Why Earth before IR testing?

[Woofie]

Too right I'm confused. The question isn't specifically about SWA but taking that as an example, if there were a phase to armour fault that would be picked up even if the armour were not connected to earth.

 

[diditrain]

Not if the armour was isolated from earth

 

[Pete999]

When you say the cpc / armour connected to earth are you just referring to swa cables and how would it not be connected to earth if glanded to a metal enclosure.

Might not be a very good termination, judging by some I have seen,

 

[Richard Burns]

However if there was a fault from a live conductor to another piece or earthed metal nearby the test from armour to live conductor woudl show as OK.
If the armour was connected to the earthing system then the short would be shown on the test result.

 

[telectrix]

However if there was a fault from a live conductor to another piece or earthed metal nearby the test from armour to live conductor woudl show as OK.
If the armour was connected to the earthing system then the short would be shown on the test result.

View attachment 41916

excellent explanation.

 

[PEG]

Too right I'm confused. The question isn't specifically about SWA but taking that as an example, if there were a phase to armour fault that would be picked up even if the armour were not connected to earth.

OK,so if you expand this notion to any other cable,the reasons for earthing that particular conductor,during that particular test,are obvious.

Another reason,if one was needed,for earthing the armour on SWA during an IR test,would be that even if the armour only provided mechanical protection,an indication of it's integrity,that is to say,how the outer sheath may be providing prevention of moisture,rust,etc,in relation to the environment (earth) is also tested.

I still have not heard the counter debate,from the OP,of why the other side of this argument,feel it is not necessary...

 

[Ian1981]

However if there was a fault from a live conductor to another piece or earthed metal nearby the test from armour to live conductor woudl show as OK.
If the armour was connected to the earthing system then the short would be shown on the test result.

View attachment 41916

Where on earth (no pun intended ) do you get these drawings from??

 

[Richard Burns]

Where on earth (no pun intended ) do you get these drawings from??

I draw them out, lines, shapes, connectors, etc.
This one is a bit odd in that it was done quickly and it is hard to indicate a bonding strap on a pipe, but I should have just done another tube inset, nope that does not work either.
I now have a very odd library of very odd diagrams.

 

[Andy78]

excellent explanation.

As always. He's a dab hand with the concise words and internet crayons.

 

[Strima]

As always. He's a dab hand with the concise words and internet crayons.

I like crayons, the black ones taste the best...

 

[Woofie]

OK,so if you expand this notion to any other cable,the reasons for earthing that particular conductor,during that particular test,are obvious.

Another reason,if one was needed,for earthing the armour on SWA during an IR test,would be that even if the armour only provided mechanical protection,an indication of it's integrity,that is to say,how the outer sheath may be providing prevention of moisture,rust,etc,in relation to the environment (earth) is also tested.

I still have not heard the counter debate,from the OP,of why the other side of this argument,feel it is not necessary...

A sadly large number of sparks I have worked with have little respect for the regs. I do not share their views. As this became a requirement relatively recently, 10 years ago, perhaps some people have not kept up with the changes and do not see the importance of it. Let's say that and give them the benefit of the doubt.

 

[Woofie]

Thanks for your help Richard Burns and the pic

 

[PEG]

I draw them out, lines, shapes, connectors, etc.
This one is a bit odd in that it was done quickly and it is hard to indicate a bonding strap on a pipe, but I should have just done another tube inset, nope that does not work either.
I now have a very odd library of very odd diagrams.

I was wondering Richard,if you could do a family portrait for me?

I could send you a photograph,or,just watch the Deliverance,and sketch two adults and two kids...it'll be near enough...

 

[The Ghost]

As I understand it, apart from other paralell faults, you want the "biggest bang" (PEFC) figure.

 

[Richard Burns]

I was wondering Richard,if you could do a family portrait for me?

I could send you a photograph,or,just watch the Deliverance,and sketch two adults and two kids...it'll be near enough...

Unfortunately my skills with irrational objects, such as people, are not quite to the same level...