences in the tests and the issues that could be seen, so once you clarify the errors in your information i can truthfully and accurately answer your posts.

IF I make assumptions it seems that you will merely flame me.

---------- Post Auto-Merged at 00:04 ---------- Previous post was made at 00:02 ----------

Oh, I can't see where Steps suggested that a Zs value implies correct connection of equipment.

There is more to the Zs test than may first be obvious depending on how you undertake it.

Please explain how a measured Zs reading will be higher than Zs = Ze + (R1+R2). Please explain why using Zs = Ze + (R1+R2) is not acceptable? and why a physical Zs test must be performed?

 

[steptoe]

Oh please mate if you follow gn3 doing a zs loop test isn't where you pick up reversed polarity. Doing a ring test or r1+r2 for a radial will pick up up wrong polarity in switches or sockets.

it wont actually,

it will only pick up crossed connections.

ie, where a line conductor has been connected to a neutral conductor etc.

it wont pick up the fact you didnt replace your earthing conductor after testing Ze either.

 

[Graham Lister]

it wont actually,it will only pick up crossed connections.

ie, where a line conductor has been connected to a neutral conductor etc.

it wont pick up the fact you didnt replace your earthing conductor after testing Ze either.

I don't make mistakes like that

. I never said I don't do a Zs test, just trying to explain it can be calculated and GN3 allows this.

---------- Post Auto-Merged at 00:31 ---------- Previous post was made at 00:28 ----------

Also trying to make the point that sidewinder is fussy ROTFWL

 

[Sidewinder]

Hi Graham,

One nil to you then yes I am fussy, mind to be fair I have never hidden the fact.

I am also, have and do admit that I am pedantic about the units and symbols.

IMHO this was borne out during my last spell of teaching 2391.

We had a VERY competent and experienced spark in his mid 50's who could explain things well and understood well.

His understanding was in both formal & colloquial terms, however his answers were always in colloquial trade terms.

He was struggling to get away from calling an insulation resistance tester or ohmmeter depending on which section of GN3 you read like many of the elder members of the fraternity a Megger!

However, one last question then, we have established that I am picky and pedantic.

However, am I wrong in expecting the Zs column to have been completed, either by calculation or by measurement?

Also, should the Ra have been marked as NA & the value have been recorded as a Ze as he did not measure resistance he measured impedance.

Graham,

I believe Steptoe has answered part of the question you posed to me.

Another section of the answer is to do with how the measurements are made.

Ze is an impedance test, this is measured with 230V a.c. sinusoidal, 50Hz, mains derived I believe, & around 10A (on a 230v circuit) on a high current loop test typically, there is various "jiggery pokery" used for a no trip test depending on make, you could refer to the EN61557 & EN 61010 series of standards.

R1+R2 is a resistance test typically measured with around 4 to 24 V d.c. and current of less than 200mA.

Measured Zs is a true impedance test.

Calculated Zs is an impedance test plus a resistance measurement.

Thus calculated & measured Zs will never be the same on the same circuit.

Either is acceptable and measured Zs should always be lower due to parallel paths.

However, there can be times when it is higher.

This could be caused by a slightly high resistance point increasing in resistance due to the energy dissipated in Joule heating raising the temperature of that point in the circuit, thus increasing the total impedance of the circuit.

An Ra test is typically undertaken with a sinusoidal current at around 128Hz.

The values in an a.c. impedance measurement will have more variables than a pure d.c. resistance measurement as an a.c. waveform will suffer from differing inductive and capacitive reactance depending on the exact make up of the circuit caused by the electromagnetic affects of the a.c. current.

Where as a pure d.c. current has less "external" influences from the circuit.

HTH.