2391 Practical

[JamesBrownLive]

The practical should be similar in most colleges as they have to be designed to the spec that C&G dictate.
The spec for assessment 4 is attached...

Widdler, do you have a larger copy of this diagram that you could attach? I'm finding it hard to make out at such a small size.

Thanks in advance.

 

[La Poste]

Another quick question.

If doing an R1+ R2 test on a SWA cable (If there is one on the test rig) would it be best to disconnect the SWA cable CPC from the MET and then connect it to the line conductor or would it be OK to leave the SWA cable CPC in the MET and just add a fly lead connecting the SWA CPC to the SWA line?

The reason I ask is the SWA armour is earthed and this will give us a parallel earth path along with the cable CPC.
The R1+R2 reading will thus be quite low.
I am not sure if it is best just to measure R1+R2 with the line and CPC and not the armour included.
Is there a recommended best practice?

It would be much quicker to connect a fly lead across the line and CPC's at the board and measure R1+R2 at the end of each cable and saving time is what it's all about but doing this to earthed SWA cable I am not sure about.
There might even be a break in the cable CPC and it will go unnoticed because the armour is being included in the test.

Thanks.

 

[La Poste]

Got one more.
The ring circuit on the three phase board, is it RCBO protected?

I'm asking because I am not sure if it will be vulnerable to a 500V IR test.
I have read it is best to remove the three phase contactor while doing the IR test but am not sure about this RCBO.

 

[Guest112]

Hi mate phase rotation wont come into it

just the 3 phase socket outlet to test as the motor circuit and jsut for R1 +R2 from whichever line is the highest
and IR
calc Zs for everything except the sockets were you can use the 13A adapter

good luck mate

In my 2391 we were required to prove phase rotation using the more advanced voltage testers at the mains during/just after the safe isolation procedure the testers with the L1 and L2 marked probes placing L1 probe on L1 and L2 probe on L2, then placing L1 probe on L2 and L2 probe on L3, and finally L1 probe on L3 and L2 probe on L1 easier if you imagine yourself holding the testers and also asked to test polarity at the mock 3 phase motor aka an adaptable box with accessible probes for testing plugged into the three phase commando socket from the DOL starter on the rig, might be different in other colleges but at mine it was required.

Also you dont do a R1+R2 on the motor circuit you do an r2 test instead

 

[Guest112]

Got one more.
The ring circuit on the three phase board, is it RCBO protected?

I'm asking because I am not sure if it will be vulnerable to a 500V IR test.
I have read it is best to remove the three phase contactor while doing the IR test but am not sure about this RCBO.

No the ring main fed from the three phase db isnt off an rcbo the only rcd in the rig is the sub main switch to the single phase db. but on the single phase db remove the dimmer switch off one of the lighting circuits befor IR testing turn off the sub main switch while testing IR on the three phase db and then test the single phase board separately after removing the dimmer switch.

 

[Guest112]

Another quick question.

If doing an R1+ R2 test on a SWA cable (If there is one on the test rig) would it be best to disconnect the SWA cable CPC from the MET and then connect it to the line conductor or would it be OK to leave the SWA cable CPC in the MET and just add a fly lead connecting the SWA CPC to the SWA line?

The reason I ask is the SWA armour is earthed and this will give us a parallel earth path along with the cable CPC.
The R1+R2 reading will thus be quite low.
I am not sure if it is best just to measure R1+R2 with the line and CPC and not the armour included.
Is there a recommended best practice?

It would be much quicker to connect a fly lead across the line and CPC's at the board and measure R1+R2 at the end of each cable and saving time is what it's all about but doing this to earthed SWA cable I am not sure about.
There might even be a break in the cable CPC and it will go unnoticed because the armour is being included in the test.

Thanks.

