guide to the 2392

[meerkat]

Hi, just passed the 2392 and have the following advice for students sitting the exam.

Ask for any paperwork regarding installation/Consumer unit at the start.

Do the safe isolation:

1. Identify means of isolation
   
2. Ask permisssion to isolate
   
3. Isolate and lock off
   
4. Inspect and prove voltage tester
   
5. Test circuits dead between L/N L/E N/E
   
6. Reprove voltage tester
   
7. Post warning notices.
   

• Remove all covers and inspect
  
• complete the inspection sheet
  
• Replace all covers except the CU
  
• Partially complete testing sheet with circuit details
  
• Start testing using the acronym C.R.I.P.E.R
  

1. Continuity of cpc's and MEBC water and gas input readings in r1+r2 box on schedule of test sheet for radial circuits.
   
2. Ring final circuit continuity, (1) r1, rn, r2, (2) cross link L/N x 2, (3) cross link L/E x 2, compare readings as a guide eg R1+R2/4 input reading obtained on schedule of test for socket circuit R1+R2.
   
3. Insulation resistance test, remove anything vulnerable to the test, eg neon's, lamps, transformers etc (Global) set @ 500V DC and 200Mohms test between L/N once, L/E twice incorporating the strappers of 2 way lighting, N/E once, anything less than 2Mohms on a global test means there's a latent defect somewhere.
   
4. Polarity done for radial circuits at C, Ring circuit continuity at (3)
   *Live Supply polarity should now be confirmed using a suitable voltage tester L/E 230v L/N 230v N/E 0v, before energising the system
   
5. E Live testing be careful, (1) Ze, first isolate supply, disconnect main earthing conductor in CU test between disconnected Earth and incoming Line and Neutral, 20ohms setting, reconnect earthing conductor. (2) PEFC set at 2000amps same test as (Ze) with earthing conductor connected . (3) PSCC set at 2000amps test between incoming Line (red probe) and Neutral (black probe) attach the green probe to the Neutral rail and link in by closing the main isolation device. make sure all mcb's and RCD are in the open/off position before closing the main isolation device.
   

Remember the highest reading of the PEFC and PSCC is the Prospective fault current recorded on the paperwork (4) Zs all circuits, close MCB's and RCD's of circuits to be tested individually, test at 20ohms at furthest point in circuit between switched Live, Earth and Neutral for lights, and L/N/E using kettle lead and plug for all other circuits. Ring circuit test every socket, record the highest reading found for Zs of sockets.

6. R rcd test set at 30mA (1) 0.5 x full load no trip 2 secs, retest at 180 no trip 2 secs, (2) 1 x full load trip in less than 300m secs, retest at 180, trip in less than 300msecs, record highest reading for x 1 reading. (3) 5 x full load test trip in less than 40msecs, retest at 180, trip in less than 40msecs record the highest reading as x 5 reading, (4) test Rcd self test button, must trip RCD.

Covers on, complete functional tests on all circuits.

Complete paperwork and fill in readings obtained on schedule of test, compare max Zs readings for type of circuit breakers/fuses used with those in the OSG or using the Rule of Thumb calculation using the figures in the BRB.

Make a note of any discrepancies found in the box at the bottom of the schedule of test tables or in the comments on existing installation box page 2.

I found:

• no brown sleeving on strappers,* cracked socket front,
  
• 3 circuits failed due to high Zs readings, when compared with acceptable max Zs figures on page 49 of the BRB remember the rule of thumb x 0.8 of actual figures in the BRB, rule of thumb not reqd for figures in the OSG.
  

Check all paperwork has been completed.

Good Luck and try to remain calm.

Go to pub and celebrate for the whole night!!!

Hope this helps (Meerkat)

Guinness Guinness

 

[Marc]

Fantastic guide, thank you.

Though you may want to insert live polarity into it.

 

[PoorFish]

thats excellent.

I have my 302 practcal soon.

This will come in very handy.

Like the CRIPPER bit.

Are thinking of doing the 2391???

I was wondering should I go straight for that one.....even though I have heard all the horror stories.

Thought maybe because im still in study mode it may help to just get on with it??

Any way thanks again for this

 

[meerkat]

Fantastic guide, thank you. Though you may want to insert live polarity into it.

Hi Marc, I think this is covered by the functional testing at the end, this means testing all circuits live using lamps and switches for lighting circuits, and a socket tester for all radial circuits/ring circuits incorporating a socket, this also confirms correct supply polarity cheers (Meerkat)

 

[meerkat]

thats excellent.I have my 302 practcal soon.

This will come in very handy.

Like the CRIPPER bit.

Are thinking of doing the 2391???

I was wondering should I go straight for that one.....even though I have heard all the horror stories.

