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Discuss How to "insulation resistance test" procedure???? in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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hey, could some explain how to do an insulation test, to niceic Test standards, of how you should do it when YOUR being assesed. correct procedures, aimed at those whos just done it and passed ;) cheers
 
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E

EasyFox

If you have done a cu change they will normally ask you to IR the immersion circuit as it's less time consuming.

Ask if the assessor wants it doing at the cu or from a socket.

Isolate circuit.

Remove all lamps/neons/heating elements/dimmers/trannies from circuit (explain why you are doing this or wait for him/her to ask the question) at this point I ask if they want the test undertaken line & neutral joined then tested to cpc or as per the full test (they always ask for the full test).

Test at 500v dc between neutral & line
Test at 500v dc line - cpc
Test at 500v dc neutral to cpc
(results will be checked against cert you've issued)

At this point you'll be asked if you think the results are ok & what the minimum allowable by 7671 is & possibly at what voltage elv equipment would be tested at.

Reconnect all terminations re-energise jobs done.
 
P

PAUL M

hey, could some explain how to do an insulation test, to niceic Test standards, of how you should do it when YOUR being assesed. correct procedures, aimed at those whos just done it and passed ;) cheers
set your meter to M ohms select 1000 v d.c. place one croc clip on nic mans right testicle and one on his left get your camera out and take a pic of his face as you press the test button:eek: value to record on cert,OUCH:D

set your meter to m ohms select 1000 v d.c. Place one croc clip on nic mans right testicle and one on his left get your camera out and take a pic of his face as you press the test button:eek: Value to record on cert,ouch:d
and before anybody else says it .yes im talking bo--ocks;)
 
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  • Thread Starter Thread Starter
  • #4
anyone like to added to easyfox's mature comment, unlike paul M's....

are you allowed to do it just from the meter tails on a new installation ? or do you have to do each circuit L - N, L - cpc, n - cpc ?
or can you do it from the main breaker and test the whole lot ?
also do you have to test each lighting circuit open and closed, or just doing it all closed ok ?

can add in there the stuff which your not allowed to do, but people still do it, making u fail?
 
P

PAUL M

anyone like to added to easyfox's mature comment, unlike paul M's....

are you allowed to do it just from the meter tails on a new installation ? or do you have to do each circuit L - N, L - cpc, n - cpc ?
or can you do it from the main breaker and test the whole lot ?
also do you have to test each lighting circuit open and closed, or just doing it all closed ok ?

can add in there the stuff which your not allowed to do, but people still do it, making u fail?
:eek:im sorry sir i thought you was allowed to have a laugh on here:eek:
 
E

EasyFox

anyone like to added to easyfox's mature comment, unlike paul M's....

are you allowed to do it just from the meter tails on a new installation ? or do you have to do each circuit L - N, L - cpc, n - cpc ?
or can you do it from the main breaker and test the whole lot ?
also do you have to test each lighting circuit open and closed, or just doing it all closed ok ?

can add in there the stuff which your not allowed to do, but people still do it, making u fail?
You'll normally be asked to perform the test on one circuit for an assessment, it's just to show you know how to do the test & understand the results you get.

Nothing wrong with testing IR on a new installation (or for pir's) across the tails but be aware of potential low results due to parrallel circuits on larger installations.

Lighting circuits should be tested with switches on & while operating all 2 way switching in both positions (thats the one that gets forgotten).

So you can see why the assessors tend to plumb for the IR testing on immersion radials, also tests to make sure you remove the element load or neon in the DP switch ;).

Stuff you'll fail or get marked down on:

Not isolating the cu before opening/removing cover
Not removing dimmers/lamps & the likes
Not testing at the correct voltage (500v for lv or 250v elv)
Not having a calbrated tester
 
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S

sparkyork

so if they ask for line and neutral together is that both wires between the teeth of the croc clips at the consumer and test to cpc. is it just the ins test that they dont like you disconnecting the cpc or is it for all tests?

rich
 
B

Bane

set your meter to M ohms select 1000 v d.c. place one croc clip on nic mans right testicle and one on his left get your camera out and take a pic of his face as you press the test button:eek: value to record on cert,OUCH:D
Ho ho ho!
 
E

EasyFox

so if they ask for line and neutral together is that both wires between the teeth of the croc clips at the consumer and test to cpc. is it just the ins test that they dont like you disconnecting the cpc or is it for all tests?

rich

I'd be surprised if they ask you to join line & neutral for this test.

But if they do; put line & neutral in one croc clip & the cpc in the other croc clip, then push the test button.
(you may be asked why this is an advantagous way to IR test some circuits & what does linking L & N achive)

You can dissconnect any cpc you like when testing just remember to re insert it prior to re-energising.