If an swa has an integral cpc disconnect it and test as standard r1+r2 as you mentioned otherwise you may miss a break in the cpc good thought. but in the 2391 prac i think the feed to the DOL starter is in swa but for that circuit you do an r2 test so this will not apply in the exam by the sounds of your posts it looks to me that you will fly through the practical assessment based on your knowledge and the preperation you seem to be putting into it beforehand good luck man

 

[La Poste]

I think the feed to the DOL starter is in swa but for that circuit you do an r2 test

I've been thinking about this.
If I do an R2 test only how will I be able to calculate whether the circuit breaker complies with max Zs in BS7671?
Presumably the circuit breaker for the three phase motor is a C type 60898, I will need to measure R1+R2 at some point or calculate it from the length of the circuit and the type of cable used.

I have yet another question.
I've been reading through some past posts here and there and have heard that some people fail because they don't place the lid on the three phase distribution board when they start to work on the single phase DB.
There is also the thought that if this were a real life situation when testing the three phase socket we would be remote from the three phase DB so do we have to lid up the Three phase board to test this socket?
How strict are these assessors?

I can understand if you walk away from the test rig to the other side of the room and leave it open you will be failed but has anyone ever heard of someone failing because they left the three phase board open when working on the single phase board or the remote three phase socket?

Thanks.

 

[Darren365]

My prac in june consisted of a 3p board feeding a ring main, motor and a fused spur in fp200 and a sub main to a single phase db with rcd main breaker feeding two lighting circuits and another circuit s/o radial perhaps? The prac exam is less difficult than the prac at the end of the am2 i found it to be quite basic , but i did ask my boss to put me on testing before the exam so in all fairness i did have a headstart on mine but i think thisis how it went:

Safe iso- permission, knock off, lock off, cover off, prove tester, ten tests, prove tester, done(also do polarity while using testers all polarity checks and phase rotation)

Ze- remove earthing conductor 3 test each phase, replace earthing conductor immiediately!!! record highest

PFC-pefc + pscc, highest of six tests double and record

test bonding to water and gas pipes acceptable reading just tick confirm on sheet (supposed long lead but can reach with meter probes)

r1+r2 all circuits on 3p board link method at db etc, r2 test on motor circuit
three step ring test on ring circuit etc

r1+r2 all circuits on single phase db link method etc proven polarity on all circuits tick boxes

Ir test on 3phase db TURNING OFF RCD FOR SUB MAIN CIRCUIT ten tests, record

Ir test on sphase db AFTER REMOVING DIMMER SWITCH or any sensitive equipment , record

Permission to energise after all covers replaced

Zs all circuits record highest on each circuit

rcd test on sub main rcd breaker functional tests then happy days just fill out sheets to fin off i have all my notes from my 2391 prac and theory so if anyone needs info give me a shout ill dig them out before it all changes of course

almost forgot insulation resistance fault rig i had to test two faults simple all mcbs on locate which conductors the fault is between and the find which circuit it is on by elimination method to find the circuit either turning off mcbs or removing neutrals etc just record the fault dead short low resistance etc

live test rig earth loop on two test will be given mock fuse types and sizes for test have to either locate fault on tester or check with books to see if zs is of acceptable value for the fuze type/size etc and i think thats it

forgot the visual inspection rig also got to loacate 12 faults on a mock rig and record them no tests only visual inpection no grommet protection ,1p2x/ip4x faults incorrect mcb ratings cable sizes etc also very simple


not sure if the test rig is the same around britain but maybe?

Hi Stan , I found your post very informative thank you. I’m an older person (47) coming into this game late but I have always worked in the industry at a lower level. My aim is to become a tester . If you have any notes I could browse i would be grateful as I like to be as prepared as possible for these exams.
Thanks mate
Darren Glover

 

[DPG]

Hi Stan , I found your post very informative thank you. I’m an older person (47) coming into this game late but I have always worked in the industry at a lower level. My aim is to become a tester . If you have any notes I could browse i would be grateful as I like to be as prepared as possible for these exams.
Thanks mate
Darren Glover

[email protected]

Welcome to the forum.

It would be worth starting a new thread to be honest, this one is rather old (2011).

 

[UNG]

Hi Stan , I found your post very informative thank you. I’m an older person (47) coming into this game late but I have always worked in the industry at a lower level. My aim is to become a tester . If you have any notes I could browse i would be grateful as I like to be as prepared as possible for these exams.
Thanks mate
Darren Glover

The member you have quoted is no longer on this forum