Insulation resistance test

[ians]

Reading through amendment 8, i noticed that you no longer have to carry out an insulation resistance test on an exsisiting installation.

[Leecatt]

Reading through amendment 8, i noticed that you no longer have to carry out an insulation resistance test on an exsisiting installation.

How do you arrive at this conclusion when page 286 question 8 clearly requests the results of the insulation test.
is there something else i am missing?

[ians]

also on page 279

8.7.8.2 The insulation resistance, measured as follows, shall be at least
1,0 MΩ:
a) to measure the insulation resistance to earth, apply the test voltage
between the earth continuity conductor and the whole system of live
conductors, or any section of it; and
b) to measure the insulation resistance between the conductors, apply
the test voltage
1) between the phase conductors, and, when relevant,
2) between the phase conductors and the neutral conductor.
8.7.8.3 When there are sub-distribution boards and the total insulation
resistance is less than 1,0 MΩ, the insulation-resistance test may be
carried out by
a) isolating and testing the wiring between the main supply and the subdistribution
boards, and
b) testing, as a separate section, each sub-distribution board connected
to all the circuits that it feeds, but the insulation resistance in each
section shall be at least 1,0 MΩ.


Now you see thats what i also thought until i read the new amendment no.8 carefully.

you will find this note...

8.7.8 Insulation resistance
NOTE 1 Before power is connected to any new or altered circuit, the test for
insulation resistance should be carried out to ensure there is no short-circuit or
high impedance faults in the installation, and that it is safe to energize. Amdt 8

NOTE 2 In the case of existing installations where the power may not be switched
off from certain circuits in order to carry out this test, the fact that the circuits are
subject to the supply voltage can be regarded as evident that the insulation
resistance is compliant. Amdt

[Dave A]

NOTE 2 In the case of existing installations where the power may not be switched
off from certain circuits in order to carry out this test, the fact that the circuits are
subject to the supply voltage can be regarded as evident that the insulation
resistance is compliant. Amdt

I suggest that only precludes installations where the power may not be switched off under any circumstances - a pretty rare occurence I should think.

[ians]

" the fact that the circuits are subject to the supply voltage can be regarded as evident that the insulation
resistance is compliant."

[Leecatt]

also on page 279

8.7.8.2 The insulation resistance, measured as follows, shall be at least
1,0 MΩ:
a) to measure the insulation resistance to earth, apply the test voltage
between the earth continuity conductor and the whole system of live
conductors, or any section of it; and
b) to measure the insulation resistance between the conductors, apply
the test voltage
1) between the phase conductors, and, when relevant,
2) between the phase conductors and the neutral conductor.
8.7.8.3 When there are sub-distribution boards and the total insulation
resistance is less than 1,0 MΩ, the insulation-resistance test may be
carried out by
a) isolating and testing the wiring between the main supply and the subdistribution
boards, and
b) testing, as a separate section, each sub-distribution board connected
to all the circuits that it feeds, but the insulation resistance in each
section shall be at least 1,0 MΩ.


Now you see thats what i also thought until i read the new amendment no.8 carefully.

you will find this note...

8.7.8 Insulation resistance
NOTE 1 Before power is connected to any new or altered circuit, the test for
insulation resistance should be carried out to ensure there is no short-circuit or
high impedance faults in the installation, and that it is safe to energize. Amdt 8

NOTE 2 In the case of existing installations where the power may not be switched
off from certain circuits in order to carry out this test, the fact that the circuits are
subject to the supply voltage can be regarded as evident that the insulation
resistance is compliant. Amdt

This is very interesting and has gone straight over my head and I am tempted to agree with Dave, only in the case where power may not be switched off

[ians]

It depends on what you are testing, if you are only doing domestic inspections, then there should be no reason why you cannot switch off. However, if you do factories and commercial inspections this could prove to be a bit tricky. I was involved with an inspection at a sugar mill, switching off the plant to do insulation resistance tests could have been tricky.

[Dave A]

I suggest the reason why the power can't be switched off would have to be very well motivated. I certainly can't see us rolling over on this without a fight - and supporting documentation.

Wouldn't you be nervous issuing a CoC without an insulation test?