Capping cables - Paranoia!

[Dambo]

A customer's having an extension built and I was in yesterday to do all the wiring for it prior to the wall being covered and plastered. I secured all the cables in capping, taking care not to catch any of the cables with the securing nails, but now i'm starting to get paranoid and thinking, what if I have?! Is there a quick way of checking to make sure that none of the cables have been affected?

 

[rugbymacc]

IR test and continuity

 

[Dambo]

IR test and continuity

I was thinking more along the lines of if i've clipped a wire with a nail instead of severing it. This way the IR and continuity tests would most likely be fine but when the extension wiring becomes live the RCD may trip.

 

[mdlinnett]

Just move the cables up and down to prove they aren't trapped.

They should move easily if the blockwork is fairly plumb without compo snots.

 

[VoltzElectrical]

i used to get paranoid about such matters, and also connection 2nd fix. 'Did i connect those phase conductors into the neutral terminal while i was thinking about my holiday?, better take it off and check... no i didn't, phew!' it all comes with the territory if you care about your work, but you gotta move on. You KNOW you didn't clip those cables cos the capping sat nice and flat on the wall. keep calm and carry on.

Cheers.

 

[Evans Electric]

DON'T PANIC , DON'T PANIC As said by Nobhead , , it comes with the territory , and its not the end of the world if you have, you'll be wondering if you locked your door next .

At worst you'd have to chase out a bit of plasterboard .

And the world turns ,and another little baby boy is born....In the Ghetto.

 

[batty]

Could always do what that idiots did on a call out I had the other day let it pass had a neutral to earth fault on lighting which turned out to be cable to wall lights this had only been done a couple of years before. Builder seemed to know about it but I ended up just disconnecting lights as the people said they don't use them. Makes you wonder what the idiot put on the certificate.

 

[gselectrical]

A customer's having an extension built and I was in yesterday to do all the wiring for it prior to the wall being covered and plastered. I secured all the cables in capping, taking care not to catch any of the cables with the securing nails, but now i'm starting to get paranoid and thinking, what if I have?! Is there a quick way of checking to make sure that none of the cables have been affected?

I get paranoid over such matters. The apprentice usually caps the cables down. And I dont really think he could give a flying fcuk whether he has caught one or not! I usually send him around with the megger afterwards. I shall continue to do this untill his "capping skills" have improved!

 

[SPECIAL LOCATION]

I was thinking more along the lines of if i've clipped a wire with a nail instead of severing it. This way the IR and continuity tests would most likely be fine but when the extension wiring becomes live the RCD may trip.

If there is sufficient continuity for an RCD to trip...

I dooos reckon there would be enough for an Insulation resistance tester to pick up a low reading?

230v supply voltage

with a 30ma leakage fault trip current conductor to Earth.

V=IxR

R=V/I

230v/30ma = 7666.66ohms

So if your RCD is going to trip cuz of a damaged cable squashed in your capping... its going to have a resistance approx 7.6Kohms or Less... ?

Now with our insulation resistance test on new cables we are looking for

probably 200Mohms+ or 999Mohms+ (depending upon what scale you meter goes up to?)

1.0Mohms absolute min standard for Regs

2.0Mohms needing further investigation...

etc..

etc...

so a 7.6Kohms fault should show up if he's there NO?

Have you ever done an Ins Res test on a wall or concrete floor?

Especially on new build stuff with all that moisture in the bricks & mortar!

Do an Ins res with all conductors bunched together on the one probe and stick the other one to Existing main earth as a good ref point,

or push your probe into some nearby bit of exposed wall...

Could even try on the 1000v scale if you have any major doubts!

Just make sure none of the other cable ends are stuffed against a metal back box !

:| opcorn

OR

you could just do as mdlinnett says (post#4)

and make sure the cables are free to move up the capping!



:Salute :Applaud

 

[Dambo]

If there is sufficient continuity for an RCD to trip...I dooos reckon there would be enough for an Insulation resistance tester to pick up a low reading?

230v supply voltage

with a 30ma leakage fault trip current conductor to Earth.

V=IxR

R=V/I

230v/30ma = 7666.66ohms

So if your RCD is going to trip cuz of a damaged cable squashed in your capping... its going to have a resistance approx 7.6Kohms or Less... ?

Now with our insulation resistance test on new cables we are looking for

probably 200Mohms+ or 999Mohms+ (depending upon what scale you meter goes up to?)

1.0Mohms absolute min standard for Regs

2.0Mohms needing further investigation...

etc..

etc...

so a 7.6Kohms fault should show up if he's there NO?

Have you ever done an Ins Res test on a wall or concrete floor?

Especially on new build stuff with all that moisture in the bricks & mortar!

Do an Ins res with all conductors bunched together on the one probe and stick the other one to Existing main earth as a good ref point,

or push your probe into some nearby bit of exposed wall...

Could even try on the 1000v scale if you have any major doubts!

Just make sure none of the other cable ends are stuffed against a metal back box !

:| opcorn

OR

you could just do as mdlinnett says (post#4)

and make sure the cables are free to move up the capping!



:Salute :Applaud

The 7.6Kohms principle sounds like a good idea. That's something I hadn't really thought of but i'll definitely use that in the future!

''Do an Ins res with all conductors bunched together on the one probe and stick the other one to Existing main earth as a good ref point,

or push your probe into some nearby bit of exposed wall...'' - You lost me a bit here though :_| None of the extension wiring is connected to the main earth of CU yet. I can carry out an IR test on the extension wiring before connecting it to the main CU to establish if the IR reading is above 7.6 Kohms.

 

[SPECIAL LOCATION]

The 7.6Kohms principle sounds like a good idea. That's something I hadn't really thought of but i'll definitely use that in the future! ''Do an Ins res with all conductors bunched together on the one probe and stick the other one to Existing main earth as a good ref point,

or push your probe into some nearby bit of exposed wall...'' - You lost me a bit here though :_| None of the extension wiring is connected to the main earth of CU yet. I can carry out an IR test on the extension wiring before connecting it to the main CU to establish if the IR reading is above 7.6 Kohms.

NO...

But if you have put a nail through one of the conductors into the wall structure...

wall structure sits on the ground

the ground made up of earth

the earth is the reference point for all voltages..

So INS RES between earth and each of your conductors would show a reading via the nail bridging the gap between conductor and earth!

:coffee .

 

[Robojin]

Just a thought,

What if you worked along the cable to a socket point, bared the conductors and checked continuity from that point to any capping on that run?