Robin 1651 (calibrated) insulation test readings, 500V-DC, L/N shorted v E.
Final circuit consists of 8m FTE2.5, 13m SWA-PVC-2.5-2-core to a CU with 12m of FTE2.5 & 20m FTE1.5 for power & lighting ring. All bulbs removed, all switches on, lighting switches are 1-way. Cable tested at source with RCD removed (ie, whole cable run).
After removing the tell-tale neon (0.32Mohm) I get an insulation resistance of 1651Mohms which seems unusually high/good.
Is the calibration stuffed or is this reading correct? Set to 2000Mohm, 500VDC (200Mohm & 20Mohm range all OR).
IIRC PVC typically has insulation resistance of 200Mohms/km, and resistance halves with every doubling of distance. So the figure is not untoward - I expected 15-25 for a 1980 final circuit. This is fully wired up, all fittings, bulbs removed, not bare reels.
Testing the meter on 3ft of shagged (technical term) butyl cable from 1947, crumbling & disintegrated insulation, showed infinity as the IR even on the 1000V-DC test. That I think is complete bollocks because it should carbon track - it could not pass.
Doing basic IR tests before a BCO outsources same and we get a PIR done generally. I have to replace a surface run of SWA elsewhere (2-core, armour exported earth) due to a nick in the sheath showing flaking rust. Conventional wisdom is not to export the earth even if no Class-1 devices (in garage). However with many 24" railway drains just 3-4ft below ground I do not feel like SDSing 4ft earth rods at random. Last person who damaged one found knee deep water & a =A37k repair bill.
Thanks.