Thought maybe because im still in study mode it may help to just get on with it??

Any way thanks again for this

Hi Poorfish, glad you liked the post, the 2392 was quite challenging for me as I am not working in the industry yet, however I will hope to sit the 2391 in the near future, although I do believe it is a lot harder than the 2392, good luck mate, (Meerkat)

 

[madeinengland]

you should do live polarity test when you liven up the instalation. before your Ze and PFC tests. it's done with a voltage indicator and done E-P 230V, E-N 0V and P-N 230V.

i've got my 2392 practical in 2 weeks but can't get in to practise because half the class are doing it next week.we've been told that no faults whatsoever should be found on the test boards as it is simply an initial verification that "YOU have just installed".

great post by the way

 

[Marc]

you should do live polarity test when you liven up the instalation. before your Ze and PFC tests. it's done with a voltage indicator and done E-P 230V, E-N 0V and P-N 230V.i've got my 2392 practical in 2 weeks but can't get in to practise because half the class are doing it next week.we've been told that no faults whatsoever should be found on the test boards as it is simply an initial verification that "YOU have just installed".

great post by the way

Expect the unexpected! I had a ring on my 302; 3 sockets gave ~.24Ω, 3 others gave ~.15Ω.

As for when to verify live polarity - it'd be best to do it before closing the main switch. I was taught CRIPPEL -

Continuity of main earth, bonding and CPCs

Ring continuity

Insulation Resistance

Polarity Dead (confirmed at C & R)

Polarity Live

Electrode

Loop

I realise it misses out RCD testing but I'd say you're less likely to forget that than you would be to forget live polarity.

 

[madeinengland]

i have been on a couple of threads talking about maximum demand for the paperwork. how did you go about it MEERKAT? our test rig is the following:

1)1x16 amp radial circuit with 1 socket.

2)1x6 amp lighting circuit with 2 way 1 lamp.

then rcd protected circuits of

3)1x40 amp cooker point with 1 socket

4)1x32 amp ring circuit with 4 sockets and 1 spur

was yours anything like this?

having discussed it on other threads and got my head round it i make it 67A.

 

[Marc]

Is max demand not largest breaker + (rest * 0.4)? I got 61.6.

Edit: Just read some of the other threads. I'd always used Tab 1B but last week was told to use largest + 40% and this would be satisfactory on the paperwork. I suppose where 2392 is concerned it should be done using tab 1B rather than a quick calculation!

 

[meerkat]

you should do live polarity test when you liven up the instalation. before your Ze and PFC tests. it's done with a voltage indicator and done E-P 230V, E-N 0V and P-N 230V.i've got my 2392 practical in 2 weeks but can't get in to practise because half the class are doing it next week.we've been told that no faults whatsoever should be found on the test boards as it is simply an initial verification that "YOU have just installed".

great post by the way

Hi Madeinengland live "supply polarity", can be checked and verified by the 2 green lights illuminating on the earth loop test meter or the 2 red lights on the RCD tester (Robin) Live "polarity" is tested at the end of all tests with all covers on by switching all MCB's the Rcd and the DP isolator on, test the light circuit lamp using the 2 way switches and test each radial or ring circuit using a socket tester, the type which has three neon lights, confirming correct polarity.

This is what we were told at college. I am sure all college teaching methods will vary slighly.

How are they going to confirm your inspection/testing ability if they dont put any small discrepancies/high readings in the circuits?

We were also told there would be no faults, because in the real world you would have installed all of these circuits, remember its a bit of a game really.

I am telling you how I found it on my assessment (fact) dont always believe what you are told, inspect and test as you have been shown record what you find, any discrepancies make a note of any high readings especially Zs readings need to be compared to the Max Zs readings in the BRB page 49 and if they are to high they Fail, for obvious reasons, if they are ok then, "happy day's" my friend

hope this helps and good luck with your exam

cheers (Meerkat)

 

[meerkat]

i have been on a couple of threads talking about maximum demand for the paperwork. how did you go about it MEERKAT? our test rig is the following:1)1x16 amp radial circuit with 1 socket.

2)1x6 amp lighting circuit with 2 way 1 lamp.

then rcd protected circuits of

3)1x40 amp cooker point with 1 socket

4)1x32 amp ring circuit with 4 sockets and 1 spur

was yours anything like this?

having discussed it on other threads and got my head round it i make it 67A.

Yes exactly the same rig, regarding max demand, depends which book you read, some say it should be calculated using the tables in OSG page 97 under individual dwellings, our tutor told us it is the service cut out fuse rating, personally I think it should be calculated using OSG.