NOW CALM DOWN
Think logical, go as slow/fast as you feel comfortable with while testing, dont try to bull**** the bloke & remember to ask questions & the time will fly by.
 
B

Bane

Think you may have been a little bit slow with that last piece of advice Easy!

Sparkyork's gone offline.
 
  • Thread Starter Thread Starter
  • #15
to recap how the steps goes, when not being assessed

step 1. safty isolate the supply

step 2. Remove all lamps/neons/heating elements/dimmers/trannies and anything vunerable from circuit

step 3. set insulation resistance tester to 500v

step 4. set instruemnt to 200Mohms if it is not self ranging

step 5. test between Line and neutral (note result)

step 6. test between line and cpc (note result)

step 7. test between neutral and cpc (note result)

step 8. reconnect all terminals correctly

........ anything else??? anything wrong???


Testing the circuits individually
lets say that test above is for testing from the tails, so when doing it individually do you have to remove the cpc and neutral, use a croc clip for them and use the probe onto the breaker?

can the test be done, having the supply isolated, all breakers on. and testing by using the probes onto the earth bar & neutral bar.
neutral bar & isolated side of the main breaker? is this ok?

thankyou in advanced, please quote where i've gone wrong ;) cheers

no one like to add...?
 
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C

Carter


Testing the circuits individually
lets say that test above is for testing from the tails, so when doing it individually do you have to remove the cpc and neutral, use a croc clip for them and use the probe onto the breaker?


If for instance you are testing between N and E from the N-bar and E-bars you will read the cumulative parallel insulation resistances or faults from all of the connected neutrals to their associated and other grouped cpc's. Nothing wrong with that per-se but you won't be reading the individual circuit's I.R. reading You need at least one of them Neut or CPC disconnected.

can the test be done, having the supply isolated, all breakers on. and testing by using the probes onto the earth bar & neutral bar.
neutral bar & isolated side of the main breaker? is this ok?
Yep! Page 36 of Guidance Note 3 says...
Simple installations that contain no distribution circuits should be tested as a whole.
- (my emphaisis)

If you haven't got a copy it further adds...
The tests should be carried out with the main switch off, all fuses in place, switches and cct breakers closed, lamps removed, and flourescent and discharge luminaires and other equipment disconnected.
Where the removal of lamps and/or the disconnection of current using eqpt is impractical, the local switches controlling such lamps and/or eqpt. should be open.

To perform the test in a complex installation it may need to be sub-divided into its component parts.
So yes you can test the installation as a whole and so long as 0.5Meg is achieved it is compliant although a reading below 2Meg would indicate a possible latent defect and would require confirmation that is a consequence of normal circuit functioning.
Diags of the procedure on pages 38/39 of GN3

If testing the whole board at the tails then you need the supply to the board OFF i.e its main switch and tails de-energised and the board's mainswitch in the ON condition.

If the supply to the board cannot be removed just lock the mainswitch off at the board and test the whole shebang from the switched side of the isolator. (now dead/use proving unit before and after)

If testing individual ccts at the load side of their breakers you need the board isolator OFF and LOCKED and the circuit's breaker set to the OFF state or you will read the paralleled I.R.s of other ccts back through the busbar.

thankyou in advanced, please quote where i've gone wrong ;) cheers

no one like to add...?
The only thing is don't just switch off, LOCK IT OFF! and then put the key in your pocket/on your keyring, don't leave it on top of the board. You'd feel a right chump if the assessor taps you on the shoulder and hands you the padlock. :(
 
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H

hmiddity

hey, could some explain how to do an insulation test, to niceic Test standards, of how you should do it when YOUR being assesed. correct procedures, aimed at those whos just done it and passed ;) cheers
Hello, Just read your comments. I am in the same position. I have a feed from the lighting circuit to a fused double pole switch which goes to a transformer for a shower pump.
What would the effect be if the neon lights and transformers were left in place?
Regards and thanks for any advice
 

telectrix

-
Mentor
Arms
Esteemed
you could not IR L/N as the transformer and neons would give a low reading. all you could do would be join L/N and IR to E.
 
H

hmiddity

you could not IR L/N as the transformer and neons would give a low reading. all you could do would be join L/N and IR to E.
Thanks for your reply.
My electrical system has a new consumer unit with two rcds. Some of the wiring is quite old and is gradually being replaced.
In one of the mcbs I have two wiring circuits, 1) is for some lighting and 2) is for the doorbell and an understairs light. Neither of the circuits has an earth cable. Also the line and neutral are separate cables. What is the best way to determine which line goes with wich neutral?
Thanks in advance for any help.
 
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