Continuity understanding

[gazdkw82]

Hi,

I'm abit confused with continuity testing. I have a questionin my learning books that gives me L1 to L2 & N1 to N2 & cpc1 to cpc2continuity readings and then a table with various socket test results L to Nand L to CPC. I have to identify which readings are ok and which are not ok andgive reasons.


Im stuck which way I should do this.

In my head a test between R1/Rn at the CU should be halfthat of both R11 reading and R22 readings? Is that correct? So how would I workout what say R1-cpc should be? Add them together and devide by 2? Once I gotthese readings, is that what I would use to compare with the socket testresults? Am I going about this the right way?


Other way I thought about it was that socket readings shouldbe ¼ that of the L1 to L2 & N1 to N2 & cpc1 to cpc2 readings is thatright?

thanks

 

[Brightspark2]

Your R1&R2 reading should be a quarter of your end to end r1 and r2 added together.

Youll get jumped on on this forum for miss using capital R and lower case r before 1,2 and n. As they have different uses.

R for cpc continuity.

r for end to end

Sent from my E5823 using Tapatalk

 

[Brightspark2]

Guidance note 3 on inspection and testing would be a good purchase for you...

Sent from my E5823 using Tapatalk

 

[gazdkw82]

Your R1&R2 reading should be a quarter of your end to end r1 and r2 added together.

Youll get jumped on on this forum for miss using capital R and lower case r before 1,2 and n. As they have different uses.

R for cpc continuity.

r for end to end

Sent from my E5823 using Tapatalk

Apologies

 

[Pete999]

Hi,

I'm abit confused with continuity testing. I have a questionin my learning books that gives me L1 to L2 & N1 to N2 & cpc1 to cpc2continuity readings and then a table with various socket test results L to Nand L to CPC. I have to identify which readings are ok and which are not ok andgive reasons.


Im stuck which way I should do this.

In my head a test between R1/Rn at the CU should be halfthat of both R11 reading and R22 readings? Is that correct? So how would I workout what say R1-cpc should be? Add them together and devide by 2? Once I gotthese readings, is that what I would use to compare with the socket testresults? Am I going about this the right way?


Other way I thought about it was that socket readings shouldbe ¼ that of the L1 to L2 & N1 to N2 & cpc1 to cpc2 readings is thatright?

thanks

https://www.youtube.com/watch?v=zSATFrqlSpg

 

[gazdkw82]

Your R1&R2 reading should be a quarter of your end to end r1 and r2 added together.

Youll get jumped on on this forum for miss using capital R and lower case r before 1,2 and n. As they have different uses.

R for cpc continuity.

r for end to end

Sent from my E5823 using Tapatalk

so for example would this be correct:

If r1 was 0.8 and r2 was 0.8

Would R1&R2 be (0.8+0.8)/4 = 0.4?

 

[telectrix]

correct. R1+R2 = (r1+r2)/4.this only applies to a ring, of course. the divide by 4 is because in a ring final, the csa is doubled, so /2. then you have conductors in parallel, so /2 again.

 

[gazdkw82]

correct. R1+R2 = (r1+r2)/4.this only applies to a ring, of course. the divide by 4 is because in a ring final, the csa is doubled, so /2. then you have conductors in parallel, so /2 again.

ok so how would i work that to get what the L to cpc at the socket value should be?

It doesn’t state what csa the cpc is. Thereading of the cpc1 to cpc2 is actually lower then r1 and r2 at 0.55. Thisstrikes me as odd because that would mean the cpc is either larger in diameterthan r1 and r2 (I seriously doubt it) or they have done that to try and see if Inotice.

So back to the question.

How would I figure that out

(0.80+0.55)/4=0.3375

 

[Andy78]

ok so how would i work that to get what the L to cpc at the socket value should be?

It doesn’t state what csa the cpc is. Thereading of the cpc1 to cpc2 is actually lower then r1 and r2 at 0.55. Thisstrikes me as odd because that would mean the cpc is either larger in diameterthan r1 and r2 (I seriously doubt it) or they have done that to try and see if Inotice.

So back to the question.

How would I figure that out

(0.80+0.55)/4=0.3375

The CPC may well be larger than the live conductors. The CPC could be a metal containment system for example.

 

[gazdkw82]

ok no problem. I have highlighted that I have noticed it and if the cpc was smaller than line and neutral the readings would be of concern.

is the formula correct




(0.80+0.55)/4=0.3375

 

[Andy78]

Yes that would be correct.

 

[PEG]

Also,all of the above,would be in an ideal world,where it is known there are no interconnections,spurs,higher resistance connections,etc.

Understanding the theory,thoroughly,is vital,as in practice,there may be issues,which cause the readings to appear "perfect",whilst hiding a different story.

Drawing out a theoretical circuit,using felt-tips of three colours can simplify things,even using a thick,green line for containment earth path,squiggly green zig-zags for IR fail,etc.

We have to keep drawing...now old Rolfs gone...:devil:

 

[gazdkw82]

Also,all of the above,would be in an ideal world,where it is known there are no interconnections,spurs,higher resistance connections,etc.

Understanding the theory,thoroughly,is vital,as in practice,there may be issues,which cause the readings to appear "perfect",whilst hiding a different story.

Drawing out a theoretical circuit,using felt-tips of three colours can simplify things,even using a thick,green line for containment earth path,squiggly green zig-zags for IR fail,etc.

We have to keep drawing...now old Rolfs gone...:devil:

Do you have an example of the drawing?

 

[PEG]

Being a bit of an IT luddite,i could show you mine,if you popped round for a brew (giggerty),but there are several reference books,which several of us have recommended in the past,by messrs Brian Scaddan and Christopher Kitcher.

The latter,wrote a guide to practical testing,ISBN 978-0-08-096907-7,and it contains drawings of the nature i have described.

The central point,of my posting,regarding the drawing out of circuits,was to ensure the "artist" fully understood what was occurring,during operation,fault or testing.

To do this,you have to ensure the drawing "speaks" to you,and all aspects of an installation,are readily apparent,and understandable.

If you can draw out,any simple circuit,in a way that you yourself understand,and could explain to others,the understanding of what is happening during a particular test is hugely simplified.

It may be the reliance on modern tech,or a fashion thing,but folk are not as eager to reach for a pen,these days,preferring to look/show,using some hand held device (battery,signal,wi-fi,permitting:yawn

...Short story,of the benefits of parchment...

A while back,i had a task to perform at one of our BNFl sites (do not go anymore,thankfully),it was two machines,with a 10m control cable,between the base,and the operating part.

The cable had 30 cores,and was terminated at each end,using eyed crimps,to a machine mounted terminal block.

We had one day to access these machines,and a young,keen technician,from the company who supplied them,was doing one,i would do the other.

We had access to machine spec,which as is the norm now,was available as single drawing downloads,a page at a time.Gone are the days of huge A0 size schematics...

I printed out a page,from each termination,taped them side by side,put my own notes on it,ready to go.

The other lad,had some tablet device,and said he would work from that.

I was done at 11am,went to check,and found him cursing...his device had loaded a drawing for one end,from a supplement,and because both drawings would not fit on his screen,and expand,the difference between the terminations,was not apparent...out came the scruffy paper unk:

Long live the pen hone: