2391 exam insulation resistence testing

[iceman]

hello can someone tell me if this will get me through this question to decribe how to undertake an insulation restence test on a new installation

or is this over kill lol


describe how to undertake an insulation resistence test on a new installation
inform people in the area
seek permission to isolate the supply
lock off the supply
prove the installation is dead useing an approved voltage indicator
confirming the approved voltage indicator is working correctly with the use of an proving unit
then test the approved voltage indicator again with the proving unit after confirming the installation is dead
warning notices are present
remove all voltage sensitive equipment
like lamps dimmers neon lamps control timers delay timers luminairs
select an insulation resistence tester check calabration of insulation resistence tester
check for signs of damage confirm with GS 38 document
check leads and probes for signs of damage
leads should be insulated with no damage to leads
leads should be correctly coloured
probes should be fused 500A
probes tips should be shrouded
probe tips should be atleast 4mm diametre preffably 2mm
set insulation resistence tester to 500v dc
with circuits breakers and switches open
test between line conductors and neutrel conductors connected together to earth at the appropriate distrbution board or for circuits not vunrable to insulation resistence testing line and neutrel seperately to earth
for circuits containing 2way switching and intermedate switching the switches must be opperated one at a time and circuits subjected to addtional insulation resistence tests
an insulation resistence value of not less than 1.0Mohm complies
with the regulations where an insulation resistence of less than 2Mohm
is recorded the possibility of a latent defect exists in these cirumstances each circuit should be tested seperatly

 

[zupos40]

hello can someone tell me if this will get me through this question to decribe how to undertake an insulation restence test on a new installation

or is this over kill lol


describe how to undertake an insulation resistence test on a new installation
inform people in the area
seek permission to isolate the supply
lock off the supply
prove the installation is dead useing an approved voltage indicator
confirming the approved voltage indicator is working correctly with the use of an proving unit
then test the approved voltage indicator again with the proving unit after confirming the installation is dead
warning notices are present
remove all voltage sensitive equipment
like lamps dimmers neon lamps control timers delay timers luminairs
select an insulation resistence tester check calabration of insulation resistence tester
check for signs of damage confirm with GS 38 document
check leads and probes for signs of damage
leads should be insulated with no damage to leads
leads should be correctly coloured
probes should be fused 500A
probes tips should be shrouded
probe tips should be atleast 4mm diametre preffably 2mm
set insulation resistence tester to 500v dc
with circuits breakers and switches open
test between line conductors and neutrel conductors connected together to earth at the appropriate distrbution board or for circuits not vunrable to insulation resistence testing line and neutrel seperately to earth
for circuits containing 2way switching and intermedate switching the switches must be opperated one at a time and circuits subjected to addtional insulation resistence tests
an insulation resistence value of not less than 1.0Mohm complies
with the regulations where an insulation resistence of less than 2Mohm
is recorded the possibility of a latent defect exists in these cirumstances each circuit should be tested seperatly

Very full answer, But beware of the time limit, when doing 2391 I was told to bullet point answer

Below is what I sent to a friend recently, not need to include part in brackets

Test Procedure for complete installation

Ø Inform house-holder, fellow workers and other trades that you are about to perform Insulation Testing and ensure they or their pets are not at risk.
Ø Perform instruments safety checks on insulation tester, does the test leads conform to GS 38 etc, does the meter pass the open circuit/short circuit tests
Ø Ensure consumer control unit is safely isolated, locked off, safety notices posted.
Ø Recheck that all lamps, neon’s, electronic, voltage sensitive and current using equipment have been disconnected.
Ø Connect red test lead to Line busbar and black lead to the neutral bar, with all c.b on and all switches on e.g. lighting, cooker, FCU etc.
Ø Set insulation test to 500V 200MΩ (note a lot of new meter auto range, you select the test voltage, the electronic does the rest)
Ø Press the Test button, record the result, once test is complete, leave leads connected for about 30 seconds in case cable etc have been charged.
Ø As nearly all installations have 2-way switches on lighting cct, you must repeat the test with the switch in a different position to ensure all strappers are checked.
Ø If the measured values are greater than 2MΩ test is complete, if less than you are required to retest each circuit individually.

 

[iceman]

thanks for ya advice i think if i do get a question on insulation resistence i think i'll leave it till last as its one of the most importent on the 2391 exam

 

[electricAl]

Hi there IceMan

Looks pretty good to me, bar a couple of points...

First off, your list is pretty comprehensive - which is good, cos you`ve covered almost everything so will get close to 15 marks, but also bad, cos you`ll only get those marks if you write all that in your actual exam & there`s a lot in your list to remember.
It`s vital if you can`t remember everything to remember the most significant lines

If you are going to forget any lines on your list may i suggest the `probes should be fused @500A`- a typo no doubt, but it`s actually 500mA.

Also, if i were you i`d mention the GS38 compliance requirement earlier - it`s just as applicable to the Voltage Indicator you introduce early on. Then include a link to it ( e.g. "as per VoltIndicator above") when describing IR Tester. So such req` such as 4mm tip length (not diameter mate) etc would be stated early on.

Deffo, as Zupo suggested, you need to include checking short & open circuit performance of IR tester prior to tests. Altho` personally i`d state you`d look for min & max readings rather than actual values - too machine specific for me.

Splittin` hairs, you don`t need to include luminaires in list of voltage sensitive devices. And technically items such as dimmers should have their contacts bridged not just simply disconnected.

And lastly - the biggo mate. The IR test is not `one of the most important questions`. One q is no more important than any other in the 2391 - only the marks available are imporrtant. There`s no sentiment involved & no distinction is made between those that answered the more crucial/tasking/difficult questions but fell down on the easier one`s, & those that did the opposite. You get what you get for each answer.

Anyway, thats more than a couple of points & i`ve had a couple of pints so i`ll be orf to me bed

But very best of luck with it - i`m sure you`ll fly thru

 

[iceman]

thanks for ya help guys i'll post up a revised list to see wot ya think ;-)

hello again guys heres my revised list i hope i got the things in the rite order this time;-)

describe how to undertake an insulation resistence test on a new installation

inform people in the area
seek permission to isolate the supply
lock off the supply
confirm all equipment metres leads and probes to GS 38 document
prove the installation is dead useing an approved voltage indicator
warning notices are present
remove all voltage sensitive equipment lamps dimmers bridged neon lamps control timers delay timers
select an insulation resistence tester
check for signs of damage
check leads and probes for signs of damage
leads should be insulated with no damage to leads
probes should be fused 500mA
probe tips should be shrouded
probe tips should be atleast 4mm in length preffably 2mm
does the metre pass the open circuit/short circuit tests
set insulation resistence tester to 500v dc
with circuits breakers and switches open
test between line and neutrel conductors connected together to earth at the appropriate distrbution board--
or for circuits not vunrable to insulation resistence testing line and neutrel seperately to earth
for circuits containing 2way switching and intermedate switching the switches must be opperated --
one at a time and circuits subjected to addtional insulation resistence tests
look for min & max readings
an insulation resistence value of not less than 1.0Mohm complies
where an insulation resistence of less than 2Mohm
is recorded the possibility of a latent defect exists and each circuit should be tested seperatly

 

[Matt Thornton]

Be aware the by doing an insulation test with line and neutral connected together and to earth you are NOT testing between line & neutral

 

[zion]

Be aware the by doing an insulation test with line and neutral connected together and to earth you are NOT testing between line & neutral

Is that a problem? The IR test will indicate a breakdown in both line and neutral to CPC. Either way all conductors are tested. Also, there will be not current flowing through the circuit (theoreticaly) if you test between line/neutral and CPC so you should not have to remove voltage sensitive equipment. Am I right? or would this constitute a fail on that part of the exam regardless. Im doing the 2391 in August!

 

[bomdiddly]

have u got the book exam success inspection and testing 2391 this gives good info on answering questions

 

[iceman]

yes iv gone threw tht now about 1000 times already lol iv just timed meself wrighting all tht out for insulation resistence testing lol took me a good 15minutes city and guilds got tht rite thn 1hour for the first 20 questions and hour and half for the last 6 questions 15mins for each of the last 6 gona be tight i guess but the first 20 questions are normaly quite quick not takin anythin for granted tho :-/ lol

 

[Risteard]

You must prove that your voltage indicator is working BEFORE AS WELL AS AFTER you prove dead. Otherwise how can you be sure that it was working?

 

[iceman]

hello again guys revised again i knew i should of left the part in regarding proving unit or known source some of you say different things lol


describe how to undertake an insulation resistence test on a new installation

inform people in the area
seek permission to isolate the supply
lock off the supply
confirm all equipment metres leads and probes to GS 38 document
select an approved voltage indicater
prove the voltage indicater is working with a proving unit or known source
prove the installation is dead useing an approved voltage indicator
then prove voltage indicater again with proving unit or known source
warning notices are present
remove all voltage sensitive equipment lamps dimmers bridged neon lamps control timers delay timers
select an insulation resistence tester
check for signs of damage
check leads and probes for signs of damage
leads should be insulated with no damage to leads
probes should be fused 500mA
probe tips should be shrouded
probe tips should be atleast 4mm in length preffably 2mm
does the metre pass the open circuit/short circuit tests
set insulation resistence tester to 500v dc
with circuits breakers and switches open
test between line and neutrel conductors connected together to earth at the appropriate distrbution board--
or for circuits not vunrable to insulation resistence testing line and neutrel seperately to earth
for circuits containing 2way switching and intermedate switching the switches must be opperated --
one at a time and circuits subjected to addtional insulation resistence tests
an insulation resistence value of not less than 1.0Mohm complies
where an insulation resistence of less than 2Mohm
is recorded the possibility of a latent defect exists and each circuit should be tested seperate

 

[Matt Thornton]

Sorry, but you are wrong, you will not be testing ALL Conductors. "Insulation resistance tests must be carried out between ALL live conductors AND between ALL live conductors AND earth".

 

[electricAl]

Iceman, when re-reading your list just now, realised a little confusion must have crept in re: an earlier suggestion i made to you...

Not wanting you to have to keep re-editing your list mate, but don`t feel right leaving it as it is - the `min/max` suggestion pertains to the open/short circuit check you should carry out on the meter, before your actual testing.

Regards, Al

 

[iceman]

hi electrical iv taken tht part out now cos it dont look rite suggesting the 1.0Mohm minimum value explains wot the expected reading should be, im leaving it like tht now everythin is there that the examiner is lookin for he cant moan at tht cos its all there straight out of GN3 ;-)

 

[electricAl]

its all there straight out of GN3 ;-)

That`s what they want - give it to `em