Electrical testing

[Welderpaul]

If I was doing an insulation resistance test on a new lighting circuit that has a load of LEDs and dimmers on etc, should I test between earth (still connected in the DB) and the line and neutral connected together?
Presume this avoids the potential difference of 500V between line and neutral but still tests both cables in reference to earth?

 

[sparkysy]

Yes, connect live & neutral together, all switches on, leave the earth in the bar connected and test.
This way you are testing the live and neutral in relation to earth.
It will not however show any live to neutral faults that may be present, but that would require the lights and switches removing to test.

 

[Welderpaul]

Thanks Sy. Would you do an insulation resistance test on a lighting circuit between line and neutral before second fixing then?

If the lighting circuit was on a ring, should the test be put on one leg of the ring only?

 

[sparkysy]

No problem
Yes nowadays due to all the electronics in seconds fix accessories we would do a 500v insulation resistance test on all cables & conductors before second fix. Then after a reduced voltage test with everything fitted.

Lighting circuits generally are wired as a radial circuit.
If it was a ring and you had continuity end to end of all conductors then you could test one end.

 

[MetalMonkey]

If in doubt always start off with a 250v IR test, and if you get a spurious reading indicating something is still in circuit you can then address it before you've stuffed 500v up its chuff!
Ask me how I know.

 

[brightspark]

make sure theres no surge protected leads plugged in when testing and no electronic equipment .it ends up toast

 

[Welderpaul]

Would you IR test the armouring on a SWA or just check it for continuity to earth?

 

[dobbslc]

Worth testing between the armour and all the cores in case it's been pierced.

 

[sparkysy]

If in doubt always start off with a 250v IR test, and if you get a spurious reading indicating something is still in circuit you can then address it before you've stuffed 500v up its chuff!
Ask me how I know.

Yeah I did that, killed two usb sockets behind bedside cabinet's in a property

SWA, Alway IR test with the armour connected to earth just in case it's been compromised somewhere.
If it's in duct there is little chance but if direct burial then there's a small chance it may have been damaged.