Insulation Resistance Test

[smithjim0001]

Any feedback on this would be handy.

If you have a property that has a lot of lamps etc.. that are too much to remove to carry out a insulation resistance test why does it work that connecting the line and neutral together and testing between the two and earth.

Can someone explain.

 

[jeremy]

With the lamps in , or anything else connected if you apply voltage to both lives you're energising both sides and then testing the IR to earth. You're testing the whole "business" side of the installation against the safety side. If it passes the test then there are no earth faults, so anyother fault should show as an overload or short circuit which if it is a working installation with no history of faults can be assumed to be free from faults? I think that's the right answer it makes sense in my head, but I'll happily be corrected!!

 

[keniff]

i think also, when you ir test the live and neutral you would get a dead short ie 0.00 because the bulbs connect the L and N and you end up with a loop back to your tester, depends how you ir test, i generally test, L-E N-E and L-N when doing the ir tests. hope that helps

 

[Guest123]

As said you will get false readings through the lamps. Also to avoid damaging the lamps and any other sensitive electronic equipment by sending 500V DC between L&N.

 

[ezzzekiel]

because l/n are joined then they are at the same potential

 

[trebor]

As others have said there are 2 issues

1) to avoid false readings with line to neutral load in circuit
2) it avoids damage to sensitive equipment as in theory there is no circuit for the test current to pass through

I say in theory above because if there is a neutral - earth fault a circuit could still be completed which is why I test neutral to earth first when vulnerable equipment is at risk