2391 Practical Question

[r10ley]

Hi everyone, I have been doing my 2391 course and am soon to take the practical. Been reading up on whats involved and have a few questions : )

I believe part of the test is a 3-phase board with a single phase CU fed from this. So here are my questions.

1. When carrying out a IR test on the 3phase board testing the board as a whole, should the single phase CU be isolated at its main switch so you are testing the cabling up to the board but not the actual board. Or should you leave the single phase isolator on so this board is included too? Also is a RCD classed as vunerable equipment when testing at 500V dc as the single phase board will probably have one? If it is does this mean you cant IR a whole CU when it contains RCDs?

2. Im also lead to believe that there is a 3-phase motor circuit fed from the 3-phase board. I am unsure as what tests will need applying to this circuit. Is it a continuity of CPCs and an IR. If so to carry out a cont. of CPCs is this just a case of linking each phase in turn to earth and testing at the extremity of the circuit? And will this also be your Zs once applied to Ze?

3. Once dead testing has been completed on the 3-phase and single phase CU is it a case of placing the cover back on the 3-phase board energising this, and then with the MCB feeding the single phase board on but the main switch of the single phase board locked off carrying out your PFC and Ze tests on it.

4. Last one I Promise! Will a seperate PIR need to be filled out for the 3-phase board and the single phase board?


Thanks for your help!

r10ley

 

[IQ Electrical]

Hi everyone, I have been doing my 2391 course and am soon to take the practical. Been reading up on whats involved and have a few questions : )

I believe part of the test is a 3-phase board with a single phase CU fed from this. So here are my questions.

1. When carrying out a IR test on the 3phase board testing the board as a whole, should the single phase CU be isolated at its main switch so you are testing the cabling up to the board but not the actual board. Or should you leave the single phase isolator on so this board is included too? Also is a RCD classed as vunerable equipment when testing at 500V dc as the single phase board will probably have one? If it is does this mean you cant IR a whole CU when it contains RCDs?

2. Im also lead to believe that there is a 3-phase motor circuit fed from the 3-phase board. I am unsure as what tests will need applying to this circuit. Is it a continuity of CPCs and an IR. If so to carry out a cont. of CPCs is this just a case of linking each phase in turn to earth and testing at the extremity of the circuit? And will this also be your Zs once applied to Ze?

3. Once dead testing has been completed on the 3-phase and single phase CU is it a case of placing the cover back on the 3-phase board energising this, and then with the MCB feeding the single phase board on but the main switch of the single phase board locked off carrying out your PFC and Ze tests on it.

4. Last one I Promise! Will a seperate PIR need to be filled out for the 3-phase board and the single phase board?


Thanks for your help!

r10ley

1 Do 2 'global' IR tests, one for the main board with the small board isolated and 1 for the small board with the small board main switch isolated.
An RCD is a vulnerable device as is the dimmer that you will link out.

2 There is no need to carry out the R1+R2 test on each line, once you have verified cpc continuity using L1, you have verified cpc continuity.
You can only measure R1+R2 up to the incoming side of the motor starter but then you must verify the continuity of cpc from the outgoing side of the starter to the socket that would supply the missing motor.

3 Most training centres are happy for all Zs tests to be calculated unless the BS 1363 plug lead can be used for live testing of socket outlets.
Once you have done the dead tests for the main board, you will have the Zs for your small board by way of Ze+(R1+R2) from the distribution circuit to the small board. You can then calculate PFC for the small board if you wish.
The Ze and PFC tests on the main board should be measured.

4 Not a separate PIR but a separate schedule of test results will be required for the small board. The schedule of inspections covers the whole installation whether there are 2 DB's or 10.


Stay calm and most of all WORK SAFELY!! Almost all practical test failures are due to safe working issues such as removing protective bonding conductors prior to isolation, energising the installation for live testing with a busbar barrier not fitted etc. etc.

 

[brucelee]

Iq is spot on exactly as i remember it lol was just going to reply until i read his post so no need as he is 100% correct lol

Iq if you have two ccus fed from same henley blocks from same supply
when carrying out a pir do i need a pir , 2 schedule of inspections for each board and two schedule of test results
I know if you have a DB supllying a sub to another ccu its only 1 schedule of inspections but whats required in the situation above i think 2 schedule of inspections

 

[IQ Electrical]

Iq is spot on exactly as i remember it lol was just going to reply until i read his post so no need as he is 100% correct lol

Iq if you have two ccus fed from same henley blocks from same supply
when carrying out a pir do i need a pir , 2 schedule of inspections for each board and two schedule of test results
I know if you have a DB supllying a sub to another ccu its only 1 schedule of inspections but whats required in the situation above i think 2 schedule of inspections

If it's the same origin and you consider the 2 DB's to be part of the same installation then you only need 1 schedule of inspections.

 

[r10ley]

Thanks for your help : D Just to clarify the circuit supplying the single phase CU, on the test results sheet it will say something like supply to Consumer unit but the test results will only relate to the two supply cables up untill the CUs main switch. Then a separate test results sheet will have all the results for the single phase CU.

Thanks again

r10ley

 

[IQ Electrical]

It will be written as 'Distribution circuit DB 2'

The Zs for that circuit in DB 1 will also be the Zs (or Zdb) of DB 2 and yes, a separate schedule of test results will be completed for DB 2.

 

[r10ley]

Thanks again, one last question I promise lol. When carrying out a test on a radial socket circuit is it a case of connecting phase to cpc to get your R1+R2 reading but also connecting phase to neutral to confirm polarity?

Thanks

r10ley

 

[IQ Electrical]

Thanks again, one last question I promise lol. When carrying out a test on a radial socket circuit is it a case of connecting phase to cpc to get your R1+R2 reading but also connecting phase to neutral to confirm polarity?

Thanks

r10ley

Precisely, the R1+R2 test will not reveal any line to cpc reversal so a quick test between line and neutral at the outlet with line + neutral linked at the DB will prove polarity.

Don't worry about asking questions here, questions and answers are a great strength of this forum!

 

[r10ley]

Thanks very much every problem ive had has been quickly solved with a quick post Thanks all!

r10ley

 

[brucelee]

If it's the same origin and you consider the 2 DB's to be part of the same installation then you only need 1 schedule of inspections.

Hi Iq thanks for reply

Yes its the same origin in the same house just has 1 wylex with inperial stranded cables no rcd and supplies all house incuding half the kitchen apart from newer half of the kitchen extension
The Other a volex split load with single rcd is supplying the newer half of the kitchen for the socket ring, FCUs supplying selv pelmet lighting on this side and downlights

 

[SirKit Breaker]

You will be walked through the test board during your course, so dont worry about how to do this, that and the other, you will also do a practice of filling in the paperwork. All the mud will clear once you start the course and have a good practice on one of the boards. The practice board wont be the one you do your exam on, but it will be very similar. Put more effort into getting the written sorted out, that s the hard part.

Cheers.......Howard