I make it lights 66% (4 A), cooker 10 +9+5 (24A), Ring 100% (32A) Radial 40% (6.4A) Total=66.4 or 67Amps

cheers (Meerkat)

 

[meerkat]

Is max demand not largest breaker + (rest * 0.4)? I got 61.6.Edit: Just read some of the other threads. I'd always used Tab 1B but last week was told to use largest + 40% and this would be satisfactory on the paperwork. I suppose where 2392 is concerned it should be done using tab 1B rather than a quick calculation!

Hi Marc, max demand should be calculated using Table 1B OSG, my tutor told me it was the rating of the service head cut out fuse, I dont agree with that personally. As my tutor did my 2392 assessment, I put the service head cut out fuse rating in the max demand box, knowing that is what he would want to find there, funny old world isnt it.

cheers (Meerkat)

 

[Marc]

It is funny! Been told all along to use 1B, week before my 302; "biggest plus 40% of rest"!

As for verifying polarity, I wouldn't fancy energising an installation with incorrect polarity! I don't know if the way the leads are connected affects whether or not the lights come on on the tester, but given they too can be connected the wrong way then you run the risk of having the centre contact of an Edison lampholder being the neutral (only one example).

I suppose there are thousands of people up and down the country all taught one way or the other!

 

[madeinengland]

Hi Madeinengland live "supply polarity", can be checked and verified by the 2 green lights illuminating on the earth loop test meter or the 2 red lights on the RCD tester (Robin) Live "polarity" is tested at the end of all tests with all covers on by switching all MCB's the Rcd and the DP isolator on, test the light circuit lamp using the 2 way switches and test each radial or ring circuit using a socket tester, the type which has three neon lights, confirming correct polarity. This is what we were told at college. I am sure all college teaching methods will vary slighly.

How are they going to confirm your inspection/testing ability if they dont put any small discrepancies/high readings in the circuits?

We were also told there would be no faults, because in the real world you would have installed all of these circuits, remember its a bit of a game really.

I am telling you how I found it on my assessment (fact) dont always believe what you are told, inspect and test as you have been shown record what you find, any discrepancies make a note of any high readings especially Zs readings need to be compared to the Max Zs readings in the BRB page 49 and if they are to high they Fail, for obvious reasons, if they are ok then, "happy day's" my friend

hope this helps and good luck with your exam

cheers (Meerkat)

yeah that's cool and i appreciate the thread.we've only been told to do live polarity with voltage indicator.but i guess when you do Zs tests it also tells you on the meter. we use kewtech at my college which is robin so same as you.

Yes exactly the same rig, regarding max demand, depends which book you read, some say it should be calculated using the tables in OSG page 97 under individual dwellings, our tutor told us it is the service cut out fuse rating, personally I think it should be calculated using OSG.I make it lights 66% (4 A), cooker 10 +9+5 (24A), Ring 100% (32A) Radial 40% (6.4A) Total=66.4 or 67Amps

cheers (Meerkat)

that is good news as i have been on a couple of threads and there are a few conflicting answers. i make it 67A so if you do and you passed that's good enough for me.

cheers.

 

[madeinengland]

Is max demand not largest breaker + (rest * 0.4)? I got 61.6.

i beleive this is called the yeeehaaaaw method!

 

[Marc]

i beleive this is called the yeeehaaaaw method!

Like I said, always done it using 1B, then was told the simplified method was acceptable. That's from the mouth of my tutor, who also assesses 2330/2392/2391! I think it depends who your assessor is on the day; they have their own interpretations of things and mark you accordingly!

 

[madeinengland]

well i hope the assessor i get is in a good mood.

 

[monkfish]

same ere bagpuss:^O

 

[ianmacd]

Largest + 40% of the others is an old skool method.

Still disagree with your calculation of the cooker circuit though as I read the OSG differently it would seem.

Nice thread though.

 

[ADS]

Hi Madeinengland live "supply polarity", can be checked and verified by the 2 green lights illuminating on the earth loop test meter or the 2 red lights on the RCD tester (Robin) Live "polarity" is tested at the end of all tests with all covers on by switching all MCB's the Rcd and the DP isolator on, test the light circuit lamp using the 2 way switches and test each radial or ring circuit using a socket tester, the type which has three neon lights, confirming correct polarity. This is what we were told at college. I am sure all college teaching methods will vary slighly.

I'm sorry, meerkat, this is totally wrong and must be corrected for anyone else reading it

Live Polarity of supply is tested and confirmed immediately after the dead tests, before the installation is energised.

The reason for this is that if the DNO fella had a bad day and got it wrong, you will know before you energise your installation.

Therefore it cannot be confirmed during Zs tests or Rcd tests or with a socket tester - as this will be too late as you're already energised.

The other 'live' test that has to be performed before energising the installation is Ze, to confirm the supply earth path.

Hope that clears things up