Further investigation IR below 2 Megohms or 20 Megohms??

RobW said:

he current online IET OSG says that further investigation is required below 20Mohms rather than the previous versions advising further investigation below 2 Megohms?

Yes, it now aligns with Guidance Note 3 - see page 69 of the 2022 version.

HOWEVER

OSG talks about 'latent defect', i.e.  something like a snagged cable - relating to new install.

And GN 3 clearly relates this figure to NEW installations.

Both, of course, without connected equipment which can also affect the reading.

mapj1 said:

Any single value is a bit of a fudge as of course it depends on how long and rambling the circuit is and what the wiring method is

Agreed ... and connected appliances may also affect the reading.

RobW said:

he current online IET OSG says that further investigation is required below 20Mohms rather than the previous versions advising further investigation below 2 Megohms?

Yes, it now aligns with Guidance Note 3 - see page 69 of the 2022 version.

HOWEVER

OSG talks about 'latent defect', i.e.  something like a snagged cable - relating to new install.

And GN 3 clearly relates this figure to NEW installations.

Both, of course, without connected equipment which can also affect the reading.

mapj1 said:

Any single value is a bit of a fudge as of course it depends on how long and rambling the circuit is and what the wiring method is

Agreed ... and connected appliances may also affect the reading.