the IR test

[james king]

hi, to day in collage we carryied out the IR test. the Q i have for all you experienced tester is that in GN3 there is a diagram of how to carry out the test. but on the diagram the test leads were connected to the eart terminal and N bar with all cables in both bars

to day in collage we tested it with the EandN wires out of the bars what is the wright and wrong way?

Q2. in GN3 it also states connecting the LandN together say in a connector block and then testing to earth is this classed as mepthod 2?

 

[SimpleSimon]

hi, to day in collage we carryied out the IR test. the Q i have for all you experienced tester is that in GN3 there is a diagram of how to carry out the test. but on the diagram the test leads were connected to the eart terminal and N bar with all cables in both bars

to day in collage we tested it with the EandN wires out of the bars what is the wright and wrong way?

Q2. in GN3 it also states connecting the LandN together say in a connector block and then testing to earth is this classed as mepthod 2?

Neither is right nor wrong. The diagram shows how to do the test across the whole installation across E and N. This would give you a reading across all circuits tested at once. However be aware that if you do this and come across a low reading you would than have to break down and test the circuits individually to find the low IR reading.

Q. 2 yes this is method 2. Use this if you cannot remove voltage sensitive equipment from circuit before testing. Perfect example is ELV downlights with transformers.

 

[james king]

so mepthod 2 bibass the the trannys? thanks for your help

 

[james king]

ok so say i am testing between live and earth but i put my probe on the Ebar and other probe in the mcb. will i pick up Efaults from that reading that accour on other ccts?

 

[SimpleSimon]

ok so say i am testing between live and earth but i put my probe on the Ebar and other probe in the mcb. will i pick up Efaults from that reading that accour on other ccts?

It could happen. So than you would have to disconnect each cpc separately and test L to E on each MCB and earth to find the problem.

 

[james king]

ok so the way im thinking is you may as well test ech cct 1by1 to make sure! although if there is no problam between NandE this would be exeptable

 

[pushrod]

ok so the way im thinking is you may as well test ech cct 1by1 to make sure! although if there is no problam between NandE this would be exeptable

No, in an exam where time is important , or on a job where time is money, testing all the circuits at once could potentially save you a lot of time.

 

[Pip]

Pushrod,

So testing the whole installation is OK, and a good thing to do on an initial look see,
but where do you enter that result on the test results sheet?

 

[malcolmsanford]

Schedule of Results

Sorry saw you already said result sheet, If you test the whole insulation and get +299 or whatever your meter reads then that in each circuit coloumn.

 

[Pip]

Nice, Thanks Malcolm

 

[pushrod]

Pushrod,

So testing the whole installation is OK, and a good thing to do on an initial look see,
but where do you enter that result on the test results sheet?

As Malcolm said, but it it still not a quick test as you would have to check the whole installation for vulnerable equipment and disconnect and things like neons, surge protection and if it was an occupied domestic house that in itself could be quite time consuming. In fact it can often be a real pain in the butt looking for that last thing which is still connected Still quicker to start with the complete installation where you can, rather than individual circuits though.

 

[Pip]

Pushrod,

Tell me about it, this is an occupied 4 bed domestic house, and finding all those extra sockets hidden behind wardrobes and beds with something plugged into them and dimmer switches to boot....
Burgular alarms picking up there feed from the lighting, door bells....

 

[pushrod]

Pushrod,

Tell me about it, this is an occupied 4 bed domestic house, and finding all those extra sockets hidden behind wardrobes and beds with something plugged into them and dimmer switches to boot....
Burgular alarms picking up there feed from the lighting, door bells....

I feel your pain...

 

[Pip]

I did find myself chasing my tail with a low IR reading on a radial circuit, and the lady of the house pointed out the bedroom TV was still plugged in!

This was an hour or so after I had been through the same thing on another circuit, and I said then that there was something not right, "There's something on this circuit" says I.....

She was listening at least.

 

[Risteard]

If you test each circuit separately instead of the installation/distribution board as a whole then you must consider the effect of the resistances in parallel to the overall insulation resistance of the installation to ensure that it is indeed no less than 1 Megohm.