insulation resistance problem

[tony mc]

Any fans or outside lights.

As everyone is saying you have something that is not disconnected,maybe loft light or hidden cupboard light with the lamps in.

 

[SimpleSimon]

Neon indicators is another. And like Tel said, if you can't disconnect short together L/N at the CU and test to E.

 

[malcolmsanford]

SELV Transformers

 

[telectrix]

Any fans or outside lights.

As everyone is saying you have something that is not disconnected,maybe loft light or hidden cupboard light with the lamps in.

loft light is a favorite. never think about it till head scratching time. also vanity lights, under cupboard lights, shaver points, all can f up your readings

 

[nickblake]

Out side PIR lights they always get me at the back of the house

 

[armbands0]

I have come across aerial amps and central heating timers connected to lighting circuits, could be your problem?

I normally do my first tests at 250V then, if looking ok, go on to 500V less likely to destroy anything.

 

[SimpleSimon]

Sorry to bee basic but as it showed L/N 0.00 on both, did you disconnect the neutral from the neutral bar and test like that. Ie you didn't pick up the reading from thr first one twice?
Sorry if I'm being pedantic.

 

[Short Circuit]

may seem obvious, but worth a try... - did you check in the loft to see if something like the alarm, or a tv amplifier has been taken off the lighting circuit! Like the other guys have said - something (load) is still on in the circuit!

 

[the pict]

Or a light in the attic I got caught with a low wattage tube heater once under the loft tank, dopey git