2391 practical help

[colink71]

ive got my 2391 practical next week. im a bit rusty on the testing, has anybody got any tips? pls

 

[telectrix]

need to be more specific.

 

[Guest112]

read gn3, theres loads of threads about the 2391 on here as tele said any specific area your unsure of??

The testing rig is a 3phase db with 4 circuits on it
motor circuit
ring main circuit
radial in fp200/pyro to a fcu
and a sub main to a single phase db above which consists of two lighting circuits and a radial socket

its a basic test rig but as you said your a bit rusty which is fair enough, i was lucky enough to be put on testing before my 2391 which helped, not so much now because i cant get off it lol, but if you could get some experience at work it'll help

 

[Rockingit]

Ultimately you either know your stuff and will therefore pass, or you don't and won't for that reason.

But the stuff that they look for is your ability to spot the faults and gremlins on a test board - 20 mins to find 12 faults if memory serves. Then you do a 'full' periodic on a different test board, so brush up on GN3 and remember the order in which you do the tests correctly - "KIPPER" - being Conductivity (R1+R2 resistance), Insulation, Polarity, Earth loop and RCD. Brush up on your SELV as well.

 

[Sparky Ninja]

Your practical will consist of 4 assessments.

Assessment 1:

Visual Inspection Exercise - 30 mins

You will be shown a test rig and given some paperwork. You will be expected to find 'x' amount of faults that are visually identifiable. These faults are dictated by City and Guilds, and are not the genius craft of the training center themselves.
No test equipment will be necessary for this assessment. The assessor will have a crib sheet with the exact faults (12 in total) and you need to identify all of them.


Assessment 2:

Insulation Resistance Exercise - 20 mins

You will be shown to another test rig where you will be introduced to the insulation test assessment. You will be expected to be able to select the necessary test, check it for calibration, check it for damage and choose the correct settings accordingly.
You will be given a sheet with the information to record 2 tests. You will carry out the first test within your first 10 minutes and the assessor will switch in another scenario for your second test, taking the final 10 minutes.
You will do bunch testing for the insulation resistance. A particular scenario will be introduced on the first test by the assessor and it will co-ordinate with the crib sheet so that they know what readings they are to expect.
For each test you will identify the location of the fault (circuit number and description), the polarity of the fault (between Live conductors or between Neutral and Earth etc) and the nature of the fault (short circuit or low resistance).


Assessment 3:

Earth Fault Loop Impedance - 10 mins

This quickie little assessment will involve you again correctly selecting and checking the necessary tester. The assessor will show you to a socket outlet where a pre-recorded or controlled value of Zs is located. You will measure the Zs, take note on your record sheet of the type of protective device and it's rating. You will then follow appendix 14 of BS7671 or use the relevant table in the OSG and calculate the adjustment to the tabulated value for correction due to the operating temperature.
You may also be given an ambient temperature, which if it is anything other than 10 degrees, will result in the application of a correction factor that you will select from the relevant areas in the OSG.

You will do this test twice in the 10 minutes.



Assessment 4:

Periodic Inspection Report - 120 mins

The big one.
You will be shown a rig consisting of a TP&N consumer unit, with another SP board fed from it. Final circuits from the TP&N will be a ring final, a fuse spur (supposed to be in MI, but oftenly now installed in FP200) and a motor control in SWA. The SP board will have a radial socket outlet, and RCD within the board, and lighting circuits consisting of two way lighting and a dimmer switch.

You will be expected to carry out a full periodic inspection and test with all the reporting carried out.

All equipment must be correctly selected, checked and used.
Great consideration needs to be given to the safe isolation procedure with regard to locking off, warning signs, proving isolation with a proving unit and a GS38 compliant tester. Make sure you put the key in your pocket when locking off.

It is part of the assessors duty to display an arrangement of test equipment beyond the requirements of your assessment, this creates the challenge for the delegate to correct select the equipment. It is also a requirement with some assessments to deliberately place a voltage indicator that does not conform to GS38, proving as to whether the delegates correctly inspects the test equipment or not on selection.

This assessment alone will require a handful of test:

Continuity of protective conductors (cpc's and bonding)
Continuity of ring final circuits
Insulation resistance (be particularly aware of the dimmer switch)
Polarity (dead, then live)
External earth fault loop impedance
Prospective fault current (PEFC, PSCC, highest value become PFC)
Earth fault loop impedance
RCD

 

[colink71]

just a breakdown of each test on the P.I.R,
do you do a R1 and R2 on the incomer and do you only do polarity on the lights and rigs.
also can you explain the procedure on I/R on the whole board rather than doing individual circuits.
and testing on the 3 phase stuff.

thanks for your replies

 

[Guest112]

dont know what you mean R1 and R2 on the incomer? thats a dead test?

first thing youll do is safe isolation = permission, remove loads, knock off main switch,lock off, key in pocket remove cover, prove tester on known source or proving unit, ten tests on the three phase to ensure its dead then prove testers again.

Ze/external earth lop impedance on the live side of the main switch (bottom) to do this you will remove the earthing conductor do three tests (each phase) and record the highest, then reconnect earthing conductor say again RECONNECT EARTHING CONDUCTOR

PFC, which is PEFC and PSCC depending on the tester you use two probes or three probes PEFC concentrates on line and earth and PSCC line and neutral, you will do both three times and you will double and record the highest reading because its three phase.

You will check the three phase polarity using the voltage detectors if you need more explanation just say

um check bonding with continuity tester supposed to be long wander lead but you can reach in the exam to prove continuity youll expect a nice low reading so just tick to confirm on the sheet,

the rest is in the gn3 mate if you havent got it for some reason just get it asap make sure you know the sequence off by heart.

I

 

[i=p/u]

im in for it in january....its good to read wild one, does polarity not count as in R1 + R2??