Basic testing

[yellowfin7]

Ok, so I am in college studying a level 2 course (2365) and its coming to the end of year were we have to do a practical installation and then testing. I've taken the test once and failed.

My tutor, taught me and others things that are contradicted both in the On Site Guide, a book by Trevor linsley and a few other resources but we have to do it his way or we fail.

We have to do a ring final, radial, lighting circuit and bonding onto copper (gas) pipe. We wired the full thing in singles on 2.5mm and 1.5mm for the lighting circuit. The radial is Steel wired armour leading to a industrial socket.

I received the notice i failed and the reasons why. I failed on my inspection and testing. The reason i failed was because of the way i tested the bonding (gas pipe). I set my megger to ohms and then put on test probe on the earth terminal and the other directly applied to the pipe. I recorded my results as instructed to do so by my tutor in previous lessons and also recorded the testers serial number. This is why i failed but no explanation of what exactly it is i did wrong. Does anyone know? my resit is in a few days and im struggling to discover my error.


Sorry if this is in the wrong section

 

[Blowcat]

The installation must be isolated when doing the test and you should have removed the bond from the main earth terminal and tested between the disconnected cable and the gas bond.

 

[SirKit Breaker]

The installation must be isolated when doing the test and you should have removed the bond from the main earth terminal and tested between the disconnected cable and the gas bond.

He has hit the nail on the head. The reason you must disconnect the main bonding conductor is to eliminate parallel paths that you may get through other connections to the earthing terminal, usually through supplementary bonding. So just to expand on Blowcats explanation.

Carry out safe isolation procedures.
Lock off.
Disconnect the main protective bonding conductor at the MET.
Connect your LOW RESISTANCE OHMMETER (not Megger) to the end of the conductor and to the pipework adjacent to the bonding clamp, and test, you must connect to the pipework to test the integrity of the clamp.
Expect a reading of about 0.05ohms.
Once you have completed the test, then before you do anything else make sure you reconnect the bonding conductor.
The test method for this is referred to as test method 2 or the long lead method, and is well covered in guidance note 3.

your tutor should have told you what you failed on and why, and then pointed you in the right direction so you cold find out what to do about it.

Cheers...............Howard

 

[SirKit Breaker]

This thread might be better in the trainee section! Don't want him shooting to bits cos he has posted in the wrong area. One for you Paul M.

Cheers...............Howard

 

[Marvo]

Hi Yellowfin7

We have a trainee section the would probably suit you well if you're currently on a training course. Please read this and do the necessary so you can be considered for access.